(Phys.org) —Astronomers trying to understand how the Sun and Earth formed, and why they have their characteristic properties, have made progress on a closely related problem: the nature of the lowest mass stars, so-called "brown dwarfs." These stars have masses of less than about 8% of the Sun's mass. They are basically failed normal stars, and lack a sufficient force of gravitational contraction to heat up their interiors to the roughly ten million kelvin temperatures needed for hydrogen burning (hydrogen burning fuels the Sun). Not surprisingly they are extremely faint and hard to detect, and as a consequence our understand of their evolution and interior properties is incomplete. Theorists predict that there could be as many brown dwarf stars as there are normal stars.
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