The extreme explosion of a young Sun-like star suggests that newly developing planets must exist in a very wild environment.
A team of scientists from the Center for Astrophysics (CfA) used the Submillimeter Array (SMA), an array of telescopes on Maunakea in Hawaii, to observe the young star HD 283572. The team watched as HD 283572 increased in brightness hundreds of times. Just a few hours of course. This observed explosion is ranked as one of the most powerful stellar explosions ever seen.
Located about 400 light-years away, HD 283572 is about 1.4 times larger 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. This means that when astronomers saw HD 283572, they were witnessing the Sun’s life stage when it was starting to form planets like Earth.
Ultimately, these findings may indicate that forming planets, including those in the solar system, must have faced turbulent conditions.
“We were surprised to see an extraordinarily bright flare from an ordinary young star,” team leader and CfA scientist Joshua Bennett Lovell said in a statement. “Any potential planet developing in this system would be hit by the intense power of this flash. I wouldn’t want to grow there!”
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Young stars are tightly coiled springs
Starbursts like those observed by Lovell and his colleagues are thought to be created by stars spinning and mixing their magnetic fields.
Just as a spring winding stores very tightly kinetic energy that needs to be released, the magnetic energy stored in these wound magnetic fields also needs to be released. For stars, this causes bursts of accelerated particles to blast off the stars’ surfaces into space.
The starbursts that accompany this burst of stellar material or plasma can increase a star’s brightness by tens or hundreds of times and across a variety of wavelengths of light. But such flares are still difficult to detect because these events occur essentially randomly, so there’s no clear idea of when to point the telescope at a star to catch the next tantrum.
This was certainly the case for HD 283572, which appeared motionless before the massive explosion.
“Every time we turned the SMA to the star after this flare, we saw nothing,” Lovell said. “Our findings confirm that these flare events are rare at millimeter wavelengths, but that they can be extremely powerful for stars of this young age.”
Over a 9-hour period, the energy of the HD 283572 explosion reached levels millions of times higher than the energy emitted by similar explosions measured near the solar system.
“This was a massive event equivalent to depleting the entire Earth’s nuclear arsenal in about a millisecond, repeatedly, for nearly half a day!” SMA Project Scientist and team member Garrett Keating said in the statement. “If we take into account the wavelengths of starlight that SMA cannot observe, we would even expect it to be orders of magnitude more energetic.”
The team detected only one flare from HD 283572, so we can’t be sure at this time exactly what triggered the massive explosion.
“Flares at these wavelengths are rare, and we expected to see nothing more than the faint glow of dust forming the planet,” Keating said. “This is a real puzzle and there are a variety of mechanisms that may be involved. Interactions with unseen companion stars or planets or periodic starspot activity are two possibilities, but there is no doubt how powerful a phenomenon this is.”
Flares like this are so powerful that they can destroy the atmospheres of newly formed planets as they develop around them.
The discovery of such an energetic explosion at this critical period in a planetary system’s life gives scientists a clue as to the types of pressures Earth and its sister planets would have faced as they formed about 4.5 billion years ago. The results may also provide clues about what extrasolar planets, or “exoplanets,” may currently be experiencing during earlier stages of their lives.
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The team behind this research continues to monitor HD 283572 to determine how often the young star explodes and to see whether these explosions affect the growth of planetary atmospheres on planets budding around it.
Additionally, a new SMA campaign will examine other young stars similar to HD 283572, determining their typical properties and brightness frequencies. By combining SMA data with longer wavelength observations, the team hopes to better understand the physics of these flares and the processes by which they originate, he said.
The team’s results have been accepted for publication in The Astrophysical Journal Letters, and the preliminary review paper is available on arXiv.