July 19, 2011

‘Super-Earth’ Viewed Through The Eyes Of An Eclipse

A group of astronomers recently spotted an exoplanetary eclipse of a star to reveal a "super-Earth."

The planet, which lies 40 light years away, was named 55 Cancri e and is twice as big as Earth and nearly nine times more massive.

Thi super-Earth planet is mostly composed of rocky material and supplemented with light elements like water and hydrogen gas. 

Scientists estimate the planet's surface is much hotter than Earth, close to 4,892 degrees Fahrenheit.

Josh Winn, the Class of 1942 Career Development Assistant Professor of Physics at MIT, said exobiologists should not look to 55 Cancri e for signs of life.  He said the temperatures are too high to sustain living organisms.

Winn said he suspects the exoplanet will attract the telescopes of many astronomers, mainly for reasons of visibility.

The researchers said the star around the planet orbits around appears to be 100 times brighter than any other star with an eclipsing planet.

"Everything we do in astronomy is starving for more light," Winn said in a press release. "The more light a star gives you, the more chances you have of learning something interesting "¦ and everyone's been waiting for a system like this that you can study in great detail."

The astronomers collected starlight data continuously for two weeks from Canada's Microvariability and Oscillations of Stars space telescope (MOST).

They directed the satellite scope toward 55 Cancri e based on a tip from doctoral student Rebekah Dawson of the Harvard-Smithsonian Center for Astrophysics.

She said 55 Cancri e was much closer to its star than previously thought, and Winn immediately saw it as an opportunity to catch sight of an eclipse.

"If [a planet] is just hugging the star, there's a greater chance of an eclipse, versus if the planet is really far out, in which case you have to be luckier to see it right in front of the star," he said in the MIT press release.

Astronomers can use an eclipse to identify a planet's diameter, mass, composition and atmospheric conditions.

The astronomers tracked the brightness of 55 Cancri e's star for two weeks and dissevered tiny dips in the data that occurred every 18 hours. 

Andrew Howard, a research astronomer at the University of California at Berkley who was not involved in the study, said spotting a miniature eclipse like this is not easy.

"This is like looking for a firefly crawling across a searchlight [by] looking for the decreasing brightness of that searchlight from 1,000 kilometers away," Howard said in a statement.  "This is just a new world."

Winn said he hopes astronomers would be inspired by the study to explore 55 Cancri e with their own tools and telescopes.

The study will be published in The Astrophysical Journal Letters.


Image Caption: A rendering of the silhouette of 55 Cancri e transiting its parent star, compared to the Earth and Jupiter transiting our sun. Image: Jason Rowe, NASA/Ames; Jaymie Matthews, UBC


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