Spitzer telescope finds distant planet that lacks methane

April 22nd, 2010 - 2:10 pm ICT by ANI  

Washington, Apr 22 (ANI): Using NASA’s Spitzer Space Telescope, scientists have made a rather strange finding about a distant planet- it lacks methane, an ingredient common to many of the planets in our solar system.

The discovery brings astronomers one-step closer to probing the atmospheres of distant planets the size of Earth.

“It’s a big puzzle. Models tell us that the carbon in this planet should be in the form of methane. Theorists are going to be quite busy trying to figure this one out,” said Kevin Stevenson, a planetary sciences graduate student at the University of Central Florida in Orlando, lead author of the study.

The methane-free planet, called GJ 436b, is about the size of Neptune, making it the smallest distant planet that any telescope has successfully “tasted,” or analysed.

Eventually, a larger space telescope could use the same kind of technique to search smaller, Earth-like worlds for methane and other chemical signs of life, such as water, oxygen and carbon dioxide.

“Ultimately, we want to find biosignatures on a small, rocky world. Oxygen, especially with even a little methane, would tell us that we humans might not be alone,” said Stevenson.

“In this case, we expected to find methane not because of the presence of life, but because of the planet’s chemistry. This type of planet should have cooked up methane. It’s like dipping bread into beaten eggs, frying it, and getting oatmeal in the end,” said Joseph Harrington.

At 800 Kelvin (or 980 degrees Fahrenheit), GJ 436b is supposed to have abundant methane and little carbon monoxide.

However, Spitzer observations have shown the opposite.

The space telescope has captured the planet’s light in six infrared wavelengths, showing evidence for carbon monoxide but not methane.

“We’re scratching our heads. But what this does tell us is that there is room for improvement in our models. Now we have actual data on faraway planets that will teach us what’s really going on in their atmospheres,” said Harrington. “.”

GJ 436b is located 33 light-years away in the constellation Leo, the Lion. It rides in a tight, 2.64-day orbit around its small star, an “M-dwarf” much cooler than our Sun.

The planet transits, or crosses in front of, its star as viewed from Earth.

Spitzer could detect the faint glow of GJ 436b by watching it slip behind its star, an event called a secondary eclipse.

The study has appeared in the journal Nature. (ANI)

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