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August 4, 2013

Antares, the bright orange heart of Scorpius, stands due south as night falls this evening. It’s one of the biggest, heaviest, and brightest stars in the galaxy. And at an age of about 10 million years, it’s also one of the youngest.

If you have binoculars, you can spot some of the galaxy’s oldest stars close to Antares. They form a globular star cluster known as M4. It’s about 7200 light—years away, making it one of the closest of all globular clusters.

M4 contains tens of thousands of stars packed into a tight ball. And almost all of them are remnants of the birth of the Milky Way galaxy, which means they’re roughly 13 billion years old.

The cluster’s most massive stars died long ago. All of the stars that still shine there are less massive than the Sun, because only such small stars can sustain nuclear reactions in their cores for 13 billion years. So even though M4 contains a lot of stars, it’s so faint that you need binoculars to see it. It looks like a small smudge of light to the right of Antares.

Astronomers have also discovered a planet in the cluster. It’s not likely to have given birth to life, though, because the cluster contains relatively little of the heavy elements needed to sustain life. And even if life did take hold there, it would have had a hard time surviving. Both of the stars in its system have long since expired — one of them as a supernova — a blast that would have sterilized nearby planets in this ancient city of stars.


Script by Damond Benningfield, Copyright 2013

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