One of our universe's biggest stars has dramatically turned into a rare, yellow 'hypergiant' star, and astronomers aren't sure when it will go supernova.

Add Yahoo as a preferred source to see more of our stories on Google. White dwarf stars, like this one shown shrouded by a planetary nebula, are much smaller than stars like our Sun. NASA/R. Ciardullo ...

AMES, Iowa – Astronomers poring over four years of data from NASA’s Kepler spacecraft have discovered a star that’s 11.2 billion years old and has at least five Earth-size planets. “We thus show that ...