Is our Sun part of a double-star system? It's not an idea students hear about in introductory astronomy courses, but there's some reason to believe the Sun has a brown dwarf companion, nicknamed the Nemesis Star.
Giant, cool quasi-stars are known as brown dwarfs; they may look like Jupiter but they are not gas giants.
Brown dwarfs are neither planets no stars; they are betwixt and between objects-less massive than a star to be able to ignite internal thermonuclear fusion, but too massive to fall within the International Astronomical Union's mealy definition of what a planet is (or isn't, depending on the current day of the week).
NASA-JPL's nifty WISE space telescope-short for Wide-Field Infrared Survey Explorer-should be able to spot Nemesis, if it exists, during its tenous remaining mission status.
Launched in 2009, the probe ran out-of-fuel just a few weeks ago. However, like the Eveready Battery bunny, it's still sending back deep-space data. WISE has discovered 19 comets, more than 33,500 asteroids including 120 near-Earth objects-so far. Astronomers are expecting lots more fun stuff in WISE's amazing post-mortem telemetry downloads. Will Nemesis be among WISE's remaining surprises? Time is running out.
The Nemesis Star theory was first proposed during the 1980s by American paleontologists Dave Raup and Jack Sepkoski with considerable work contributed by astrophysicist Richard A. Muller. The trio tried to explain cyclical mass extinctions here on Earth with the idea that a red dwarf star, located 1.5 light years away from us, was the culprit.
The Nemesis theory proposes that the Sun's unseen quasi-stellar companion periodically disturbs the Oort Cloud, in the outer reaches of the solar system to hurtle dinosaur-killing asteroids and comets Sunward. It may even indirectly affect climate change. If Nemesis doesn't quite capture the drama of it all for ya, how about the nickname a few researchers have called this hypothetical object-the Death Star, a nod the giant battlestation of the "Star Wars" sci-fi saga.
According to NASA-JPL's WISE mission website, brown dwarfs have less than eight percent of the mass of the Sun; this means that the fusion reaction that keeps the Sun hot can't get started. And because brown dwarfs can't be observed in visible light (you can spot them in infrared light), they go undetected in the night sky.
Brown dwarfs can be the same size as Jupiter, but there the comparison stops. These objects are ultra heavy, with masses up to 80 times that of a typical Jovian world. In fact, many brown dwarfs might be the center of their own solar systems.
The paleontologists David Raup and Jack Sepkoski claim that, over the last 250 million years, life on Earth has faced extinction in a 26-million-year cycle. Astronomers proposed comet impacts as a possible cause for these catastrophes.
Ok, Nemesis is admittedly a cool theory, but where's the beef?
There's one possible signature of Nemesis: it's a dwarf-planet called called Sedna.
Sedna was discovered in 2003 by American astronomer Mike Brown. This icy world-named after an Eskimo goddess of the underworld-orbits the Sun far beyond Pluto.
According to Brown, Sedna shouldn't be there. "There's no way to put Sedna where it is," he said. "It never comes close enough to be affected by the Sun, but it never goes far enough away from the Sun to be affected by other stars."
Even Brown admits he may be overlooking something distant and slow moving affecting Sedna's odd orbit-Nemesis.
NASA-JPL's WISE mission should complete its map of the entire sky by the end of this month. If Nemesis is discovered among the digital data-which not be processed for motnhs-you'll hear about; such a discovery would make front-page news around the world.
Lou Varricchio, M.Sc. was a science writer at the NASA Ames Research Center in California. He is a NASA-JPL Solar System Ambassador in Vermont and available, free-of-charge, for public and school presentations about space and NASA missions. E-mail him at: firstname.lastname@example.org.