Millennia ago astronomers noted the colors of stars, and ever since at least the Iron Age, it hasn’t been too big a leap to associate those colors with temperatures. Take an iron bar and put it ...

Both Mars and Antares share the same color and have a similar brightness. Mars also makes regular passes of the star as it wends its way around the zodiac. When its brightness equals or exceeds ...

“For Antares, from the fact that it did not change color since the second millennium [B.C.E.], we conclude that it is either on the second or third [Hertzsprung gap] crossing,” Neuhäuser says.