The Sun regularly produces energetic outbursts of electromagnetic radiation called solar flares. When these flares are accompanied by flows of plasma, they are known as coronal mass ejections (CMEs). Now, astronomers at the Netherlands Institute for Radio Astronomy (ASTRON) have spotted a similar event occurring on a star other than our Sun – the first unambiguous detection of a CME outside our solar system.

Astronomers have long predicted that the radio emissions associated with CMEs from other stars should be detectable. However, Joseph Callingham, who led the ASTRON study, says that he and his colleagues needed the highly sensitive low-frequency radio telescope LOFAR – plus ESA’s XMM-Newton space observatory and “some smart software” developed by Cyril Tasse and Philippe Zarka at the Observatoire de Paris-PSL, France – to find one.

A short, intense radio signal from StKM 1-1262

Using these tools, the team detected short, intense radio signals from a star located around 40 light-years away from Earth. This star, called StKM 1-1262, is very different from our Sun. At only around half of the Sun’s mass, it is classed as an M-dwarf star. It also rotates 20 times faster and boasts a magnetic field 300 times stronger. Nevertheless, the burst it produced had the same frequency, time and polarization properties as the plasma emission from an event called a solar type II burst that astronomers identify as a fast CME when it comes from the Sun.

“This work opens up a new observational frontier for studying and understanding eruptions and space weather around other stars,” says Henrik Eklund, an ESA research fellow working at the European Space Research and Technology Centre (ESTEC) in Noordwijk, Netherlands, who was not involved in the study. “We’re no longer limited to extrapolating our understanding of the Sun’s CMEs to other stars.”

Implications for life on exoplanets

The high speed of this burst – around 2400 km/s – would be atypical for our own Sun, with only around 1 in every 20 solar CMEs reaching that level. However, the ASTRON team says that M-dwarfs like StKM 1-1262 could emit CMEs of this type as often as once a day.

According to Eklund, this has implications for extraterrestrial life, as most of the known planets in the Milky Way are thought to orbit stars of this type, and such bursts could be powerful enough to strip their atmospheres. “It seems that intense space weather may be even more extreme around smaller stars – the primary hosts of potentially habitable exoplanets,” he says. “This has important implications for how these planets keep hold of their atmospheres and possibly remain habitable over time.”

Erik Kuulkers, a project scientist at XMM-Newton who was also not directly involved in the study, suggests that this atmosphere-stripping ability could modify the way we hunt for life in stellar systems akin to our Solar System. “A planet’s habitability for life as we know it is defined by its distance from its parent star – whether or not it sits within the star’s ‘habitable zone’, a region where liquid water can exist on the surface of planets with suitable atmospheres,” Kuulkers says. “What if that star was especially active, regularly producing CMEs, however? A planet regularly bombarded by these ejections might lose its atmosphere entirely, leaving behind a barren uninhabitable world, despite its orbit being ‘just right’.

Kuulkers adds that the study’s results also contain lessons for our own Solar System. “Why is there still life on Earth despite the violent material being thrown at us?” he asks. “It is because we are safeguarded by our atmosphere.”

Seeking more data

The ASTRON team’s next step will be to look for more stars like StKM 1-1262, which Kuulkers agrees is a good idea. “The more events we can find, the more we learn about CMEs and their impact on a star’s environment,” he says. Additional observations at other wavelengths “would help”, he adds, “but we have to admit that events like the strong one reported on in this work don’t happen too often, so we also need to be lucky enough to be looking at the right star at the right time.”

For now, the ASTRON researchers, who report their work in Nature, say they have reached the limit of what they can detect with LOFAR. “The next step is to use the next generation Square Kilometre Array, which will let us find many more such stars since it is so much more sensitive,” Callingham tells Physics World.

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The Sun frequently ejects high-energy bursts of plasma that then travel through interplanetary space. These so-called coronal mass ejections (CMEs) are accompanied by strong magnetic fields, which, when they interact with the Earth’s atmosphere, can trigger solar storms that can severely damage satellite systems and power grids.

In the early days of the solar system, the Sun was far more active than it is today and ejected much bigger CMEs. These might have been energetic enough to affect our planet’s atmosphere and therefore influence how life emerged and evolved on Earth, according to some researchers.

Since it is impossible to study the early Sun, astronomers use proxies – that is, stars that resemble it. These “exo-suns” are young G-, K- and M-type stars and are far more active than our Sun is today. They frequently produce CMEs with energies far larger than the most energetic solar flares recorded in recent times, which might not only affect their planets’ atmospheres, but may also affect the chemistry on these planets.

Until now, direct observational evidence for eruptive CME-like phenomena on young solar analogues has been limited. This is because clear signatures of stellar eruptions are often masked by the brightness of their host stars and flares on these. Measurements of Doppler shifts in optical lines have allowed astronomers to detect a few possible stellar eruptions associated with giant superflares on a young solar analogue, but these detections have been limited to single-wavelength data at “low temperatures” of around 10⁴ K. Studies at higher temperatures have been few and far between. And although scientists have tried out promising techniques, such as X-ray and UV dimming, to advance their understanding of these “cool” stars, few simultaneous multi-wavelength observations have been made.

A large Carrington-class flare from EK Draconis

On 29 March 2024, astronomers at Kyoto University in Japan detected a large Carrington-class flare – or superflare – in the far-ultraviolet from EK Draconis, a G-type star located approximately 112 light-years away from the Sun. Thanks to simultaneous observations in the ultraviolet and optical ranges of the electromagnetic spectrum, they say they have now been able to obtain the first direct evidence for a multi-temperature CME from this young solar analogue (which is around 50 to 125 million years old and has a radius similar to the Sun).

The researchers’ campaign spanned four consecutive nights from 29 March to 1 April 2024. They made their ultraviolet observations with the Hubble Space Telescope and the Transiting Exoplanet Survey Satellite (TESS) and performed optical monitoring using three ground-based telescopes in Japan, Korea and the US.

They found that the far-ultraviolet and optical lines were Doppler shifted during and just before the superflare, with the ultraviolet observations showing blueshifted emission indicative of hot plasma. About 10 minutes later, the optical telescopes observed blueshifted absorption in the hydrogen Hα line, which indicates cooler gases. According to the team’s calculations, the hot plasma had a temperature of 100 000 K and was ejected at speeds of 300–550 km/s, while the “cooler” gas (with a temperature of 10 000 K) was ejected at 70 km/s.

“These findings imply that it is the hot plasma rather than the cool plasma that carries kinetic energy into planetary space,” explains study leader Kosuke Namekata. “The existence of this plasma suggests that such CMEs from our Sun in the past, if frequent and strong, could have driven shocks and energetic particles capable of eroding or chemically altering the atmosphere of the early Earth and the other planets in our solar system.”

“The discovery,” he tells Physics World, “provides the first observational link between solar and stellar eruptions, bridging stellar astrophysics, solar physics and planetary science.”

Looking forward, the researchers, who report their work in Nature Astronomy, now plan to conduct similar, multiwavelength campaigns on other young solar analogues to determine how frequently such eruptions occur and how they vary from star to star.

“In the near future, next-generation ultraviolet space telescopes such as JAXA’s LAPYUTA and NASA’s ESCAPADE, coordinated with ground-based facilities, will allow us to trace these events more systematically and understand their cumulative impact on planetary atmospheres,” says Namekata.

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When a star rapidly accumulates gas and dust during its early growth phase, it’s called an accretion burst. Now, for the first time, astronomers have observed a planet doing the same thing. The discovery, made using the European Southern Observatory’s Very Large Telescope (VLT) and the James Webb Space Telescope (JWST), shows that the infancy of certain planetary-mass objects and that of newborn stars may share similar characteristics.

In their study, which is detailed in The Astrophysical Journal Letters, astronomers led by Víctor Almendros-Abad at Italy’s Palermo Astronomical Observatory; Ray Jayawardhana of Johns Hopkins University in the US; and Belinda Damian and Aleks Scholz of the University of St Andrews, UK, focused on a planet known as Cha1107-7626. Located around 620 light-years from Earth, this planet has a mass approximately five to 10 times that of Jupiter. Unlike Jupiter, though, it does not orbit around a central star. Instead, it floats freely in space as a “rogue” planet, one of many identified in recent years.

An accretion burst in Cha1107-7626

Like other rogue planets, Cha1107-7626 was known to be surrounded by a disk of dust and gas. When material from this disk spirals, or accretes, onto the planet, the planet grows.

What Almendros-Abad and colleagues discovered is that this process is not uniform. Using the VLT’s XSHOOTER and the NIRSpec and MIRI instruments on JWST, they found that Cha1107-7626 experienced a burst of accretion beginning in June 2025. This is the first time anyone has seen an accretion burst in an object with such a low mass, and the peak accretion rate of six billion tonnes per second makes it the strongest accretion episode ever recorded in a planetary-mass object. It may not be over, either. At the end of August, when the observing campaign ended, the burst was still ongoing.

An infancy similar to a star’s

The team identified several parallels between Cha1107-7626’s accretion burst and those that young stars experience. Among them were clear signs that gas is being funnelled onto the planet. “This indicates that magnetic fields structure the flow of gas, which is again something well known from stars,” explains Scholz. “Overall, our discovery is establishing interesting, perhaps surprising parallels between stars and planets, which I’m not sure we fully understand yet.”

The astronomers also found that the chemistry of the disc around the planet changed during accretion, with water being present in this phase even though it hadn’t been before. This effect has previously been spotted in stars, but never in a planet until now.

“We’re struck by quite how much the infancy of free-floating planetary-mass objects resembles that of stars like the Sun,” Jayawardhana says. “Our new findings underscore that similarity and imply that some objects comparable to giant planets form the way stars do, from contracting clouds of gas and dust accompanied by disks of their own, and they go through growth episodes just like newborn stars.”

The researchers have been studying similar objects for many years and earlier this year published results based on JWST observations that featured a small sample of planetary-mass objects. “This particular study is part of that sample,” Scholz tells Physics World, “and we obtained the present results because Victor wanted to look in detail at the accretion flow onto Cha1107-7626, and in the process discovered the burst.”

The researchers say they are “keeping an eye” on Cha1107-7626 and other such objects that are still growing because their environment is dynamic and unstable. “More to the point, we really don’t understand what drives these accretion events, and we need detailed follow-up to figure out the underlying reasons for these processes,” Scholz says.

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