Saturn, you’ve got company. A planet orbiting the young, sun-like star J1407 in the southern constellation Centaurus has a ring system that makes yours look, well, microscopic. Not only is the planet they encircle much more massive than either Jupiter or Saturn, but the rings are 200 times as wide and packed with material. Discovered in 2012, it’s the first system of its kind to be found in another solar system.
Eric Mamajek (University of Rochester) and Matthew Kenworthy (Leiden Observatory) co-authored a recent paper detailing their discovery. The system consists of 37 rings with a total diameter of 74.5 million miles (120 million km). That’s 438 times the size of Saturn’s primary rings. If you plucked out the Sun and put J1407b in its place, its ring system would reach more than three-quarters of the way to Earth.
Let’s look at it another way. Step outside one of these winter mornings for a peek at Saturn in Scorpius. To your eye it looks exactly like a star. 10x binoculars begin to reveal an oval shape that hints at the planet’s rings. If we could replace Saturn with J1407b, the exoplanet’s rings would span 35° of sky or twice the length of the constellation Orion the Hunter. Can you imagine that?
Let me temper our excitement a teeny bit by saying we’re not including Saturn’s Phoebe Ring, an extremely faint and tenuous ring discovered in 2009 by NASA’s Spitzer SpaceTelescope. Tilted 27° to the main ring plane with a diameter up to 7.4 million miles it broadens Saturn’s domain considerably, but there’s hardly anything there compared to the massiveness of J1407b’s lovely loops.
Each of J1407b’s rings extends up to several tens of millions of miles in diameter; the mass of the entire system comes to around 100 million times that of Earth’s moon. That’s a lot of stuff to make moons out of and exactly what the researchers believe is happening. They’ve got evidence of it, too.
There are gaps in the system carved out by possible “exomoons” coalescing from the material like a miniature version of our own solar system which evolved from a similar though much larger cloud of dust and gas 4.6 billion years ago. One gap, located 41 million miles (61 million km) from the massive planet at the hub, has been cleared by a satellite with an estimated mass 4⁄5 that of Earth.
Mamajek and Kenworthy discovered the rings while analyzing data from the SuperWASP (Wide Angle Search for Planets) program. SuperWASP employs eight cameras at each of two robotic observatories that operate year-round and cover the entire sky, both northern and southern hemispheres. Millions of stars are photographed simultaneously with the hope of catching one in the act of being eclipsed by an orbiting planet. During an eclipse, the star fades and then returns to its original brightness as the planet blocks the light and moves on.
The researchers studied a 12th magnitude orange dwarf star with the swanky name of 1SWASP J140747.93-394542.6 (full name for J1407) which underwent a series of deep eclipses lasting 56 days back in April-May 2007.
“The eclipse lasted for several weeks, but you see rapid changes on time scales of tens of minutes as a result of fine structures in the rings,” said Kenworthy. Each ring caused a dip in the star’s light up to 95% implying that the rings are thick and massive. Lots of material there likely means lots of future moons.
Though J1407b is much too far away to observe the rings directly, they made a detailed model of the ring system based on the rapid brightness variations in the star light passing through it. The object at the center of this celestial pinwheel is almost certainly a planet but has yet to be seen. No surprise, as it’s so much smaller than the rings which surround it.
Besides finding another Saturn, a wonderful discovery in itself, we can now watch as a disk of dust around another planet gets its rings carved by exomoons. Sometimes the universe is simply … unbelievable.