Astronomers say new ‘super-Earth’ is 36 light-years distant, might hold water


An artist’s impression of a newly-discovered planet orbiting a star in the southern constellation Vela. The "super-Earth" is about 3.5 times heavier than Earth and at the right temperature where it could possibly have liquid water on its surface. (European Southern Observatory/M. Kornmesser)
September 12, 2011

Astronomers on Monday announced the discovery of 50 new planets circling stars beyond the sun, including one “super-Earth” that is the right distance from its star to possibly have water.

“If we are really, really lucky, this planet could be a habitat” like Earth, said Lisa Kaltenegger of the Max Planck Institute for Astronomy in Heidelberg, Germany.

The planet, dubbed HD85512b, circles an orange star somewhat smaller and cooler than our sun about 36 light-years away. The star, HD85512, is visible in the southern sky in the constellation Vela.

The newly found planet circles this star every 59 days, putting it at the edge of the “habitable zone” where water could exist if atmospheric conditions were right.

In a teleconference, Kaltenegger said that the planet is at the warm edge of its star’s habitable zone, as if “standing next to a bonfire.” That means the planet would require a lot of cloud cover — which reflects starlight — to keep the surface cool enough to prevent any water from boiling, she said.

Astronomers have not determined whether the new super-Earth is rocky like the Earth or gassy like Jupiter, let alone whether it has an atmosphere. The new super-Earth is 3.5 times the mass of Earth.

Astronomers inferred the existence of the planet by watching its star wobble ever so slightly. The speed of the wobble indicated the existence of a planet tugging at the star.

This “radial velocity” technique has been productive, offering astronomers working at La Silla Paranal Observatory in Chile evidence of the 50 new “exoplanets” announced Monday. The planet-hunting instrument, called HARPS, are operated by the European Southern Observatory.

Sixteen of the new planets announced Monday, including the new super-Earth, are of the right mass to be made of rock instead of gas.

“We are building up a target list of super-Earths in the habitable zone,” Kaltenegger said.

To determine whether the planet has an atmosphere, astronomers need to capture an image of the planet — which they have not done — and analyze the light for signs of water, carbon dioxide and other gases. No existing telescope is sensitive enough for that task.

But a new telescope to begin construction next year, the European Extremely Large Telescope, will be up to the task, said Markus Kissler-Patig of the European Southern Observatory. It will be “technically capable of finding life around the nearest stars,” he said, by analyzing the atmosphere of exoplanets. The new super-Earth is a “prime target” for the new telescope.

Since 1995, astronomers have found more than 600 planets beyond Earth, according to a catalog.

In the accelerating race to bag and tag planets outside our solar system, HD85512b marks the second super-Earth found at the right distance from its star to possibly hold water, considered a vital ingredient for life. The first, called Gliese 581d, was discovered by the same telescope in Chile in 2007.

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