Astronomers don't normally use canine clichés, but if they did, they might employ one -- it's not the size of the dog in the fight, it's the size of the fight in the dog -- to describe a small but energetic red dwarf in a binary system known as DG Canum Venaticorum, or DG CVn. That's because red dwarfs like DG CVn serve a serious electromagnetic punch in a small package.
Astronomers know this because NASA's Swift satellite recently spotted a series of massive solar flares erupting from one of the two dim red dwarfs, each measuring about a third of the sun's mass and size. The hottest of the flares was estimated to be roughly 10,000 times more powerful than the largest flare ever recorded leaping from the sun, and astronomers estimate the red dwarf flare was 360 million degrees Fahrenheit, more than 12 times hotter than the sun's core.
While the pair of red dwarfs is small, it's also young and full of energy. The age of this particular binary system is about 30 million years, less than one percent of the age of Earth's solar system. Most of the stars neighboring our solar system are middle-aged, but younger systems do occasionally pass by, giving scientists a chance to study what it is to be an adolescent star.
"We used to think major flaring episodes from red dwarfs lasted no more than a day, but Swift detected at least seven powerful eruptions over a period of about two weeks," explained Stephen Drake, a researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "This was a very complex event."
Solar flares on distant stars are generated the same way they are here in our solar system. The combination of heat and the star's spinning motion twist and tangle volatile magnetic fields. As they become increasingly distorted they build up tension and energy that is eventually released when what's called magnetic reconnection finally destabilizes the fields. The explosive release features an emission of all sorts of electromagnetic radiation, including radio waves, ultraviolet and X-ray light.
Part of the reason a young dwarf star is capable of producing huge flares, scientists say, is because it spins at a much faster rate than larger, older stars like our sun.
Researchers say they'll continue to monitor this pair of red dwarfs to better understand how younger star systems behave over time.
"This system is poorly studied because it wasn't on our watch list of stars capable of producing large flares," said Rachel Osten, an astronomer with NASA's James Webb Space Telescope. "We had no idea DG CVn had this in it."