Survivor

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A planet that orbits a star in the Little Bear has had a traumatic few million years. It either survived a merger of its two stars, or it was born from the debris created by that collision.

Halla orbits the star 8 Ursae Minoris, which is old and bloated. The planet is more massive than Jupiter, the giant of our own solar system.

Halla orbits the star once every three months, at about half the distance from Earth to the Sun. When it was discovered, astronomers thought it must have survived being engulfed by its star, which should have been much bigger in the past.

Scientists continued studying the system with telescopes in space and on the ground. And they found a couple of other possible explanations.

One says the planet originally orbited two stars. The stars merged to make a single star. Perhaps surprisingly, that kept the star we see today from growing as big as it would have otherwise. So Halla kept on orbiting despite the fireworks.

Another possibility is that the merger produced big clouds of debris, and Halla took shape from that material.

The surviving star eventually will puff up even more, then shed its outer layers — another traumatic event for Halla.

8 Ursae Minoris is in Ursa Minor, the Little Bear. Some of its stars form the Little Dipper, which is in the north at nightfall. The star is near the lower right corner of the dipper this evening, but you need binoculars to see it.
 

Script by Damond Benningfield

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