recursal/Fanatic-Fandom huggingface dataset:
NGC 55

**NGC 55**, also occasionally referred to as **The Whale Galaxy**, is a Magellanic type barred spiral galaxy located about 6.5 million light-years away in the constellation Sculptor. Along with its neighbor NGC 300, it is one of the closest galaxies to the Local Group, probably lying between the Milky Way and the Sculptor Group. It has an estimated mass of (2.0 ± 0.4) × 1010 M☉.

## Nearby galaxies and group information

NGC 55 and the spiral galaxy NGC 300 have traditionally been identified as members of the Sculptor Group, a nearby group of galaxies in the constellation of the same name. However, recent distance measurements indicate that the two galaxies actually lie in the foreground.

It is likely that NGC 55 and NGC 300 form a gravitationally bound pair.

## Visual appearance

The *Webb Society Deep-Sky Observer's Handbook* writes the following about NGC 55: "Nearly edge-on and appears asymmetrical with some signs of dust near the bulge, which is diffuse, broad and somewhat elongated with the south edge sharp; southeast of the bulge it is strongly curved and lined with 4 or 5 faint knots; north edge of the curve is sharp." Burnham calls it "one of the outstanding galaxies of the southern heavens", somewhat resembling a smaller version of the Large Magellanic Cloud.

## See also

* NGC 4236
* NGC 4631

## Notes

1. **^** average(6.9 ± 0.7, 7.5 ± 1.1) = ((6.9 + 7.5) / 2) ± ((0.72 + 1.12)0.5 / 2) = 7.2 ± 0.7
Cosmos Universe Wiki

**Welcome to the Cosmos Universe Wiki!**

*Recent changes / Getting Started* / *User help page*

The universe is a large, large place, with all sorts of amazing, untold wonders waiting to be discovered. The Universe Derivative Wiki strives to be the most accurate and extensive resources of all things; including planets (in and even outside of our Solar System), stars, black holes, moons, asteroids, galaxies, nebulas, and even telescopes and space exploration, that **anyone** can edit and expand! There have been 193 pages since April 8, 2021.
Some of the information and photos in this wiki are from Wikipedia, NASA, Hubble Telescope etc., not me. If you are uploading the image(s) to website, you should include the source of the image where necessary.

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Astronomy is the study of the whole universe and their contents, as well as the celestial bodies. If you're interested in the subject, but you don't know where to start, try reading about some astronomical objects, including:

* Astronomy
* The Universe and Big Bang, Cosmos
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Triton

**Triton** is the largest natural satellite of the planet Neptune, and the first Neptunian moon to be discovered. The discovery was made on October 10, 1846, by English astronomer William Lassell. It is the only large moon in the Solar System with a retrograde orbit, an orbit in the direction opposite to its planet's rotation. At 2,705 kilometres (~1,680 mi) in diameter, it is the seventh-largest moon in the Solar System, the only satellite of Neptune massive enough to be in hydrostatic equilibrium, the second-largest planetary moon in relation to its primary (after Earth's Moon), and larger than Pluto. Because of its retrograde orbit and composition similar to Pluto, Triton is thought to have been a dwarf planet, captured from the Kuiper belt.

Triton has a surface of mostly frozen nitrogen, a mostly water-ice crust, an icy mantle and a substantial core of rock and metal. The core makes up two thirds of its total mass. The mean density is 2,061 kg/m3, reflecting a composition of approximately 15–35% water ice.

During its 1989 flyby of Triton, *Voyager 2* found surface temperatures of 38 K (−235 °C) and also discovered active geysers; *Voyager 2* remains the only spacecraft to visit Triton. Triton is one of the few moons in the Solar System known to be geologically active (the others being Jupiter's Io and Europa, and Saturn's Enceladus and Titan). As a consequence, its surface is relatively young, with few obvious impact craters. Intricate cryovolcanic and tectonic terrains suggest a complex geological history. Part of its surface has geysers erupting sublimated nitrogen gas, contributing to a tenuous nitrogen atmosphere less than 1⁄70,000 the pressure of Earth's atmosphere at sea level. *Voyager 2* was able to study only about 40% of its surface, and future missions have been proposed to revisit the Neptune system with a focus on Triton.
Mu Cephei

**Mu Cephei** (Latinized from **μ Cephei**, abbreviated **Mu Cep** or **μ Cep**), also known as **Herschel's Garnet Star** or **HD 206936**, is a red supergiant or hypergiant star in the constellation Cepheus. It appears garnet red and is located at the edge of the IC 1396 nebula. Since 1943, the spectrum of this star has served as a spectral standard by which other stars are classified.

Mu Cephei is visually nearly 100,000 times brighter than the Sun, with an absolute visual magnitude of −7.6. It is also one of the largest known stars with a radius around or over 1,000 times that of the sun (R), and were it placed in the Sun's position it would engulf the orbit of Mars and Jupiter.
Supernova

A **supernova** is a stellar explosion that produces an extremely bright object made of plasma that declines to invisibility over weeks or months. There are several different types of supernovae and two possible routes to their formation. A massive star may cease to generate fusion energy from fusing the nuclei of atoms in its core and collapse inward under the force of its own gravity to form a neutron star or black hole, or a white dwarf star may accumulate material from a companion star until it nears its Chandrasekhar limit and undergoes runaway nuclear fusion in its interior, completely disrupting it (note that this should not be confused with a surface thermonuclear explosion on a white dwarf called a nova). In either case, the resulting supernova explosion expels much or all of the stellar material with great force.

The explosion drives a blast wave into the surrounding space, forming a supernova remnant. One famous example of this process is the remnant of SN 1604, shown to the right.

"Nova" (pl. *novae*) is Latin for "new", referring to what appears to be a very bright new star shining in the celestial sphere; the prefix "super" distinguishes this from an ordinary nova, which also involves a star increasing in brightness, though to a lesser extent and through a different mechanism. However, it is misleading to consider a supernova as a new star, because it really represents the death of a star (or at least its radical transformation into something else).
Amalthea

**Amalthea** is a moon of Jupiter. It has the third closest orbit around Jupiter among known moons and was the fifth moon of Jupiter to be discovered, so it is also known as **Jupiter V**. It is also the fifth largest moon of Jupiter, after the four Galilean Moons. Edward Emerson Barnard discovered the moon on 9 September 1892 and named it after Amalthea of Greek mythology. It was the last natural satellite to be discovered by direct visual observation; all later moons were discovered by photographic or digital imaging.

Amalthea is in a close orbit around Jupiter and is within the outer edge of the Amalthea Gossamer Ring which is formed from dust ejected from its surface. Jupiter would appear 46.5 degrees in diameter from its surface. Amalthea is the largest of the inner satellites of Jupiter and is irregularly shaped and reddish in color. It is thought to consist of porous water ice with unknown amounts of other materials. Its surface features include large craters and ridges.

Close range images of Amalthea were taken in 1979 by the *Voyager 1* and *2* spacecraft, and in more detail by the *Galileo* orbiter in the 1990s.
Black dwarf

A **black dwarf** is a theoretical astronomical object, constituting the remains of a Sun-sized star which has fused all of its original hydrogen and helium fuel to heavier elements such as carbon, oxygen and nitrogen and subsequently lost its remaining energy due to radiation. In other words, a black dwarf is a white dwarf that has cooled down so that it no longer emits heat or light. None are known to exist in our universe, as the time taken for a white dwarf to cool to such a degree is hypothesized to be longer than the age of the universe.

Even at the time when black dwarfs exist they may be extremely difficult to detect, emitting very little thermal radiation (if any) at a temperature not much above that of the cosmic microwave background radiation. They may be detectable through their gravitational influence.

Black dwarfs should not be confused with brown dwarfs, which are formed when gas contracts to form a star, but does not possess enough mass to initiate and sustain hydrogen nuclear fusion. "Brown dwarfs" were at times called "black dwarfs" in the 1960s. Neither should black dwarfs be confused with black holes or neutron stars, as neither is the result of the cooling of a white dwarf.

Both black dwarfs and white dwarfs are degenerate dwarfs.

## References

* Richmond, Michael. Late stages of evolution for low-mass stars (English). Rochester Institute of Technology. Retrieved on August 4, 2006.
51 Pegasi b

**51 Pegasi b**, officially named **Dimidium** /dɪˈmɪdiəm/, and formerly unofficially dubbed **Bellerophon** /bɛˈlɛrəfɒn/, is an extrasolar planet approximately 50 light-years (15 parsecs) away in the constellation of Pegasus. It was the first exoplanet to be discovered orbiting a main-sequence star, the Sun-like 51 Pegasi, and marked a breakthrough in astronomical research. It is the prototype for a class of planets called hot Jupiters.

In 2017, traces of water were discovered in the planet's atmosphere. In 2019, the Nobel Prize in Physics was awarded in part for the discovery of 51 Pegasi b.

## Claims of direct detection of visible light

The first ever direct detection of the visible light spectrum reflected from an exoplanet has been made by an international team of astronomers on 51 Pegasi b. The astronomers studied light from 51 Pegasi b using the High Accuracy Radial velocity Planet Searcher (HARPS) instrument at the European Southern Observatory's La Silla Observatory in Chile. This detection allowed the inference of a mass of 0.46 Jupiter masses. The optical detection could not be replicated in 2020, implying the planet has an albedo below 0.15. Measurements in 2021 have marginally detected a polarized reflected light signal, which, while they cannot place limits on the albedo without assumptions made about the scattering mechanisms, could suggest a high albedo.

## See also

* PSR B1257+12 B
* PZ Telescopii b
* HD 209458 b
Kepler-22b

**Kepler-22b**, also known by its Kepler object of interest designation **KOI-087.01**, is an extrasolar planet orbiting within the habitable zone of the Sun-like star Kepler-22. It is located about 587 light-years (180 pc) from Earth in the constellation of Cygnus. It was discovered by NASA's *Kepler Space Telescope* in December 2011 and was the first known transiting planet to orbit within the habitable zone of a Sun-like star. Kepler-22 is too dim to be seen with the naked eye.

Kepler-22b's size is roughly twice that of Earth. Its mass and surface composition are unknown. An Earth-like composition for the planet has been ruled out. It is likely to have a volatile-rich composition with a liquid or gaseous outer shell. The only parameters of the planet's orbit that are currently available are its orbital period, which is about 290 days, and its inclination, which is approximately 90°. Evidence suggests that the planet has a moderate surface temperature, assuming that the surface is not subject to extreme greenhouse heating. In the absence of an atmosphere, its equilibrium temperature (assuming an Earth-like albedo) would be approximately 262 K (−11 °C), compared to Earth's 255 K (−18 °C)

The planet's first transit was observed on 12 May 2009. Confirmation of the existence of Kepler-22b was announced on 5 December 2011.
2020 AV2

**594913 ꞌAylóꞌchaxnim** (provisional designation **2020 AV2**) is a large near-Earth asteroid discovered by the Zwicky Transient Facility on 4 January 2020. It is the first asteroid discovered to have an orbit completely within Venus's orbit, and is thus the first and only known member of the provisionally named Vatira population of Atira-class asteroids. ꞌAylóꞌchaxnim has the smallest known aphelion and third-smallest known semi-major axis among all asteroids. With an absolute magnitude approximately 16.2, the asteroid is expected to be larger than 1 km in diameter.

ꞌAylóꞌchaxnim had likely originated from the main asteroid belt, where its orbit was locked in a secular resonance that caused its orbital eccentricity to gradually increase over time, evolving onto an Earth-crossing orbit. Subsequent close encounters with Earth, Venus, and Mercury resulted in gravitational perturbations of the asteroid's orbit, reducing its momentum and causing it to orbit closer to the Sun. Such inward orbital migration of objects is thought to be rare. Near-Earth asteroids transitioning into the Vatira region often have unstable, short-term orbits due to frequent gravitational perturbations by Venus and Mercury. ꞌAylóꞌchaxnim rarely crosses the orbits of Mercury and Venus, which reduces the number of close encounters with either planet that would otherwise perturb ꞌAylóꞌchaxnim's orbit. Nevertheless its orbit is likely to be stable for less than a million years, unless it is on (or enters soon) a nearby 3:2 mean-motion resonance with Venus, which could extend its stability to a few million years.
Europa

**Europa**, or **Jupiter II**, is the smallest of the four Galilean moons orbiting Jupiter, and the sixth-closest to the planet of all the 79 known moons of Jupiter. It is also the sixth-largest moon in the Solar System. Europa was discovered in 1610 by Galileo Galilei and was named after Europa, the Phoenician mother of King Minos of Crete and lover of Zeus (the Greek equivalent of the Roman god Jupiter).

Slightly smaller than Earth's Moon, Europa is primarily made of silicate rock and has a water-ice crust and probably an iron–nickel core. It has a very thin atmosphere, composed primarily of oxygen. Its surface is striated by cracks and streaks, but craters are relatively few. In addition to Earth-bound telescope observations, Europa has been examined by a succession of space-probe flybys, the first occurring in the early 1970s.

Europa has the smoothest surface of any known solid object in the Solar System. The apparent youth and smoothness of the surface have led to the hypothesis that a water ocean exists beneath the surface, which could conceivably harbor extraterrestrial life. The predominant model suggests that heat from tidal flexing causes the ocean to remain liquid and drives ice movement similar to plate tectonics, absorbing chemicals from the surface into the ocean below. Sea salt from a subsurface ocean may be coating some geological features on Europa, suggesting that the ocean is interacting with the sea floor. This may be important in determining whether Europa could be habitable. In addition, the Hubble Space Telescope detected water vapor plumes similar to those observed on Saturn's moon Enceladus, which are thought to be caused by erupting cryogeysers.

## Size, mass and orbit

Europa is slightly smaller than the Moon. At just over 3,100 kilometres (1,900 mi) in diameter, it is the sixth-largest moon and fifteenth-largest object in the Solar System. Though by a wide margin the least massive of the Galilean satellites, it is nonetheless more massive than all known moons in the Solar System smaller than itself combined. Its mass is 4.80x10^22 kg, also the lightest Galilean moon, or of Jupiter. The orbital period of Europa is 3.54 days and the orbital distance is 671,000 kilometres, twice further than the Moon.
Terrestrial planets

A **terrestrial planet** is a planet which is primarily composed of silicate rocks. The term is derived from the Latin word for Earth, "*Terra*", so an alternate definition would be that these are planets which are, in some notable fashion, "Earth-like". Terrestrial planets are substantially different from gas giants, which may not have solid surfaces and are composed mostly of some combination of hydrogen, helium, and water existing in various physical states. Terrestrial planets all have roughly the same structure: a central metallic core, mostly iron, with a surrounding silicate mantle. The Moon is similar, but lacks an iron core. Terrestrial planets have canyons, craters, mountains, and volcanoes.

Terrestrial planets possess secondary atmospheres; atmospheres generated through internal vulcanism or comet impacts, as opposed to the gas giants, which possess primary atmospheres, atmospheres captured directly from the original solar nebula.Earth's solar system has four terrestrial planets: Mercury, Venus, Earth and Mars. During the formation of the solar system, there were probably many more (planetesimals), but they have all merged with or been destroyed by the four remaining worlds in the solar nebula. Only one terrestrial planet, Earth, is known to have an active hydrosphere.

## Extrasolar terrestrial planets

The majority of planets found outside our solar system to date have been gas giants, simply because gas giants are larger and therefore easier to see or infer from observation. However, a number of extrasolar planets are known or suspected to be terrestrial. The first terrestrial planets ever detected outside our solar system were detected by Aleksander Wolszczan orbiting the pulsar PSR B1257+12. Their masses being 0.02, 4.3, and 3.9 Earth masses. The planets were observed because their transit caused interruptions in the pulsar's radio emissions. Had they not been orbiting around a pulsar, they would never have been found.
T Tauri star

In process of star formation, **T Tauri stars** (**TTS**) are a class of variable stars that are less than about ten million years old. This class is named after the prototype, T Tauri, a young star in the Taurus star-forming region. They are found near molecular clouds and identified by their optical variability and strong chromospheric lines. T Tauri stars are pre-main-sequence stars in the process of contracting to the main sequence along the Hayashi track, a luminosity–temperature relationship obeyed by infant stars of less than 3 solar masses (M☉) in the pre-main-sequence phase of stellar evolution. It ends when a star of 0.5 M☉ or larger develops a radiative zone, or when a smaller star commences nuclear fusion on the main sequence.

## History

While T Tauri itself was discovered in 1852, the T Tauri class of stars were initially defined by Alfred Harrison Joy in 1945.

## Characteristics

T Tauri stars comprise the youngest visible F, G, K and M spectral type stars (<2 M☉). Their surface temperatures are similar to those of main-sequence stars of the same mass, but they are significantly more luminous because their radii are larger. Their central temperatures are too low for hydrogen fusion. Instead, they are powered by gravitational energy released as the stars contract, while moving towards the main sequence, which they reach after about 100 million years. They typically rotate with a period between one and twelve days, compared to a month for the Sun, and are very active and variable.

There is evidence of large areas of starspot coverage, and they have intense and variable X-ray and radio emissions (approximately 1000 times that of the Sun). Many have extremely powerful stellar winds; some eject gas in high-velocity bipolar jets. Another source of brightness variability are clumps (protoplanets and planetesimals) in the disk surrounding T Tauri stars.
Hades

**Hades** is The Teen God of the Underworld. 💘

He is always behind Zeus and Poseidon. He's nonchalant, he's often distracted, and always a step behind others.

## **Biography**

### Personality

Hades doesn't talk much, he is quiet about everything, specially his feelings.

### Appearance

Hades is a young god with tan skin, black hair, and hazel eyes, although his eyes has a yellow-colored glow.

## **Relationships**

### Love Interests

* **Persephone** - meeting with the sensitive and popular Hades will create tensions between Persephone and Demeter, but will allow Persephone to discover her divine role and turn into a majestic Princess of the Underworld. They are in a secret relationship with each other, but Hades wants to confess his feelings to her, while Persephone is afraid of publicly pursuing one another and avoids him, but this is due to Hades's jealous ex-lover Minthe's doing.
* **Minthe** - The two of them were former lovers. She is obviously not over him and is extremely jealous of his ad Persephone's feelings for one another.

### Best Friends

* **Cerberus** - Hades is always with his three-headed puppy Cerberus.
* **Zeus**
* **Poseidon**
* **Artemis**

## **Trivia**

* It was revealed that Hades and Persephone will almost have a kissing scene in the series but it will not happen because someone catch them before they do it.
Thorne–Żytkow object

A **Thorne–Żytkow object** (**TŻO** or **TZO**), also known as a hybrid star, is a conjectured type of star wherein a red giant or red supergiant contains a neutron star at its core, formed from the collision of the giant with the neutron star. Such objects were hypothesized by Kip Thorne and Anna Żytkow in 1977. In 2014, it was discovered that the star HV 2112, located in the Small Magellanic Cloud (SMC), was a strong candidate. Another possible candidate is the star HV 11417, also located in the SMC.

## Formation

A Thorne–Żytkow object is formed when a neutron star collides with another star, typically a red giant or supergiant. The colliding objects can simply be wandering stars. This is only likely to occur in extremely crowded globular clusters. Alternatively, the neutron star could form in a binary system when one of the two stars goes supernova. Because no supernova is perfectly symmetric, and because the binding energy of the binary changes with the mass lost in the supernova, the neutron star will be left with some velocity relative to its original orbit. This kick may cause its new orbit to intersect with its companion, or, if its companion is a main-sequence star, it may be engulfed when its companion evolves into a red giant.

If a neutron star and a white dwarf merge, this could form a Thorne–Żytkow object with the properties of an R Coronae Borealis variable.

## Observation history

In 2014, a team led by Emily Levesque argued that the star HV 2112 had unusually high abundances of elements such as molybdenum, rubidium, lithium, and calcium, and a high luminosity. Since both are expected characteristics of Thorne–Żytkow objects, this led the team to suggest that HV 2112 might be the first discovery of a TZO. However, this claim was challenged in a 2018 paper by Emma Beasor and collaborators, who argued that there is no evidence for HV 2112 having any unusual abundance patterns beyond a possible enrichment of lithium and that its luminosity is too low. They put forth another candidate, HV 11417, based on an apparent over-abundance of rubidium and a similar luminosity as HV 2112. However, HV 11417 has since been identified as a likely foreground halo star.

## TZO candidates

* HV 2112 (Small Magellanic Cloud) - Classified as a supergiant TZO candidate or an AGB star
* HV 11417 (Small Magellanic Cloud) - Classified as an AGB star or a foreground halo star
* V595 Cassiopeiae
* IO Persei
* KN Cassiopeiae
* U Aquarii - This star was catalogued as a R Coronae Borealis variable.
* VZ Sagitarii - This star was catalogued as a R Coronae Borealis variable.

## See also

* Neutron star
* Red giant
* Quasar
* Quasi star
IC 1101

**IC 1101** is a class S0 supergiant (cD) lenticular galaxy at the center of the Abell 2029 galaxy cluster. It has an isophotal diameter at about 123.65 to 169.61 kiloparsecs (400,000 to 550,000 ly). It possesses a diffuse core which is the largest known core of any galaxy to date, and also hosts a supermassive black hole that is one of the largest black holes known. The galaxy is located at 354.0 megaparsecs (1.15 billion light-years) from Earth. The galaxy was discovered on 19 June 1790, by the British astronomer William Herschel.

It is the largest galaxy known to be discovered, with a diameter of 5 million light years.
MACS J1149 Lensed Star 1

**MACS J1149 Lensed Star 1**, also known as **Icarus**, is a blue supergiant star observed through a gravitational lens. It is the second most distant individual star to have been detected so far (second only to WHL0137-LS, a.k.a. Earendel, as of March 2022), at approximately 14 billion light-years from Earth (redshift z=1.49; comoving distance of 14.4 billion light-years; lookback time of 9.34 billion years). Light from the star was emitted 4.4 billion years after the Big Bang. According to co-discoverer Patrick Kelly, the star is at least a hundred times more distant than the next-farthest non-supernova star observed, SDSS J1229+1122, and is the first magnified individual star seen.
Asteroid Belt

The **asteroid belt** or **main belt** is a ring of small and large rocks and dust between the orbits of Mars and Jupiter. The biggest object in the asteroid belt is Ceres, a dwarf planet. The Kirkwood gaps separate the asteroid belt into several groups. Largest asteroids include Vesta, Pallas and 21 Lutetia.

Most asteroids orbit at 2 to 3 times the distance between Earth and the Sun. Planets that are "inside" - or before - the asteroid belt (which means they are closer to the sun) are called *inner planets.* Planets that are "outside" - that is, after - the asteroid belt are called *outer planets*: so Mercury, Venus, Earth, and Mars are *inner planets,* while Jupiter, Saturn, Uranus and Neptune are the *outer planets.*

## Origin

In 1802, shortly after discovering 2 Pallas, Heinrich Olbers suggested to William Herschel that Ceres and Pallas were fragments of a much larger planet that once occupied the Mars–Jupiter region, this planet having suffered an internal explosion or a cometary impact many million years before. This hypothesis has fallen from favor. The large amount of energy needed to destroy a planet, and with the belt's low combined mass (only about 4% of the mass of the Moon) do not support the hypothesis. Also, the significant chemical differences between the asteroids are difficult to explain if they come from the same planet. Today, most scientists accept that the asteroids never formed a planet at all.

In general, the formation and evolution of the Solar System happened when a cloud of interstellar dust and gas collapsed under the influence of gravity to form the Sun and planetesimals, and eventually the planets. This gravitational accretion led to the formation of the rocky planets and the gas giants. Planetesimals in the region which would become the asteroid belt were too strongly disturbed by Jupiter's gravity to form a planet. Instead they continued to orbit the Sun as before, while occasionally colliding. In regions where the velocity of the collisions was too high, the shattering of planetesimals was more common than accretion, preventing the formation of planet-sized bodies.

## See also

* Asteroid
* Kuiper Belt
* Dwarf Planet
Wolf-Rayet star

**Wolf–Rayet stars**, often abbreviated as **WR stars**, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of ionised helium and highly ionised nitrogen or carbon. The spectra indicate very high surface enhancement of heavy elements, depletion of hydrogen, and strong stellar winds. The surface temperatures of known Wolf–Rayet stars range from 20,000 K to around 210,000 K, hotter than almost all other kinds of stars. They were previously called **W-type stars** referring to their spectral classification.

Classic (or Population I) Wolf–Rayet stars are evolved, massive stars that have completely lost their outer hydrogen and are fusing helium or heavier elements in the core. A subset of the population I WR stars show hydrogen lines in their spectra and are known as WNh stars; they are young extremely massive stars still fusing hydrogen at the core, with helium and nitrogen exposed at the surface by strong mixing and radiation-driven mass loss. A separate group of stars with WR spectra are the central stars of planetary nebulae, post-asymptotic giant branch stars that were similar to the Sun while on the main sequence, but have now ceased fusion and shed their atmospheres to reveal a bare carbon-oxygen core.

All Wolf–Rayet stars are highly luminous objects due to their high temperatures—thousands of times the luminosity of the Sun (L☉) for the CSPNe, hundreds of thousands the luminosity for the Population I WR stars, to over a million the luminosity for the WNh stars—although not exceptionally bright visually since most of their radiation output is in the ultraviolet. The naked-eye stars Gamma Velorum and Theta Muscae, as well as one of the most massive known stars, R136a1 in 30 Doradus, are all Wolf–Rayet stars.

## See also

* Planetary nebula
* Stellar classification
Electroweak star

An **electroweak star** is a theoretical type of exotic star, whereby the gravitational collapse of the star is prevented by radiation pressure resulting from electroweak burning, that is, the energy released by conversion of quarks to leptons through the electroweak force. This process occurs in a volume at the star's core approximately the size of an apple, containing about two Earth masses and reaching temperatures on the order of 1015 K.

## Formation

The stage of life of a star that produces an electroweak star is theorized to occur after a supernova collapse. Electroweak stars are denser than quark stars, and may form when quark degeneracy pressure is no longer able to withstand gravitational attraction, but may still be withstood by electroweak burning radiation pressure. This phase of a star's life may last upwards of 10 million years.

The energy output of an electroweak star is limited by the quark supply rate, which is dictated by gravitational collapse. Each interaction converts nine quarks into three anti-leptons, violating conservation of baryon and lepton number while preserving B−L, generating around 300 GeV per interaction. The energy diffuses out of the star as a mixture of neutrinos and photons. Electroweak stars could be identified through the equal number of neutrinos emitted of all three generations, taking into account neutrino oscillation.

## See also

* Electroweak force
* Quark star
* Preon star
* Lepton
* Quark
* Degenerate matter
* Degenerate star
67P/Churyumov-Gerasimenko

**67P/Churyumov–Gerasimenko** (abbreviated as **67P** or **67P/C–G**) is a Jupiter-family comet, originally from the Kuiper belt, with a current orbital period of 6.45 years, a rotation period of approximately 12.4 hours and a maximum velocity of 135,000 km/h (38 km/s; 84,000 mph). Churyumov–Gerasimenko is approximately 4.3 by 4.1 km (2.7 by 2.5 mi) at its longest and widest dimensions. It was first observed on photographic plates in 1969 by Soviet astronomers Klim Ivanovych Churyumov and Svetlana Ivanovna Gerasimenko, after whom it is named. It most recently came to perihelion (closest approach to the Sun) on 2 November 2021, and will return in April 2028.

Churyumov–Gerasimenko was the destination of the European Space Agency's *Rosetta* mission, launched on 2 March 2004. *Rosetta* rendezvoused with Churyumov–Gerasimenko on 6 August 2014 and entered orbit on 10 September 2014. *Rosetta*'s lander, *Philae*, landed on the comet's surface on 12 November 2014, becoming the first spacecraft to land on a comet nucleus. On 30 September 2016, the *Rosetta* spacecraft ended its mission by landing on the comet in its Ma'at region.
Proxima Centauri

**Proxima Centauri** is a small, low-mass star located 4.2465 light-years (1.3020 pc) away from the Sun in the southern constellation of Centaurus. Its Latin name means the "nearest [star] of Centaurus". This object was discovered in 1915 by Robert Innes and is the nearest-known star to the Sun. With a quiescent apparent magnitude 11.13, it is too faint to be seen with the unaided eye. Proxima Centauri is a member of the Alpha Centauri star system, being identified as component **Alpha Centauri C**, and is 2.18° to the southwest of the Alpha Centauri AB pair. It is currently 12,950 AU (0.2 ly) from AB, which it orbits with a period of about 550,000 years.

Proxima Centauri is a red dwarf star with a mass about an eighth (12.5%) of the Sun's mass, and average density about 33 times that of the Sun. Because of Proxima Centauri's proximity to Earth, its angular diameter can be measured directly. Its actual diameter is about one-seventh (14%) the diameter of the Sun.

## See Also

* List of Nearest Stars
* Red Dwarf
* Centaurus
Light year

A **light-year**, also written **light year**, is both a unit of length and time that light travels in one standard Earth year (365.25 days). Its symbol is **ly**, an abbreviation of "light-year". The vast distances are sometimes measured by astronomers the light year in parsecs. A light year is a distance of exactly 9.461 trillion ilometres.  This is exactly about 5.9 trillion miles.

Light travels at a rate of exactly 299,792,458 meters per second. This is just short of 300 kilometres per second and a little over 184,000 miles per second. The calculations above are based on the standard day of 24 hours, or 1/365.25 of a year. This is 31,557,600 seconds travelled in the standard year by light in a vacuum.

## History

The first successful measurement of a light year was in 1838 by German astronomer and mathematician, Friedrich Bessel. After a transit of Venus in 1759 had made an accurate measurement of the distance between the sun and earth, a unit known as the "astronomical unit" had been used to measure space. Using this distance (around 93 million miles), had simplified measurements to stars based on parallax calculations.

A parallax is the apparent distance a stationery object moves when viewed from opposite ends of a measured distance. This is easily visualized by holding one's thumb up to cover an object at a distance and switching between closed eyes to view said object.  In like manner, distances to stars within about 1,600 light years are now (since 1989) able to be ascertained.  Further developments are hoped to increase the accurate measurement ten-fold.
HD 189733 b

**HD 189733 b** is an exoplanet approximately 64.5 light-years (19.8 pc) away from the Solar System in the constellation of Vulpecula. Astronomers in France discovered the planet orbiting the star HD 189733 on October 5, 2005, by observing its transit across the star's face. With a mass 16.2% higher than that of Jupiter and a radius 13.8% greater, HD 189733 b orbits its host star once every 2.2 days at an orbital speed of 152.5 kilometers per second (152,500 meters per second; 341,100 miles per hour), making it a hot Jupiter with poor prospects for extraterrestrial life.

The closest transiting hot Jupiter to Earth, HD 189733 b is a subject of extensive atmospheric examination. Accordingly, scientists have extensively studied the exoplanet's atmosphere with high- and low-resolution instruments, both from the ground and space. As a result, HD 189733 b was the first exoplanet to have its thermal map constructed (possibly to be detected through polarimetry), its overall color determined (deep blue), transit in the X-ray spectrum, and carbon dioxide confirmed in its atmosphere.

In July 2014, NASA announced finding very dry atmospheres on three exoplanets (HD 189733b, HD 209458b, WASP-12b) orbiting Sun-like stars.
TOI 1338 b

**TOI 1338** is a circumbinary planet located in the constellation Pictor, about 1,320 light-years from Earth, almost the size of Saturn and is 6.9 times bigger than Earth.

The acronym TOI stands for "TESS Objects of Interest." The planet was found by Wolf Cukier, a high school student, who joined the Goddard Space Flight Center as a summer intern. He looked through light curves that were flagged as eclipsing binaries by volunteers of the Planet Hunters citizen science project. Cukier and six of the planet hunter volunteers are co-authors of the publication.

## See also

* Circumbinary planet
* Binary star
Gas giants

A **gas giant** (sometimes also known as a Jovian planet after the planet Jupiter) is a large planet that is not primarily composed of rock or other solid matter. Gas giants may have a rocky or metallic core—in fact, such a core is thought to be required for a gas giant to form—but the majority of its mass is in the form of gas (or gas compressed into a liquid state), mainly hydrogen and helium.

Unlike rocky planets, which have a clearly defined difference between atmosphere and surface, gas giants do not have a well-defined surface; their atmospheres simply become gradually denser toward the core, perhaps with liquid or liquid-like states in between. One cannot "land on" such planets in the traditional sense. Thus, terms such as diameter, surface area, volume, surface temperature and surface density may refer only to the outermost layer visible from space.

There are four gas giants in our solar system: Jupiter, Saturn, Uranus, and Neptune. Uranus and Neptune may be considered as a separate subclass of giant planets, 'ice giants', or 'Uranian planets', as they are mostly composed of ice, rock and gas, unlike the "traditional" gas giants Jupiter or Saturn. However, they share the same qualities of the lack of the solid surface; their differences stem from the fact that their proportion of hydrogen and helium is lower, due to their greater distance from the Sun.
VFTS 352

**VFTS 352** is a contact binary star system 160,000 light-years (49,000 pc) away in the Tarantula Nebula, which is part of the Large Magellanic Cloud. It is the most massive and earliest spectral type overcontact system known.

The discovery of this O-type binary star system made use of the European Southern Observatory's Very Large Telescope, and the description was published on 13 October 2015. VFTS 352 is composed of two very hot (40,000 °C), bright and massive stars of equal size that orbit each other in little more than a day. The stars are so close that their atmospheres overlap. Both stars are rotating at a rate equal to their orbital period; that is, they are tidally locked. Extreme stars like the two components of VFTS 352 are thought to be the main producers of elements such as oxygen.

The future of VFTS 352 is uncertain, and there are two possible scenarios. If the two stars merge, a very rapidly rotating star will be produced. If it keeps spinning rapidly it might end its life in a long-duration gamma-ray burst. In a second hypothetical scenario, the components would end their lives in supernova explosions, forming a close binary black hole system, hence a potential gravitational wave source through black hole–black hole merger.
Rosette Nebula

The **Rosette Nebula** (also known as **Caldwell 49**) is an H II region located near one end of a giant molecular cloud in the Monoceros region of the Milky Way Galaxy. The open cluster NGC 2244 (Caldwell 50) is closely associated with the nebulosity, the stars of the cluster having been formed from the nebula's matter.

The cluster and nebula lie at a distance of 5,000 light-years from Earth and measure roughly 130 light years in diameter. The radiation from the young stars excites the atoms in the nebula, causing them to emit radiation themselves producing the emission nebula we see. The mass of the nebula is estimated to be around 10,000 solar masses.

A survey of the nebula with the Chandra X-ray Observatory has revealed the presence of numerous new-born stars inside optical Rosette Nebula and studded within a dense molecular cloud. Altogether, approximately 2500 young stars lie in this star-forming complex, including the massive O-type stars, which are primarily responsible for blowing the ionized bubble. Most of the ongoing star-formation activity is occurring in the dense molecular cloud to the south east of the bubble. A diffuse X-ray glow is also seen between the stars in the bubble, which has been attributed to a super-hot plasma with temperatures ranging from 1 to 10 million K. This is significantly hotter than the 10,000 K plasmas seen in HII regions, and is likely attributed to the shock-heated winds from the massive O-type stars.

On April 16, 2019 the Oklahoma Legislature passed HB1292 making the Rosette Nebula as the official state astronomical object. Oklahoma Governor Kevin Stitt signed it into law April 22, 2019.
Pluto

**Pluto**, formal designation **134340 Pluto**, is the second-most-massive known dwarf planet in the Solar System (after Eris) and the tenth-most-massive body observed directly orbiting the Sun. Originally classified as the ninth planet from the Sun, Pluto was recategorized as a dwarf planet due to the discovery that it is one of several large bodies within the Kuiper belt.
Like other members of the Kuiper belt, Pluto is composed primarily of rock and ice and is relatively small: approximately a sixth (1/6) the mass of the Earth's Moon and a third (1/3) its volume. It has an highly inclined orbit that takes it from 30 to 49 AU (4.4–7.4 billion km) from the Sun. This causes Pluto to periodically come closer to the Sun than Neptune. As of 2011, it is 32.1 AU (5,770,000,000 km) from the Sun. From its discovery in 1930 until 2006, Pluto was classified as a planet. In the late 1970s, following the discovery of minor planet 2060 Chiron in the outer Solar System and the recognition of Pluto's relatively low mass, its status as a major planet began to be questioned. In the late 20th and early 21st century, many objects similar to Pluto were discovered in the outer Solar System, notably the scattered disc object Eris in 2005, which is 27% more massive than Pluto. On August 24, 2006, the International Astronomical Union (IAU) defined what it means to be a "planet" within the Solar System. This definition excluded Pluto as a planet and added it as a member of the new category "dwarf planet" along with Eris and Ceres.

## Physical Characteristics

Pluto's visual apparent magnitude averages 15.1, brightening to 13.65 at perihelion. The distance from Sun is 5,770,000,000 km, 47 times of Earth and 1/4 of Neptune. However, due to its distance and small size Pluto is not visible on naked eye and only visible with a telescope, around 30 cm (12 in) aperture being desirable. It looks star-like and without a visible disk even in large telescopes, because its angular diameter is only 0.11&#176;.

Pluto's mass is 1.31×1022 kg, less than 0.24 percent that of the Earth, while its diameter is 2,306 kilometres, or roughly 2/3 of the Moon. Pluto's atmosphere complicates determining its true solid size within a certain margin. Observations by the Hubble Space Telescope place Pluto's density at between 1,800 and 2,100 kg/m3 (1.8 and 2.1 g/cm3), suggesting its internal composition consists of roughly 50–70 percent rock and 30–50 percent ice by mass. Because radioactive minerals would eventually heat the ices enough for the rock to separate from them, scientists expect that Pluto's internal structure is differentiated, with the rocky material having settled into a dense core surrounded by a mantle of ice.

## Moons

Pluto has four known natural satellites: Charon, first identified in 1978 by astronomer James Christy; Nix and Hydra, both discovered in 2005, and S/2011 P 1 (provisional name, also known as P4), identified by the Hubble Space Telescope in 2011.
Centaurus

**Centaurus** /sɛnˈtɔːrəs, -ˈtɑːr-/ is a bright constellation in the southern sky. One of the largest constellations, Centaurus was included among the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. In Greek mythology, Centaurus represents a centaur; a creature that is half human, half horse (another constellation named after a centaur is one from the zodiac: Sagittarius). Notable stars include Alpha Centauri, the nearest star system to the Solar System, its neighbour in the sky Beta Centauri, and V766 Centauri, one of the largest stars yet discovered. The constellation also contains Omega Centauri, the brightest globular cluster as visible from Earth and the largest identified in the Milky Way, possibly a remnant of a dwarf galaxy.

## Features

Centaurus contains several very bright stars. Its alpha and beta stars are used as "pointer stars" to help observers find the constellation Crux. Centaurus has 281 stars above magnitude 6.5, meaning that they are visible to the unaided eye, the most of any constellation. Alpha Centauri, the closest star system to the Sun, has a high proper motion; it will be a mere half-degree from Beta Centauri in approximately 4000 years.

Alpha Centauri is a triple star system composed of a binary system orbited by Proxima Centauri, currently the nearest star to the Sun. Traditionally called Rigil Kentaurus or Toliman, meaning "foot of the centaur", the system has an overall magnitude of −0.28 and is 4.4 light-years from Earth. The primary and secondary are both yellow-hued stars; the first is of magnitude −0.01 and the second: 1.35. Proxima, the tertiary star, is a red dwarf of magnitude 11.0; it appears almost 2 degrees away from the close pairing of Alpha and has a period of approximately one million years. Also a flare star, Proxima has minutes-long outbursts where it brightens by over a magnitude. The Alpha couple revolve in 80-year periodicity and will next appear closest as seen from Earth's telescopes in 2037 and 2038, together as they appear to the naked eye they present the third-brightest "star" in the night sky.

## See also

* Alpha Centauri
* Omega Centauri
* List of Brightest Stars
2M1207b

**2M1207b** is an extrasolar planet orbiting the brown dwarf 2M1207, a star in the constellation Hydra approximately 200 light years from Earth. Notable as one of the first extrasolar planets to be directly observed (by infrared imaging), it was discovered in early 2005 by the Very Large Telescope at the Paranal Observatory in Chile by a team from European Southern Observatory led by Gael Chauvin. It is believed to be about five times the mass of Jupiter and orbits its sun at a distance nearly twice as far as Neptune is from the Earth's Sun.

Provisionally named 2M1207b, the gas giant planet is, like its primary, very hot; the estimated surface temperature is roughly 1250 K (976°C or 1790°Fahrenheit). The planet's mass is about five times that of Jupiter, well below the calculated limit for deuterium fusion in brown dwarves, which is 10-13 Jupiter masses. The projected distance between 2M1207b and its primary is around 41 AU (similar to the mean distance between Pluto and the Sun), giving it an estimated orbital period of around 1700 years. The infrared spectrum of the planet indicates the presence of water molecules in its atmosphere. The planet is not a likely candidate to support life, neither on its surface nor on any satellites.

## Discovery and identification

2M1207b is about 100 times fainter in the sky than its companion star, and was first spotted as a "faint reddish speck of light" in 2004, and was inconclusively imaged by the Hubble Space Telescope later that year. Images taken in February and March 2004 by the Very Large Telescope array were more conclusive, and suggest a mass of about 5 Jupiters, although other methods suggest a slightly smaller mass. As with any astronomical object, adjacency in the sky does not necessarily mean that two objects are gravitationally bound (see optical binary); however, observations over time show with high confidence that the two objects (2M1207 and 2M1207b) show similar proper motion in the sky and are therefore part of the same stellar system.
Kapteyn's Star

**Kapteyn's Star** is a class M1 red subdwarf about 12.83 light-years from Earth in the southern constellation Pictor; it is the closest halo star to the Solar System. With a magnitude of nearly 9 it is visible through binoculars or a telescope.

Its diameter is 30% of the Sun's, but its luminosity just 1.2% that of the Sun. It may have once been part of the globular cluster Omega Centauri, itself a likely dwarf galaxy swallowed up by the Milky Way in the distant past. The discovery of two planets—Kapteyn b and Kapteyn c—was announced in 2014 and has a mixed history of rejections and confirmations as of 2021.