Red dwarf

Red dwarf stars are the smallest stars that fuse Hydrogen to Helium in their core.

Physical properties

Like all Hydrogen fusing stars the energy from the fusion balances against gravitational contraction, to keep the stars at their current size.

Red dward stars are the least massive stars on the main sequence. More massive stars, like Sol, our sun, have to fuse their Hydrogen at a faster rate, to balance their greater mass. Stars the size of Sol will fuse all their available Hydrogen in roughly 10 billion years. Sirius roughly twice the mass of Sol, will fuse all their available Hydrogen in roughly one billion years. 150 solar masses is believed to be the theoretical maximum size of a conventional star, and their great mass means they will consume fuse all their available Hydrogen in a mere ten million years.

Red dwarf stars are expected to need up to three trillion years to consume all their Hydrogen.

Are red dwarf stars circled by planets capable of harboring life?

In the 21st century, using more advanced telescopes, astronomers have confirmed the existence of hundreds of exoplanets orbiting red dwarf stars. However, two factors may reduce the likelihood of these exoplanets harbouring life. Red dwarf stars are believed to have a flare period, where they have brief stellar flares, intense enough to strip the atmosphere from a planet the size of Planet Earth. Second, due to their small mass, planets in their habitable zone are anticipated to be tidally locked, so one side always faces the star.