Tuesday, November 27, 2012

Astronomy Round-Up: Super-Earths, Broken Satellites, and Rogue Planets

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Rogue Planet

By Tom Ingram
Tom Ingram

     Astronomers have been doing brisk business over the last few weeks. Recently there have been a number of important discoveries about the nature of our universe. Here’s a roundup of three of them.

Researchers led by Mikko Tuomi of the University of Hertfordshire in the UK have announced the discovery of three new “super-Earth” planets orbiting the star HD 40307 – and one of them is in the star’s habitable zone. The term “super-Earth” is a little misleading, because it implies that the planet is like Earth, only bigger and better. In reality, a super-Earth is just a terrestrial planet that is up to ten times more massive than Earth – in other words, a rocky planet larger than Earth but smaller than Uranus.

HD 40307 was previously known to have three planets in its orbit. These planets, also super-Earths, orbit close to the star, too close to support life. Now the researchers have discovered three additional planets. The outermost of these, a planet seven times the mass of Earth, orbits HD 40307 at a distance similar to the Earth’s from the Sun. It exists in HD 40307’s “Goldilocks zone” (i.e., habitable zone), meaning the planet could support liquid water and a stable atmosphere. It also rotates on its axis in a way similar to Earth, suggesting the possibility of a day-night cycle like our own.

The discovery was made possible by a new technique for analyzing data from the HARPS spectrograph. HARPS senses the changes in the colour of a star’s light due to the gravitational pull of its planets. By filtering out noise from the star itself, the scientists were able to find extremely weak, previously undetectable signals indicating the presence of these three planets. . . .

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