Thursday, April 29, 2010

Planeta Distante sin ingrediente común

Recientemente se descubrió un exoplaneta que carece de un compuesto común en los planetas de nuestro sistema solar y de aquellos exoplanetas examinados hasta la fecha; Metano.

A continuación se muestra parte del artículo que explica con mayor detalle este fenómeno (está en inglés).

NASA's Spitzer Space Telescope has discovered something odd about a distant planet — it lacks methane, an ingredient common to many of the planets in our solar system.

"It's a big puzzle," said Kevin Stevenson, a planetary sciences student at the University of Central Florida in Orlando. "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."

The discovery brings astronomers one step closer to probing the atmospheres of distant planets the size of Earth. The methane-free planet, called GJ 436b, is about the size of Neptune, making it the smallest distant planet that any telescope has successfully analyzed. Eventually, a larger space telescope could use the same kind of technique to search smaller, earthlike 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," said Joseph Harrington of the University of Central Florida. "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."

Methane is present on our life-bearing planet, manufactured primarily by microbes living in cows and soaking in waterlogged rice fields. All of the giant planets in our solar system have methane, too, despite their lack of cows. Neptune is blue because of this chemical, which absorbs red light. Methane is a common ingredient of relatively cool bodies, including "failed" stars, which are called brown dwarfs.

In fact, any world with the common atmospheric mixes of hydrogen, carbon, and oxygen and a temperature up to 1340° Fahrenheit (730° Celsius) is expected to have a large amount of methane and a small amount of carbon monoxide. The carbon should "prefer" to be in the form of methane at these temperatures.

At 980° F (530° C), GJ 436b is supposed to have abundant methane and little carbon monoxide. 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.

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