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Palomar 5

StarDate: 
May 19, 2022

A star cluster on the outskirts of the galaxy is falling apart. Its stars are being pulled away, forming a ribbon tens of thousands of light-years long. And one of the causes may be a clump of black holes at the cluster’s heart.

Palomar 5 is a globular cluster — a giant ball of stars. It’s one of the Milky Way’s least impressive globulars. It’s about 10,000 times the mass of the Sun — much lighter than almost any other cluster. And its stars are much more thinly spread.

A study last year placed the blame on a clump of black holes.

Researchers simulated possible interactions within Palomar 5 until they got a match with what we see. They found that Palomar 5 might have started out like most globulars. Many of its big, massive stars quickly exploded, leaving only their dead cores: black holes. Today, there could be a hundred black holes that are roughly 20 times the mass of the Sun.

The black holes kicked other stars out of the cluster’s heart, pushing the black holes closer together. That allowed the gravity of the rest of the galaxy to strip away many stars from the cluster’s fringes. Today, they form a long trail through the galaxy’s outskirts.

A billion years from now, all the stars may have been stripped away, leaving only the black holes. After that, they, too, will go their own ways.

Palomar 5 is in Serpens, which is in the southeast at nightfall. It takes a telescope to spot Palomar 5 — a cluster that’s falling apart.

Script by Damond Benningfield

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