NASA’s Goddard Space Flight Centre has revealed details of a stellar flare detected by its Swift satellite earlier this year, which was significantly larger than any solar flare on record.
This ‘super flare’ originated from one of two red dwarfs in a binary star system about 60 lightyears away, known as DG Canum Venaticorum, or DG CVn.
The Swift satellite’s instruments were triggered by a rising tide of X-rays from one of these young stars on 23 April and astrophysicists around the world were notified of the activity.
For about three minutes after this initial blast, the X-ray brightness of the super flare was greater than the combined luminosity of both stars combined and, at its peak, reached a temperature of 200m degrees Celsius – more than 12 times hotter than the centre of the sun.
X-class super flare
Stellar explosions such as this are classed as B, C, M or X based on their X-ray emissions, with X being the strongest class. In March this year, a rare X-class solar flare from our own sun was recorded by an international team of researchers, including academics in Trinity College Dublin.
The largest solar flare from our sun was recorded in November 2003 and this was rated as X 45, which was so powerful that it overloaded the sensors measuring it.
The super flare from DG CVn, however, was more than 10,000 times more powerful with a rating of about X 100,000.
What’s more, this was only the beginning of a complex event that continued for almost 20 days, with at least seven more powerful flares following the initial blast.
It was previously thought that major flares from red dwarfs do not last more than a day, but this event has proven to be the strongest, hottest, and longest-lasting sequence of stellar flares ever recorded from a nearby red dwarf star.
Both the stars in DG CVn are about one-third the size of our solar system’s sun with about 1,000th the luminosity, but they orbit each other so closely that it was difficult for the Swift satellite to pinpoint which star was the source of the super flare.
“This system is poorly studied because it wasn’t on our watch list of stars capable of producing large flares,” said astronomer Rachel Osten, a deputy project scientist for NASA’s James Webb Space Telescope. “We had no idea DG CVn had this in it.”
How do solar flares occur?
Red dwarfs are young stars and DG CVn’s are spinning at a rate about 30 times faster than our sun. This fast rotation amplifies magnetic fields and, in active regions where these fields become twisted and distorted, energy is accumulated and eventually released as an explosive flare.
These flares emit radiation across the electromagnetic spectrum and those from our own sun can disrupt radio waves and telecommunication systems.
NASA estimates that the DG CVn system was born about 30m years ago, making it less than 0.7pc the age of our solar system. It’s believed that our young sun may have exhibited similar behaviour but its rotation has since slowed down and, thus, so has the activity in its atmosphere.