Hubble spots traces of methane on distant planet
Scientists detected traces of the first organic molecules in the atmosphere of a planet orbiting a far-off star, a development that may lead to the ability to uncover the signatures of life on worlds outside our solar system.
Using the Hubble Space Telescope’s infrared camera, a team led by researchers at the Jet Propulsion Laboratory in La Canada Flintridge found methane and water in the atmosphere of a planet orbiting a star roughly 63 light-years away.
The Jupiter-size planet orbits far too close to its parent star in the constellation Vulpecula for life as we understand it, the team reported Wednesday in the journal Nature.
But Mark Swain, an exoplanet specialist who led the research, described the technique the scientists had used as “a crucial stepping stone to eventually characterizing pre-biotic molecules on planets where life could exist.”
One expert praised the work but said she would like to see more proof.
“This is really pushing the telescope to its limits,” said Sarah Seager, a planetary scientist at MIT. “I’m cautiously optimistic” that the finding is real.
Water and methane are not necessarily the building blocks of life on giant planets such as this one, HD 189733b, Seager said. Their gravity is so great that they retain all of the original chemicals and compounds they started with.
The detection of methane, composed of four atoms of hydrogen and one of carbon, on a smaller planet would be a better indication of biological processes. Whatever natural methane they had at their formation would have long since escaped to space. An indication of a lot of methane would mean that something is continuing to feed the atmosphere with it. On Earth, many life forms give off methane.
The gas can also be a precursor to life.
“Under the right conditions, it can form amino acids, which are the building blocks of life,” Swain said.
Of the 200 or so exoplanets discovered so far, most are like grown children who refuse to move out, sticking close to their parent stars. This planet has a two-day orbit, which puts it so close to its star that it would quickly cook any life forms before they got started.
Finding these big, skirt-hugging planets is easier than finding their more independent siblings because they are so close to their parents that they cause a tiny wobble in the stars’ movements. HD 189733b was found by measuring the slight dimming of the star’s light caused by the planet crossing in front of it. The signature for methane was found in a spectroscope analysis of the light.
Scientists are pinning their hopes of finding Earth-like exoplanets, those smaller and farther out, on the next generation of telescopes, specifically the James Webb Space Telescope. Scheduled for launch in 2013, it will have a 21-foot-diameter mirror, allowing it to gather six times as much light as Hubble.
The James Webb will orbit 1 million miles from Earth, much farther than Hubble, allowing the infrared instruments to screen out the heat and light reflected from the planet.
“I’m really excited about five years from now,” said Seager, when the Webb telescope will be able to pinpoint “super Earths.” These are planets bigger than Earth but located in the so-called Goldilocks zone around stars where it’s neither too cold nor too hot.
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