Astronomers say they have found the first ringed planet beyond our solar system, a super world with a girdle of halos 200 times bigger than Saturn's.
"It'd be huge. You'd see the rings and the gaps in the rings quite easily from Earth," Matthew Kenworthy of the Leiden Observatory in the Netherlands said.
"It'd be several times the size of the full moon."
Professor Kenworthy and Eric Mamajec of New York's University of Rochester trawled through a database of millions of stars photographed by telescopes around the world in an exoplanet search project called SuperWASP.
Exoplanets, worlds beyond our solar system, are observed from Earth through changes in the brightness of their central star.
The light is partly blocked, generally for a few hours, when the planet passes between Earth and its star.
In the case of star J1407, the astronomers observed an unusual and active light display that lasted two months.
Data on the star was gathered between 2005 and 2008, and "right slap-bang in the middle of the year 2007 the light curve goes crazy. It suddenly starts flickering and twinkling.
"It was a very strange-looking thing that nobody had ever seen before," Professor Kenworthy said.
The team concluded the only explanation was a vast disk of spaced rings around a planet that had moved between Earth and J1407, blocking the starlight in bursts.
"This is the first time somebody's seen such a giant ring system outside the solar system - any ring structure at all around what we think is a planet," Professor Kenworthy said.
The research has been accepted for publication by the Astrophysical Journal, he added.
The rings begin at a distance of about 30 million kilometres from the planet and stretch out to a distance of 90 million kilometres.
And they are probably made of dust, as planet J1407b is too hot - about 1,000 to 2,000 degrees Celsius - to support ice rings like those orbiting Saturn.
Professor Kenworthy said the planet itself was probably about 10 to 40 times the mass of Jupiter.
J1407 and its planet are about 16 million years old, which makes it an infant in terms of stellar age.
The Sun and Earth are 4.5 billion years old.
Professor Kenworthy said the find provided the first direct evidence for theories about planetary ring formation.
It is widely believed that big clouds of gas and dust collapse to form stars orbited by a thick disk of debris.
This later collects into planets, themselves orbited by rings of debris that clump together over a few million years to form moons.
"If our hypothesis is true and it [J1407b] really is a ring system, and we think it is the best explanation, then this is the first direct evidence of that process," Professor Kenworthy said.
With thanks to The ABC