Astronomers have tracked the location of perhaps the most unique fast radio burst to date. Not only is it the closest extragalactic signal detected but it is coming from a rather unusual location, different than most other assumed sources of FRBs. This discovery sheds light on new potential reasons for the existence of these bursts.
10 Things you need to know about the nearest extragalactic fast radio burst
1. Scientists have failed to solve the mystery of fast radio bursts since the first one was discovered in old data in 2007. Each one of these signals lasts milliseconds and has the energy our Sun emits in a whole year or more.
2. Scientists have been detecting these signals for years although their apparent brief duration makes it nearly impossible to track them to their sources. Even if they succeed, it never is a certain point in space but rather galaxies or clusters.
3. Such is the case of FRB 20200120E, which was originally detected in January 2020. It has been tracked to a globular cluster located in a galaxy 11.7 million light-years away, making it an extragalactic signal. That is, when it comes from outside the Milky Way galaxy.
4. The location is unusual because the globular cluster consists of old stars, the type of celestial objects that are not typically linked to FRBs.
5. To date, this is the nearest extragalactic fast radio burst and there is a significant difference in distance from the next-closest one, more than 400 million light-years away. This one has been tracked to a nearby galaxy – M81, known to be one of the brightest galaxies in the sky.
6. The most important characteristic of FRB 20200120E is that it is a repeating signal, which makes it one of few from about 1000 detected so far. This was the only reason astronomers were able to track it to its source.
7. The fast radio bursts were not significantly bright but since they were repeating, astronomers identified the source direction.
8. It appeared that the signals had not been traveling a large distance. Scientists were even considering the possibility that the source might have been within the Milky Way. For example, last year, astronomers finally tracked down an FRB to a magnetar within our own galaxy.
This proved to be clear evidence that magnetars should be considered the most probable source for these signals in space. Yet, the extragalactic fast radio burst is coming from a completely different place.
9. Astronomers do not normally search for neutron stars or magnetars in globular clusters because these objects tend to form from stars with great masses which are typically not present in clusters with old stars with low masses. Yet, there are cases when rapidly rotating neutron stars have been found in such, caused by the interaction of stars within the densely populated globular clusters.
10. With this said, the source of the extragalactic fast radio burst will likely not be a magnetar. There are several theories, including the interactions between a neutron star and a white dwarf, or even an accreting black hole. The problem is that there is no X-ray or gamma-ray activity that would support the ideas of these phenomena.
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• Drake, N. (2021, May 27). Mysterious radio burst from space is unusually close-and especially baffling. Science.
• Kirsten, F., Marcote, B., Nimmo, K., Hessels, J. W. T., Bhardwaj, M., Tendulkar, S. P., Keimpema, A., Yang, J., Snelders, M. P., Scholz, P., Pearlman, A. B., Law, C. J., Peters, W. M., Giroletti, M., Hewitt, D. M., Bach, U., Bezukovs, V., Burgay, M., Buttaccio, S. T., … Vlemmings, W. (2021, May 24). A repeating fast radio burst source in a globular cluster. arXiv.org.
• Starr, M. (n.d.). We’ve Detected the Closest Extragalactic FRB Yet, but It’s From an Unexpected Place. ScienceAlert.