Hidden exoplanet seen by scientist in Hubble's archives

Washington, April 2 (ANI): A scientist has identified an exoplanet that went undetected in Hubble images taken in 1998.

The scientist, David Lafreniere of the University of Toronto, Ontario, Canada, detected the planet that was hidden in Hubble images taken with the telescope's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) in 1998.

The planet, estimated to be at least seven times Jupiter's mass, was originally discovered in images taken with the Keck and Gemini North telescopes in 2007 and 2008.

It is the outermost of three massive planets known to orbit the dusty young star HR 8799, which is 130 light-years away.

NICMOS could not see the other two planets because its coronagraphic spot - a device which blots out the glare of the star - also interferes with observing the two inner planets.

"We've shown that NICMOS is more powerful than previously thought for imaging planets," said Lafreniere.

"Our new image-processing technique efficiently subtracts the glare from a star that spills over the coronagraph's edge, allowing us to see planets that are one-tenth the brightness of what could be detected before with Hubble," he added.

Lafreniere adapted an image reconstruction technique that was first developed for ground-based observatories.

Using the new technique, he recovered the planet in NICMOS observations taken 10 years before the Keck/Gemini discovery.

The Hubble picture not only provides important confirmation of the planet's existence, it provides a longer baseline for demonstrating that the object is in an orbit about the star.

NICMOS's view provided new insights into the physical characteristics of the planet as well.

"The planet seems to be only partially cloud covered and we could be detecting the absorption of water vapor in the atmosphere," said Travis Barman of Lowell Observatory, Flagstaff, Arizona.

"The infrared light measured from the Hubble data is consistent with a spectrum showing a broad water absorption feature, but the level of absorption seen is lower than it would be if the photosphere were completely devoid of dust," Barman said.

"Dust clouds can smooth out many of the spectral features that would otherwise be there -- including water absorption bands," he added.

According to Barman, "Measuring the water absorption properties will tell us a great deal about the temperatures and pressures in the atmospheres, in addition to the cloud coverage."

"If we can accurately measure the water absorption features for the outermost planet around HR 8799, we will learn a great deal about their atmospheric properties," he said. (ANI)