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At the 119th meeting of the American Astronomical Society in Austin, Texas, an international team of astronomers working at the Cerro Tololo Inter-American Observatory in Chile presented their findings: they had discovered a small object, surrounded by dust rings, orbiting a star.
“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,” Eric Mamajek stated in a University of Rochester press release. Mamajek is the Assistant professor in Physics and Astronomer at the University of Rochester. “But many questions remain about what exactly has been discovered.”
In 2007, Mamajek and his colleagues began investigating light curves – measuring changes in light intensity – of stars in the Scorpius-Centaurus association (the nearest massive star formation region) which lies 420 light-years away from the Earth. For a particular star, they noticed multiple erratic blips in its light.
The star, dubbed 1SWASP J140747.93-394542.6, is similar to the Sun in mass and composition, though it is extremely young, having an age of only sixteen million years. In comparison, the Sun is approximately five billion years old.
The object in question that was causing the blips could not have been a planet or another star. When a spherical body crosses in front of a star, the intensity of light from the star gradually dims and increases for a certain amount of time habitually. ?However, the transit of this object was too complex: the light’s intensity changed irregularly, and as much as 95% of the star’s light was blocked.
The team surmised that the abnormal blips were caused by dust from rings, and then concluded that what they had detected was a ringed body. However, none of the members are positive as to what the object could possibly be. Ideas range from a low-mass star or brown dwarf, a protoplanet, or a small planet whose rings may be forming into a moon.
The four rings that have been detected thus far are named “Rochester”, “Sutherland”, “Campanas,” and “Tololo.” The outermost ring’s orbital radius is tens of millions of kilometers, so the size and mass of the rings are much more immense than Saturn’s. According to the team, the object is a “Saturn on steroids.”
The team will calculate the radial velocity of the star and then measure the object’s gravitational tug on the star in order to find out the object’s mass and density. Hopefully, they will obtain the information from the Large Synoptic Survey Telescope (LSST), which is currently being built in Chile.
The team believes they could be observing a later stage of planet formation. “Our inner solar system could’ve looked like this long ago in its first tens of millions of years,” Mamajek says. “I think these rings are how we’re going to study moon-forming disks around gas giants.”