An extreme flare from a young star that looks like the sun suggests the budding planets must exist in a pretty wild environment.
A team of scientists from the Center for Astrophysics (CfA) used the Submillimeter Array (SMA), a set of telescopes on Maunakea in Hawaii, to observe the young star HD 283572. The crew watched as the brightness of HD 283572 increased hundreds of times. over the course of just a few hours. This observed eruption ranks as one of the most powerful stellar flares ever seen.
Located about 400 light years away, HD 283572 is about 1.4 times more massive than the Sun, but at just under 3 million years old, it is a thousand times younger than our star, which is about 4.6 billion years old. of years. That means that when astronomers saw HD 283572, they witnessed it in the same stage of life that the sun was in when it began to form planets, like Earth.
As a result, these findings could indicate that forming planets, including those in the solar system, must face turbulent conditions.
“We were surprised to see an extraordinarily bright flare coming from an ordinary young star,” explained team leader and CfA scientist Joshua Bennett Lovell. he said in a statement. “Any potential planet developing in this system would have been hit by the intense power of this flare. I wouldn’t want to grow there!”
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Young stars are tightly coiled springs.
Stellar flares like those observed by Lovell and his colleagues are thought to be created when stars spin and tangle their magnetic fields.
Just as a spring coiled too tightly stores kinetic energy that must be released, the magnetic energy stored in these coiled magnetic fields must be released. In the case of stars, this causes explosions of accelerated particles to pass through their surfaces and out into space.
The stellar flares that accompany this eruption of stellar matter, or plasma, can increase the brightness of a star tens or hundreds of times and over a range of light wavelengths. However, detecting such flares remains a challenge because these events essentially occur at random, so there is no clear idea of when to point a telescope at a star to detect its next flare.
This was certainly the case for HD 283572, which appeared dormant before its tremendous eruption.
“Every time we pointed the SMA at the star after this flare, we saw nothing,” Lovell explained. “Our findings confirm that these flare events are rare at millimeter wavelengths, but can be extremely powerful for stars of this age.”
Over a 9-hour period, the energy of the HD 283572 flare reached levels millions of times greater than the energy released by similar flares measured in the vicinity of the solar system.
“This was an immense event, equivalent to expending Earth’s entire nuclear arsenal in about a millisecond, over and over again, for almost half a day!” SMA project scientist and team member Garrett Keating said in the statement. “If we take into account the wavelengths of light from the star that SMA did not observe, we expect that it might even have been much more energetic.”
The team only detected one flare from HD 283572, so we currently can’t be sure what exactly triggered the massive explosion.
“Flares at these wavelengths are rare and we had not anticipated seeing anything more than the faint glow of dust forming on the planets,” Keating said. “It’s a real enigma, and there are a variety of mechanisms that could be at play. Interactions with unseen companion stars or planets or periodic starspot activity are two possibilities, but what remains beyond doubt is how powerful was this event.”
Flares like this are so powerful that they can destroy atmospheres as they develop around young, forming planets.
The discovery of such an energetic flare at this crucial period in the life of a planetary system gives scientists a clue about the type of pressures that Earth and its sister planets would have experienced during their formation about 4.5 billion years ago. The results could also provide clues about what extrasolar planets or “exoplanets” earlier in their lives may be experiencing right now.
The team behind this research continues to monitor HD 283572 to determine how often the young star erupts and to see if this eruption could be affecting the growth of planetary atmospheres on the budding planets surrounding it.
Additionally, a new SMA campaign will study other young stars similar to HD 283572 to determine their typical properties and flare frequencies. By combining the SMA data with longer wavelength observations, the team hopes to better understand the physics of these eruptions and the processes from which they arise.
The team’s results have been accepted for publication in The Astrophysical Journal Letters, with a prior peer-review article available at arXiv.