New method of finding extrasolar planets: by observing dust

Friday, October 17, 2008

A glow called the zodiacal light can be seen in the sky before sunrise or after sunset. It's formed by sunlight scattered off of dust near the plane of Earth's orbit.
Credit: Yuri Beletsky/ESO Paranal

This article shows a new interesting method to find extrasolar planets, by observing the dust in a solar system which is disturbed in a certain way by the orbit of a planet. The dust in a solar system apparently forms a ring-like shape in accordance with the orbital resonance it has with a planet and that's what can be picked up. The article explains it much better than I could though:
"The particles spiral inward and then become temporarily trapped in resonances with the planet," Kuchner explains. A resonance occurs whenever a particle's orbital period is a small-number ratio -- such as two-thirds or five-sixths -- of the planet's.

For example, if a dust particle makes three orbits around its star every time the planet completes one, the particle repeatedly will feel an extra gravitational tug at the same point in its orbit. For a time, this extra nudge can offset the drag force from starlight and the dust can settle into subtle ring-like structures.
Also, this method will apparently be possible before we are able to directly image planets:
"It may be a while before we can directly image earthlike planets around other stars but, before then, we'll be able to detect the ornate and beautiful rings they carve in interplanetary dust," says Christopher Stark, the study's lead researcher at the University of Maryland, College Park.


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