recursal/Fanatic-Fandom huggingface dataset:
Neutron star

A **neutron star** is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white holes, quark stars, and strange stars), neutron stars are the smallest and densest currently known class of stellar objects. Neutron stars have a radius on the order of 10 kilometres (6 mi) and a mass of about 1.4 solar masses. They result from the supernova explosion of a massive star, combined with gravitational collapse, that compresses the core past white dwarf star density to that of atomic nuclei.

Once formed, they no longer actively generate heat, and cool over time; however, they may still evolve further through collision or accretion. Most of the basic models for these objects imply that neutron stars are composed almost entirely of neutrons (subatomic particles with no net electrical charge and with slightly larger mass than protons); the electrons and protons present in normal matter combine to produce neutrons at the conditions in a neutron star.

Neutron stars that can be observed are very hot and typically have a surface temperature of around 600000 K. Neutron star material is remarkably dense: a normal-sized matchbox containing neutron-star material would have a weight of approximately 3 billion tonnes, the same weight as a 0.5 cubic kilometre chunk of the Earth (a cube with edges of about 800 metres) from Earth's surface. Their magnetic fields are between 108 and 1015 (100 million and 1 quadrillion) times stronger than Earth's magnetic field. The gravitational field at the neutron star's surface is about 2×1011 (200 billion) times that of Earth's gravitational field.

As the star's core collapses, its rotation rate increases as a result of conservation of angular momentum, and newly formed neutron stars hence rotate at up to several hundred times per second. Some neutron stars emit beams of electromagnetic radiation that make them detectable as pulsars. Indeed, the discovery of pulsars by Jocelyn Bell Burnell and Antony Hewish in 1967 was the first observational suggestion that neutron stars exist. The radiation from pulsars is thought to be primarily emitted from regions near their magnetic poles. If the magnetic poles do not coincide with the rotational axis of the neutron star, the emission beam will sweep the sky, and when seen from a distance, if the observer is somewhere in the path of the beam, it will appear as pulses of radiation coming from a fixed point in space (the so-called "lighthouse effect"). The fastest-spinning neutron star known is PSR J1748-2446ad, rotating at a rate of 716 times a second, giving a linear speed at the surface on the order of 0.24 *c* (nearly a quarter the speed of light).

## See also

* PSR J0348+0432
* Vela pulsar
* White Dwarf
* Black Dwarf
* Thorne-Zytkow object
Titania

**Titania** (/tɪˈtɑːniə/), also designated **Uranus III**, is the largest of the moons of Uranus and the eighth largest moon in the Solar System at a diameter of 1,577 kilometres. Discovered by William Herschel in 1787, Titania is named after the queen of the fairies in Shakespeare's *A Midsummer Night's Dream*. Its orbit lies inside Uranus's magnetosphere.

Titania consists of approximately equal amounts of ice and rock, and is probably differentiated into a rocky core and an icy mantle. A layer of liquid water may be present at the core–mantle boundary. The surface of Titania, which is relatively dark and slightly red in color, appears to have been shaped by both impacts and endogenic processes. It is covered with numerous impact craters reaching up to 326 kilometres (203 mi) in diameter, but is less heavily cratered than Oberon, outermost of the five large moons of Uranus. Titania probably underwent an early endogenic resurfacing event which obliterated its older, heavily cratered surface. Titania's surface is cut by a system of enormous canyons and scarps, the result of the expansion of its interior during the later stages of its evolution. Like all major moons of Uranus, Titania probably formed from an accretion disk which surrounded the planet just after its formation.

Infrared spectroscopy conducted from 2001 to 2005 revealed the presence of water ice as well as frozen carbon dioxide on the surface of Titania, which in turn suggested that the moon may have a tenuous carbon dioxide atmosphere with a surface pressure of about 10 nanopascals (10−13 bar). Measurements during Titania's occultation of a star put an upper limit on the surface pressure of any possible atmosphere at 1–2 mPa (10–20 nbar).
Sun/Old Sun

The **Sun**, sometimes called Sol, is the star in our solar system. The planet Earth and all of her sister planets, both the other terrestrial planets and the gas giants, orbit the Sun in accordance with Newton's Laws of Gravity. Other bodies that orbit the Sun include asteroids, meteoroids, comets, Trans-Neptunian objects, and, of course, dust.

## Physical and other characteristics

The Sun is a main sequence star, with a spectral class of G2, meaning that it is somewhat bigger and hotter than the average star but far smaller than a red giant star. A G2 star has a main sequence lifetime of about 10 billion years, and the Sun is probably about 5 billion years old, as determined by nucleocosmochronology.

At the center of the sun, thermonuclear reactions convert hydrogen into helium. This releases energy which escapes from the surface of the Sun as light. Physicists are able to replicate thermonuclear reactions with hydrogen bombs.

All matter in the Sun is in the form of plasma due to its extreme temperature. This makes it possible for the sun to rotate faster at its equator than it does at higher latitudes, since the Sun is not a solid body. The differential rotation of the Sun's latitudes causes its magnetic field lines to become twisted together over time, causing magnetic field loops to erupt from the sun's surface and trigger the formation of the Sun's dramatic sunspots and solar prominences.

For some time it was thought that the number of neutrinos produced by the nuclear reaction in the Sun was only one third of the number predicted by theory, a result that was termed the solar neutrino problem. When it was recently found that neutrinos had mass, and could therefore transform into harder-to-detect varieties of neutrinos while en route from the Sun to Earth, measurement and theory were reconciled.

Observation of the Sun can reveal such phenomena as:

* Sunspots
* Faculae
* Solar flares
* Solar prominences
	+ quiescent prominences
	+ eruptive prominences

(**Caution: looking directly at the sun can cause blindness.**)

Other terms related to the Sun :

* Solar wind
	+ Aurora borealis
	+ Aurora australis
* Photosphere
* Chromosphere
* Corona
* Airglow
* Eclipse

See also: Sun mythology
Solar system:

**Sun** - Mercury - Venus - Earth - Mars - Asteroids - Jupiter - Saturn - Uranus - Neptune - Pluto - Comets

* Timeline of solar astronomy

Several newspapers are called The Sun.
Butterfly Cluster

The **Butterfly Cluster** (cataloged as **Messier 6** or **M6**, and as **NGC 6405**) is an open cluster of stars in the southern constellation of Scorpius. Its name derives from the vague resemblance of its shape to a butterfly. The Trumpler classification of II 3 r encodes it is rich in stars, ranks II out of IV for disparateness and greatly mixes bright with faint components. It is 3.5° to the northwest of Messier 7, both north of the tail of Scorpius.

The first astronomer to record the Butterfly Cluster's existence was Giovanni Battista Hodierna in 1654. However, Robert Burnham Jr. has proposed that the 1st century astronomer Ptolemy may have seen it with the naked eye while observing its neighbor the Ptolemy Cluster (M7). Credit for the discovery is usually given to Jean-Philippe Loys de Chéseaux in 1746. Charles Messier observed the cluster on May 23, 1764 and added it to his Messier Catalog.

Estimates of the Butterfly Cluster's distance have varied over the years. Wu et al. (2009) found a distance estimate of 1,590 light-years, giving it a spatial dimension of some 12 light years. Modern measurements show its total visual brightness to be magnitude 4.2. The cluster is estimated to be 94.2 million years old. Cluster members show a slightly higher abundance of elements heavier than helium compared to the Sun; what astronomers refer to as the metallicity.

120 stars, ranging down to visual magnitude 15.1, have been identified as most likely cluster members. Most of the bright stars in this cluster are hot, blue B-type stars but the brightest member is a K-type orange giant star, BM Scorpii, which contrasts sharply with its blue neighbours in photographs. BM Scorpii, is classed as a semiregular variable star, its brightness varying from magnitude +5.5 to magnitude +7.0. There are also eight candidate chemically peculiar stars.

The cluster is located 24.59 kly from the Galactic Center and is following an orbit through the Milky Way galaxy with a low eccentricity of 0.03 and an orbital period of 204.2 Myr. At present it is 23 ly (7 pc) below the galactic plane, and it will cross the plane every 29.4 Myr.

As of January 2022, the Butterfly Cluster is one of the few remaining objects within the Messier Catalog to not have been photographed by the Hubble Space Telescope.

## See also

* List of open clusters
* List of Messier objects

## References

1. ↑ From trigonometry: radius = distance × sin( diameter\_angle / 2 ) = 1,590 × sin( 25′/2 ) = 6 ly.
2. ↑ Wu, Zhen-Yu; et al. (November 2009), "The orbits of open clusters in the Galaxy", *Monthly Notices of the Royal Astronomical Society*, **399** (4): 2146–2164, arXiv:0909.3737, Bibcode:2009MNRAS.399.2146W, doi:10.1111/j.1365-2966.2009.15416.x, S2CID 6066790.
C Dino x Mizli Fanfic

C dino was walking home one day. He was tired because he ate too much food during lunch period. He was about to vomit on the street, but then realized thats cringe bro so he went up to the nearest person, which was TheOneMizli, and threw up all over him. But little did he know that mizli was a vomitsexual and the they proceeded to have seggs all night ahhhahahahahaa UWU OOOOOOOOHHHH Daddddy! They screamed violently while trying to rape each other. They both died that day because of overmasterbation.
C dino X Raboot 12345, Part 2. Raboot's Delivery

C Dino was kind of bored looking for Raboot. He decided to make a discord account and do a little trolling. He got banned from Discord, because the head discord mod thought he was a female, found out he wasn't and banned him forever, the mod then continued to talk to his anime waifu, Wario. C dino became pissed at discord, and decided he was going to raid discord HQ. However, since Jar Jar Binks had more than triple of his IQ, C dino had to think about his plan.

Meanwhile, Raboot was still travelling across the state to deliver the "candy" to Jebus Crisp. In Montana, after about 6.9 hours (nice) he finnally found Jebus :flushed: and knocked into his house. Jebus was reading Cdino X Milizi fanfic on the Dracozolt wiki, when he heard a knock on his door.

"Bruh Im reading shit on the Dracozolt wiki, who is this?" Jebus asked, angriliy

"Its me, Raboot, I have some white candy for you." Raboot responded, tired from his long 6.9 hour (nice) journey.

Jebus angrily takes the "candy" and gives it back.

" I don't need the candy, you can have it." He said, with a smile.

Raboot sighed and left, and Jebus read more pages on the Dracozolt wiki.

Jebus realise nobody was around, so he unzipped his costume, inside, was Bobux Man

Bobux Man laughs wildily, and pulls out a device that was tracking Raboot.

"Phase one is complete, time to prepare for phase two." Bobux man said with an evil grin.

(To Be Continued, New Part on Thursday :flushed:)
C dino x Raboot12345, Part 4. The sussy imposter appears!

Dust started spinning around, and both Raboot and C dino knew that this foe would be tougher than any other opponent they have ever faced. The enemy appeared, he looked like a character from amongus except gigantic. The creature started screaming "I AM THE SUSSY impostor!" "I WILL HELP BOBUX MAN DESTROY THE DARCOZOLT WIKI!" C dino aimed his blade and started charging at the beast. Raboot charged at Bobux man, jumping up in the air and pointing his weapon downwards at Bobux man. C dino was more sussy than ever, his impostor level was too sus. He was almost equal in power to the impostor creature that he was facing.

"HA HA!" "I'M GOING TO SPAM THE N WORD IN YOUR KID FRIENDLY MINECRAFT DISCORD SERVER!" The monster shouted with malicious intent. Raboot and C dino were both completely struck by what the monster had said, they couldn't even move. The impostor swung at the two before they could move and they were down for a bit. The impostor and Bobux man walked all the away to the epic amongus servers where they keep all the amongus game running. He logged into one of the computers there, signed into discord, and joined their kid friendly minecraft server. C dino and Raboot were on the ground, and then it struck them. "OH NO!" "THEY'RE GONNA SPAM THE N WORD ON OUR KID FRIENDLY MINECRAFT SERVER!"

They both ran towards the amongus official servers, sprinting at speeds not comparable to any other human. Even Usain Bolt would lose in a race against these two based mogus players. A milisecond before Bobux man and The impostor monster could spam the N word in their server, Raboot and C dino charged at the two foes stunning them for enough time so that they could prevent them from spamming the N word. C dino and Raboot started to beat the enemies to death with a amongus plushies filled to the brim with rocks and other sharp objects. The two enemies begged for mercy over and over, but it was too late. C dino and Raboot both T-bagged on the corpes of the two cringeheads and went to live many more days on the dracozolt wiki... or so they thought.
Eskimo Nebula

The **Eskimo Nebula** (**NGC 2392**), also known as the **Clown-faced Nebula**, **Lion Nebula**, or **Caldwell 39**, is a bipolar double-shell planetary nebula with a diameter of roughly \* light years. NGC 2392 lies about 6500 light-years away, and is visible with a small telescope in the constellation of Gemini. At the center of NGC 2392, there is an O-type star with a spectral type of O(H)6f.
Black hole

A **black hole** is a region of space from which nothing, not even light, can escape. According to the general theory of relativity, it starts existing when spacetime gets curved by a huge mass. There is a sphere around the black hole. If something goes inside the sphere, it can not leave. This sphere is called the event horizon. A black hole is black because it absorbs all the light that hits it. It reflects nothing, just like a perfect black body in thermodynamics. Under quantum mechanics, black holes have a temperature and emit Hawking radiation, which makes them slowly get smaller.

Objects whose gravitational fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace. In 1916, Karl Schwarzschild found the first modern solution of general relativity that would characterize a black hole. David Finkelstein, in 1958, first published the interpretation of "black hole" as a region of space from which nothing can escape. Black holes were long considered a mathematical curiosity; it was not until the 1960s that theoretical work showed they were a generic prediction of general relativity. The discovery of neutron stars by astronomers in 1967 sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality. The first black hole known was Cygnus X-1, identified by several researchers independently in 1971.

Black holes of stellar mass form when massive stars collapse at the end of their life cycle. After a black hole has formed, it can grow by absorbing mass from its surroundings. Supermassive black holes of millions of solar masses may form by absorbing other stars and merging with other black holes. There is consensus that supermassive black holes exist in the centres of most galaxies, such as a supermassive black hole of more than four million solar masses is near the Sagittarius A\* part of the Milky Way galaxy.

There are three types of black holes: stellar black holes (between 1 and 100,000 solar mass), supermassive black holes (between 100,000 to 100 million solar mass) and ultramassive black holes (between 100 million to 100 billion solar mass).

## See also

* List of black holes
* Event horizon
* Stellar black hole
* Supermassive black hole

## External links

* Black Hole Comparison on YouTube
* https://www.space.com/15421-black-holes-facts-formation-discovery-sdcmp.html
Capella

Capella Aa, a K0III star

**Capella** is the brightest star in the northern constellation of Auriga. It has the Bayer designation **α Aurigae**, which is Latinised to **Alpha Aurigae** and abbreviated **Alpha Aur** or **α Aur**. Capella is the sixth-brightest star in the night sky, and the third-brightest in the northern celestial hemisphere after Arcturus and Vega. A prominent object in the northern winter sky, it is circumpolar to observers north of 44°N. Its name meaning "little goat" in Latin, Capella depicted the goat Amalthea that suckled Zeus in classical mythology. Capella is relatively close, at 42.9 light-years (13.2 pc) from the Sun. It is one of the brightest X-ray sources in the sky, thought to come primarily from the corona of Capella Aa.

Although it appears to be a single star to the naked eye, Capella is actually a quadruple star system organized in two binary pairs, made up of the stars Capella Aa, Capella Ab, Capella H and Capella L. The primary pair, Capella Aa and Capella Ab, are two bright-yellow giant stars, both of which are around 2.5 times as massive as the Sun. The secondary pair, Capella H and Capella L, are around 10,000 astronomical units (AU) from the first and are two faint, small and relatively cool red dwarfs.
Large Magellanic Cloud

The **Large Magellanic Cloud** (**LMC**), or Nubecula Major is a satellite galaxy of the Milky Way. At a distance of around 50 kiloparsecs (≈160,000 light-years), the LMC is the second- or third-closest galaxy to the Milky Way, after the Sagittarius Dwarf Spheroidal (~16 kpc) and the possible dwarf irregular galaxy known as the Canis Major Overdensity. Based on readily visible stars and a mass of approximately 10 billion solar masses, the diameter of the LMC is about 14,000 light-years (4.3 kpc). It is roughly a hundredth as massive as the Milky Way and is the fourth-largest galaxy in the Local Group, after the Andromeda Galaxy (M31), the Milky Way and the Triangulum Galaxy (M33). The Milky Way and the LMC are predicted to merge in approximately 2.4 billion years.

## History of observation

Both clouds have been easily visible for southern nighttime observers well back into prehistory. It has been claimed that the first-known written mention of the Large Magellanic Cloud was by the Persian astronomer 'Abd al-Rahman al-Sufi Shirazi (later known in Europe as "Azophi"), in his *Book of Fixed Stars* around 964 AD. However, this seems to be a misunderstanding of a reference to some stars south of Canopus which he admits he has not seen. The first confirmed recorded observation was in 1503–1504 by Amerigo Vespucci in a letter about his third voyage. He mentioned "three Canopes [*sic*], two bright and one obscure"; "bright" refers to the two Magellanic Clouds, and "obscure" refers to the Coalsack.

Measurements with the Hubble Space Telescope, announced in 2006, suggest the Large and Small Magellanic Clouds may be moving too quickly to be orbiting the Milky Way. Astronomers discovered a new black hole inside the Large Magellanic Cloud in November 2021 using the European Southern Observatory's Very Large Telescope in Chile. Astronomers claim its gravity is influenced by a nearby star, which is about five times the mass of our Sun.

## Geometry and distance

The Large Magellanic Cloud has a prominent central bar and spiral arm. The central bar seems to be warped so that the east and west ends are nearer the Milky Way than the middle. In 2014, measurements from the Hubble Space Telescope made it possible to determine a rotation period of 250 million years.

Distance to the LMC has been calculated using standard candles; Cepheid variables are one of the most popular. These have been shown to have a relationship between their absolute luminosity and the period over which their brightness varies. However the variable of metallicity may also need to be taken as a component of this as consensus is this likely affects their period-luminosity relations. Unfortunately, those in the Milky Way typically used to calibrate the relation are more metal-rich than those found in the LMC. Modern 8-meter-class optical telescopes have discovered eclipsing binaries throughout the Local Group. Parameters of these systems can be measured without mass or compositional assumptions. The light echoes of supernova 1987A are also geometric measurements, without any stellar models or assumptions.
Pillars of Creation

***Pillars of Creation*** is a photograph taken by the Hubble Space Telescope of elephant trunks of interstellar gas and dust in the Eagle Nebula, in the Serpens constellation, some 7,000 light-years (2,100 pc) from Earth. They are so named because the gas and dust are in the process of creating new stars, while also being eroded by the light from nearby stars that have recently formed. Taken on April 1, 1995, it was named one of the top ten photographs from Hubble by Space.com. The astronomers responsible for the photo were Jeff Hester and Paul Scowen from Arizona State University. The region was rephotographed by ESA's Herschel Space Observatory in 2011, and again by Hubble in 2014 with a newer camera.

Released in 2007, Chandra X-ray Observatory (AXAF) had observed the area in 2001; it did not find many X-ray sources in the towers but was able to observe sources at various X-ray energy levels in the area from young stars.

The image is noted for its global culture impact, with National Geographic noting on its 20th anniversary that the image had been featured on everything from "t-shirts to coffee-mugs".

## Supernova explosion

Images taken with the Spitzer Space Telescope uncovered a cloud of hot dust in the vicinity of the Pillars of Creation that Nicolas Flagey accounted to be a shock wave produced by a supernova. The appearance of the cloud suggests the supernova shockwave would have destroyed the Pillars of Creation 6,000 years ago.
New Horizons

***New Horizons*** is an interplanetary space probe that was launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institute (SWRI), with a team led by S. Alan Stern, the spacecraft was launched in 2006 with the primary mission to perform a flyby study of the Pluto system in 2015, and a secondary mission to fly by and study one or more other Kuiper belt objects (KBOs) in the decade to follow. It is the fifth of five artificial objects to achieve the escape velocity that will allow them to leave the Solar System.

On January 19, 2006, *New Horizons* was launched from Cape Canaveral Air Force Station by an Atlas V rocket directly into an Earth-and-solar escape trajectory with a speed of about 69 km/s. After a brief encounter with asteroid 132524 APL, *New Horizons* proceeded to Jupiter, making its closest approach on February 28, 2007, at a distance of 69. The Jupiter flyby provided a gravity assist that increased *New Horizons* speed; the flyby also enabled a general test of *New Horizons* scientific capabilities, returning data about the planet's atmosphere, moons, and magnetosphere.

Most of the post-Jupiter voyage was spent in hibernation mode to preserve on-board systems, except for brief annual checkouts. On December 6, 2014, *New Horizons* was brought back online for the Pluto encounter, and instrument check-out began. On January 15, 2015, the *New Horizons* spacecraft began its approach phase to Pluto.

On July 14, 2015, at 11:49 UTC, it flew Template:Cvt above the surface of Pluto, making it the first spacecraft to explore the dwarf planet. On October 25, 2016, at 21:48 UTC, the last of the recorded data from the Pluto flyby was received from *New Horizons*. Having completed its flyby of Pluto, *New Horizons* has maneuvered for a flyby of Kuiper belt object 4869582014 MU, expected to take place on January 1, 2019, when it will be 43.4 AU from the Sun.

*New Horizons* was launched on January 19, 2006, directly into an Earth-and-solar-escape trajectory with an Earth-relative velocity of about after its last engine was shut down. Thus, the spacecraft left Earth at the greatest-ever launch speed for a man-made object. It flew by the orbit of Mars on April 7, 2006, Jupiter on February 28, 2007, the orbit of Saturn on June 8, 2008; and the orbit of Uranus on March 18, 2011. As of February 2012, its distance to Pluto is less than 10 AU (more than 20 AU from Earth).
Brown dwarf

**Brown dwarfs** are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen into helium in their cores, unlike a main-sequence star. Instead, they have a mass between the most massive gas giant planets and the least massive stars, approximately 13 to 80 times the mass of Jupiter. However, they can fuse deuterium (2H), and the most massive ones (> 65 Jupiters) can fuse lithium.

Astronomers classify self-luminous objects by spectral class, a distinction intimately tied to the surface temperature, and brown dwarfs occupy types M, L, T, and Y. As brown dwarfs do not undergo stable hydrogen fusion, they cool down over time, progressively passing through later spectral types as they age.
KOI-4878.01

**KOI-4878.01** is an exoplanet candidate that orbits the F-type main-sequence star KOI-4878. It is located about 1075 light years (329 parsecs) from Earth. The features of the planet are very similar to that of Earth, and if it is confirmed, it would be one of the most Earth-like planets found. The orbital period of the exoplanet is around 449 Earth days. It is very likely located within the habitable zone of its parent star.

KOI-4878.01's mass is somewhere between 0.4 - 3.0 Earth masses; likely about 0.99 Earth masses. The exoplanet has a slightly larger radius than Earth: 1.05 Earth radii.
Planetary orbit

In celestial mechanics, an **orbit** is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a planet, moon, asteroid, or Lagrange point. Normally, orbit refers to a regularly repeating trajectory, although it may also refer to a non-repeating trajectory. To a close approximation, planets and satellites follow elliptic orbits, with the center of mass being orbited at a focal point of the ellipse, as described by Kepler's laws of planetary motion.

For most situations, orbital motion is adequately approximated by Newtonian mechanics, which explains gravity as a force obeying an inverse-square law. However, Albert Einstein's general theory of relativity, which accounts for gravity as due to curvature of spacetime, with orbits following geodesics, provides a more accurate calculation and understanding of the exact mechanics of orbital motion.

Within a planetary system, planets, dwarf planets, asteroids and other minor planets, comets, and space debris orbit the system's barycenter in elliptical orbits. A comet in a parabolic or hyperbolic orbit about a barycenter is not gravitationally bound to the star and therefore is not considered part of the star's planetary system. Bodies that are gravitationally bound to one of the planets in a planetary system, either natural or artificial satellites, follow orbits about a barycenter near or within that planet.

## Planetary systems

Owing to mutual gravitational perturbations, the eccentricities of the planetary orbits vary over time. Mercury, the smallest planet in the Solar System, has the most eccentric orbit. At the present epoch, Mars has the next largest eccentricity while the smallest orbital eccentricities are seen with Venus and Neptune.

As two objects orbit each other, the periapsis is that point at which the two objects are closest to each other and the apoapsis is that point at which they are the farthest. (More specific terms are used for specific bodies. For example, *perigee* and *apogee* are the lowest and highest parts of an orbit around Earth, while *perihelion* and *aphelion* are the closest and farthest points of an orbit around the Sun.)

### Orbital plane

The analysis so far has been two dimensional; it turns out that an unperturbed orbit is two-dimensional in a plane fixed in space, and thus the extension to three dimensions requires simply rotating the two-dimensional plane into the required angle relative to the poles of the planetary body involved. The rotation to do this in three dimensions requires three numbers to uniquely determine; traditionally these are expressed as three angles.

### Orbital period

*Main article: Orbital period*

The orbital period is simply how long an orbiting body takes to complete one orbit.

### Tidal locking

Some bodies are tidally locked with other bodies, meaning that one side of the celestial body is permanently facing its host object. This is the case for Earth-Moon and Pluto-Charon system.

## See also

* Planetary system
* Planetary orbit
* Orbital period
Rogue planet

A **rogue planet** is a planet that either has an extremely elongated orbit around its star so that it is not on the same orbital plane as the other planets in the system, or it is an interstellar planet, a planet that drifts freely through space and doesn't orbit a star at all. If the orbit is extremely elongated or sharply inclined the planet could take hundreds or thousands of years to make a complete orbit around the system. The strange orbit of a rogue planet may make it undetectable and unknown to an observer on any of the other normally aligned planets in a solar system.

There are many theories on how rogue worlds are created; they could be massive brown dwarfs, or be terrestrial planets that for some reason break free of their solar system orbits and are flung away into space. Some planets orbiting a star may have been captured rogue worlds.

Since most definitions of "planet" describe in some fashion, "an object which orbits a star", the idea of rogue planets casts doubt on the very nature of what a planet is. Some definition concerning origin, such as "an object that formed from a star's accretion disk" would be required to include rogue planets in the same class as the planets in our solar system. The theory of rogue planets could also account for some of the so called dark matter detected in space.

The planet Nibiru, the "12th planet" in the writings of Zecharia Sitchin, based on his extra-terrestrial interpretation of Sumerian mythology, could be considered a rogue planet, since it supposedly possesses a highly elliptical, 3657-year orbit. However there is no scientific evidence for such a planet and his claims are largely considered pseudoscience.
UY Scuti

**UY Scuti** (**BD-12°5055**) is a red supergiant star in the constellation Scutum. It is considered one of the largest known stars by radius and is also a pulsating variable star, with a maximum brightness of magnitude 8.29 and a minimum of magnitude 10.56. It has an estimated radius of 1,708 solar radii (1.188×109 kilometres; 7.94 astronomical units), thus a volume nearly 5 billion times that of the Sun. It is approximately 2.9 kiloparsecs (9,500 light-years) from Earth. If placed at the center of the Solar System, its photosphere would at least engulf the orbit of Jupiter.
Atlas

**Atlas** is an inner satellite of Saturn which was discovered by Richard Terrile in 1980 from Voyager photos and was designated **S/1980 S 28**. In 1983 it was officially named after Atlas of Greek mythology, because it "holds the rings on its shoulders" like the Titan Atlas held the sky up above the Earth. It is also designated **Saturn XV**.

Atlas is the closest satellite to the sharp outer edge of the A ring, and was long thought to be a shepherd satellite for this ring. However, now it is known that the outer edge of the ring is instead maintained by a 7:6 orbital resonance with the larger but more distant moons Janus and Epimetheus. In 2004 a faint, thin ring, temporarily designated R/2004 S 1, was discovered in the Atlantean orbit.

High-resolution images taken in June 2005 by *Cassini* revealed Atlas to have a roughly spherical centre surrounded by a large, smooth equatorial ridge. The most likely explanation for this unusual and prominent structure is that ring material swept up by the moon accumulates on the moon, with a strong preference for the equator due to the ring's thinness. In fact, the size of the equatorial ridge is comparable with the expected Roche lobe of the moon. This would mean that for any additional particles impacting the equator, the centrifugal force will nearly overcome Atlas's tiny gravity, and they will probably be lost.

Atlas is significantly perturbed by Prometheus and to a lesser degree by Pandora, leading to excursions in longitude of up to 600 km (~0.25°) away from the precessing Keplerian orbit with a rough period of about 3 years. Because the orbits of Prometheus and Pandora are chaotic, it is suspected that Atlas's may be as well.
Haumea

**Haumea** (minor-planet designation **136108 Haumea**) is a dwarf planet located beyond Neptune's orbit. Haumea's mass is about one-third that of Pluto, and 1/1400 that of Earth. Although its shape has not been directly observed, calculations from its light curve are consistent with it being a Jacobi ellipsoid (the shape it would be if it were a dwarf planet), with its major axis twice as long as its minor. In October 2017, astronomers announced the discovery of a ring system around Haumea, representing the first ring system discovered for a trans-Neptunian object. Haumea's gravity was until recently thought to be sufficient for it to have relaxed into hydrostatic equilibrium, though that is now unclear. Haumea's elongated shape together with its rapid rotation, rings, and high albedo (from a surface of crystalline water ice), are thought to be the consequences of a giant collision, which left Haumea the largest member of a collisional family that includes several large trans-Neptunian objects.

Furthermore, it is possible that Haumea may have a tenuous ring system along with their moons.
Asteroid

An **asteroid** is a predominantly rocky body of the inner Solar System. Historically, these terms have been applied to any astronomical object orbiting the Sun that did not resolve into a disc in a telescope and was not observed to have characteristics of an active comet such as a tail. As minor planets in the outer Solar System were discovered that were found to have volatile-rich surfaces similar to comets, these came to be distinguished from the objects found in the main asteroid belt. Thus the term "asteroid" now generally refers to the minor planets of the inner Solar System, including those co-orbital with Jupiter. Larger asteroids are often called planetoids.

## See also

* List of asteroids
* Asteroid Belt

Millions of asteroids exist: many are shattered remnants of planetesimals, bodies within the young Sun's solar nebula that never grew large enough to become planets. The vast majority of known asteroids orbit within the main asteroid belt located between the orbits of Mars and Jupiter, or are co-orbital with Jupiter (the Jupiter trojans). However, other orbital families exist with significant populations. The sizes of asteroids varies greatly; the largest, Ceres, is almost 1,000 km (600 mi) across and massive enough to qualify as a dwarf planet.
Andromeda Galaxy

The **Andromeda Galaxy,** also known as **Messier 31**, **M31**, or **NGC 224** is a barred spiral galaxy with diameter of about 220,000 ly approximately 2.5 million light-years (770 kiloparsecs) from Earth and the nearest large galaxy to the Milky Way. The galaxy's name stems from the area of Earth's sky in which it appears, the constellation of Andromeda, which itself is named after the Ethiopian (or Phoenician) princess who was the wife of Perseus in Greek mythology.

The estimated mass of the Andromeda Galaxy is of the same as that of the Milky Way, at 1 trillion solar masses (2.0×1042 kilograms). The mass of either galaxy is difficult to estimate with any accuracy, but it was long thought that the Andromeda Galaxy is more massive than the Milky Way by a margin of some 25% to 50%. This has been called into question by a 2018 study that cited a lower estimate on the mass of the Andromeda Galaxy, combined with preliminary reports on a 2019 study estimating a higher mass of the Milky Way. The Andromeda Galaxy has a diameter of about 220,000 ly (67 kpc), making it the largest member of the Local Group in terms of extension.

The Milky Way and Andromeda galaxies are expected to collide in around 4-5 billion years, merging to form a giant elliptical galaxy or a large lenticular galaxy. With an apparent magnitude of 3.4, the Andromeda Galaxy is among the brightest of the Messier objects, making it visible to the naked eye from Earth on moonless nights, even when viewed from areas with moderate light pollution.
Star System

A **star system** or **stellar system** is a system comprised of a star or group of stars, and, perhaps, planetary systems of smaller bodies (such as planets or asteroids), in gravitational association. The solar system is, properly, the star system comprised of our Sun and other bodies, such as the Earth, in orbit around it. (The word *solar* is taken from *Sol*, the Latin word for "Sun.")

## Binary star systems

A star system of two stars is known as a *physical double star*, *binary star*, or *binary star system*. If there are no tidal effects, no perturbation from other forces, and no transfer of mass from one star to the other, such a system is stable, and both stars will trace out an elliptical orbit around the center of mass of the system indefinitely.

## Systems with two or more stars

Systems with more than two stars are also possible; for example, a star cluster or galaxy is a kind of star system. Because of the large size of these systems, their dynamics are much more complicated than that of the binary star. However, it is also possible to have star systems with a small number (greater than two) of stars and simple orbital dynamics. These systems are called **multiple star systems**, or **physical multiple stars**.

### Nomenclature

Multiple star systems or physical multiple stars are called *triple*, *trinary* or *ternary* if they contain three stars; *quadruple* or *quaternary* if they contain four stars; *quintuple* with five stars; *sextuple* with six stars; *septuple* with seven stars; and so on.

### Triple star systems

Triple systems are by far the most common type of multiple system. For example, in the 1999 revision of Tokovinin's catalog of physical multiple stars, 551 out of the 728 systems described are triple. In accordance with the hierarchical principle, triple star systems generally contain a close binary pair which has a more distant companion.

## Examples

Some star systems are:

* Our own solar system, with the Sun at its centre (one star)
* Sirius (two stars)
* Alpha Centauri (three stars) [*debated - see Proxima Centauri*]
* 4 Centauri (four stars)
* Nu Scorpii (seven stars)
* Cygnus X-1 (one star and one black hole)

## See also

* Solar system
* Binary star
* Star cluster
* Triple star
* Planetary system
* Galaxy
List of exoplanets

This is a **list of exoplanets**. As of 1 April 2022, there are 4,984 confirmed exoplanets in 3,673 planetary systems, with 815 systems having more than one planet. Most of these were discovered by the Kepler space telescope. There are an additional 2,058 potential exoplanets from Kepler's first mission yet to be confirmed, as well as 1,024 from its "Second Light" mission and 3,505 from the Transiting Exoplanet Survey Satellite (TESS) mission.

For yearly lists on physical, orbital and other properties, as well as on discovery circumstances and other aspects, *see § Specific exoplanet lists*.

## Nomenclature

The convention for designating exoplanets is an extension of the system used for designating multiple-star systems as adopted by the International Astronomical Union (IAU). For exoplanets orbiting a single star, the IAU designation is formed by taking the designated or proper name of its parent star, and adding a lower case letter. Letters are given in order of each planet's discovery around the parent star, so that the first planet discovered in a system is designated "b" (the parent star is considered to be "a") and later planets are given subsequent letters. If several planets in the same system are discovered at the same time, the closest one to the star gets the next letter, followed by the other planets in order of orbital size. A provisional IAU-sanctioned standard exists to accommodate the designation of circumbinary planets. A limited number of exoplanets have IAU-sanctioned proper names. Other naming systems exist.

## Exoplanet lists

* List of exoplanets discovered before 2000 (32)
* List of exoplanets discovered between 2000–2009 (379)
* List of exoplanets discovered in 2010-2019 (439)

## External links

* The NASA Exoplanet Archive
* The Extrasolar Planet Encyclopaedia — Catalog Listing accessed in 2015-09-28
* Exoplanet Data Explorer accessed in 2015-09-28
NGC 4449

**NGC 4449**, also known as **Caldwell 21**, is an irregular Magellanic type galaxy in the constellation Canes Venatici, being located about 13 million light-years away. It is part of the M94 Group or Canes Venatici I Group that is relatively close to the Local Group hosting our Milky Way galaxy.

## Characteristics

This galaxy is similar in nature to the Milky Way's satellite galaxy, the Large Magellanic Cloud (LMC), though is not as bright nor as large. NGC 4449 has a general bar shape, also characteristic of the LMC, with scattered young blue star clusters. Unlike the Large Magellanic Cloud, however, NGC 4449 is considered a starburst galaxy due to its high rate of star formation (twice the one of the LMC) and includes several massive and young star clusters, one of them in the galaxy's center.

Photos of the galaxy show the pinkish glow of atomic hydrogen gas, the telltale tracer of massive star forming regions. NGC 4449 is surrounded by a large envelope of neutral hydrogen that extends over an area of 75 arc minutes (14 times larger than the optical diameter of the galaxy). The envelope shows distortions and irregularities likely caused by interactions with nearby galaxies.

Interactions with nearby galaxies are thought to have influenced star formation in NGC 4449 and, in fact, in 2012 two small galaxies have been discovered interacting with this galaxy: a very low surface brightness disrupted dwarf spheroidal with the same stellar mass as NGC 4449's halo but with a ratio of dark matter to stellar matter between 5 and 10 times that of NGC 4449 and a highly flattened globular cluster with two tails of young stars that may be the nucleus of a gas-rich galaxy. Both satellites have apparently been disrupted by NGC 4449 and are now being absorbed by it. At least one ultraluminous X-ray source (ULX) is known in NGC 4449, called NGC 4449 X7. There are three candidates that have been identified as optical counterparts to NGC 4449 X7 (i.e. they may be associated with the ULX). They are all early (B-type to F-type) supergiants that are estimated to be about 40 to 50 million years old and about 8 times the mass of the Sun.
Aldebaran

**Aldebaran** /ælˈdɛbərən/, designated **α Tauri** (Latinized to **Alpha Tauri**), is a giant star measured to be about 65 light-years from the Sun in the zodiac constellation Taurus. It is the brightest star in Taurus and generally the fourteenth-brightest star in the night sky, though it varies slowly in brightness between magnitude 0.75 and 0.95. Aldebaran is believed to host a planet several times the mass of Jupiter, named Aldebaran b.

Aldebaran is cooler than the Sun with a surface temperature of 3,900 K, but its radius is about 44 times the Sun's, so it is over 400 times as luminous. It spins slowly and takes 520 days to complete a rotation.

The planetary exploration probe Pioneer 10 is heading in the general direction of the star and should make its closest approach in about two million years.
2015 TG387

**541132 Leleākūhonua,** provisionally designated **2015 TG387**, is an extreme trans-Neptunian object and sednoid in the outermost part of the Solar System. It was first observed on 13 October 2015, by astronomers at the Mauna Kea Observatories, Hawaii. Based on its discovery date near Halloween and the letters in its provisional designation 2015 TG387, the object was informally nicknamed "The Goblin" by its discoverers and later named *Leleākūhonua*, comparing its orbit to the flight of the Pacific golden plover. It was the third sednoid discovered, after Sedna and 2012 VP113, and measures around 220 kilometers (140 miles) in diameter.

*Leleākūhonua* orbits the Sun at a distance of 65–2000 AU once roughly every 32,000 years (semi-major axis of ~1080 AU). Its orbit has a very high eccentricity of 0.94 and an inclination of 12° with respect to the ecliptic. It belongs to the extreme trans-Neptunian objects defined by their large semi-major axis and is the third sednoid ever to be discovered, after Sedna and 2012 VP113 ("Biden"). Along with the similar orbits of other distant trans-Neptunian objects, the orbit of *Leleākūhonua* suggests, but does not prove, the existence of a hypothetical Planet Nine in the outer Solar System.
Epsilon Eridani

**Epsilon Eridani** (Latinized from **ε Eridani**), formally named **Ran**, is a star in the southern constellation of Eridanus, at a declination of 9.46° south of the celestial equator. This allows it to be visible from most of Earth's surface. At a distance of 10.5 light-years (3.2 parsecs) from the Sun, it has an apparent magnitude of 3.73. It is the third-closest individual star or star system visible to the unaided eye.

The star is estimated to be less than a billion years old. Because of its relative youth, Epsilon Eridani has a higher level of magnetic activity than the present-day Sun, with a stellar wind 30 times as strong. Its rotation period is 11.2 days at the equator. Epsilon Eridani is smaller and less massive than the Sun, and has a comparatively lower level of elements heavier than helium. It is a main-sequence star of spectral class K2, which means that energy generated at the core through nuclear fusion of hydrogen is emitted from the surface at a temperature of about 5,000 K (8,500 °F), giving it an orange hue.