Solar System Chatter

The Light Echoes Settle It

NASA/CXC/U. Wisconsin/S. Heinz
NASA/CXC/U. Wisconsin/S. Heinz
Measuring distances over the vast reaches of the galaxy can be difficult for astronomers, but sometimes they get a little help. These huge rings of light (see image) are called “light echoes,” and emanate from an X-ray blast produced by the double star system Circinus X-1 in 2013. The X-ray energy is now reflecting off nearby dust. NASA’s Chandra X-Ray Observatory has been taking sensitive measurements of the system, which has allowed astronomers to triangulate its location, similar to the way bats use sonar. The results have settled a debate on its distance: 30,700 light years away, twice as far as a previously published distance.

Heather Goss is the Departments Editor at Air & Space.

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chandra, x-ray