Australasian Science: Australia's authority on science since 1938

Planets Are the Norm, Not the Exception

By Stephen Luntz

There are probably many more planets in our galaxy than stars.

The full text of this article can be purchased from Informit.

There are probably many more planets in our galaxy than stars, according to an international study published in Nature.

Over recent years the subtle movements in nearby stars, triggered by the gravitational effects of their companions, have been used to detect hundreds of planets. The Kepler space telescope, which is watching the dimming caused by planets passing across the face of the Sun, has turned the rate of discovery into an avalanche, with more than 2000 prospective planets revealed last year.

However, both techniques are limited, revealing only planets lying close to the parent star.

Microlensing, on the other hand, works best with planets orbiting at about twice the Earth–Sun distance, and can often pick up planets far further out, providing a much better guide to the true nature of other stellar systems.

Microlensing occurs when the gravity of a large object bends light from a more distant star around it, causing a temporary brightening of the object behind. On any given night one in a million stars lying in the direction of the centre of the galaxy will be lensing a more distant object.

“We have a couple of survey scopes watching millions of stars for signs of microlensing events,” says Dr Stefan Dieters of the University of Tasmania. “From these we pick the 50 or 60 most promising each year to watch in more detail.”

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The full text of this article can be purchased from Informit.