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Melissa Halford, a lecturer in Auburn University’s Physics Department in the College of Sciences and Mathematics, comments below on recent reports of repeating radio signals that are coming from outside of our galaxy. She notes that astronomers don’t quite know what is causing this to occur, but several possibilities have been proposed.

What might be causing these repeating radio signals that are coming from outside of our galaxy?

Astronomers don’t yet know what causes fast radio bursts, but several possibilities have been proposed. Their brightness and location outside our galaxy mean that they must be very energetic events. Some possible explanations involve compact objects like neutron stars. Because the bursts of radiation are very rapid, they are thought to come from something small—large objects are unlikely to produce this kind of signal because the time it takes for light to travel across the object is longer than the duration of the burst. The repeating nature of some of these signals may relate to the orbit of an object. But it’s still a mystery.

Is it uncommon for us to detect on Earth radio signals that are being sent from another galaxy?

Radio signals from other galaxies aren’t unusual—there are numerous astrophysical processes that produce radio waves. What is unusual about fast radio bursts is how luminous they are. In that sense, these kinds of signals do seem to be uncommon.

Is there more the scientific community could be doing to seek out possible signals coming from space, and if so what might we be able to learn from a greater collection of such data?

The number of detected fast radio bursts is still relatively small and there’s a lot that we don’t know about them. Building up a larger sample of detections is a critical step toward answering questions about these events, including the obvious question of what causes them. More data will allow scientists to see patterns in how these events are similar to each other and how they differ. Continued searches for these signals will aid that effort.