Exoplanet Proxima Centauri b may not be the most suitable place to search for alien life after all.
While observing the red dwarf Proxima Centauri with nine ground and space instruments in 2019, astronomers recorded a flash, which turned out to be one of the most powerful flares ever recorded. The burst lasted only a few seconds, but during this period the star increased its brightness in the ultraviolet range by 14 thousand times.
What is Proxima Centauri?
Proxima Centauri is our closest neighboring star, located 1.3 parsecs (4.2 light-years) away from the center of the Solar System. It belongs to the class of red dwarfs. A planet rotates near it, potentially with a mass close to the mass of the Earth.
The distance between it and the star is 0.05 astronomical units, and the equilibrium temperature of its surface is about 230 Kelvin (minus 40 degrees Celsius). Recently, researchers have discovered a second more massive planet in the system, in a wider orbit.
What is a red dwarf outbreak?
Low-mass red dwarfs, or stars of spectral class M, are the most common luminaries of the Milky Way. In addition, Earth-sized planets often revolve around them, with temperatures that hypothetically would allow liquid water to exist on their surfaces.
However, M-dwarfs show higher levels of stellar activity and flares throughout their lives compared to sun-like stars. Such large repetitive flares and the energy particles released during them can destroy ozone in the planets’ atmospheres, raising questions about their viability.
Proxima Centauri demonstrates typical M-dwarf flares, so it is used as a reference to study the potential effects of the activity of such stars and strong stellar winds on exoplanets.
Proxima Centauri’s record-breaking flare
Researchers observed Proxima Centauri for 40 hours in April-July 2019 using nine ground-based and space-based telescopes operating at different radiation lengths.
On May 1, 2019, they witnessed an outbreak that lasted less than ten seconds. During this time, the ALMA telescope complex recorded a thousand-fold increase in the brightness of the star’s radio radiation, and the Hubble telescope recorded a 14,000 times increase in the brightness in the ultraviolet range.
The corresponding increase in the brightness of the radiation in the optical range, which was observed by TESS, was only 0.9% and peaked in about one minute.
What does this tell us about the star system?
Since exoplanet Proxima b was confirmed in 2016, Proxima Centauri has been considered as one of the most likely places where we could find either habitable planets or alien life. The reasons include its closeness to us, the fact that there is an Earth-like exoplanet, and the mysterious radio bursts that scientists have caught coming from its direction.
These factors have made Proxima Centauri a focal point for astronomical studies and probably the first exploration target for the distant future when our technological advancement allows us to send a mission there. Until then, scientists will continue monitoring and studying it.
The record-breaking flare captured in 2019, however, now suggests that Proxima Centauri’s extreme activity means that its nearest exoplanet may not be habitable. This, of course, does not mean that other undiscovered bodies with wider orbits could not be suitable for alien life. But in order to be sure, we need better observations.
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• MacGregor, M., Weinberger, A., Loyd, R., Shkolnik, E., Barclay, T., Howard, W., . . . Matthews, J. (2021, April 19). Discovery of an extremely short DURATION flare from Proxima Centauri using MILLIMETER THROUGH FUV Observations.
• NASA. (2021, April 23). Neighboring star’s bad Behavior: Large and FREQUENT FLARES.
• Strain, D. (2021, April 21). Humongous flare from sun’s nearest neighbor breaks records.
• Williams, M. (2021, April 23). A recent Megaflare shows that Proxima Centauri is not a nice place to live.