An international team involving UCL astronomers has observed the first clear signal of a giant stellar eruption from a star beyond our solar system.
The stellar eruption is analogous to a coronal mass ejection (CME) seen on our Sun, and implies a devastating impact for any planet unlucky enough to orbit the star.
The study, led by ASTRON (Netherlands Institute for Radio Astronomy) and the Observatoire de Paris-PSL, found the short, intense burst of radio waves from a nearby red dwarf star, located just 130 light years away, using Europe’s powerful LOFAR radio telescope.
Coronal mass ejections are large eruptions of magnetised plasma from stars and play a major role in shaping space weather in our solar system - such as driving the beautiful aurorae we see on Earth. While such events have long been expected to occur on other stars, this is the first time one has been observed through its characteristic radio signal. The study was published in Nature.
Co-author Dr Hamish Reid, of UCL’s Mullard Space Science Laboratory, said: "This is the first direct observation of stellar space weather. About 130 light years away, a stellar coronal mass ejection from an M dwarf star caused a shock wave which produced a radio signal so luminous, we could detect it from the Earth.
"These expulsions of plasma and magnetic field can affect planetary atmospheres and may affect the building blocks of life on other planets. In our search for habitable worlds in other stellar systems, we must consider the strength of the local space weather.
"If this burst of plasma had come from the Sun, the radio signal it produced would be 10,000 times brighter than anything of this kind we have seen before. Such an event would likely have disastrous effects if it had hit the Earth. Fortunately, our Sun will not produce a coronal mass ejection like this as the solar magnetic field that drives these events is weaker than those from M dwarf stars."
Co-author Dr Joe Callingham, based at ASTRON, said: "For the first time, we have evidence that hot plasma has been ejected from another star into interplanetary space. This gives us a chance to move beyond theory based solely on the Sun.
"We show that this eruption would be devastating for a planet around such a star,. The CME has the power to compress an Earth-like magnetosphere all the way down to the planet’s surface, temporarily removing the planet’s atmospheric protection. This means such eruptions could determine whether a planet is potentially habitable."
Red dwarf stars, which are 10% to 50% the mass of the Sun, are the most common hosts of Earth mass planets. But because their habitable zones, where liquid water could exist on their surface, are so close in, orbiting worlds are likely subjected to far more intense stellar storms than Earth.
Co-lead author Dr Cyril Tasse of the Observatoire de Paris-PSL said: "This discovery shows us that violent space weather is not unique to our Sun. We now know planets around small stars are facing frequent, powerful blasts. Thanks to the advanced data-processing methods developed at the Observatoire de Paris-PSL, we now have a way to measure just how extreme those conditions are."
The finding opens a new window on to the study of space weather in other solar systems, with major implications for the search for a habitable planet. Upcoming observatories such as the Square Kilometre Array will allow astronomers to uncover many more of these stellar eruptions and understand how they shape the fate of exoplanets.
Co-author Professor Martin Hardcastle, of the University of Hertfordshire, said: "Our findings tell us that some nearby stars are simply too violently active for their planets to support life. It is possible that this behaviour is common among red dwarf stars, but we don’t yet know for sure.
"What we have shown is that such extreme activity is possible - and that opens up a new way to identify which stars are most likely to host habitable planets."
LOFAR is operated by ASTRON as a European Research Infrastructure Consortium (ERIC).
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