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This article originally appeared on The conversation. The post contributed to the article at Space.com’s Expert voices: Op-Ed & Insights.
If you look in the southern sky, you can see the “pointer” stars, pointing to the southern cross. One of those pointers is Alpha Centauri, which is actually a pair of Sun-like stars that are too close to each other to be seen with the naked eye.
There is also a third member of the Alpha Centauri system: Proxima Centauri (Proxima Cen for short), which encircles the two central stars in a wide orbit. It is the closest neighbor to the Sun, at a distance of only 4.2 light years.
It is possible that one of the planets in Proxima Cen is suitable for life. However, we recently detected the signature of fierce space weather from Proxima Cen, implying that an orbiting planet could be blown up with dangerous particles and magnetic fields.
Our neighbor is not like the sun
Our sun is a relatively unremarkable yellow dwarf star, home to the only known life-carrying planet in the Universe: our Earth.
Proxima Cen is very different. It is a red dwarf star, with a diameter of only 15% that of the sun, and a surface temperature of 3000 K (degrees Kelvin), much cooler than the 6000K of the sun.
Because Proxima Cen is relatively cool, the “Goldilocks zone” of the orbits around it – where the temperature is just right for liquid water – is about one-twentieth of the distance between the Earth and the sun. We are interested in the planets in the Goldilocks zone of a star because liquid water is necessary for life as we know it.
Read more: Say hello to the closest exoplanet neighbor to Earth: Proxima Centauri b
We know that Proxima Cen has at least two planets: Proxima Cen b, a rocky “super-Earth” located in the middle of the Goldilocks area of Proxima Cen, and Proxima Cen c, a “sub-Neptune” located further away.
For years, astronomers have suspected that planets like Proxima Cen b could be life-threatening hotbeds because they are so close to their host stars. Many red dwarf stars produce frequent, powerful flares – bursts of intense radiation traveling through space. If planets like Proxima Cen b do not have protective characteristics such as a thick atmosphere or a strong magnetic field, they would be exposed to dangerous levels of radiation.
But what is the weather like around these stars?
Another important factor in determining how welcoming they are to life is the “space weather” of red dwarfs. While flares involve intense bursts of light, space weather events mean that the star’s magnetic field and charged particles can interact directly with the planets.
The most energetic space weather events are known as coronal mass ejections (or CMEs). These massive eruptions escape a star’s atmosphere and travel through space at millions of kilometers per hour.
If space weather conditions are extreme enough, the planetary atmosphere can be blown out and its magnetic field can be pushed back, leaving the surface exposed to deadly torch radiation.
CMEs have been detected around the Sun since the 1970s, but detecting space weather events around distant stars is much more difficult.
For weather updates, tune in to the radio
CMEs on the Sun produce characteristic bursts of radio noise, such as “type II” and “type IV” bursts. By detecting similar signatures on other stars, we can indirectly identify stellar CMEs.
In early 2019, we pointed our telescopes at Proxima Cen for 11 nights. We used CSIRO’s new radio telescope, the Australian Square Kilometer Array Pathfinder (ASKAP), as well as NASA’s Zadko telescope, ANU 2.3m telescope, and Transiting Exoplanet Survey Satellite (TESS).
Our goal was to detect the signature of a CME.
On the night of May 2, 2019, we observed a massive optical flare with an estimated total energy production of 16 septillion joules. (This is almost 17 million years of Australia’s current electricity production.) On the Sun, such large flares only occur once every ten or two years. But on Proxima Cen, they happen every few weeks.
Using ASKAP, we observed a spectacular sequence of intense radio bursts.
With the amazing details revealed with ASKAP, we were able to see that we had detected the best example of a solar-type type IV radio burst from another star to date.
This explosion of radio waves implies that the space weather environment around Proxima Cen is quite violent.
‘A shallow do not do the spring’
In 1859, British astronomers Richard Carrington and Richard Hodgson made the first observations of a solar flare, which was followed by a huge space weather storm called the “Carrington Event”. We now know that the storm was caused by a massive coronal mass ejection hitting the Earth.
Carrington noted the coincidence between these extraordinary events, but was careful to link them, famously stating “a swallow doesn’t make a summer.” We now find ourselves in a similar situation at Carrington.
We observed a radio burst signature involving a CME eruption from Proxima Cen. But to confirm the relationship of these radio stellar bursts to CMEs, we need to harness information from other wavelengths. Once we can do that, soon we should know exactly how dangerous it is to live next to a star like Proxima Centauri.
Read more: Is Alpha Centauri the right place to seek life elsewhere?
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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