vania-janet/multiturn-rag-retrieval-data huggingface dataset:
NASA's Hubble Finds that Aging Brown Dwarfs Grow Lonely - NASA Science
The name "brown dwarf" is a misnomer because the object would typically appear red to the naked eye. It is brightest in infrared light. Many brown dwarfs have binary companions. But as they age, the binary system gravitationally falls apart, and each dwarf goes its separate way, according to a recent Hubble Space Telescope study.

The background stars in this illustration are a science visualization assembled from the Gaia spacecraft star catalog. The synthesized stars are accurate in terms of position, brightness, and color. Because this is not an image of the Milky Way, missing are glowing nebulae and dark dust clouds.NASA, ESA, Joseph Olmsted (STScI)Astronomers using Hubble confirm that companions are extremely rare around the lowest-mass and coldest brown dwarfs. Hubble can detect binaries as close to each other as a 300-million-mile separation – the approximate separation between our Sun and the asteroid belt. But they didn't find any binary pairs in a sample of  brown dwarfs in the solar neighborhood. This implies that a binary pair of dwarfs is so weakly linked by gravity that they drift apart over a few hundred million years due to the pull of bypassing stars."Our survey confirms that widely separated companions are extremely rare among the lowest-mass and coldest isolated brown dwarfs, even though binary brown dwarfs are observed at younger ages. This suggests that such systems do not survive over time," said lead author Clémence Fontanive of the Trottier Institute for Research on Exoplanets, Université de Montréal, Canada.In a similar survey Fontanive conducted a couple of years ago, Hubble looked at extremely young brown dwarfs and some had binary companions, confirming that star-forming mechanisms do produce binary pairs among low-mass brown dwarfs. The lack of binary companions for older brown dwarfs suggests that some may have started out as binaries, but parted ways over time.The new Hubble findings, published in The Monthly Notices of the Royal Astronomical Society, further support the theory that brown dwarfs are born the same way as stars, through the gravitational collapse of a cloud of molecular hydrogen. The difference being that they do not have enough mass to sustain nuclear fusion of hydrogen for generating energy, whereas stars do.
Astrophysics Science Division Colloquium Series Schedule: Spring 2024
Revealing the Lifecycle of Interstellar Dust with Polarimetry
Brandon S. Hensley
JPL/Caltech
Tuesday, Feb 27, 2024

Abstract
Observations of polarized dust emission from the Planck satellite challenged our classical models of interstellar dust grains. In this talk, I will argue that initially distinct populations of carbonaceous and silicate stardust get rapidly homogenized in the ISM into a composite material ("astrodust"). I will show that the astrodust+PAH model is compatible with current observational constraints on dust extinction and emission in the diffuse ISM, and that it provides a more natural explanation for the observed polarized emission than do two-component models. I will discuss implications for the lifecycle of dust in galaxies and highlight the power of future polarimetric observations on platforms like the PRIMA far-infrared probe to illuminate the formation and evolution of dust.

Primordial Black Holes as Dark Matter
Florian Kühnel
Max Planck Institute for Physics
Thursday, Feb 29, 2024

Abstract
Primordial black holes are black holes that may have formed in the early Universe. Their masses potentially span a range from as low as the Planck mass up to many orders of magnitude above the solar mass. This, in particular, includes those black holes recently discovered by LIGO/Virgo, and these may conceivably be primordial in origin. Furthermore, there are now numerous recent hints for compact bodies constituting (part of) the dark matter. After a general introduction of the topic, I will talk about those, their connection and future detection possibilities.

Chandra & the SuperMassiveBlackHole - Galaxy Interaction
Giuseppina Fabbiano
Center for Astrophysics, Harvard & Smithsonian
Tuesday, Mar 5, 2024

Abstract
Launched from Cape Canaveral on July 23, 1999, Chandra is the NASA Great Observatory for the X-ray band. Now in its 25th year of operations, Chandra has revolutionized our view of the X-ray sky, thanks to its sub-arcsecond imaging and spectral capabilities.
Astrophysics Science Division Colloquium Series Schedule: Spring 2024
The first is when the binary is seen close to edge on; in that case, the binary produces self-lensing flares (SLFs) when one of the black holes moves in front of the background black hole. This causes the emission to be gravitationally lensed. This signal can additionally hold information on the size and shape of the emission morphology of the lensed black hole. Secondly, I will argue that when the binary is close to merger, the accretion is disrupted, turning the binary X-ray dark. I will argue that the upcoming time-domain surveys and X-ray mission might be able to observe these signatures, and that they could be crucial for LISA source identification.

It Takes Two to Tango: Modeling Binary Stellar Populations in the Gravitational Wave Era
Jeff Andrews
University of Florida
Thursday, Apr 16, 2024

Abstract
Between the discovery of gravitational waves from over a hundred merging compact objects and the advent of micro-arcsecond astrometry realized by the Gaia space telescope, the study of the complexities of binary stellar evolution - including mass transfer, tides, and r-process nucleosynthesis - has taken on a new urgency. In this talk, I will describe the current status of modeling binary star populations as well as several critical shortcomings that multiple groups throughout the field are working to address. In particular, I will introduce our binary population synthesis code, POSYDON, which combines large grids of MESA simulations with machine learning algorithms to produce the next generation of binary population models. In addition to their implications for the origin of gravitational wave sources, these models promise to improve our interpretation of a wide range of stellar population observations, ranging from nearby open clusters to galaxies at high redshift. Finally, I will speculate on the importance of forthcoming observations to constrain key binary evolution processes.

Observational Benchmarks of Chemical Evolution from Extreme Emission Line Galaxies
Danielle Berg
University of Texas in Austin
Thursday, Apr 18, 2024

Abstract
The advent of the James Webb Space Telescope has opened our first window onto detailed abundance studies of high redshift (z > 6) extreme emission line galaxies.
Astrophysics Science Division Colloquium Series Schedule: Spring 2024
Sasha (A.) Kashlinsky (NASA GSFC, 665)

Feb 20
No Colloquium - President's Day Weekend

Feb 27
Revealing the Lifecycle of Interstellar Dust with Polarimetry
	Brandon S. Hensley (JPL/Caltech)

Feb 29
Special Day & Time: 1:45-3 PM
Primordial Black Holes as Dark Matter
	Florian Kühnel (Max Planck Institute for Physics)

March

Mar 5
Chandra & the SuperMassiveBlackHole - Galaxy Interaction
	Giuseppina Fabbiano (Center for Astrophysics, Harvard & Smithsonian)

Mar 12
Resonant Evolution: How emergent dynamics have shaped the Milky Way
	Kathryne J. Daniel (University of Arizona, Steward Observatory)

Mar 19
Special Location: B34, W305
Planning electromagnetic observations of LISA massive black hole binaries
	Jessie Runnoe (Vanderbilt University)

Mar 26
Fast and Slow transients with the Allen Telescope Array
	Wael Farah (Allen Telescope Array, SETI Institute)

April

Apr 2
Tell-tale electromagnetic signatures of massive black hole binaries
	Jordy Davelaar (CCA/Flatiron Institute and Columbia University)

Apr 9
No Colloquium - AAS HEAD Meeting

Apr 16
Special Location: B34, W305
It Takes Two to Tango: Modeling Binary Stellar Populations in the Gravitational Wave Era
	Jeff Andrews (University of Florida)

Apr 18
Special Day & Location: B34, W305
Observational Benchmarks of Chemical Evolution from Extreme Emission Line Galaxies
	Danielle Berg (University of Texas in Austin)

Apr 23
The hot circumgalactic medium
	Smita Mathur (Ohio State)

Apr 30
Special Location: B34, W120B
Exploiting the power of nearby laboratories to uncover the history of galaxies
	Svea S Hernandez (STScI)

May

May 7
Uncovering the Elusive Origin of Fast Radio Bursts and other Radio Transients
	Tarraneh Eftekhar (Northwestern University)

May 14
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Astrophysics Science Division Colloquium Series Schedule: Spring 2024
Experimental astrophysicists are building large radio telescopes that in principle are sensitive enough to detect the 21cm signals emitted by neutral hydrogen during this important epoch in the universe's history. The Hydrogen Epoch of Reionization Array (HERA) is a second-generation low-frequency radio array designed to detect these signals. HERA is under phased construction in the Karoo Highlands of South Africa, and we are collecting data as the array grows. The status of measurements with HERA will be reported, including 21cm power spectrum limits and their implications for the heating of the intergalactic medium.

The Topology of Chaos: A Nonlinear Perspective on Accreting Compact Objects
Rebecca A. Phillipson
Villanova University
Tuesday, Jan 30, 2024

Abstract
Accreting compact objects such as neutron stars and black holes in X-ray Binaries (XRBs) and the supermassive black holes at the center of galaxies, called Active Galactic Nuclei (AGN), exhibit complex variability in their emission. The variability is ubiquitous and operates over a wide range of timescales from seconds up to years. Traditional studies of XRBs and AGN in large time domain surveys aim to connect stochastic characterizations of the variability to the underlying physical processes responsible for accretion onto the compact object, but frequently fail to capture nonlinear or higher-order modes of variability. Methods from topology and nonlinear dynamics distinguish between deterministic, chaotic, and stochastic behavior, and can be used to identify modes of variability that relate to dominant accretion processes. I will review several applications of nonlinear dynamics and chaos theory to the study of both XRBs and AGN that show a connection between nonlinear behavior and the underlying accretion processes. I will outline an approach from nonlinear time series analysis - called recurrence analysis - applied to the systematic and ensemble study of variable sources that can inform current and future time domain missions.

The cosmic journey of the elements, from dust to life
Lia Corrales
University of Michigan
Tuesday, Feb 06, 2024

Abstract
To understand our origins, we must understand the role that interstellar dust plays in delivering heavy elements to planetary systems.
Education News & Blogs – NASA Jet Propulsion Laboratory
Have students dig into the science of black holes or even try out an experiment to learn how a black hole collision helped prove the existence of gravitational waves. Meanwhile, teachers can learn about all the ways their work has inspired us. Learning Resources Slideshow Black Holes: By the Numbers What are black holes and how do they form? Lesson Dropping In With Gravitational Waves Students develop a model to represent the collision of two black holes, the gravitational waves that result and the waves' propagation through spacetime. Articles Teachable Moments: Black Holes Learn about the latest discoveries in black hole science and how to make connections to what students are learning. Share Thank You, Teachers! Employees at NASA's Jet Propulsion Laboratory give thanks to the teachers who helped them reach for the stars. All Month – Launch Into SummerSpeaking of black holes, don't let students' learning fall into one as the summer gets into full swing. Send them off with links to these DIY summer projects. There's even more for parents and families on our Learning Space With NASA at Home page, which also has information to help direct students' learning during out-of-school time.Learning Resources Student Resources Summer Activities for Students Explore Earth and space with these hands-on projects, slideshows, videos, and more for K-12 students. Student Resources Learning Space With NASA Explore space and science activities you can do with NASA at home. Find video tutorials, DIY projects, slideshows, games and more! 
TAGS: Teachers, Classroom, Lessons, Educators, K-12, Parents, Students, Resources

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Kim Orr, Web Producer, NASA-JPL Education Office

Kim Orr is a web and content producer for the Education Office at NASA's Jet Propulsion Laboratory. Her pastimes are laughing and going on Indiana Jones style adventures. 

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Stars in an Exoplanet World - NASA Science
The white dwarf star is obliterated, sending its debris hurtling into space.X-ray: NASA/CXC/RIKEN & GSFC/T. Sato et al; Optical: DSSNeutron stars and pulsarsIf the collapsing stellar core at the center of a supernova contains between about 1.4 and 3 solar masses, the collapse continues until electrons and protons combine to form neutrons, producing a neutron star. Neutron stars are incredibly dense. Because it contains so much mass packed into such a small volume, the gravity at the surface of a neutron star is immense. Like white dwarfs, if a neutron star forms in a multiple star system it can accrete gas by stripping it from nearby companions.Neutron stars also have powerful magnetic fields that can accelerate atomic particles around its magnetic poles, producing powerful beams of radiation. Those beams sweep around like massive searchlights as the star rotates. If such a beam is oriented so that it periodically points toward Earth, we observe it as regular pulses of radiation that occur whenever the magnetic pole sweeps past our line of sight. In this case, the neutron star is known as a pulsar.Black holesIf the collapsed stellar core is larger than three solar masses, it collapses completely to form a black hole: an infinitely dense object whose gravity is so strong that nothing can escape, not even light.Because photons are what our instruments are designed to see, black holes can only be detected indirectly. Indirect observations are possible because the gravitational field of a black hole is so powerful that any nearby material – often the outer layers of a companion star – is caught up and dragged in. As matter spirals into a black hole, it forms a disk, called an accretion disk, that is heated to enormous temperatures, emitting copious quantities of X-rays and gamma-rays that indicate the presence of the underlying hidden companion.Black holes that are quiet and not actively "feeding" on accretion disks can also be detected indirectly by observing the motions of nearby stars.
Sensing the Universe - NASA Science
One example is the expanding debris of exploded stars called supernova shock waves.Since cosmic rays are charged – positively charged protons or nuclei, negatively charged electrons – their paths through space can be deflected by the magnetic fields of stars and other objects.Gravitational WavesGravitational waves are ripples in space-time, the fabric of the universe, that travel at the speed of light. Gravitational waves are created when objects speed up, slow down, or change direction. And just like light, they come in different wavelengths and frequencies. All accelerating masses generate gravitational waves, including pencils, people, and planets. But we can currently detect only those produced by superdense stellar remnants – black holes and neutron stars. Even the strongest waves detectable at Earth distort our planet’s shape by only about 1% the size of an atom.The length of a gravitational wave, or ripple in space-time, depends on its source, as illustrated here. Scientists need different kinds of detectors to study as much of the spectrum as possible.NASA's Goddard Space Flight Center/Conceptual Image LabAlbert Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity. Scientists gained confidence in their existence by watching the orbits of some binary systems but didn’t directly observe them until 2015 when the National Science Foundation’s Laser Interferometer Gravitational Wave Observatory (LIGO) detected ripples from the collision and merger of two stellar-mass black holes. The upcoming European Space Agency-led Laser Interferometer Space Antenna (LISA) is designed to detect gravitational waves from pairs of supermassive black holes in merging galaxies.Scientists are also using pulsar timing arrays – specific sets of millisecond pulsars, rapidly rotating cores of stars that exploded as supernovae ­– to hunt for some kinds of gravitational waves. Millisecond pulsars sweep beams of radiation, from radio to gamma rays, past our line of sight, appearing to pulse with incredible regularity – like cosmic clocks. As long gravitational waves pass between one of these pulsars and Earth, they delay or advance the light arrival time by billionths of a second.
Imagine the Universe!
Tell me about X-rays from black holes.
 Tell me more about black holes.

black-hole dynamic laws; laws of black-hole dynamics

First law of black hole dynamics:
	For interactions between black holes and normal matter, the conservation laws of mass-energy, electric charge, linear momentum, and angular momentum, hold. This is analogous to the first law of thermodynamics.
	Second law of black hole dynamics:
	With black-hole interactions, or interactions between black holes and normal matter, the sum of the surface areas of all black holes involved can never decrease. This is analogous to the second law of thermodynamics, with the surface areas of the black holes being a measure of the entropy of the system.

blackbody radiation
Blackbody radiation is produced by an object which is a perfect absorber of heat. Perfect absorbers must also be perfect radiators. For a blackbody at a temperature T, the intensity of radiation emitted I at a particular energy E is given by Plank's law:
 I(E,T) = 2 E3[h2c2(eE/kT - 1)]-1
where h is Planck's constant, k is Boltzmann's constant, and c is the the speed of light.
blackbody temperature
The temperature of an object if it is re-radiating all the thermal energy that has been added to it; if an object is not a blackbody radiator, it will not re-radiate all the excess heat and the leftover will go toward increasing its temperature.
blueshift
An apparent shift toward shorter wavelengths of spectral lines in the radiation emitted by an object caused by motion between the object and the observer which decreases the distance between them. See also Doppler effect.
bolometric luminosity
The total energy radiated by an object at all wavelengths, usually given in joules per second (identical to watts).
Boltzmann constant; k (L. Boltzmann)
A constant which describes the relationship between temperature and kinetic energy for molecules in an ideal gas. It is equal to 1.380622 x 10-23 J/K (see scientific notation).