Breakthrough lets scientists identify makeup of extrasolar worlds
A U.S. space telescope has for the first time captured enough light from planets outside of our solar system to identify the properties of molecules in their atmosphere.
The breakthrough could one day help scientists detect life on those extrasolar worlds, or exoplanets, the U.S. National Aeronautics and Space Administration said late Tuesday.
NASA's Spitzer space-based infrared telescope captured the data from two gaseous exoplanets known as "hot Jupiters" because of their proximity to their suns and their resemblance to our solar system's gas giant. One in the constellation Vulpecula, designated HD 189733b, is 595.5 trillion kilometres or 62.94 light years from Earth, and the other, HD 209458b in the Pegasus constellation, is 1.45 quadrillion kilometres or 153.78 light years away.
A trillion is a million million or a one followed by 12 zeroes. A quadrillion is a million billion or one followed by 15 zeroes. A light year is the distance light travels in one year.
The telescope collected the spectrum from each of the two planets by using an instrument called a spectrograph, which splits light into different wavelengths in a manner similar to the way in which a prism splits light into a mini-rainbow.
Lines or "fingerprints" that appear in the spectrograph's image indicate the presence of specific elements such as hydrogen or oxygen. The fingerprint or signature of an element always appears in the same place on the spectrum and combinations can indicate the presence of certain chemicals.
By analyzing a planet's spectrum, scientists can figure out the composition of the atmosphere.
"The theorists' heads were spinning when they saw the data," Jeremy Richardson of NASA's Goddard Space Flight Center inGreenbelt, Md., said in a written statement.
No water in atmosphere
The data collected suggest that both planets are drier and cloudier than expected — scientists had theorized that hot Jupiters would have plenty of water in their atmospheres but none was found around the exoplanets studied.
One of the exoplanets, HD 209458b, has sand grains called silicates floating in its atmosphere, which suggests water exists there, but is hidden under high dust clouds of a kind that don't exist around planets in our own solar system.
"It is virtually impossible for water, in the form of vapor, to be absent from the planet, so it must be hidden, probably by the dusty cloud layer we detected in our spectrum," Richardson said. He is the lead author of a paper in the Feb. 22 issue of the science journal Nature that describes a spectrum for HD 209458b.
There are about 200 known exoplanets in the universe.