Red Giant

A red giant is an aging star swollen to enormous size — our Sun will become one in about 5 billion years.

A red giant is an old star that has exhausted the hydrogen in its core, swelling its outer layers enormously while its surface cools and reddens. The best-known example, Betelgeuse in Orion, is a red supergiant roughly 700 light-years away — placed at the Sun's position it would extend past the orbit of Jupiter. Its "Great Dimming" from October 2019 to early 2020, when it lost more than two-thirds of its brightness, was traced to a dust cloud the star had ejected. The Sun itself will become a red giant in about 5 billion years and engulf Mercury and Venus.