60-Second Space

Milky Way and Satellite Galaxies Are Rare Arrangement

Only about 0.5 percent of Milky Way-like galaxies have companions like our satellite galaxies, the Magellanic Clouds. John Matson reports

Our Milky Way galaxy has two large satellite galaxies orbiting it. They’re known as the Large and Small Magellanic Clouds. And humans have been aware of the existence of these celestial objects for at least a millennium.

Recently, researchers were curious about whether our configuration is fairly typical, or an astronomical anomaly. In other words, is our corner of the cosmos ordinary?

Now a new study finds that the Milky Way and its companion galaxies are an unusual combination, but they’re not one of a kind.

Astronomers in the U.K. and Australia looked at thousands of galaxies to try to find an analogue of our arrangement. The search turned up two close replicas: each with a Milky Way–like galaxy accompanied by two galaxies comparable to the Magellanic Clouds.

But the researchers also concluded that such arrangements are pretty rare. Only half a percent of Milky Way–like galaxies have companions like ours. [Aaron S. G. Robotham et al., Galaxy And Mass Assembly (GAMA): in search of Milky Way Magellanic Cloud analogues, Monthly Notices of the Royal Astronomical Society]

The Magellanic Clouds may be transitory features. In a few billion years the Milky Way may absorb them completely. So someday our corner of the cosmos could be pretty ordinary after all.

—John Matson

[The above text is a transcript of this podcast.]

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