March 1, 2024

Extreme flare in young Sun-like stars signals wild environment for exoplanet development

An artist’s rendering of an outburst from HD 283572, a nearby young star. Credit: CfA/Melissa Weiss

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 insight into how young Sun-like stars behave early in their lives and its impact on the development of any of their newborn planets.

Researchers at the Smithsonian Astrophysical Observatory (SAO), part of the Center for Astrophysics | Harvard & Smithsonian (CfA), led 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 an array of telescopes on Mauna Kea in Hawaii designed specifically to detect millimeter-wave light.

At less than 3 million years old, HD 283572 is a thousand times younger than the Sun, at the age when Earth-like planets begin to form around stars. A team led by Dr. . However, they found something completely different.

“We were surprised to see an extraordinarily bright explosion from an ordinary young star,” said Lovell. “Explosions 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 factors of tens or hundreds at different wavelengths of light. As stars rotate, their magnetic fields can increase and regions of greater magnetic energy develop. Like a very tight spring, this stored magnetic energy must eventually be released. In the case of stars, this produces intense accelerations of charged particles, which explode through their surfaces.

One challenge with observing such explosions is that it’s never exactly clear when a star might explode next, and capturing them can be particularly challenging at millimeter wavelengths.

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

Extreme flare in young Sun-like stars signals wild environment for exoplanet development

Images of the young star HD 283572 and the surrounding countryside. The large image shows optical and infrared data from the Digitized Sky Survey (DSS), and HD 283572 is the bright star near the middle of the image, highlighted by a square. The insets show Submillimeter Array (SMA) images centered on HD 283572 taken on January 14 and 17, 2022, and March 27, 2023. The red font in the center panel shows the flash witnessed on January 17. The star was not detected by SMA on the other two days, nor in five other SMA observations not shown here. The DSS image is 20 arcminutes in diameter (2.3 light-years at HD 283572’s 400 light-year distance) and the SMA images are 24 arcseconds in diameter. Credit: CfA/JB Lovell et al.

The team measured the energy of HD 283572’s explosion and found that, over a 9-hour period, it released about a million times more energy than any millimeter explosion seen in the Sun’s closest neighboring stars. most powerful reported.

This was an immense event, equivalent to expending Earth’s entire nuclear arsenal in about a millisecond, repeatedly, for almost half a day!” said SAO researcher Dr. Garrett Keating, second author of the study and SMA project scientist “If we consider the wavelengths of light from the star that the SMA did not observe, we expect that it may have been many times more energetic.”

With only one outbreak detected, however, it remains unclear exactly what triggered the event.

“It’s a real puzzle, and there are a number of mechanisms that could be at play. Interactions with unseen companion stars or planets or periodic star spot activity are two possibilities, but what remains beyond doubt is how powerful this event was ” said Keating. . “Any potential planet developing in this system would have been hit by the intense power of this explosion. I wouldn’t want to grow there!”

The star’s young age and Sun-like nature provide essential clues about the typical environments that any young, developing planet like Earth might experience. Powerful explosions can limit the growth of planets’ atmospheres or seriously damage atmospheres that have already developed.

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

“We are running a new SMA campaign right now to study young stars similar to HD283572. How often do they shine and what are their typical properties? By combining SMA data with longer wavelength observations, we are also able to probe the physics of flares and their emission mechanisms. I worked on this using archival data from the Very Large Array,” said Ramisa Akther Rahman, a senior at the College of William and Mary who was a 2023 summer intern with Dr. Lovell in the SAO’s Program of Research Experience for Undergraduate Studies.

The results are published in The letters from the astrophysical journal.

More information:
Joshua Bennett Lovell et al, SMA Detection of an Extreme Millimeter Flare from the Young Class III Star HD 283572, The letters from the astrophysical journal (2024). DOI: 10.3847/2041-8213/ad18ba

Provided by the Harvard-Smithsonian Center for Astrophysics

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