CapitalistImperialistPig

Red dwarfs, or M-dwarfs, are the most common type of star as well as the smallest and dimmest main-sequence (hydrogen burning) stars. Because of their low luminosity and because many of them are fully convective and hence can burn a large fraction of their total hydrogen, they are very long lived, in many cases hundreds of times longer than our Sun. These trillion year lifetimes are much longer than the present age of the universe. Because they are so common, and because their small size makes it relatively easy to observe transits of their exoplanets, they are a favored place to look for Earthlike planets. Such planets would have some funky properties. If they are in the habitable zone, the zone where temperatures permit liquid water to exist on planetary surfaces, they would be tidally locked to their star, keeping one face always toward it. Despite their dimness, red dwarf stars have a great deal of magnetic activity, and their titanic solar storms bombard their planets with ...

The metallicity of a star, we might recall, measures how much of its material consists of elements heavier than hydrogen and helium, that is, those elements that were manufactured in earlier generations of stars that subsequently spewed their contents across the cosmos. Our Sun, for example, has about 1 iron atom for every 20,000 hydrogen atoms. Metallicities of other stars are measured on a logarithmic scale on which the Sun is defined to have metallicity zero. Thus, a star with metallicity -4 has an iron fraction only 1/10000 that of the Sun (1 iron atom for every 200 million hydrogen atoms). The most metal poor stars of all seem to have metallicities of about -4.5, while the most metal rich are near 1, with ten times more iron than the Sun. Since the very first generation of stars had no metals at all, these would have been off the scale in the negative direction, but none of these so-called Population III stars seem to have survived to the present. The kinds of planets a st...