Saturn-like ring system discovered orbiting another star

Artist's conception of the Saturn-like ring system. Credit: Michael Osadciw/University of Rochester

For the first time, astronomers have found a ring system orbiting another star that seems to be similar to the rings of Saturn in our own solar system. It encircles a low-mass object which orbits the star, but it isn’t clear yet if that object is a planet, a very low-mass star or a brown dwarf star.

The scientists used data from the international SuperWASP (Wide Angle Search for Planets) and the All Sky Automated Survey (ASAS) project to study the light curves of young Sun-like stars in the Scorpius-Centaurus region of our galaxy.

This star, 1SWASP J140747.93-394542.6., is about 420 light-years away. It is similar in mass to the Sun, but is much younger, only about 16 million years old.

The ring appears to be a multi-ring system, with at least three or four rings and two or three gaps, another similarity to Saturn’s rings. These are much larger however; Saturn’s rings are a few hundred thousand kilometres across, while these ones are tens of millions of kilometres.

According to Eric Mamajek, Assistant Professor of Physics and Astronomy at the University of Rochester, “When I first saw the light curve, I knew we had found a very weird and unique object. After we ruled out the eclipse being due to a spherical star or a circumstellar disk passing in front of the star, I realized that the only plausible explanation was some sort of dust ring system orbiting a smaller companion—basically a ‘Saturn on steroids.’ We suspect this new star is being eclipsed by a low-mass object with an orbiting disk that has multiple thin rings of dust debris.”

He continued: “This marks the first time astronomers have detected an extrasolar ring system transiting a Sun-like star, and the first system of discrete, thin, dust rings detected around a very low-mass object outside of our solar system. But many questions remain about what exactly has been discovered.”

If the object is less than 13 MJ (Jupiter masses), it is most likely a planet. If however it is between 13 MJ and 75 MJ, than it is probably a brown dwarf star.

Mamajek says that more definite conclusions about these rings will take another couple of years or so of analysis. Finding other ones would of course also be helpful.

Saturn, with its majestic rings, is one of the most beautiful places in the solar system. Jupiter, Uranus and Neptune also all have rings, albeit not as striking as Saturn’s. As we continue to find exoplanets by the thousands, how many of those may also be graced by rings? There might be a wide variety of ringed planets out there, all beautifully unique.

The findings will be published in an upcoming issue of the Astronomical Journal.

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