Using data from NASA’s Spitzer Space Telescope, a team led by Western space scientists Megan Tannock and Stanimir Metchev has identified the three fastest-spinning brown dwarfs ever found. More massive than most planets but not quite heavy enough to ignite like stars, brown dwarfs are cosmic in-betweeners. And though they aren’t as well-known as stars and planets to most people, they are thought to number in the billions in our galaxy.
In a study appearing in the Astronomical Journal, the international research team that made the new speed measurements argue that these three rapid rotators could be approaching a spin speed limit for all brown dwarfs, beyond which they would break apart. The rapidly rotating brown dwarfs are all about the same diameter as Jupiter but between 40 and 70 times more massive. They each rotate about once per hour, while the next-fastest known brown dwarfs rotate about once every 1.4 hours and Jupiter spins once every 10 hours. Based on their size, that means the largest of the three brown dwarfs whips around at more than 60 miles per second (100 kilometers per second), or about 220,000 miles per hour (360,000 kilometers per hour).
“We seem to have come across a speed limit on the rotation of brown dwarfs,” said Tannock, a Western PhD candidate. “Despite extensive searches, from our own team and others, no brown dwarfs have been found to rotate any faster. In fact, any faster spins may lead to the brown dwarf tearing itself apart.”