Constraining the Sommerfeld enhancement with Cherenkov telescope observations of dwarf galaxies
The presence of dark matter in the halo of our galaxy could be revealed through indirect detection of annihilation products. Dark matter annihilation is one of the possible interpretations of the recent measured excesses in positron and electron fluxes, once boost factors of the order of or more are taken into account. Such boost factors are actually achievable through the velocity-dependent Sommerfeld enhancement of the annihilation cross-section. Here we study the expected -ray flux from two local dwarf galaxies for which air Cerenkov measurements are available, namely Draco and Sagittarius. We use velocity dispersion measurements to model the dark matter halos of the dwarfs, and the results of numerical simulations to model the presence of an associated population of subhalos. We incorporate the Sommerfeld enhancement of the annihilation cross-section. We compare our predictions with observations of Draco and Sagittarius performed by MAGIC and HESS, respectively. We also compare our results with the sensitivities of Fermi and of the future Cherenkov Telescope Array. We find that the boost factor due to the Sommerfeld enhancement is already constrained by the MAGIC and HESS data, with enhancements greater than being excluded. While Fermi will not be able to detect -rays from the dwarf galaxies s even with the most optimistic Sommerfeld effect, we show that the Cherenkov Telescope Array will be able to test enhancements greater than .
Detection of a rise in the high energy cosmic ray fraction by the PAMELA satellite experiment [Adriani et al. (2008)] and of a peak in the flux by the ATIC balloon experiment [Chang et al. 2008] has stimulated considerable recent theoretical activity in indirect detection signatures of particle dark matter via annihilations of the SUSY LSP and other massive particle candidates [Hooper and Zurek (2009), de Boer (2009), Grajek et al. (2008), Hooper et al. (2008), Liu et al. (2008), Cholis et al. (2008), Donato et al. (2008), Cirelli and Strumia (2008), Bergström et al. (2008)]. Several hurdles must be surmounted if these signals are to be associated with dark matter annihilations, Firstly, a high boost factor is needed within a kiloparsec of the solar circle [Cirelli et al. (2008a)]. Secondly, the boost factor must be suppressed in the inner galaxy to avoid excessive gamma ray emission, synchrotron radio emission, and production [Bertone et al. (2008)]. Thirdly, the annihilation channels must be largely lepton–dominated [Cirelli et al. (2008b)].
The last of these requirements is addressed in various particle physics models for the dark matter candidate [Cirelli et al. (2008b)]. Here we explore the implications of the first two of these requirements. The first is resolved via the Sommerfeld enhancement of the annihilation cross-section in local dark halo substructure [Lattanzi and Silk (2008), Arkani-Hamed et al. (2008)].This boost is especially relevant on scales that are hitherto unresolved by numerical simulations [Springel et al. (2008a)]. Indeed, the second requirement can be understood because the unresolved substructures that dominates the local boost are tidally disrupted in the inner galaxy [Lattanzi and Silk (2008)]. However it is essential to test these assumptions, especially because they go beyond the range of current simulations.
If the Sommerfeld enhancement is indeed dominated by unresolved cold halo substructures, we show here that gamma rays from nearby dark matter–dominated dwarf galaxies may be detectable with experiments such as MAGIC and HESS. Moreover these experiments but in particular the future CTA, may allow imaging of both the smooth and subhalo components of nearby dwarfs such as Draco and Sagitarius.
2 -ray flux from Dark Matter annihilation in Draco and Sagittarius
The observed photon flux from DM annihilation can be written as
where is the mass of the halo, the distance from the observer, denotes the dark matter particle mass and is the differential photon spectrum per annihilation relative to the final state , with branching ratio . The volume integral refers to the line of sight and is defined by the angular resolution of the instrument and by the direction of observation. is the distance from the halo center. is the dark matter density profile inside the halo, being the concentration parameter of the halo, defined as the ratio between virial radius and scale radius and computed following the prescriptions of [Bullock et al.(2001)] [B01]. The annihilation cross section for a typical DM candidate is found to be appropriate for thermal relics that satisfy the cosmological constraints on the present abundance of dark matter in the universe.
In cases where the Sommerfeld enhancement is present (see the next section for the details of the model) we replace the term in eq. 1 with the velocity-dependent expression where the enhancement depends on the halo mass which in turn fixes the average velocity dispersion, and from the radial coordinate R inside the halo, which takes into account the features of the velocity dispersion curve that has lower values closer to the center of the galaxy hosted by the DM halo. The highest values for are obtained for very high DM particle masses (of the order of a few TeV). In this mass region, the primordial annihilation cross-section can be as high as , and we will use this upper value as a reference throughout our paper.
Including the Sommerfeld enhancement, Eq. 1 will transform into
2.1 The particle physics sector
The dark matter annihilation cross section can be enhanced, with respect to its primordial value, in the presence of the so-called Sommerfeld effect. This is a (non-relativistic) quantum effect occurring when the slow-moving annihilating particles interact through a potential [Sommerfeld (1931)]. From the point of view of quantum field theory, the Sommerfeld effect is due to the resummation of ladder diagrams like the one shown in Fig. 1.
The idea that the gamma-ray flux from dark matter annihilations can be enhanced in this way was first proposed in a pioneering paper by [Hisano et al. (2004)] (see also [Hisano et al. (2005)]). Recently, the possibility of explaining the large boost factor required by PAMELA using this mechanism has stimulated several studies of this effect (see for example [Cirelli et al. (2007), March-Russell et al. (2008), Arkani-Hamed et al. (2008), Pospelov and Ritz (2008), Lattanzi and Silk (2008), March-Russell and West (2008)]). In the following, we will briefly summarize some basic properties of the Sommerfeld enhancement.
In the presence of the enhancement, the effective s-wave annihilation cross section times velocity can be written as:
where denotes the tree level s-wave annihilation cross section, and we have explicitly indicated the dependence of the Sommerfeld enhancement on the particle mass and velocity . The Sommerfeld enhancement can be obtained solving the Schrödinger equation for the reduced two-body wave function :
with the boundary condition . The Sommerfeld factor is then given by .
In the following we will consider particles interacting through a Yukawa-like potential:
where is the mass of the exchange boson mediating the interaction. When we will have to specify numerical values for the interaction parameters, we will take and , corresponding to particles interacting through the exchange of a boson.
The Sommerfeld enhancement is effective in the low-velocity regime, and disappears () in the limit . In general, one can distinguish two distinct behaviours, resonant and non-resonant, depending on the value of the annihilating particle mass. In the non-resonant case, the cross section is enhanced for : up to a saturation value, roughly given by . This value occurs for . In the resonant case, occurring for particular values of the mass of the annihilating particle, the cross-section follows the non-resonant behaviour until ; below this critical value, the enhancement grows like before saturating. The Sommerfeld boost can then reach very large values. These different behaviours can be observed in Fig. 2.
We consider a WIMP dark matter candidate that annihilates mainly to weak gauge bosons. If the dark matter is a Majorana particle, such as for example the supersymmetric neutralino, its annihilation into fermionic final states is helicity-suppressed by a factor . For a dark matter particle in the 1 to 10 TeV range, this is a factor even for the heaviest possible final state, i.e. the top quark. However, for completeness we have also considered the heavy quark and lepton annihilation channels. The differential photon spectra per annihilation for the various final states have been computed using PYTHIA [Sjöstrand et al. 2001], including also the contribution from final state radiation.
We consider values of the particle mass very close to the first resonance that can be seen in the top panel of Fig. 2, i.e , in order to obtain the large boost factor required to explain the positron excess. In particular, we consider the following values for the mass of the particle: . Being so close to the resonance, even a relatively small change in the mass of the particle can produce order of magnitude changes in the Sommerfeld boost. In fact, the maximum achievable boost goes from for to for . We show the boost as a function of velocity in Fig. 3; its main properties, i.e. the maximum value and the saturation velocity , are summarised in Table 1 for the different masses As we show in the next sections, these large boost factors can be tested through Cherenkov telescope observations of dwarf galaxies.
2.2 The astrophysical sector: smooth dark matter halo
We deal with two dark matter-dominated dwarf galaxies of our Local Group, namely Draco and Sagittarius. We have chosen such galaxies because they have been observed by the Air Cherenkov Telescopes. Draco, which is visible from the northern hemisphere, has been observed by MAGIC [Albert et al. (2008)], while the flux of -rays from Sagittarius, which is closer to the Galactic Centre and visible from the southern hemisphere, has been measured by HESS [Aharonian et al. (2008)].
Both MAGIC and HESS did not observe any signal and therefore put upper limits on the -ray coming from these sources.
The Draco galaxy lies about 80 kpc away from us, at the zenith with respect to the Galactic Center. In order to model its dark matter halo, we use the density profile obtained by [Walker et al. (2007)], who fitted the velocity dispersion measurements of its stellar population adopting a one-component King profile for the luminous component, and a Navarro, Frenk and White (NFW) profile [Navarro et al. (1996), Navarro et al. (1997)] with constant anisotropy parameter for the DM one. We find that the data of [Walker et al. (2007)] are well fitted by a total initial virial mass of , and NFW scale parameters and . The virial radius which encloses this initial mass is . As confirmed by the recent high resolution N-body simulations Aquarius [Springel et al. (2008a), Springel et al. (2008b)] and Via Lactea II [Diemand et al. (2008)], the satellites, or subhalos, of our Galaxy suffer from external tidal stripping due to the interaction with the Milky Way. To account for gravitational tides, we follow [Hayashi et al. (2003)] and assume that all the mass beyond the subhalo tidal radius is lost in a single orbit without affecting its central density profile. The tidal radius is defined as the distance from the subhalo center at which the tidal forces of the host potential equal the self-gravity of the subhalo. In the Roche limit, it is expressed as:
where r is the distance from the halo center, the subhalo mass and the host halo mass enclosed in a sphere of radius r.
In our case, the host halo is the Milky Way, which we describe with an NFW profile (, , ).
At the distance of Draco, we find . We note that the condition holds, which guarantees that the binding energy is negative and the system is not dispersed by tides.
The Sagittarius dwarf galaxy is located at a distance of about 24 kpc from us, at low latitudes. Its vicinity to the Galactic Center causes significant tidal stripping due to the interaction with the gravitational potential of the Milky Way. Yet the surviving stellar component suggests that its inner dark matter halo also survives.
The observations show that Sagittarius is indeed dark matter-dominated with a central stellar velocity dispersion of about 10 km s [Ibata et al. (1997)], similar to the one observed in Draco.
We modeled the inner regions of the DM halo of the Sagittarius dwarf with the same scale parameters as Draco (see also [Evans et al. (2004)]) obtained assuming a NFW mass density profile and an initial mass of M.
At the distance of Sagittarius, the tidal radius is , still larger than the scale radius.
The astrophysical contribution to the -ray emission from the smooth component of a DM halo can be written as the volume integral
where is the line-of-sight coordinate, the solid angle corresponding to the angular resolution of the instrument, and the angle of view from the GC; in the case of ACTs, and .
The integral along the line-of-sight will be different from zero only in the interval
In the case of the dwarf galaxies, their mass and therefore the masses of the sub-subhalos lie in the region at low where the Sommerfeld enhancement saturates. This is true for every DM mass except for the one which lies closest to the resonance (in our model, ). In this case, however, the radial dependence of the enhancement produces a variation of a few percent. As a first approximation, we can write
where the latter term is just the astrophysical contribution to the -ray flux, without taking into account any enhancement coming from particle physics. We will however compute our prediction according to Eq. 7 in the case of , when comparing our results to the existing data.
The result of the computation of for Draco and Sagittarius are depicted in Fig.4 as a function of .
2.3 The astrophysical sector: substructures
Both the Aquarius and the Via Lactea II simulations have succeeded in observing sub-subhalos, that is to say substructures inside the satellites of the Milky Way-like host halo.
We will therefore populate the dwarf galaxies with sub-subhaloes with masses as small as , which correspond to the typical Jeans mass for a generic CDM weakly interacting massive particle (WIMP) particle with [Green et al.(2004), Green et al.(2005)]. Such a minimum mass may vary between and depending on the particle physics [Profumo et al.(2006)].
We follow the results of Via Lactea II to model the population of sub-substructures. We then adopt a sub-substructure mass function at z=0
and we model the radial distribution following [Kuhlen et al. (2008)]:
where is the scale radius of the host halo and is the radial coordinate inside the host halo.
We normalize the subhalo distribution function such that 10 % of the mass of the host halo () before the tidal stripping is distributed in substructures with masses between and .
The resulting distribution function is
As a second step, we cut off all the subhalos which lie beyond .
This is indeed an upper value for the number of surviving sub-subhaloes, since we are not considering here the fifty percent of the subhalos that exit the virial radius of the parent halo during their
first orbit [Tormen et al. (2005)] and are therefore dispersed into the halo of the Milky Way.
In the case of Draco, we end up with about 16% of
the present Draco mass (inside ) condensed in sub-subhalos with
masses in the range [.
As far as Sagittarius is concerned, we get sub-subhalos, accounting for
4 percent of the total bound mass. As expected, the tidal disruption in this case is more efficient and
sweeps away most of the substructures.
The contribution of such a population of sub-substructures to the annihilation signal can be written as [Pieri et al (2008a)]:
where the contribution from each sub-subhalo () is convolved with its distribution function (). is the lognormal distribution of the concentration parameter with dispersion = 0.24 [Bullock et al.(2001)] and mean value :
Again, the integral along the line-of-sight will be different from zero only in the interval [.
For each sub-substructure, we use an NFW density profile whose concentration parameter depends on its mass and on its position inside the host halo, according to the results of Via Lactea II :
The mass dependence is taken from B01 and extrapolated with a double power law down to the smallest masses, and is the virial radius of the host halo.
We numerically integrate Eq. 12 and estimate the
contribution to from the sub-substructures in a
solid angle along the direction .
The result of the computation of for the subhalo population of Draco and Sagittarius are depicted in Fig.4 as a function of . The presence of sub-subhalos is unimportant in the case of Sagittarius. In the case of Draco, it becomes relevant only away from its center, where gives anyway a flux which is one order of magnitude smaller.
2.4 Comparison with the experimental data
The MAGIC and HESS ACTs have put upper limits on the -ray fluxes from Draco and Sagittarius, respectively.
The upper limit for Draco integrated over energies above 140 GeV is .
In the case of Sagittarius, this limit is , integrated above 250 GeV.
In Fig. 5 and 6 we compare these values with the prediction of the -ray flux from DM annihilations. We compute the flux for the DM mass values give the greatest Sommerfeld enhancement, following eqs. 1 and 2.
We can observe that the data from both MAGIC and HESS already exclude the greatest values for the enhancement. The most stringent limit is given by HESS, which constrains to be smaller than .
We have repeated our computation in the case of photon energies greater than 1 GeV, to compare with the sensitivity of Fermi to point sources [Baltz 2008]. We find that the detection of dwarf galaxies with Fermi is out of the range of experimental feasibility (see also [Pieri et al (2008b)]), even in the serendipitous case where DM particles could have the enhancement necessary to produce the excess in electrons and positrons. This means that the ACTs
provide the only possibility for discovering a possible source of -rays from DM annihilations in the
dwarfs, in the scenario where DM may be responsible for the positron excess.
We have therefore compared our predictions above 1 TeV with the expected sensitivity of the next-generation Cherenkov Telescope Array (CTA). The result is shown in Fig. 7. If CTA will be built in the southern hemisphere, it will be able to test the enhancement down to the value of . In the case of no discovery, this means that the mechanism producing the electron-positron excess does not come from annihilating DM, since the allowed boost factors would be too low to explain the excess.
The results discussed so far have been obtained considering a dark matter particle of mass TeV annihilating exclusively into gauge bosons. Consideration instead of heavy quarks or leptons as possible final states changes the predicted fluxes by factors of order unity, thus leaving our conclusions basically unchanged. In particular, a particle that annihilates only to heavy quarks would produce a flux 1.6-1.7 times larger than that shown in the figures, for all experiments. The limits on the Sommerfeld boost would then be proportionally tighter. In the case of a particle annihilating to leptons, the change in the flux depends on the energy threshold: for MAGIC, HESS and CTA it is respectively 0.5, 0.8, and 3.8 times the flux from the gauge boson channel.
2.4.1 Constraints from the HESS observation of the Galactic Center source
The HESS telescope has extensively observed the Galactic Center (GC) source, measuring an integrated flux above 1 TeV of in 2003 and 2004 [Aharonian et al. (2006)].
The Via Lactea II and Aquarius fits to the inner region of the Milky Way are not conclusive.
Apart from the fact that the simulations do not include baryons which may play an important role at the GC, they disagree on the central slope which better fits the data.
While Aquarius is better fitted with an Einasto profile with , and
(model GC-A), Via Lactea II finds an inner slope of -1.24, i.e. steeper than the NFW one, with and (GC-B), although they allow a fit with an NFW profile assuming and (GC-C).
The line-of-sight integral for an angular resolution of varies from 0.022 (GC-A) to 0.167 (GC-B) to 3.11 (GC-C). The HESS measurement allows us to set upper limits on the possible contribution
due to the particle physics sectors. That is to say, we may allow a maximum particle physics contribution ranging from (GC-A) to (GC-C). Without taking into account the Sommerfeld enhancement, the particle physics contribution to the flux is (averaged over
the mass range that we have explored here, 4.3 TeV 4.55 TeV).
Our conclusion is that the maximum enhancement due to the Sommerfeld effect ranges from 60 (GC-C) through 1120 (GC-B) to 8500 (GC-A).
The Sommerfeld enhancement computed for ranges from 2140 ( = 4.55 TeV) to 880 ( = 4.3 TeV) so that, in the Aquarius model the upper limit does not exclude any DM mass, while in the NFW case there is still room left for a 4.3 TeV DM particle.
The previous estimates are competitive with HESS limits on Sagittarius, although suffering from the large uncertainty about the Galactic Center physics. It is anyway remarkable that the observation of Sagittarius with the CTA could give better limits than the GC region, in models with no DM spike at the GC.
The excess in cosmic-ray positrons and electrons has motivated a wealth of theoretical efforts in order to be explained in terms of DM. In particular, the annihilation mechanism has been revised in the light of the Sommerfeld enhancement, a velocity-dependent effect. Such an effect is maximal in the dwarf galaxies and in their substructures. The enhancement actually saturates for DM halo masses smaller than the dwarf scale. In this work, we have computed the expected -ray flux from the Draco and the Sagittarius dwarfs galaxies, for which observational data are available from the ACTs. We have adapted the smooth halo density profile in order to fit the measurements of velocity dispersions, and we have modeled the presence of a sub-subhalo population inside the dwarfs according to the results of the most recent N-body simulations of a Milky-Way sized halo. We found that the measurements of MAGIC and HESS are able to constrain the enhancement and put an upper limit on it of . We have shown that the future CTA would be able to test values of the Sommerfeld enhancement as small as . Since such small values could not explain the excess in positrons/electrons, this means that the CTA would be able to confirm or exclude the interpretation of the excess in terms of annihilating DM. Finally, we have shown that, in the case where annihilating DM is responsible for the excess, Fermi will not be able to observe any signal.
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BAIKONUR, Kazakhstan – A Souyz space capsule has blasted off from the Russian manned launch facility in Kazakhstan, carrying a Russian, an American and a Japanese to the International Space Station.
The rocket lifted off at 3:02 a.m Wednesday (2102 GMT Tuesday) and is to dock with the orbiting laboratory about six hours later.
The capsule is carrying Oleg Kononenko of Russia, NASA’s Kjell Lindgren and Kimiya Yui of Japan. They will join Gennady Padalka, Mikhail Kornienko and Scott Kelly. The latter two are more than four months into a nearly year-long mission on the space station.
Wednesday’s launch was postponed by about two months after the April failure of an unmanned Russian cargo ship, which raised concerns about Russian rocketry. Another Russian cargo ship was successfully launched in early July.
- Retail-restaurant roundup: Build-your-own pizza concept hits snag as SPIN folds; Chipotle
- Man arrested on suspicion of firing shotgun, setting a fire and smashing windows in a San
- IKEA in Costa Mesa evacuated
- 4-year-old Irvine boy killed after being struck by car while crossing street on scooter
- 3 injured in 2-vehicle crash in Lake Forest


Friday, JANUARY 8 The Moon spends the day in observant, deep-feeling Scorpio. Both Mercury and Venus change signs today. Mercury heads into the sign of Aquarius, where
Friday, JANUARY 8
The Moon spends the day in observant, deep-feeling Scorpio. Both Mercury and Venus change signs today. Mercury heads into the sign of Aquarius, where it will transit for longer than usual–until March 15th–due to an upcoming retrograde cycle starting on the 30th. When Mercury is in Aquarius, we are hungry for knowledge and open to new and original ideas. Our thinking is progressive and objective. Our communication and thought patterns are spontaneous and liberal, and perhaps somewhat fragmented.
Venus moves into Capricorn today, and until February 1st, we are more likely to form connections with people who support our ambitions. We value enduring relationships, reliability, and faithfulness. We take expressing our feelings seriously and could take our time warming up to others.
The Sun forms a sextile with Neptune late morning, and we take things as they come, finding meaning in our experiences more readily than usual. This influence stimulates our imagination and sets an excellent mood for respecting our intuition. We’re tuned in, inspired, and charitable. We see things from a perspective that celebrates our differences. What feels like serendipity experienced now may have to do with a good sense of timing and a feeling of being in sync with the universe.
However, as the day advances, tonight’s Mercury-Mars square can agitate. We should watch for hasty communications and skipping steps. We can find ourselves too quickly in disagreement with others, most likely because we’re communicating ineffectively or impatiently. We may be competing for the floor when expressing our ideas, thoughts, and opinions, making it difficult to engage in healthy dialogue.
The void Moon occurs from 8:58 PM EST, with the Moon’s last aspect before changing signs (a sextile to Pluto), until the Moon enters Sagittarius tomorrow, Saturday, January 9th, at 6:15 AM EST.
Overview of the Day (Friday) EST


Carter, James,Hernández, Ma. () Once upon a star :a poetic journey through spaceMLA Citation
Carter, James,Hernández, MarOnce Upon A Star: A Poetic Journey Through Space. : . Print.
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Once upon a star : a poetic journey through space /
James Carter ; illustrated by Mar Hernández.
|Other Names:||Hernández, Mar|
|Published:||New York : Doubleday Books for Young Readers, |
|Edition:||First American edition.|
|Topics:||Cosmology - Juvenile poetry. | Cosmology - Juvenile literature. | Cosmology - Poetry. | Cosmology. | JUVENILE NONFICTION / Science & Nature / Astronomy. | JUVENILE NONFICTION / Science & Nature / Earth Sciences. | JUVENILE NONFICTION / Technology / Aeronautics, Astronautics & Space Science.|
|Regions:||Universe - Juvenile poetry. | Universe - Juvenile literature. | Universe. | Universe - Poetry. | Universe. | Universe.|
|Genres:||Juvenile works. | Poetry. | Nonfiction. | Picture books for children. | Poetry.|


Probing reionization and large-scale structure with the South Pole Telescope
The South Pole Telescope (SPT) is a 10-meter telescope designed to survey the millimeter-wave sky, taking advantage of the exceptional observing conditions at the Amundsen-Scott South Pole Station. The telescope and its ground-breaking 960-element bolometric camera were successfully installed at the South Pole in 2007. Since then, SPT has embarked upon a large, three-frequency survey covering 6% of the entire sky. I will report on the multi-frequency power spectrum results for this survey, including a detection of the thermal Sunyaev-Zel'dovich (SZ) power and improved upper limits on the kinetic SZ power. I will discuss how we can use the kinetic SZ power and CMB polarization data to determine when the epoch of reionization began, when it ended and how long it lasted.
Date: Mardi, le 7 février 2012 Heure: 16:00 Lieu: Université McGill Ernest Rutherford Physics Building, R.E. Bell Conference Room (room 103) Contact: Robert Rutledge


Astronomers have discovered a barren cosmological orb 1.8 billion light-years wide.
Dubbed the “supervoid,” this immense stretch of relative emptiness (compared to the rest of the universe) helps solve one question scientists have been teasing apart for a decade. At the same time, it brings up a host of other questions that foreshadow an era of “exotic physics,” physics that will seem new and strange even to our most seasoned experts.
The supervoid has about 20% less cosmic material—galaxies, dust, etc.—than our part of the universe or any other area with typical density. It’s not exactly a void, since it’s not entirely empty. But when juxtaposed against other chunks of space, the supervoid appears a frigid wasteland.
“Frigid” may actually be the opportune word here. Scientists had been searching for a void in this region because they knew about the universe’s so-called “Cold Spot,” a part of the sky discovered 10 years ago that is unusually large and cold compared to what the CMB (cosmic microwave background) radiation—the thermal radiation leftover from the Big Bang—would have predicted for it. Over the last several years, they knew that if they could confirm that this part of the universe has a very low density, that would help explain why the Cold Spot exists, since photons speeding through an accelerating universe lose energy and cool as they cross a void.
Here’s Hannah Devlin, explains further at The Guardian:
This is because the photons convert kinetic energy to gravitational potential as they travel to the heart of the void and get further from denser surrounding patches of universe—think of it as climbing a hill. In a stationary universe, the situation would be symmetrical and so the photons would regain the lost energy on the way out of the void (down the hill). In an accelerated expansion of the universe, however, everything is effectively becoming less dense as space is stretched out, so voids become relatively shallower over time. This means by the time the light descends the virtual hill, the hill has become flatter and the light cannot pick up all the energy it lost on the way in. This means the light exits with a longer wavelength, corresponding to a cooler temperature.
To find the void, a team led by István Szapudi of the University of Hawaii at Manoa and András Kovács of the Eötvös Loránd University in Budapest calculated the number of galaxies in a patch of sky about 3 billion light years away from Earth. They used Hawaii’s Pan-STARRS1 telescope and NASA’s Wide Field Survey Explorer satellite to get an accurate measure.
Their results, published in the Monthly Notices of the Royal Astronomical Society , showed that there is in fact a huge, sparsely-populated region centered on the Cold Spot. Here’s Devlin again:
The structure may sound unremarkable—hardly a standalone object even—but scientists say it is unprecedented given how evenly distributed the universe normally is at this spatial scale. “This is the greatest supervoid ever discovered,” Kovács said. “In combination of size and emptiness, our supervoid is still a very rare event. We can only expect a few supervoids this big in the observable universe.”
Unfortunately, the void accounts for only 10% of the difference between the Cold Spot’s low temperature and other average temperatures in surrounding galaxies. So astronomers now have some new questions to ponder: What else might be contributing to the Cold Spot’s brittle temperatures? And how did the supervoid itself come into being? They will likely be addressed in the near future, but in the meantime, scientists will use this finding as added evidence for the presence of dark matter.
Photo Credit: ESA and the Planck Collaboration


Volume 566, June 2014
|Number of page(s)||9|
|Section||Stellar structure and evolution|
|Published online||23 June 2014|
XMM-Newton and Swift observations of WZ Sagittae: spectral and timing analysis
1 Department of Mathematics and Physics E. De Giorg, University of Salento, via per Arnesano, CP 193, 73100 Lecce, Italy
2 INFN, Sez. di Lecce, via per Arnesano, CP 193, 73100 Lecce, Italy
3 European Space Astronomy Centre, SRE-O, PO Box 78, 28691 Villanueva de la Cañada ( Madrid), Spain
4 CRESST and X-ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt MD 20771, USA
5 Department of Physics, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore MD 21250, USA
Received: 19 October 2013
Accepted: 19 April 2014
Context. WZ Sagittae is the prototype object of a subclass of dwarf novae with rare and long (super)outbursts, in which a white dwarf primary accretes matter from a low mass companion. High-energy observations offer the possibility of a better understanding of the disk-accretion mechanism in WZ Sge-like binaries.
Aims. We used archival XMM-Newton and Swift data to characterize the X-ray spectral and temporal properties of WZ Sge in quiescence.
Methods. We performed a detailed timing analysis of the simultaneous X-ray and UV light curves obtained with the EPIC and OM instruments on board XMM-Newton in 2003. We employed several techniques in this study, including a correlation study between the two curves. We also performed an X-ray spectral analysis using the EPIC data and Swift/XRT data obtained in 2011.
Results. We find that the X-ray intensity is clearly modulated at a period of ≃28.96 s, confirming previously published preliminary results. We find that the X-ray spectral shape of WZ Sge remains practically unchanged between the XMM-Newton and Swift observations. However, after correcting for interstellar absorption, the intrinsic luminosity is estimated to be LXUna = (2.65 ± 0.06) × 1030 erg s-1 and LXUna = (1.57 ± 0.03) × 1030 erg s-1 in 2003 and 2011, respectively. During the Swift/XRT observation, the observed flux is a factor ≃2 lower than that observed by XMM-Newton but is similar to the quiescent levels that are observed various times before the 2001 outburst.
Key words: binaries: general / white dwarfs / X-rays: binaries
© ESO, 2014
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For the past few years SpaceDaily has published a series of detailed articles on the upcoming mission to Saturn which will get underway later this year as NASA's Cassini spacecraft approaches Saturn ahead of a 90 minute engine burn to place the billion dollar spacecraft in orbit about Saturn.
Cassini is one of the most ambitious missions ever and central to the mission is the goal of placing a high performance spacecraft in orbit about Saturn. The initial orbital tour will take nearly three years. In addition one of the early highlights will be the deployment of the secondary Huygens spacecraft into the atmosphere of Titan.
Ahead of the main mission, long time space author David Harland has written a desktop manual entitled "Mission to Saturn" that should be on the desk of every planetary scientist with an interest in Saturn.
For readers with a non professional interest in space exploration - "Mission to Saturn" is a highly accessible book that provides substantial detail on the history of Saturn exploration - both from Earth and space based telescopes, and via the three previous spacecraft that have flown by Saturn.
Cassini has already shown off its colors with its flyby of Jupiter - that was essentially a Voyager-class mission for "free" - and which saw breathtaking images returned of Jupiter and its various moons.
Without doubt, Cassini when it arrives at Saturn is going to give the world a much needed break from its Earthly worries as we behold worlds only ever glimpsed before for a few hours as our first robotic explorers sped by on route to the stars.
SpaceDaily can recommend with confidence Mission to Saturn as a book anyone with more than a cursory interest in Saturn, will enjoy reading as we await the main event.
SpaceDaily Book Score - Five Stars - Buy from Amazon or your favorite quality book store.
More about Cassini at NASA
More about Huygens at ESA
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Titan: Sol's Biggest Lightweight
Cameron Park - March 20, 2001
In our continuing series on the upcoming Cassini mission to Saturn and Titan, Bruce Moomaw provides SpaceDaily readers with an insight into the science and technology that will make or break our first expedition to the surface of a gas giant's moon.
Cassini's Epic Tour of the Rings
Cameron Park - May 15, 2001
In our previous installment on Cassini mission to Saturn we looked at the activities the Huygens entry probe would conduct during its active phase as it parachutes into the atmosphere of Titan. but this brief visit to Titan is only the beginning of Cassini's epic survey of Saturn, its rings, and its moons as it orbits the Sol's mightiest ringed world.
Cassini's Tour de Saturn
Cameron Park - May 25, 2001
In my last article on the Cassini Saturn probe, I described the first of the four "phases" of its four-year orbital tour of Saturn and its rings and moons, during which it will use a constant sequence of gravity-assist flybys of Titan - 44 flybys during its 74 orbits around Saturn during those four years - to keep radically modifying its orbit to study different parts of the Saturn system. Each phase represents a period in which Cassini will carry out orbital maneuvers of a different general type to make a particular kind of scientific observation.
Ringing Out The Bugs On Route To Saturn And Titan
Cameron Park - June 26, 2001
Working the problem has been a keystone of the space program for decades. Whatever the cause of a problem, if at all possible, a solution must be found. And for the past year a deep space mission team has been working to solve a communication problem that will happen in 2004 when for a few hours two spacecraft communicate as they set about exploring Sol's biggest lightweight Titan during the first phase of Cassini's four-year mission to Saturn.
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Conditions in space caused by the Sun
Activity on the Sun’s surface, the photosphere, its inner atmosphere, the chromosphere, and in its hot outer atmosphere, the corona, ejects gas and particles into space, carried away at high speeds by the solar wind. The effects of these particles on Earth and the rest of the solar system is known as Space Weather.
The Earth is protected from the solar wind by its surrounding magnetic field, the magnetosphere and the Van Allen radiation belts. At its prettiest, the solar particles enter the Earth’s atmosphere to create the aurorae. However, when solar activity is more violent, the solar wind is stronger and solar flares or coronal mass ejections can occur, firing vast numbers of highly energetic particles into space. These larger solar events can damage satellites and disrupt power grids. Astronomers keep an eye on solar activity and space weather to be prepared for all eventualities.
For further information follow these links:
Live feed of Space Weather information from Twitter:


Jan 29, 2015 07:12 PM EST
Fast winds over California postponed a NASA satellite launch today, but researchers with the space agency say that the mission is far from over. Set to launch this morning, Jan. 29, the Soil Moisture Active Passive (SMAP) spacecraft developed by NASA's Jet Propulsion Laboratory may have had a setback but it still has plans to map the world in a way researchers have never done before.
Designed to detect the moisture content in land surfaces, and also determine whether land is frozen or not during its three-year mission in Earth's outer orbit, the SMAP spacecraft is planning to give environmental researchers a whole new view of the planet on a global scale by providing measurements for virtually every geographic location as it orbits the Earth.
"The relevance is (soil moisture) is a pretty sensitive indicator of future water availability and can be used in climate models to help improve forecasts," Project Manager for SMAP, Kent Kellogg says. "One of the really nice things about this mission is we have a lot of relevance for climate science, but the data is also very useful for everyday practical applications. It will improve weather forecasting significantly, drought and flood forecasting, food productivity and diseases."
The satellite will be capable of looking beneath the clouds, vegetation and other surfaces, and will produce new global maps every two to three days. "It's unique because for the first time they are combining a radar instrument, which has a really fine resolution and detail in what it sees, and also a radiometer, which can see through clouds and has other benefits," researcher with the National Snow and Ice Data Center in Boulder and the Data Management Lead for the SMAP mission, Amanda Leon says.
Though the mission has been placed on hold, as NASA waits for another launch in more suitable weather conditions, the plans are still set in stone and soon environmentalists and researchers alike will be able to have moisture information only a click away.
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Welcome to the University of Texas Skywatchers' Report for Monday December 18th through Sunday January 7th 2007.
The new moon for the month of December is on Wednesday the 20th. The moon is at first quarter on Wednesday the 27th. The first full moon for 2007 will be on Wednesday January 3rd. The full moon for the month of January is the Moon After Yule and the Old Moon.
The winter solstice for the northern hemisphere occurs on Thursday December 21st at 6:22 p.m. central standard time. Some calendars may list Friday the 22nd as the first day of winter, which it is if you use Greenwich time, where the solstice occurs at 22 minutes after midnight on the 22nd.
The cluster of planets around the sun is joined by the moon on December 18th though the 22nd. Mercury, Mars and Jupiter are visible in the morning shortly before sunrise and Venus can be glimpsed in the west after sunset. Over the next few weeks Mercury will be sinking back towards the sun and will reach superior conjunction on Sunday January 7th.
Saturn is rising at 9:45 p.m. on December 20th, and will be up at 9:15th by December 27th. On January 3rd, look for Saturn in the east shortly after 8:45 p.m. The moon will be above Saturn on January 5th and below Saturn on the 6th.
Public viewing on UT campus telescopes is finished for 2006. Open nights will resume in the second half of January 2007.
Thank you for calling the University of Texas Skywatchers' Report and Happy Holidays!


Degradation assessment of LYRA after 5 years on orbit - Technology Demonstration -
We present a long-term assessment of the radiometric calibration and degradation of the Large Yield Radiometer (LYRA), which has been on orbit since 2009. LYRA is an ultraviolet (UV) solar radiometer and is the first space experiment using aboard a pioneering diamond detector technology. We show that LYRA has degraded after the commissioning phase but is still exploitable scientifically after almost 5 years on orbit thanks to its redundancy design and calibration strategy correcting for instrument degradation. We focus on the inflight detector’s calibration and show that diamond photodetectors have not degraded while silicon reference photodiodes that are even less exposed to the Sun show an increase of their dark current and a decrease of their photoresponse.
KeywordsUV solar radiometer Onboard calibration Degradation Diamond detector
The detectors are either silicon photodiodes (Si-AXUV, type AXUV20 from former International Radiation Detectors, now OptoDiode Corp.) or diamond detectors, the latter having been specifically designed for LYRA . A detailed description of LYRA performances can be found in .
In this paper, an assessment of the LYRA instrument’s performance and degradation is presented based on our onboard calibration strategy which includes −1- detector dark current (DC) measurements with LYRA covers closed, −2- onboard Light Emitting Diodes (LEDs) signal acquisition to assess the detector stability and to disentangle aging of the detectors from the optical filters, −3- parallel data acquisition sequence (redundancy concept) where data from two LYRA units can be acquired in parallel to inter-calibrate their spectral channels and −4- inter-calibration planning which combines LYRA observations with currently operating UV solar instruments.
2 Onboard detector calibration
The radiometric calibration stability over years of mission time is a goal for a solar instrument such as LYRA. The bi-weekly onboard detector calibration sequence consists of 40 min of dark current (DC) measurement with the covers closed, followed by 100 min with the visible (VIS) LED emitting at around 470 nm, 100 min with (UV) LED emitting at around 365 nm and again 40 min DC acquisition (see in Fig. 8). The sequence is first applied to the nominal unit 2 and to the first backup unit 3, after which this is repeated with unit 1. For LYRA, two types of diamond detectors had been developed by IMOMEC (University of Limburg, Belgium): metal–semiconductor–metal (MSM) photoconductors  and PIN (with the n-doped layer on top) photodiodes . Si-AXUV photodiodes were selected as reference detectors  for comparison with the newly developed diamond devices. All LYRA detectors had been measured regarding their quantum efficiency, stability, response uniformity and linearity showing good radiometric characteristics under laboratory conditions .
2.1 Dark current measurements
Relative variation of the dark current (ΔDC) measured between semester S1 (2010) and S9 (2014). FWHM: Full Width at Half Maximum of the filter transmission range. It should be mentioned that Al and Zr filters used in ch 3 and ch 4, respectively show high transmittance below 3.3 and 1.5 nm wavelength, respectively
Unit - channel
Bandwidth FWHM / nm
ΔDC (47 °C)/ %
Cumul. solar exposure (days)
+4.6 ± 5
+ 0.2 ± 0.2
+4.0 ± 2
+2.0 ± 2
−32 ± 5
+0.2 ± 0.2
−10 ± 2
−26 ± 5
+14 ± 2
+0.2 ± 0.2
+13.5 ± 2
+14 ± 2
The DC decrease in unit 2 is not fully understood. However, a possible explanation could be related to desorption of surface contaminants (mainly water) which increase conductivity. Due to the hydrogen-terminated MSM diamond surface  and the proximity of its interdigitated finger electrodes (15 μm), diamond MSM detectors are very sensitive to the ambient environment and to surface contamination. Special precautions were taken to keep the diamond MSM detectors in a dry inert environment by purging LYRA continuously with nitrogen and keeping covers always closed during on-ground activities but this was perhaps not sufficient.
As shown in Table 1, diamond MSMs of unit 1, that are less exposed to the Sun, show a non-significant increase of their DC during the same period. The relative DC variation (ΔDC) is approximately +4.0 % at 47 °C within the measurement uncertainty. It should be mentioned that the large error bar used, i.e., ±2 to ±5 %, is mainly related to the time needed for each MSM detector to reach a stable signal. Indeed although diamond MSM detectors have negligibly small DC at room temperature (typically 1 to 2 pA at 5 V bias voltage for a 5-mm diameter active area), they show a slow but persistent decrease of their DC, which varies with the cumulated duration and the flux of previous UV radiation exposures  but mainly with the electric field applied between the metal fingers electrodes. Solutions and progress have been already reported: new diamond MSM device architecture with optimized metal layers and with 5 μm (instead of 15) spacing between the interdigitated finger contacts have been investigated and showed excellent results in terms of stability and homogeneity .
Different mechanisms could contribute to the DC increase of Si-AXUV photodiodes however it is well known that UV radiation as well as ionizing particles induce ionization damages in the Si–SiO2 interface, resulting in the formation of oxide-trapped charges and interface states that affect the performance of the device [15, 16].
2.2 LED measurements
It is important to mention that a stable sensitivity to the onboard LEDs does not exclude the presence of a UV radiation-induced thin surface contamination layer on the detector, which is transparent in the near UV and visible ranges but very absorptive in the EUV-VUV spectral range. Ideally, the responsivity change should be monitored over the spectral range in which the detector is used.
3 Exploitation of the redundancy concept
It should be added that in order to reduce the uncertainty of the integrated signal, LYRA uses three reference calibration voltages (0, 2.5 and 5 V) to calibrate its VFCs (AD652). After almost 5 years in orbit, the 8 VFCs show good stability with time (relative variation of 0.029 % at 5 V) and also as a function of the temperature (1.45 10−3 %/K at 5 V).
Long-term UV solar irradiance measurement can only be achieved by combining observations of several space-based instruments. Since January 2010 LYRA has been continuously observing the Sun and, after correction, it could be calibrated with the help of a combined solar spectrum by the Solar Stellar Irradiance Comparison Experiment (SOLSTICE) onboard the Solar Radiation and Climate Experience (SORCE) and the Solar EUV Experiment (SEE) on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission. In addition, first results indicated that the spatial resolution of SWAP on PROBA2 complements well the high temporal resolution of the EUV LYRA channels . SWAP—the Sun Watcher using APS and image Processing—is an EUV solar telescope centered at 17.4 nm and the first on orbit that benefits from CMOS Active Pixel Sensor technology [24, 25]. The long-term variations of the EUV irradiance measured by LYRA are also compared with the EUV Variability Experiment (EVE) on board the Solar Dynamics Observatory (SDO) satellite . It has been shown that the LYRA channel 2–4 data correlate well with the EVE/ESP (EUV Spectro-Photometer) level-1 data between 2010 and 2013 . LYRA channel 2–4 is also in good agreement with the EVE/MEGS (Multiple EUV Grating Spectrograph) channels . However, LYRA channel 2–3 has shown a much smaller variability due to the degradation of the longer wavelengths included in its passband i.e., above approximately 19 nm. A new inter calibration campaign with EVE/MEGS is under study with improved degradation correction of LYRA channels and will be the subject of a future publication.
The calibrated data (in physical units), corrected from the temperature effects DC, and degradation-trends are available on the LYRA website (proba2.sidc.be/data/LYRA).
Since 2010, LYRA has been exposed to a severe environment and it has consequently experienced significant degradation. The observed degradation is caused mainly by the presence of contaminant species (organics, siloxanes and water) on the optical filter surface, which reduce the UV light transmission. Currently, there is no possibility of mitigating contamination in space once molecules have settled irreversibly after UV-polymerization, which is a classical concern for UV solar instruments. However, methods to largely recover the LYRA calibration were established and successfully implemented. In-flight detector monitoring shows that diamond detectors (both MSM and PIN) exhibit insignificant degradation after almost 5 years on orbit. By its nature, diamond has a much lower thermally induced DC and is a radiation-hard semiconductor, which significantly extend the stability of the LYRA radiometric calibration. Conversely, and despite a much lower duty cycle, the Si-AXUV photodiodes used as reference detectors show an increase of their dark current and a higher decrease of their photoresponse, as demonstrated by the onboard UV LEDs for the EUV LYRA channels, suggesting damage in the oxide passivation layer. Exposure to radiation is often the main reason for detector degradation, and its impacts (ionization and displacement-damage) are frequently underestimated. LYRA profits additionally from a redundancy design concept for tracking instrument degradation. Complemented by other solar inter-calibration instruments, LYRA started its new real-time space weather services. Finally, the successful PROBA2 technological mission offers a unique opportunity to validate diamond detector technology from which lessons are derived for future solar UV radiometers.
LYRA is a project of the Centre Spatial de Liège, the Physikalisch-Meteorologisches Observatorium Davos and the Royal Observatory of Belgium funded by the Belgian Federal Science Policy Office (BELSPO) and by the Swiss Bundesamt für Bildung und Wissenschaft. This work was made possible thanks to the Solar-Terrestrial Centre of Excellence (STCE), a collaborative framework funded by BELSPO.
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Open Access This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.


Monday, August 21, 2017
11:00am - 4:00pm
FREE admission (Viewing glasses available for the first 40 people)
Come to Owl’s Hill Meadow to view the solar eclipse. You bring the picnic!
The Solar Eclipse Viewing event at Owl's Hill Nature Sanctuary is sold out. Please check our calendar for all our public program days.


The sticker is available in two choices - with white stars for dark walls or grey stars for pale walls. It is also available in 3 sizes to suit your decor.
SMALL: The moon measures 27cm across.
MEDIUM: The moon measures 55cm across.
LARGE: The moon measures 87cm across.
The set contains the moon plus 230 stars. You can also choose to add an extra set of stars, please select white or grey from the drop-down.The stickers are easily applied - just peel and stick - and are made of fabric adhesive so they can be removed, repositioned and reapplied over and over. They are free from vinyl, PVC, BPA and phthalates so make a great choice for nurseries and kids' rooms.
To infinity and beyond! Create an amazing space scene with our Space Rocket wall stickers....
Add a fun touch to nurseries and children's rooms with these polka dot wall stickers...
A blue whale and her calf are accompanied by a diver feature in this wall...
Simply stars! Lots of little stars in a variety of colours to decorate walls and...


- Roberto Molar Candanosa
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- Cell phone
If you have one of those household drawers where random stuff collects, you might want to rummage through it looking for an old pair of eclipse viewing glasses. It was just back in August 2017 when we needed special light-blocking eyewear to view a total solar eclipse that cut a swath across the country. Dubbed "The Great American Eclipse," its "zone of totality"—the shadowed region where the sun is completely blocked by the moon—stretched in a narrow band from Oregon to South Carolina. (Outside this band, Baltimore experienced a partial eclipse that year with 80% of the sun blocked by the moon.)
On April 8, the moon and the sun will again do their sky-darkening celestial dance. This time, the band of totality stretches from Mazatlan on Mexico's west coast and moves northeast through Texas as part of sweeping cross-country arc ending in Newfoundland, Canada. Major cities in its path include San Antonio, Dallas, Little Rock, Indianapolis, Cleveland, and Buffalo. With deference to Bonnie Tyler's chart-topping hit, maybe this one could be dubbed "Total Eclipse of the Heartland." In Baltimore, the optimal viewing time is expected to be 3:21 p.m. EDT, with the partial phases extending from about 2 p.m. to 4:30 or so.
Is there anything special about this latest total solar eclipse?
Well, for one thing there won't be another total solar eclipse visible in the U.S. until 2044. But this eclipse will be different from the one in 2017. The moon's orbit is slightly elliptical. So the angular size of the moon is a little smaller when it's farther away, and a little bigger when it's closer. This year the moon is closer to us than in 2017. The length of the time that you were in shadow in 2017, if you were right on the totality center line, was a little over two minutes. And this time it will be over four minutes long—all because the moon is closer. And the path of totality will be wider as well.
What should we consider if we want to travel to experience totality?
Clouds! [laughter] The difficulty with this one is that the northeast in April is not known for being spectacularly clear. So it'll get dark in the totality zone but whether you can actually see the eclipse or not is just going to depend on the weather. I think a lot of people are heading down south to Texas and Mexico hoping that the weather is a little clearer down that way.
What can we expect here in Baltimore?
It will be another partial eclipse here with some 90% of the sun covered. If you have the special glasses and look at it, you will see the bright disc of the sun with a substantial chunk taken out of it that will change over time. It'll get to a certain point, maximize, and uncover again. You might see the character of the light change a little bit if it's clear here. It's an odd light. The light levels go down, and if the sun's out, it is still producing crisp shadows. This is in contrast to evening twilight when things kind of soften in terms of the shadows.
Is it worth getting closer to the totality but not all the way in it?
Not really. The amazing thing about an eclipse is that you could be where the sun is 99% covered and it's not the same as being 100% when the solar disc is completely covered and you see the corona around the outside. In a 99% eclipse, you still have a piece of the sun that's uncovered and its light completely dominates so you don't see the corona. So people who say, "oh, I'm close to totality—I'm going to stay here" will not experience totality or see the corona.
Tell us more about the corona.
It's basically the tenuous outer layers of the solar atmosphere. When you see the bright sun, that's called the photosphere. You can see sunspots and things there. That's the so-called surface of the sun. (Well, the sun doesn't have a hard surface like the earth, but basically, there's a photosphere where the light escapes and that's what we see.) There is a tenuous region of the extended solar atmosphere called the corona, where magnetic fields and high-energy particles come out of the sun and ionize the tenuous gas around the sun. That's the halo around the sun you can see when the bright disc is completely covered during totality. During totality, you can look at it without glasses and take pictures of it.
It's pretty amazing, huh?
Absolutely spectacular. And not just the eclipse itself, but then just seeing the surroundings get dark in the middle of the day. Sometimes animals and insects and birds and whatnot start to do funny things because they don't understand what's going on. We experienced totality in the Tetons in 2017. You could see the shadow coming and then it sweeps over you and all of a sudden, you're in the dark. The only other time I experienced it was as a college student in 1972. We we're driving across Canada listening on transistor radios to figure out what the weather was going to be like and where we should try to go. It sounded like Nova Scotia had the best chance of being clear, so we kept going east until we got to Nova Scotia, and that's where we watched it.
Wait, you went up to Nova Scotia to see the total eclipse of the sun? Did Carly Simon write her chart-topping hit "Your So Vain" about you?
Sadly, no. I went in a college van, not a Lear jet!


Analemma Wines -
The analemma is a figure 8 shape of the Sun’s annual migratory path between the northern and southern hemispheres as seen from the Earth. This pattern is caused by the tilt of the Earth’s axis and is a visual cue of the Sun’s movement through the calendar year.
The ribbon-like figure of the analemma is similar to the symbol of infinity. We draw inspiration from this image of “boundlessness” or “beyond calculation.” So much of what we enjoy as humans cannot be summarized by science or measured by calculation. Joy, love, pleasure, and a smile are all examples of immeasurable essences that are meaningful aspects of everyday life. Our experience reveals that the pleasure derived from wine falls into this unquantifiable category.


By Prakash Chandra
To paraphrase a famous quote, it may have been one small step in launching rockets, but a giant leap for a country’s space ambitions. The debut experimental flight of India’s Geosynchronous Satellite Launch Vehicle Mark III (GSLV Mk III) on Thursday must have dispelled whatever doubts that lingered in the minds of India’s space scientists about their flagship launcher’s capabilities. For, India’s most powerful rocket was yet to prove its reliability, having failed in four of its previous seven flights.
The Mk III did not launch any satellite. Instead, the 630-tonne rocket carried aloft the hopes of Indian Space Research Organisation (Isro) scientists as they validated its flight parameters and stability during its suborbital hop of the planet at a height of around 126 km.
The success of this launch is crucial for two reasons. One, Isro plans to send two astronauts into space at some point as part of its human space flight programme, an ambition that hinges on an effective Mk III lifting a manned spacecraft to low Earth orbit (LEO). A prototype of the 3.65-tonne crew module to be used for India’s first manned mission rode on the Mk III on its maiden experimental flight on Thursday.
Manned space flight capability will enable India to enter an advanced field where there are few competitors, especially given Isro’s credentials as a unique organisation where the return on investment is very high. Even on a modest budget, the space agency has achieved so much. At some point, privatisation of India’s space sector could lead to a further lowering of costs, which would enable Isro to even compete in space tourism.
The second reason is that only a reliable Mk III booster, which can deliver four-tonne payloads to geosynchronous transfer orbit (GTO), will help India capture a sizeable chunk of the global satellite launch market. The GSLV now needs just one more test flight to become commercially operational and enter the niche market for four-tonne satellites, currently the exclusive preserve of American space boosters and the European Space Agency’s Ariane rockets. The biggest challenge before Isro in operationalising the Mk III and achieving these two goals is the development of an indigenous cryogenic engine, which is crucial for the Mk III.
Cryogenic engines use fuels like oxygen and hydrogen in liquid form — stored at extremely low temperatures —to produce enormous amounts of thrust per unit mass (engineering parlance for the mass of fuel the engine requires to provide maximum thrust for a specific period such as, say, pounds of fuel per hour per pound of thrust). Rockets powered by cryogenic motors, therefore, need to carry much less fuel than would otherwise be required.
But developing a cryogenic engine from such propellants is a huge challenge, and India’s indigenously developed cryo engine is still some way off. For Thursday’s launch, the Mark III carried a dummy cryo engine with inert nitrogen to simulate the characteristics of the actual flight version. The launch otherwise tested the performance of the rocket —avionics, stage separation, etc — and the re-entry characteristics of the crew module. No engine was fired at the third stage.
India’s space engineers can be justifiably proud of standing up to the exaggerated jitters of the world’s most advanced space-faring nation in the early 1990s — that India might use its space launch capabilities for military purposes. (At that time, under US pressure, Russia reneged on its original deal to transfer cryogenic technology to India, forcing India to buy off-the-shelf cryo engines from Russia.)
But now that Isro has developed its own cryo engine that will be testflown on the GSLV’s next flight, it can put the unpleasant past firmly behind it and literally aim for the stars. There is a long way to go, though, before Mark IIIs routinely hoist fourtonne and heavier payloads to GTO.
Rockets belonging to the Mk III class are the workhorse launchers for US, Russian, European and Chinese space agencies. The future of the global satellite launch market is all about communication satellites, and it is imperative for Isro to augment its launch capability constantly to compete with powerful rockets like the European Ariane and America’s Delta and Atlas that dominate the business of heavy-lift launchers.
An operational Mk III will even give Isro the capability to build an orbiting space station. The space agency, however, cannot afford to ignore the fact that by then, other players would probably have saturated the market and pushed the bar still higher.
the second reason is that only a reliable mk iii booster, which can deliver four-tonne payloads to geosynchronous transfer orbit (gto), will help india capture a sizeable chunk of the global satellite launch market. the gslv now needs just one more test flight to become commercially operational and enter the niche market for four-tonne satellites, currently the exclusive preserve of american space boosters and the european space agencyâ s ariane rockets. the biggest challenge before isro in operationalising the mk iii and achieving these two goals is the development of an indigenous cryogenic engine, which is crucial for the mk iii.... Read More
Views expressed above are the author's own.


GLOBAL FORECAST (15/01/2022 12:00 - 15/01/2022 18:00)
The geometric figure in the sky Needle that occurs in the period described shows very weak transformational and restructuring cosmic energies. This geometric structure manifests itself when, viewed from the Earth in the Solar System, combinations occur between four luminaries, planets or other important cosmic factors. The quadruple combination symbolizes the creation of some material base for the manifestation of the planetary energy.
The very form of this cosmic combination represents triangle. This threefold relation between cosmic factors is much stronger than the normal aspect in Astrology.
In this case these objects are coming into the following angular sequence: 30°-150°-180° or Ceres (C) q North Node (¤) i Moon (W) o South Node (¥) w←.
This structure in the Cosmos is occurs relatively rarely in the Universe, and it shows that the Wisely Intelligent Powers use this celestial structure in special cases to turn the human civilization into a special and unique direction.
Since this configuration possesses the quality of asymmetry, it becomes clear that the celestial energies are not so intense by their nature, and one can more easily master and transform them to his/her advantage.
In a global sense, The participation of the Moon in more complex cosmic connections means that they will be further enhanced, and the energy of the Universe will be directed also towards the wide public masses.


- Iranian calendar
The Iranian calendar or Solar Hejri (
19 March|| Demise of Muhammadand Martyrdom of Imam Hassan|| |
20 March|| Nationalization of the oil industries || |
4 June|| Anniversary of the passing of ImamKhomeini|| || 1989
5 June|| Anniversary of the uprising against the Shah || |
3 October|| Martyrdom of ImamAli || |
15 October|| End of Ramadan|| Eid-e-Fitr|
- ] .
The year was computed from the
vernal equinox, and each month was determined by the transit of the sun into the corresponding zodiac region, a system that incorporated improvements on the ancient Indian system ofthe Surya Siddhanta("Surya"=solar, "Siddhanta"=analysis, 4th c. CE), also the basis of most Hindu calendars. Since the solar transit times can have 24-hour variations, the length of the months vary slightly in different years (each month can be between 29 and 32 days). For example, the months in two last years of the Jalali calendar had:
Because months were computed based on precise times of solar transit between zodiacal regions, seasonal drift never exceeded one day, and also there was no need for a leap year in the Jalali calendar. However, this calendar was very difficult to compute; it required the full
ephemeriscomputations / actual observations to determine solar motion trajectories. Some claim that simplifications introduced in the intervening years may have introduced a system with 8 leap days in every cycle of 33 years. (Different rules, such as the 2820-year cycle, have also been accredited to Khayyam). However, the original Jalali calendar based on observations (or predictions) of solar transit would not have needed either leap years or seasonal adjustments.
The team also came up with the computation of the length of a solar year as 365.24219858156 days. The number of decimal digits reflects their high confidence in this computation. Though it may not have been known at the time, the length of theyear is changing in the sixth decimal place over a person'slifetime. Nonetheless, the result is astoundingly accurate: the length ofthe year at various points are:
* 365.2421986 days: Isfahan team, 1079
* 365.242196 days: end of the 19th century
* 365.242190 days: end of 20th c. (today)
However, owing to the variations in month lengths, and also the difficulty in computing the calendar itself, the Iranian calendar was modified to simplify these aspects in 1925 (1304 AP).
Iranian Calendar Reform: 1925
February 21, 1911, the second Persian parliament mandated government use of a simplified calendric computation system based on the solar calendar. The present Iranian calendar was legally adopted on March 31, 1925, under the early Pahlavi dynasty. The law said that the first day of the year should be the first day of spring in "the true solar year", "as it has been" (کماکان). It also fixed the number of days in each month, which previously varied by year with the tropical zodiac. It revived the ancient Persian names, which are still used. It specified the origin of the calendar (Hegira of Muhammadfrom Meccato Medinain 622 CE). It also deprecated the 12-year cycles of the Chinese-Uighur calendar which were not officially sanctioned but were commonly used.
The first six months (Farvardin–Shahrivar) have 31 days, the next five (Mehr–Bahman) have 30 days, and the last month (Esfand) has 29 days or 30 days in leap years. The reason the first six months have 31 days and the rest 30 may have to do with the fact that the sun moves slightly more slowly along the ecliptic in the northern spring and summer than in the northern autumn and winter.Fact|date=November 2007
Afghanistan legally adopted this calendar in 1957,Fact|date=November 2007 but with different month names. The Afghan
Pashtolanguage in Afghanistan uses the Pashto names of the zodiac signs. The Afghan Dari language in Afghanistan, uses the Dari names of the zodiacsigns.
The Persian calendar produces a five-year leap year interval after about every seven four-year leap year intervals. It usually follows a 33-year cycle with occasional interruptions by single 29-year or 37-year subcycles. By contrast, some less accurate predictive algorithms are suggestion based on confusion between average tropical year (365.2422 days, approximated with near 128-year cycles or 2820-year great cycles) and the mean interval between spring equinoxes (365.2424 days, approximated with a near 33-year cycle).
The Iranian calendar year begins at the start of Spring in the northern hemisphere: on the midnight between the two consecutive
solar noons which include the instant of the Northern spring equinox, when the sun enters the northern hemisphere. If between two consecutive noons the sun's altitude rises through its equinoctial altitude, then the first noon is on the last day of one calendar year and the second noon is on the first day ( Nowruz) of the next year.The calendar has 12 months with Persian names.
The first day of the calendar year is also the day of the greatest festival of the year in Iran, Afghanistan and surrounding regions, called
Nowruz(two morphemes: IPA|now (new) and IPA|ruz (day), meaning "new day").
Days of the week
In the Iranian calendar, every week begins on Saturday and ends on Friday. The days of the week are called: IPA|ʃanbeh (شنبه in native script), IPA|jekʃanbeh (یکشنبه), IPA|doʃanbeh (دوشنبه), IPA|seʃanbeh (سه شنبه), IPA|tʃahɒrʃanbeh (چهارشنبه), IPA|pandʒʃanbeh (پنجشنبه), and IPA|dʒomhe (جمعه originally in Arabic) or IPA|ɒdineh (آدینه) (in IPA|pɒrsi). In most Islamic countries, IPA|dʒumʕa is the holiday.
Calculating the day of the week is easy, using an anchor date. One good such date is Sunday, 1 Farvardin 1372, which equals 21 March 1993. Assuming the 33-year cycle approximation, move back by one weekday to jump ahead by one 33-year cycle. Similarly, to jump back by one 33-year cycle, move ahead by one weekday.
As in the
Gregorian calendar, dates move forward exactly one day of the week with each passing year, except if there is an intervening leap day when they move two days. The anchor date 1 Farvardin 1372 is chosen so that its 4th, 8th, ..., 32nd anniversaries come immediately after leap days, yet the anchor date itself does not immediately follow a leap day.
The image below shows the difference between the Iranian calendar (using the 33-year arithmetic approximation) and the seasons. The Y axis is "days error" and the X axis is Gregorian calendar years. Each point represents a single date on a given year. The error shifts by about 1/4 day per year, and is corrected by a leap year every 4th year regularly, and one 5 year leap period to complete a 33-year cycle. One can notice a gradual shift upwards over the 500 years shown. The Gregorian calendar, introduced in 1582, is almost as accurate in the long term, but has larger swings of seasonal errors over centuries.
* [http://pmc.khone.ir/ Persian Multi Calendar] This is a free and open source calendar program running under Windows, containing all three calendars Jalali (Persian), Hijri (Islamic) and Gregorian with much more features.
* [http://www.alavi.us/toolbar/ An Iranian calendar toolbar for Internet Explorer and Firefox]
* [http://www.aaahoo.com/main/dispCalendar.asp?ULanID=E&PR=y Online Persian Calendar from aaahoo portal]
* [http://www.payvand.com/calendar Online Persian Calendar Generator and Convertor]
* [http://www.nongnu.org/afghancalendar Online Afghan Calendar with Gregorian, Hejrah-e shamsi and Hejrah-e qamari dates]
* [http://www.iranchamber.com/calendar/converter/iranian_calendar_converter.php An online Jalali(shamsi)/Gregorian/Islamic(hijri) Date Convertor]
* [http://www.tondering.dk/claus/cal/node7.html The Persian Calendar] : How the leap years are calculated
* [http://msdn2.microsoft.com/en-us/library/system.globalization.persiancalendar.aspx System.Globalization.PersianCalendar class documentation in MSDN Library] (The implementation of Persian Calendar in Microsoft .NET Framework 2.0)
* [http://www.alavi.us/jcal/ An Interactive Iranian Calendar]
* [http://www.calendar-ir.narod.ru/ An online Persian/Gregorian date convertor, Persian calendar for mobile (j2me)]
* [http://ahura.TheLalis.com The Zoroastrian Calendar]
* [http://www.iranian.com/History/April99/Months/index.html Meaning of the names of the months in the Persian Calendar]
* [http://psoft.ir/ Sun Calendar] This is a Persian solar calendar plus some useful tools such as date converters.
Wikimedia Foundation. 2010.
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Asteroid 163899, also known as 2003 SD220, is a potentially hazardous asteroid about 1.5 miles across and it is expected to pass perilously close to Earth on December 24, Christmas Eve, according to NASA astronomers.
Asteroid 2003 SD220 is one of the biggest, near Earth asteroids (NEAs) to make such a close approach to Earth in recent years. The asteroid is so big that it could cause continent-wide catastrophe if it hits Earth. An impact by an asteroid in the 1.5-mile-range could trigger earthquakes and tsunamis that could engulf an entire continent.
Astronomers are concerned about 2003 SD220 because it is one of the largest NEAs to make a close approach to Earth in recent years. At an estimated distance of 6.7 million miles — a hair’s breadth on the cosmic scale of distances – it could come on a collision course with Earth in the future due to physical effects, such as the Yarkovksy effect which induces subtle changes in the orbits of NEAs.
Astronomers have detected two cases of Yarkovsky effect using radar observation methods. The effect was first detected in the asteroid 6489 Golevka using the Arecibo radio telescope. The asteroid was observed to drift 15 km from its original course over a twelve-year period from 1991 to 2003.
According to NASA, asteroid 163899 (2003 SD220) was detected by the NEOWISE spacecraft on November 16. The asteroid is high on the list of 17 “top-priority” near-Earth asteroids for close radar observation by astronomers due to the potential threat they pose to Earth.
Astronomers fear that ten of a group of asteroids — including 2003 SD220 — could be much larger than suspected. Six of the group — including 2003 SD220 — are classified as potentially hazardous asteroids (PHAs).
The six are considered potentially hazardous asteroids because scientists know too little about their trajectories despite the fact that their orbital trajectories bring them very close to Earth.
Space rocks falling into the PHA category are generally larger than 100 meters and approach Earth closer than 0.05 AU (approx 7.5 million kilometers or 4.65 million miles).
Currently, NASA does not know of any PHA on a collision course with Earth but astronomers are searching actively. There is a risk that the trajectory of any of the known objects could undergo subtle changes due, for instance, to the gravitational fields through which their orbital paths pass that could bring them on collision course with Earth.
Reports of the close approach of asteroid 2003 SD220 on December 24 have sparked speculations online among Planet X or Nibiru cataclysm believers. Conspiracy theorists are spooked by the timing of the approach of 2003 SD220, following the close approach of asteroid 2015 TB145 last Halloween. Some conspiracy theorists are speculating that some invisible hand could be “pushing them (large asteroids) towards Earth,” while others are speculating that the gravitational pull of 2003 SD220 could trigger earthquakes and disrupt continents.
Speculations are rife at a time that Nibiru cataclysm conspiracy theorists are making predictions that Planet X will be visible from Earth during December and that it will probably crash into Earth during the same month. According to Nibiru cataclysm doomsday prophets, the rogue planet will appear in the skies as a massive behemoth, about four times the size of Jupiter.
The force of its gravitational pull as it passes close to Earth will rip up the continents and cause a massive shower of comets that wipes out life from Earth, according to conspiracy theorists.
But, of course, conspiracy theorists have predicted Planet X or Nibiru cataclysm for decades and so far their predictions of doom have failed.
NASA astronomers with the Near-Earth Objects Observation program and astronomers at the Arecibo observatory in Puerto Rico will conduct radar observations of 2003 SD220 as it approaches Earth. Radar observation is considered one of the most effective techniques for determining the physical and orbital properties of NEAs and PHAs.
According to a report by a team of experts working with NASA, “Radar is particularly effective at detecting satellites around near earth asteroids having discovered two-thirds of all known binaries and all the known or suspected triple systems.”
[Image via NASA/Wikimedia]


This week officials warned that Earth was going to get with large solar flare from the Sun, which could potentially affect satellites, internet connections, and more.
Officials at the US National Oceanic and Atmospheric Administration (NOAA) warned that a coronal magnetic ejection (CME) was on a direct collision course with Earth and was expected to arrive on October 12. NOAA warned that the effects of the CME would cause minor geomagnetic storms in Earth's atmosphere, which could result in auroras being seen in locations such as north of England and Northern Island.
The CME has impacted Earth, and officials are happy to report that everything went as anticipated. Solar wind speed increased by nearly 62 miles a second, and total interplanetary magnetic field (IMF) strength quickly elevated to over 15 nT. Additionally, NOAA states on its website that the CME arrival caused a G1-G2 geomagnetic storm which is categorized as "minor - moderate". The geomagnetic storm caused gorgeous auroras to be spotted in the sky. Those can be seen in the above video.


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Objective solar filter – with Baader solar filter foil, for 250 mm telescopes
Solar filters are mounted in front of the telescope and reduce solar radiation to safe levels and suitable for direct observation of the sun.
Solar filters are equipped with the safe and renowned AstroSolar filter foil by Baader Planetarium. The filter foil’s quality is superior to most glass solar filters making the image quality sharper and more contrasty than standard mylar and polymer foils. The sun is depicted in neutral white color and with a resolution that’s only limited by the seeing conditions and the physical characteristics of your telescope.
Celestron Solar Filters with Baader AstroSolar foil provide full protection agains harmful UV and infrared rays. UV is completely absorbed, rated as ND-5, which means that the film allows passage of 1/100.000 percentage of visible light (.001%) and thermal radiation is reflected by 99.999%. The amount of light that enters the telescope is equal to the brightness of the moon.
Glass filters can break or suffer fine spots with high transmission letting UV and IR pass because they are mostly coated at only one side. The Baader foil is coated on both sides offering double security. And what is more, the foil offers some flexibility and high resistance against ripping. Breaking is absolutely impossible. The cell is very lightweight and made of weather proof ABS plastic. As long as the proper size is chosen, optimal fit to the telescope is guaranteed.


“Look. All this Space And U really think We are Alone?”
By Carley Huxley
Are we alone? There are trillions of stars in the universe – each one a solar system. Is it arrogant to think we’re the only sentient beings in the Universe? Carley poses that question to us.
Printed on 8-1/2" x 11" card stock, suitable for framing. Susan will add touches of 18K gold highlights.


The launch is now scheduled for Saturday May 30 at 20:22 UK time (19:22 GMT).
The mighty rocket will be carrying two Astronauts to the International Space Station inside a new Crew Dragon Spacecraft. This is the first ever commercial launch of Astronauts into space by a private company, SpaceX Crew Dragon Demo-2.
After lift off, you may be able to see the Crew Dragon spacecraft on its first orbit passing over the United Kingdom. An unmissable and historic sight!
Unlike the earlier scrubbed launch on Wednesday, you won’t see the craft over the UK 15 – 20 minutes later, but you may be able to see it pass over the UK/ Europe around 22:15 UK time the same evening.
The pass will be very low in the sky near the horizon and will be a challenge to spot. It may be too low to be visible in Scotland, Northern Ireland and Northern England.
This will be the only time we will be able to see the spacecraft fly over before docking the following day.
For full information please visit https://www.meteorwatch.org/crew-dragon-watch-the-launch-then-see-it-fly-over-uk/