The smallest star in the universe is a Red Dwarf; the smallest star possible. As we have yet to catalogue every star in the entire universe, the classification of “smallest star” would be like classifying the smallest lake or the smallest river. That being said, one of the smallest stars known is the Gliese 623b, a star that is one tenth the mass of the sun and 60,000 times less bright. This star is the one to the right of the large star in the middle. To give you an idea, if this star was our sun, it would only be 8 times brighter than the full moon. This star was discovered in 1994 using the Hubble Telescope.
Red Dwarf stars are the most numerous classification of star in the universe, and the most difficult to spot. They cannot be seen with the naked eye. They burn long and slow, and therefore the oldest Red Dwarf is the same age as that of our universe. It is thought that once these stars run out of usable hydrogen, they slowly become dimmer and dimmer, but since any Red Dwarfs to enter this stage would have to be older than our universe, there are none in known existence. Red Dwarfs turn hydrogen into helium using the proton proton chain mechanism. The smallest Red Dwarf possible is only 0.4 times the mass of the sun.
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