There’s a massive storm raging on this Jupiter-sized star

By Joel Hruska 

The Kepler space telescope has expanded our understanding of planetary systems since it first launched, but it’s shedding light on unique types of stars and stellar phenomena as well. Researchers have now reported finding a highly unusual star, with a raging storm on its surface. The star, W1906+40, is roughly Jupiter-sized, and packs a maelstrom over its north pole that’s been visible for at least two years.

One of the things that makes W1906+40 interesting is that it’s an L-dwarf star, also known as a brown dwarf. Brown dwarf stars blur the line between huge gas giants and red dwarf stars. Stars form when clouds of gas and dust collapse together. As the gas compresses, the core of the cloud heats up, while the outer layers cool. In a conventional star, the core eventually becomes dense enough to sustain hydrogen fusion. A stable star, like our own, achieves a balance between gravitational compression and the energy released by internal fusion.

Brown dwarf stars, in contrast, never become quite dense enough to fuse hydrogen. The brown dwarf can still hold substantial reserves of thermal energy and may fuse lithium early in its life cycle, but they ultimately fade away.One of the aspects of brown dwarfs that make them difficult to discern from gas giants is that they’re all within 10-15% of Jupiter’s size, though they contain as much as 80x Jupiter’s mass. I don’t want to leave you with the impression that there’s no discernable difference between a brown dwarf and a gas giant, because there definitely are — but brown dwarfs are where the line between planet and star begins to get blurry. And now, thanks to Kepler, we have a new set of unusual characteristics — a brown dwarf with a storm the size of Jupiter’s Great Red Spot.

“The star is the size of Jupiter, and its storm is the size of Jupiter’s Great Red Spot,” said John Gizis of the University of Delaware, Newark. “We know this newfound storm has lasted at least two years, and probably longer.” Gizis is the lead author of a new study appearing in The Astrophysical Journal.”

With surface temperatures of “just” 3500 degrees Fahrenheit, W1906+40 is cool enough to have an atmosphere made of minerals. While it’s not the first “cloudy” brown dwarf observed from Earth, it’s certainly the only one to sustain a storm of this size for such a long period of time.

One other interesting item of note. Jupiter is often referred to as a “failed star,” based on a misreading of Carl Sagan’s “Cosmos,” where he noted that “Had Jupiter been several dozen times more massive, the matter in its interior would have undergone thermonuclear reactions… The largest planet is a star that failed.” The second sentence was probably never intended to refer to Jupiter, specifically, but to note that the line between a failed star and a gas giant isn’t always clear.

Jupiter couldn’t accurately be called a failed star for a simple reason — there’s not enough mass in the entire rest of the solar system to convert Jupiter into a brown dwarf. Jupiter’s mass is 317.8x larger than the Earth’s, 95.2x larger than Saturn, 14.5x larger than Uranus, and 17.1x larger than Neptune. Add up every other planet, moon, and asteroid in our solar system, and you’d only increase Jupiter’s mass by roughly 40%. That’s nowhere near enough material to create even a brown dwarf, much less a star that would fuse hydrogen.