What if the sun were half as big?
Credit: Karl Tate / Life’s Little Mysteries
At that size, the sun would be much cooler and redder, a stellar variety known as a “red dwarf.” The band around it that would be suitable for life, known as the “habitable zone,” would be much smaller, and Earth would not be in it because our water would freeze solid. Mercury, on the other hand, would be sitting pretty. [Get the full explanation]