The volume is 65.438+00 billion times that of the sun and 65.438+300 billion times that of the earth! How big is the largest star in the universe?
The stars visible to the naked eye in the night sky seem to be just unremarkable stars, but most of them are bigger than the sun. For example, the radius of Vega is 2.4 times that of the sun, arcturus is 25.4 times that of the sun, Tientsin is 203 times that of the sun, and Betelgeuse is 887 times that of the sun.
So how big is the biggest star in the universe?
For a long time, the shield constellation UY, which is 5 100 light years away from us, has been regarded as the largest star, and its radius was originally estimated to be 1708 times that of the sun. However, according to the latest observation data released by Gaia satellite, the shield constellation UY is not as big as previously estimated, and its actual radius is only 755 times that of the sun, which is not as big as Betelgeuse.
At present, there are dozens of stars whose radius is more than 1000 times that of the sun, and larger stars are even larger than UY's original estimate, such as WOH G64 located in the Large Magellanic Cloud 16000 light years, whose radius is estimated to be 1730 times that of the sun. HV 888, another star in the large magellanic cloud, is larger, and its radius is 1974 times that of the sun.
According to the existing observation data, the largest star is Stephenson 2- 18 (Stephenson 2- 18, or RSGC2- 18), and its radius is as high as 2 150 times that of the sun, that is,14.96 million kilometers. If converted into volume, Stephenson 2- 18 can hold about 10 billion suns and 13 billion earths.
Stephenson 2- 18 is incredibly big. If placed in the center of the solar system, the innermost six planets are all inside, and its outer layer (photosphere) is outside Saturn's orbit. In this case, Uranus will be the nearest planet.
So, how did this huge star form?
Stephenson 2- 18 is a red Supergiant star, which is dying. When the star consumes the core hydrogen fuel, it will start helium nuclear fusion, releasing more energy, and at the same time causing the outer layer to expand violently, thus forming a red giant, which is what our sun will experience in 5 billion years. If a very massive star evolves to the final stage, it will expand into a larger red Supergiant star, which is the origin of Stephenson 2- 18.
Due to its huge volume and limited gravity, the outer layer of Stephenson 2- 18 is losing a lot of mass. Eventually, when the core of this star produces pig iron, its hydrostatic balance will be completely broken, which will lead to a supernova explosion.
It is estimated that Stephenson 2- 18 can generate 440,000 times the energy (luminosity) of the current sun. Due to the violent expansion of its volume, its surface temperature has dropped to 2930℃, which is much colder than the surface of the sun.
Since Stephenson 2- 18 has such high luminosity, can we see it with naked eyes on earth?
Stephenson 2- 18 is located in the direction of the earth shield, 20,000 light years away from the earth, which means it is located in the Milky Way. However, the distance of 20,000 light-years is still far away. When it reaches the earth, the light it emits has become dim and invisible to the naked eye.