Sirus, the brightest star in the night sky, is a binary star consisting of Sirius B, a massive white dwarf and Sirius A, an A-type main sequence star. This long lifetime is one reason red dwarfs are considered to be good sources for planets hosting life, because they are stable for such a long time. A red dwarf, which is half as massive as the sun, can last 80 to 100 billion years, which is far longer than the universe's age of 13.8 billion years. While the sun will spend about 10 billion years on the main sequence, a star 10 times as massive will stick around for only 20 million years. A higher-mass star may have more material, but it burns through it faster due to higher core temperatures caused by greater gravitational forces. How long a main sequence star lives depends on how massive it is. Fusion produces an outward pressure that balances with the inward pressure caused by gravity, stabilizing the star. The star turns on and becomes a main sequence star, powered by hydrogen fusion. But if the body has sufficient mass, the collapsing gas and dust burns hotter, eventually reaching temperatures sufficient to fuse hydrogen into helium.
Instead, they become brown dwarfs, stars that never ignite. Smaller bodies - with less than 0.08 the sun's mass - cannot reach the stage of nuclear fusion at their core.
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