Extreme flare on young Sun-like star signals wild environment for exoplanet development

Astronomers have detected an extreme flare from a young star that became more than a hundred times brighter in just a few hours. This discovery offers new insights into the behavior of young Sun-like stars early in their lives and their impact on the development of each of their newborn planets.

Researchers at the Smithsonian Astrophysical Observatory (SAO), part of the Center for Astrophysics | Harvard & Smithsonian (CfA) made this discovery using submillimeter array (SMA) observations of HD 283572, a star 40% more massive than the sun located about 400 light years away. The SMA is a collection of telescopes located on Mauna Kea in Hawaii, designed specifically to detect millimeter wave light.

Less than 3 million years old, HD 283572 is more than a thousand times younger than the sun, the age when Earth-like planets begin to form around stars. A team led by Dr Joshua Bennett Lovell, an SAO astronomer and SMA fellow at CfA, was using the SMA to search for dusty material produced during the formation of young planets that have a faint but detectable glow at millimeter wavelengths , or radio. . However, they found something completely different.

“We were surprised to see an extraordinarily bright flare coming from an ordinary young star,” Lovell said. “Flashes at these wavelengths are rare, and we didn’t expect to see anything other than the faint glow of planet-forming dust.”

Stellar flares can increase a star’s brightness by tens or hundreds at different wavelengths of light. As stars rotate, their magnetic fields can twist and develop regions of increased magnetic energy. Like an over-tightened spring, this stored magnetic energy must eventually be released. In the case of stars, this produces intense accelerations of charged particles passing through their surfaces.

A challenge for observing such flares is that it is never clear precisely when a star might next erupt, and capturing them can be particularly difficult at millimeter wavelengths.

“HD 283572 appeared dormant for months before we observed its eruption,” Lovell said. “Every time we pointed the SMA at the star after this flare, we saw nothing. Our results confirm that these flares are rare at millimeter wavelengths but can be extremely powerful for stars at this young age.”

The team measured the energy of HD 283572’s flare and found that over a 9-hour period, it released about a million times more energy than any millimeter-scale flare observed on neighboring stars closest to the Sun. This is one of the most powerful eruptions of its type reported.

This is a huge event, equivalent to expending Earth’s entire nuclear arsenal in about a millisecond, over and over again, for almost half a day! Dr. Garrett Keating, second author of the study and SMA project scientist. “If “If we take into account the wavelengths of light from the star that the SMA did not observe, we think it would have could even have been several times more energetic.”

However, with only one eruption detected, it is still unclear what exactly triggered the event.

“It’s a real puzzle, and a whole host of mechanisms could be at play. Interactions with unseen companion stars or planets or the periodic activity of starspots are two possibilities, but what is beyond doubt, that’s the power of this event,” Keating said. . “Any potential planets growing in this system would have been hammered by the intense power of this eruption. I wouldn’t want to grow up there!”

The star’s young age and sun-like nature provide essential clues about the typical environments that any young, developing planet like Earth may experience. Powerful flares can limit the growth of planetary atmospheres or severely damage already developed atmospheres.

Further observations are underway to understand how often HD 283572 experiences flaring activity and whether flares around this type of young star inhibit the growth of planetary atmospheres.

“We are currently carrying out a new SMA campaign to study young stars similar to HD283572. How often do they burst and what are their typical properties? By combining the SMA data with longer wavelength observations, we are also in able to probe the physics of “Rashes and their emission mechanisms. I worked on this using archival data from the Very Large Array,” said Ramisa Akther Rahman, an undergraduate student at the College of William and Mary, who was a 2023 summer intern with Dr. Lovell at SAO .Research experience program for undergraduate students.

The results are published in Letters from the astrophysical journal.