May 20, 2012
Newly Discovered Planet May Be Obliterated By Its Own Sun
A newly discovered possible exoplanet some 1,500 light years away is being shredded by the intense heat of its parent star.
The team from NASA and MIT found that the planet circles its host star every 15 hours, making it one of the shortest planetary orbits ever observed, which implies that the planet orbits very close to the star. Being so close would heat the surface to at least 3,600 degrees Fahrenheit, causing rocky material on the surface to melt and evaporate. The disintegrating material would form a wind carrying both gas and dust into space. As the planet speeds around the star, the dense clouds of dust form a trail much like that of a comet. This trail of dust helps to explain why the star dims every 15 hours.
“We think this dust is made up of submicron-sized particles,” said co-author Saul Rappaport, a professor emeritus of physics at MIT. “It would be like looking through a Los Angeles smog.”
The findings, published in the Astrophysical Journal, are based on data taken from the Kepler Space Telescope (KST). KST records the brightness of each star it observes at regular intervals; scientists then analyze the data to see if there are any signs of planets orbiting these observed stars.
That´s how they found the latest planet. Although, the data shows more than just a regular dip in the star´s brightness. Rappaport and his colleagues came across a curious light pattern from the KIC 12557548 star. By measuring the star´s light curves, the team found that light from the star dropped by different intensities every 15 hours, suggesting something was blocking the star regularly, but by varying degrees.
The team went over possible theories for why they were seeing this strange light pattern. One possibility was that two planets were orbiting each other while orbiting the star. Rappaport suggested that the pair of planets would pass by the star at different orientations, blocking out different amounts of light on each pass.
However, the team could find no evidence to support that hypothesis; they decided the dimming every 15 hours was far too short a period to allow sufficient room for two planetary bodies orbiting each other, in the same way that Earth and the moon together orbit the sun.
Instead, the team theorized that the varying intensities of light were the result of a possible shape-shifting body.
“I´m not sure how we came to this epiphany,” Rappaport said. “But it had to be something that was fundamentally changing. It was not a solid body, but rather, dust coming off the planet.”
After accepting this scenario to be the best closest possible reason for the light dimming they were observing the team looked into various ways that dust could be created and blown off the planet.
They surmised that the planet must have a weak gravitational field in order for gas and dust to escape the planet´s gravitational pull. They also ruled that the planet needs to be extremely hot -- 3,600 degrees F hot. Then the team discussed two possible scenarios for how the planetary dust might form: volcanic eruptions or vaporizing metals. The data indicated the latter was more probable.
With that in mind, Rappaport and colleagues created a model of the planet, its long, trailing cloud of dust, and the brightness of the star as the planet passed by. Their simulations show a strong connection with the data that KST was producing. The team concluded that at the rate the planet is losing material, it will be totally obliterated within 100 million years.
“We´re actually now very happy about the asymmetry in the eclipse profile,” Rappaport said. “At first we didn´t understand this picture. But once we developed this theory, we realized this dust tail has to be here. If it´s not, this picture is wrong.”
Dan Fabrycky, a member of the Kepler Observatory science team, but not part of the latest study, said research shows that “planets are not eternal objects, they can die extraordinary deaths, and this might be a case where the planet might evaporate entirely in the future.”