Sen—Astronomers have discovered the first ring system to be found outside our Solar System—and it puts Saturn's own spectacular collection well and truly in the shade.
The rings, which encircle either a young giant planet or brown dwarf, were discovered because they eclipse the object's Sun-like star, labelled J1407 and lying about 420 light years from Earth in the constellation Centaurus.
They are more than 200 times larger than the rings of Saturn and were discovered in 2012 by Eric Mamajek, professor of physics and astronomy at the University of Rochester and his team. Their belief was that they were caused by a moon-forming disk or debris.
Now Matthew Kenworthy of Leiden Observatory, in the Netherlands, has led a new analysis of data from SuperWASP, a survey designed to detect gas giants moving in front of their parent star. This showed over 30 rings, tens of millions of kilometres in diameter, while gaps in the rings suggest that satellites may have formed.
“The star is much too far away to observe the rings directly, but we could make a detailed model based on the rapid brightness variations in the star light passing through the ring system. If we could replace Saturn’s rings with the rings around J1407b, they would be easily visible at night and be many times larger than the full moon,” Kenworthy said.
“This planet is much larger than Jupiter or Saturn, and its ring system is roughly 200 times larger than Saturn’s rings are today,” said co-author Mamajek. “You could think of it as kind of a super Saturn.”
Kenworthy used adaptive optics and Doppler spectroscopy to estimate the mass of the ringed object. They conclude that the companion is likely to be an unseen giant planet with a gigantic ring system responsible for the repeated dimming of J1407’s light.
The diameter of the ring system is nearly 120 million kilometres and contains roughly an Earth’s-worth of mass in light-obscuring dust particles.
Mamajek sais: “In the case of J1407, we see the rings blocking as much as 95 per cent of the light of this young Sun-like star for days, so there is a lot of material there that could then form satellites.”
The astronomers have found at least one gap in the ring structure, which is a feature common in Satirn's rings too.
“One obvious explanation is that a satellite formed and carved out this gap,” said Kenworthy. “The mass of the satellite could be between that of Earth and Mars. The satellite would have an orbital period of approximately two years around J1407b.”
The rings should thin over the next several million years and eventually disappear as satellites form from the material in the disks. The ringed companion J1407b has an estimated orbital period roughly a decade in length. The mass of J1407b is most likely about 10 to 40 Jupiter masses.
“The planetary science community has theorized for decades that planets like Jupiter and Saturn would have had, at an early stage, disks around them that then led to the formation of satellites,” Mamajek explains. “However, until we discovered this object in 2012, no-one had seen such a ring system.”
Amateur astronomers are encouraged to help detect the next eclipse of the rings, to help determine details of the period and mass of the ringed companion. Observations of J1407 can be reported to the American Association of Variable Star Observers (AAVSO).
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