Monday, July 12, 2010

Earth's Dusty Path Around the Sun

"Sun's Dust Ring Could Help Find Exo-Earths"
Wired Science (July 8, 2010)

"Earth-like exoplanets could announce their presence through trailing clumps of dust — and new observations of the Earth's own dust cloud could provide a way to find them. Over the course of five years, the Spitzer Space Telescope drifted through a diffuse but extensive ring of dust particles that orbit the sun in lockstep with the Earth, showing astronomers for the first time what the dusty signature of an exo-Earth might look like.

" 'For the first time we can measure the structure of that cloud along the Earth's orbit, using this moving space probe that travels through the cloud,' said astronomer William T. Reach of the Universities Space Research Association, the author of a paper to appear in the journal Icarus. 'We can use that as a key, as a template, to understand the dust around other stars.'..."

This isn't the zodiacal cloud, that pancake of dust that surrounds our sun, or isn't the entire cloud at any rate.

This ring of dust orbits with Earth, with the thickest concentration just behind our planet. Back to the article:

"...Most of the dust in the plane of the solar system, called the zodiacal cloud, will eventually spiral into the sun. But particles of the right size, tens of micrometers across, can feel a little gravitational push as they float by the Earth. That push counteracts the sun's pull just enough to hold the dust particles in a loose halo around the sun. The subtle interactions of the Earth and the dust grains' movements lead to the backward-facing clump...."

Using data from the Spitzer Space Telescope, researchers can make models of what dust rings of planets like Earth, orbiting other stars, might reasonably look like to out telescopes. This could be a useful tool in detecting "exo-Earths."

Or any other relatively small, rocky planet at about our distance from its star. Existing methods for finding exoplanets are pretty good at finding really big ones that are very close to their stars. The sort of world we're standing on - not so much.

This could lead to the discovery of many more planets - or, maybe, add evidence for the argument that the sort of planetary system we're in is rare.

Either way, it'll be interesting.

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