Astronomers have detected an extreme eruption from a young star that became more than a hundred times brighter in only a few hours.
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This discovery offers new insight into how young sun-like stars behave early in their lives, and their impact on the development of any of their newborn planets.
Researchers at the Smithsonian Astrophysical Observatory (SAO), part of the Center for Astrophysics | Harvard and Smithsonian (CfA), led this discovery using Submillimeter Array (SMA) observations of HD 283572, a star 40 percent more massive than the sun located about 400 light-years away.
The SMA is an array of telescopes on Mauna Kea in Hawaii that is specifically designed to detect millimeter-wave light.
At less than 3 million years old, HD 283572 is over a thousand times younger than the sun, at 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 the dusty material produced in the formation of young planets that have a faint but detectable glow at millimeter, or radio, wavelengths. However, they found something altogether different.
"We were surprised to see an extraordinarily bright flare from an ordinary young star," said Lovell. "Flares at these wavelengths are rare, and we had not anticipated seeing anything but 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 wind up and develop regions of increased magnetic energy.
Like a spring wound too tight, this stored magnetic energy eventually must be released.
In the case of stars, this produces intense accelerations of charged particles, which blast through their surfaces.
A challenge for observing such flares is that it is never precisely clear when a star might flare next, and catching them can be particularly challenging at millimeter wavelengths.
"HD 283572 appeared dormant for months before we caught its eruption," said Lovell. "Every time we pointed the SMA back at the star after this flare, we saw nothing. Our findings confirm that these flare events are rare at millimeter wavelengths but that these can be extremely powerful for stars at this young age." ■