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Messier 22

August 24, 2015

There’s more than one way to “discover” an astronomical object. The most obvious is to just see it. And by that standard, the object known as Messier 22 was discovered as soon as people started paying attention to the night sky. It looks like a hazy smudge of light close to the lid of the teapot — a pattern of eight bright stars in Sagittarius. You need dark skies to see it, though.

But there’s another way to discover something, and that is to understand its true nature. By that standard, M22 was discovered 350 years ago this week by Abraham Ihle, an amateur astronomer in Germany.

Ihle was using a small telescope to study the planet Saturn, which was passing through Sagittarius at the time. When he looked at that nearby hazy patch of light, he found that it was a swarm of thousands of individual stars.

Today, that swarm is known as a globular cluster — a collection of many stars packed into a tight ball. In fact, M22 was the first globular to be seen as anything other than a fuzzy ball of light.

Like all globulars, M22 contains some of the oldest stars in the galaxy. That indicates that these clusters were some of the first clumps of stars to form in the entire galaxy.

M22 also contains black holes and several free-floating planets — objects bigger than Earth that don’t orbit any star. They help make M22 one of the most diverse and interesting globulars in the galaxy.


Script by Damond Benningfield, Copyright 2015

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