Wednesday, August 4, 2010

Top 10 Biggest Star Ever

Below is a Top 10 list of the largest known stars by radius (half of the diameter). The unit of measurement used is the radius of the Sun (approximately 695,500 kilometers, or 432,450 miles). The exact order of this list is not complete yet, nor is it completely well defined: There are sometime high uncertainties in derived values and sizes.The distances to most of these stars are uncertain to differing degrees and this uncertainty affects the size measurements.Several large stars have extended atmospheres, are embedded in mostly opaque dust shells or disks, and pulsate, such that determining their radii is not well defined. Estimates for VV Cephei A are especially uncertain.

1 :- VY Canis Majoris


VY Canis Majoris (VY CMa) is a red hypergiant star located in the constellation Canis Major. At between 1800 and 2100 solar radii (approx 2.7 billion km across or 1.7 billion miles), 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 hypergiant 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 2000 days


2 :- VV Cephei A


VV Cephei, also known as HD 208816, is an eclipsing binary star system located in the constellation Cepheus, At between 1,600–1,900 solar radii approximately 2,400 light years from Earth.

A red hypergiant fills the system's Roche lobe when closest to its companion blue star, the latter appearing to be on the main sequence. Matter flows from the red hypergiant onto the blue companion.


3 :- Mu Cephei

Mu Cephei also known as Herschel 's Garnet Star, is a red super giant star in the constellation Cepheus. At 1,550 solar radii It is one of the largest and most luminous stars known in the Milky Way. It appears garnet red and is given the spectral class of M2Ia.


4 :- WOH G64


WOH G64 is a red hypergiant in the Large Magellanic Cloud. With 2000 times the radius of the Sun . The size of WOH G64 At 1,540 solar radii is estimated at 2,785,000,000 km.


5 :- V354 Cephei


V354 Cephei is a red hypergiant star (pulsating variable star) located within the Milky Way. It is located approximately 9,000 light-years away from our Sun and is currently considered the fifth largest known star, with a radius estimate of 1520 times that of the Sun, or 1,057,160,000 km. Assuming the size estimate is correct, if it were placed in the center of our Solar System, it would extend to 7 AU (between the orbits of Jupiter and Saturn).


6 :- RW Cephei


RW Cephei is an M-class red hypergiant star in the constellation Cepheus. Six of the largest stars known, RW Cephei is estimated at 1,260–1,610 solar radii. RW Cephei, while nearly as large as the orbit of Jupiter, is not as large as other stars in the constellation of Cephus, namely V354 Cephei and VV Cephei A.


7 :- KW Sagittarii


KW Sagittarii is a red hypergiant, It is located approximately between 9,000-13,000 light-years away from our Sun. It is 1460 solar diameters, in fact Seven of the largest known stars, its luminosity is 370,000 times the Sun's. It is located in the constellation Sagittarius.


8 :- KY Cygni


KY Cygni is a red Super Giant star (spectral class M3m) located in the constellation Cygnus. It is Eight of the largest stars known, at about 1,420 times the Sun's diameter, and is also one of the most luminous, with about 300,000 times the Sun's luminosity. It is approximately 5,200 light-years away.


9 :- Betelgeuse (Alpha Orionis)


Betelgeuse is a semiregular variable star whose apparent magnitude ranges between 0.2 and 1.2, the most for any first magnitude star. It is the ninth brightest star in the night sky located around 640 light-years from Earth. Although given the Bayer designation Alpha Orionis (α Orionis / α Ori), Betelgeuse is but the second brightest star in the constellation Orion, outshone by Rigel (Beta Orionis) almost all the time. The star marks the upper right vertex of the Winter Triangle and center of the Winter Hexagon.

Classified as a red Super Giant, Betelgeuse is one of the largest and most luminous stars known. For comparison, if the star were at the center of our solar system its surface would extend past the orbit of Jupiter, wholly engulfing Mercury, Venus, the Earth and Mars. The angular diameter of Betelgeuse was first measured in 1920–1921 by Albert Abraham Michelson and Francis G. Pease using the 100 in (2.5 m) John D. Hooker astronomical interferometer telescope atop Mount Wilson Observatory.

Astronomers believe Betelgeuse is only 10 million years old, but has evolved rapidly because of its high mass. Due to its age, Betelgeuse is expected to explode as a supernova, possibly within the next millennium.


10 :- Antares (Alpha Scorpii)


Antares is a red Super Giant 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 slow variable star with an average magnitude of +1.09.

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