New paper observes explosive starburst that confirms coronal mass ejections pose threat to exoplanets

Coronal mass ejections from the sun are among the most violent events in our solar system — so much so that with one approaching Earth today, NASA and Blue Origin called off the second launch attempt of the twin ESCAPADE spacecraft, which coincidentally are bound for Mars to help scientists determine if these explosive, energetic bursts of magnetized plasma were responsible for stripping the red planet of its atmosphere.

They very well could be, based on a paper published Wednesday in the journal Nature about the first confirmed sighting of a coronal mass ejection (CME) from a star outside our solar system.

Joe Callingham and his colleagues at the Netherlands Institute for Radio Astronomy (ASTRON) near Groningen harnessed a novel combination of their own ground-based radio telescope array and a space-based X-ray telescope. They say that these observations confirm the long-suspected theory that CMEs are not a phenomenon limited to our own sun — and therefore pose a threat to the atmospheres of exoplanets orbiting other stars.

Such an eruption “would be devastating for a planet [orbiting] around such a star,” Callingham said in a post about the research on ASTRON’s website. “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.”

Until now, astronomers have only been able to infer that other stars have experienced plasma eruptions via techniques that include measuring the dimming of a star’s light emissions in the extreme ultraviolet and X-ray bands. But the electron-and-proton plasma of a CME is not bright enough at these wavelengths, the ASTRON researchers write, to determine if a plasma disturbance is contained within a star’s magnetosphere or if it actually erupted into deep space.

Another reason for uncertainty is that one of the most common type of stars to host orbiting exoplanets are M dwarfs, which are much smaller and less luminous than our sun. “The magnetic field strengths on other stars are very different to that of the Sun, being more than 1000 times stronger on some M dwarfs,” Callingham told me by email. “It was thought that maybe this means the magnetic field would ‘catch’ any CME that occurs, such that it would never hit an exoplanet but stay near the star.”

To find out if that was the case, his team decided to look for the telltale sign of a hot magnetic plasma erupting out into deep space: a shock wave. They harnessed ASTRON’s Low Frequency Array, or LOFAR, a widely distributed set of radio telescope ground antennas, to scan 86,000 stars. Using data processing techniques developed by Callingham’s co-authors Cyril Tasse and Philippe Zarka at the Observatoire de Paris, they found something in one of their eight-hour northern sky sweeps: a 2-minute-long, sub-300-megahertz radio burst with a “striking similarity” to shockwave signatures of solar CMEs.

They then trained the European Space Agency’s XMM-Newton X-ray telescope, which is in a high elliptical orbit around Earth, on the radio source to assess the temperature, brightness and motion of the phenomenon — and found it was indeed characteristic of a CME shooting way out into space. The source star was an M dwarf 130 light years away, half the mass of our sun, rotating 20 times faster and with a magnetic field 300 times stronger.

The finding may invoke a reconsideration of the habitable “Goldilocks” zone for exoplanets around particularly active stars and “has important implications for how these planets keep hold of their atmospheres and possibly remain habitable over time” wrote Henrik Eklund, an ESA researcher in the Netherlands, in agency’s commentary on the research performed using its space-based X-ray telescope.

Exciting as this confirmation is for astronomers, though, Callingham told me, it may dismay some would-be spacefarers wanting to settle on exoplanets: “It may be that the most common stars in the galaxy are not good hosts and we will not find Earth 2.0 around them. And showing CMEs can erupt from them makes them even more godforsaken than before.”