Astronomers have detected a bright, long-duration optical flare accompanied by intense radio bursts from Proxima Centauri, the Sun’s nearest stellar neighbor. Their results are an important step to using radio signals from distant stars to effectively produce space weather reports.
Proxima Centauri, the smallest member of the Alpha Centauri system, is an M5.5-type star located 4.244 light-years away in the southern constellation of Centaurus.
The star has a measured radius of 14% the radius of the Sun, a mass of about 12% solar, and an effective temperature of only around 3,050 K (2,777 degrees Celsius, or 5,031 degrees Fahrenheit).
Proxima Centauri has a very slow rotation of 83 days and a long-term activity cycle with a period of approximately 7 years. Its habitable zone ranges from distances of 0.05 to 0.1 AU.
“Astronomers have recently found there are two Earth-like rocky planets around Proxima Centauri, one within the habitable zone where any water could be in liquid form,” said lead author Dr. Andrew Zic, an astronomer in the School of Physics at the University of Sydney and CSIRO Astronomy and Space Science.
“But given Proxima Centauri is a cool, small red-dwarf star, it means this habitable zone is very close to the star; much closer in than Mercury is to our Sun.”
“What our research shows is that this makes the planets very vulnerable to dangerous ionizing radiation that could effectively sterilize the planets.”
Dr. Zic and colleagues used CSIRO’s Australian Square Kilometre Array Pathfinder (ASKAP) telescope, the Zadko Telescope, and NASA’s Transiting Exoplanet Survey Satellite to monitor Proxima Centauri at optical and radio wavelengths.
They detected a bright, long-duration optical flare, accompanied by a series of intense, coherent radio bursts.
These detections include the first example of a stellar radio burst temporally coincident with a flare, strongly indicating a causal relationship between these events.
“Our own Sun regularly emits hot clouds of ionized particles during what we call coronal mass ejections,” Dr. Zic said.
“But given the Sun is much hotter than Proxima Centauri and other red-dwarf stars, our habitable zone is far from the Sun’s surface, meaning the Earth is a relatively long way from these events.”
“Further, the Earth has a very powerful planetary magnetic field that shields us from these intense blasts of solar plasma.”
“M-dwarf radio bursts might happen for different reasons than on the Sun, where they are usually associated with coronal mass ejections.”
“But it’s highly likely that there are similar events associated with the stellar flares and radio bursts we have seen in this study.”
“Our research helps understand the dramatic effects of space weather on solar systems beyond our own,” said co-author Dr. Bruce Gendre, an astronomer at the University of Western Australia and the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav).
“Understanding space weather is critical for understanding how our own planet biosphere evolved — but also for what the future is.”
“This is an exciting result from ASKAP,” said co-author Professor Tara Murphy, deputy head of the School of Physics at the University of Sydney and an astronomer at OzGrav.
“The incredible data quality allowed us to view the stellar flare from Proxima Centauri over its full evolution in amazing detail.”
“Most importantly, we can see polarized light, which is a signature of these events. It’s a bit like looking at the star with sunglasses on.”
A paper on the findings was published in the Astrophysical Journal.