This article was originally published Conversation. The publication contributed to an article on Space.com Expert voices: Op-Ed and Insight.
If you look in the southern sky you can point to the “pointer” stars, the Southern Cross. One of these pointers is Alpha Centauri, which is actually a pair of sun-like stars that are close to each other to tell apart by eye.
There is also a third member of the Alpha Centauri system: Proxima Centauri (proxima sen for short), which orbits the two central stars in a wide orbit. This is the closest neighborhood to the sun, just 4.2 light years away.
It is possible that a planet of Proxima Sen is suitable for life. However, we have recently found the signature of the terrible space weather from Proxima Sen, which indicates that the orbiting planet could be blasted by hazardous particles and magnetic fields.
Our neighbor is not like the sun
Our Sun is a relatively incredible yellow dwarf star that eclipses the only known life-planet in the universe: our Earth.
Proxima sen is very different. It is a red dwarf star with a diameter of only 15% of the Sun, and a surface temperature of 3,000 K (degrees Kelvin), which is colder than 6,000 K of the Sun.
Because Proxima Sen is relatively nice, the “Goldilocks X zone” of orbits around it – where the temperature is right for liquid water – is about one-twentieth of the distance from the Sun to Earth. We are interested in the planets in the star’s Goldilocks realm because we know that liquid water is necessary for life.
read more: Say hello to the nearest exoplanet neighbor: Proxima Centauri B.
We know that Proxima Sen has at least two planets: Proxima Sen B, a rocky “super-earth” located in the middle of the Goldilocks zone of Proxima Sen, and Proxima Sen C, located next to “Sub Neptune”.
For years astronomers have thought that planets like Proxima San B could be a life-threatening home because they are so close to their host stars. Many red dwarf stars produce frequent, powerful flares – intense explosions of radiation moving through space. If planets like Proxima Sen B do not have protective features such as a thick atmosphere or a strong magnetic field, they will be exposed to dangerous levels of radiation.
But what about the weather around these stars?
The red dwarf’s “space weather” is another important factor in determining how hospitable they are for life. When flares are involved in intense bursts of light, space weather events mean magnetic field and charged particles from the star can interact directly with the planets.
The most exciting space weather events are known as coronal mass ejection (or CME). This massive burst star escapes the atmosphere and travels millions of kilometers per hour.
If the weather conditions in space are extreme enough, the planet’s atmosphere can be blown up and its magnetic field pushed backwards, exposing the surface to lethal flare radiation.
CME has been explored around the Sun since the 1970s, but it is very difficult to detect space weather events around distant stars.
For weather updates, tune in to the radio
CME on the Sun Radio produces characteristic explosions of sound, such as “type II” and “type IV” explosions. By finding similar signatures on other stars, we can identify the CMEs of diagonal stars.
In early 2019, we showcased our telescopes on Proxima Sen for 11 nights. We used CSIRO’s new radio telescope, the Australian Australian Square Kilometer Array Pathfinder (ASKAP), as well as the Zedco Telescope, the ANU 2.3M Telescope and NASA’s Transiting Exoplanet Survey Satellite (TSS).
Our goal was to find the signature of the CME.
On the night of May 2, 2019, we observed a giant optical flame with an estimated total energy radiation output of 16 septilian joules. (This is Australia’s current electricity generation, valued at about 17 million years.) At the Sun, this only happens once every year or two decades. But at Proxima Sen, they happen every few weeks.
Using ASKAP, we observed a spectacular sequence of intense radio explosions.
With the astonishing details revealed with ASKAP, we can see that we have found an excellent example of a solar-like type IV radio burst from another star to date.
This explosion of radio waves indicates that the atmosphere in the space around Proxima Sen is quite violent.
‘A swallow doesn’t make summer’
In 1859, British astronomers Richard Carrington and Richard Hodgson made the first observations of a solar flare, followed by a massive space weather storm called the “Carrington Event”. We now know that this hurricane was caused by a huge coronal mass ejection hitting the earth.
Carrington noted the coincidence between these extraordinary events, but cautioned to draw a connection between them, saying, “One swallow does not make summer.” Now we find ourselves in a situation similar to Carrington.
We have seen the signature of the radio hit indicating CME coming out of Proxima Sen. But to confirm the relation of these stellar radio explosions to the CME, we need to collect information of other wavelengths. Once we can do this, we should immediately know how dangerous it is to live next to a star like Proxima Centauri.
read more: Is Alpha Centauri the perfect place to explore life elsewhere?
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