Friday, September 2, 2011

The Biggest Stars In The Universe

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Star Size Comparison: The biggest/largest known stars in the Universe.

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VY Canis Majoris (VY CMa) is a red hypergiant star located in the constellation Canis Major. With a size of 2600 solar radii, it is the largest known star and also one of the most luminous known. It is located about 1.5 kiloparsecs (4.6×1016 km) or about 4,900 light years away from Earth. Unlike most stars, which occur in either binary or multiple star systems, VY CMa is a single star. It is categorized as a semiregular variable and has an estimated period of 6,275,081 days, or just under 17,200 years.

Antares is a red supergiant star in the Milky Way galaxy and the sixteenth brightest star in the nighttime sky (sometimes listed as fifteenth brightest, if the two brighter components of the Capella quadruple star system are counted as one star). Along with Aldebaran, Spica, and Regulus it is one of the four brightest stars near the ecliptic. Antares is a variable star, whose apparent magnitude varies from +0.9 to +1.8.

The Pistol Star is a blue hypergiant and is one of the most luminous known stars in the Milky Way Galaxy. It is one of many massive young stars in the Quintuplet cluster in the Galactic Center region. The star owes its name to the shape of the Pistol Nebula, which it illuminates. It is located approximately 25,000 light years from Earth in the direction of Sagittarius. It would be visible to the naked eye as a fourth magnitude star, if it were not for the interstellar dust that completely hides it from view in visible light.

Rigel (β Ori / β Orionis / Beta Orionis) is the brightest star in the constellation Orion and the sixth brightest star in the sky, with visual magnitude 0.18. Although it has the Bayer designation "beta", it is almost always brighter than Alpha Orionis (Betelgeuse).

Aldebaran (α Tau, α Tauri, Alpha Tauri) is an orange giant star located about 65 light years away in the zodiac constellation of Taurus. With an average apparent magnitude of 0.87 it is the brightest star in the constellation and is one of the brightest stars in the nighttime sky. The name Aldebaran is Arabic (الدبران al-dabarān) and translates literally as "the follower", presumably because this bright star appears to follow the Pleiades, or Seven Sisters star cluster in the night sky. This star is also called the Bull's Eye because of its striking orange color and its location in the bull's head shaped asterism. NASA's Pioneer 10 spacecraft, which flew by Jupiter in 1973, is currently traveling in the direction and will reach it in about two million years.

Arcturus (α Boo / α Boötis / Alpha Boötis) is the brightest star in the constellation Boötes. With a visual magnitude of −0.05, it is also the third brightest star in the night sky, after Sirius and Canopus. It is, however, fainter than the combined light of the two main components of Alpha Centauri, which are too close together for the eye to resolve as separate sources of light, making Arcturus appear to be the fourth brightest. It is the second brightest star visible from northern latitudes and the brightest star in the northern celestial hemisphere. The star is in the Local Interstellar Cloud.

Pollux (β Gem / β Geminorum / Beta Geminorum) is an orange giant star approximately 34 light-years from the Earth in the constellation of Gemini (the Twins). Pollux is the brightest star in the constellation, brighter than Castor (Alpha Geminorum). As of 2006, Pollux was confirmed to have an extrasolar planet orbiting it.

Sirius is the brightest star in the night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The name Sirius is derived from the Ancient Greek Σείριος. The star has the Bayer designation α Canis Majoris (α CMa, or Alpha Canis Majoris). What the naked eye perceives as a single star is actually a binary star system, consisting of a white main sequence star of spectral type A1V, termed Sirius A, and a faint white dwarf companion of spectral type DA2, termed Sirius B.

The Sun is the star at the center of the Solar System. The Sun has a diameter of about 1,392,000 kilometres (865,000 mi) (about 109 Earths), and by itself accounts for about 99.86% of the Solar System's mass; the remainder consists of the planets (including Earth), asteroids, meteoroids, comets, and dust in orbit. About three-fourths of the Sun's mass consists of hydrogen, while most of the rest is helium.


Animations: morn1415, NASA, ESO, Hubblecast

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