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NASA Discovers Closest Rocky Planet Outside The Solar System

NASA has discovered Earth’s new next-door neighbor.

NASA announced on Thursday that astronomers using the Spitzer Space Telescope have confirmed the discovery of the closest rocky planet outside the solar system. The close proximity of this alien world makes it an ideal target for extensive research in the years to come.

The planet, dubbed HD 219134b, orbits its host star just 21 light-years away in the constellation Cassiopeia. The find comes just one week after NASA announced the discovery of the first Earth-sized planet found to orbit a star similar to the sun. [Read more: NASA Discovers First Earth-Sized Planet Orbiting Sun-Like Star]

“Transiting exoplanets are worth their weight in gold because they can be extensively characterized,” Michael Werner, project scientist for the Spitzer mission said in a statement. “This exoplanet will be one of the most studied for decades to come.”

The planet has a mass 4.5 times that of Earth’s and is approximately 60% larger, putting it in a class of exoplanets — a term for planets that orbit a star, stellar remnant or brown dwarf beyond the solar system — known as “super-Earths.”

The planet orbits too close to its parent star to be habitable, however, its relatively close distance to Earth makes it an excellent planet to study using both ground and space-based telescopes. The planet is so close to Earth that its star, known as HD 219134, is visible to the naked eye under a dark night sky.

This sky map highlights the location of HD 219134 (right), parent star to the nearest confirmed rocky planet found to date outside of the solar system. The star resides just off the constellation Cassiopeia (left) and can be seen with the naked eye in dark skies. Image Credit: NASA / JPL-Caltech / DSS

This sky map highlights the location of HD 219134 (right), parent star to the nearest confirmed rocky planet found to date outside of the solar system. The star resides just off the constellation Cassiopeia (left) and can be seen with the naked eye in dark skies. Image Credit: NASA / JPL-Caltech / DSS

“Most of the known planets are hundreds of light-years away. This one is practically a next-door neighbor,” said astronomer Lars A. Buchhave of the Harvard-Smithsonian Center for Astrophysics who co-authored a study the planet is a subject of, which accepted for publication in the journal Astronomy and Astrophysics.

While HD 219134b is the closest known rocky planet to Earth, it is not the closest planet discovered outside the solar system. GJ674b, discovered in 2007, is the closest known planet to Earth at only 14.8 light-years away. However, the composition of this world is unknown and it may be a gas giant.

“Thanks to NASA’s Kepler mission, we know super-Earths are ubiquitous in our galaxy, but we still know very little about them,” the study’s co-author Michael Gillon of the University of Liege in Belgium, and lead scientist for the Spitzer detection of the transit said in a statement. “Now we have a local specimen to study in greater detail. It can be considered a kind of Rosetta Stone for the study of super-Earths.”

The planet was initially discovered using HARPS-North instrument on the Italian Galileo National Telescope in the Canary Islands and later confirmed by observations from NASA’s Spitzer Space Telescope. The planet will be an ideal candidate for study by the James Webb Space Telescope set to launch in 2018.