Monday, March 13, 2006

"Cold Earth" Detected Orbiting Distant Star.

Another startling discovery was announced concerning a "cold Earth" orbiting a distant star. This story comes at you courtesy of via Yahoo News. Excerpt:

Astronomers announced today the discovery of a frigid extrasolar planet several times larger than Earth orbiting a small red dwarf star roughly 9,000 light years away.

The finding alters astronomers' perceptions of planetary system formation and the distribution of planets in the galaxy, suggesting that large rock-ice worlds might outnumber gas giants like Jupiter. The newfound planet is about 13 times more massive than Earth and likely has an icy and rocky but barren terrestrial surface, and it is one of the coldest planets ever discovered outside of our solar system.

It orbits 250 million miles away from a red dwarf star, which is about half the size of our Sun and much cooler. The orbital distance is about the same as our solar system's asteroid belt is from the Sun.

The planet is similar in rocky structure to Earth and it is described a "super-Earth." But being so far away from a red dwarf means that its surface temperature is an inhospitable -330 degrees Fahrenheit (-201 Celsius), about the same as Uranus. That's too cold for liquid water or life as we know it.

Further analysis of the system revealed the absence of Jupiter-like gas giants, and scientists suspect the system literally ran out of gas and failed to form any. This may have starved the newfound planet of the raw materials it needed to turn into a gas giant itself.

"This icy super-Earth dominates the region around its star that in our solar system is populated by the gas-giant planets, Jupiter and Saturn. We've never seen a system like this before, because we've never had the means to find them," said study author Andrew Gould of The Ohio State University and leader of the MicroFUN planet-searching team.

Astronomers discovered this latest planet, catalogued as OGLE-2005-BLG-169lb, with a technique called microlensing, an effect where the gravity of a foreground star makes a more distant star appear brighter. If the foreground star is orbited by a planet, the planet's gravity can periodically warp the brightness of the background star by tiny amounts.

This shift is a telltale indicator of a planet, but is so brief that scientists must monitor the star closely and make multiple observations to confirm the planet's existence. In this case, the scientists were concerned that the warp wasn't caused by a planet, so they wrote a special computer program to speed up their models and confirm the existence of the Neptune-sized object.

The more we search, combined with the various new ways of searching, the more we find that planets are fairly common. And now, we seem to be finding planets that are closer to the size of Earth than ever. Is it just a matter of time before we stumble on to worlds that are even more similar to our own? Well, it would help if these worlds orbited stable, Main Sequence stars like our Sun rather than red dwarfs, which are prone to heavy flare activity, or hot, white stars that bathe their planets in continuous deadly radiation.

The next challenge will be to conquer the problem of the large distances involved in interstellar communication and travel, but for now, just establishing that there are planets out there that are somewhat similar to our own gives us hope that we'll have a reason for seeking these worlds out.

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