Red Giant

stars · space · stellar evolution · astronomy

Massive and cool. Red giants are huge compared to regular stars, but their surfaces are much cooler than young stars, only reaching about 5,000 K or colder. This cooler temperature is what gives them their distinctive red or orange glow.

Hot core, cool outside. Even though the outside is cooler and redder, a red giant's core is actually very hot and dense. The star is burning fuel in unusual ways that cause it to puff up like a balloon.

Late in life. Red giants are stars in their old age. Our Sun will eventually become a red giant in about 5 billion years and will grow so large it might swallow Mercury, Venus, and Earth.

Colorful variety. Red giants range in color from yellow-white to reddish-orange depending on their exact temperature and makeup. Some are even made mostly of carbon, which changes their appearance in interesting ways.

Common in the universe. Red giants are found throughout our galaxy and beyond. Betelgeuse, a famous red giant in the constellation Orion, is so huge that if it replaced our Sun, its surface would extend far beyond Jupiter's orbit.