Reaching for the… Gliese581?

By DION PRETORIUS

Details of the first earth-like planet ever discovered, Gliese 581g, were just released by the University of California. What have they found?

Astronomers have found what seems to be the first earth-like planet in our galaxy, 20, 000 light years from earth. Astronomers at the University of California and the Carnegie Institution of Washington were examining planets orbiting around the red dwarf star, Gliese 581, when they found an interesting planet they named ‘G’.

Planet G lies in what scientists call the ‘habitable zone’ of its solar system. This means it sits the right distance from the sun to have liquid water on its surface, giving the possibility of life.

To have found a planet that is so close to earth that has such similar characteristics to our planet has given astronomers a lot to be excited about. To the layman, 20, 000 light years may sound far, but our galaxy is nearly 100 000 light years across. This could mean there are several planets like earth in our galaxy, and maybe even more in the other estimated 200 billion galaxies in our universe. If one can be found so close to our planet, what’s to say there aren’t more even further out?

Vogt and his team, in their report released to arXiv.org, have said this planet could be the beginning of a second Age of Discovery. Others, such as astronomer and researcher at Mt Stromlo Observatory, Dr. Daniel Bayliss, are more conservative. “It’s a little bit early,” he said, “but I’m looking forward to finding out whether (habitable planets) are rare or not.”

How did these astronomers find Gliese 581g?

Astronomers lead by Steven Vogt at the University of California, Santa Cruz, and by Paul Butler of the Carnegie Institution of Washington observed the planetary movements in the Gliese 581 solar system. Searching for radial velocities, the astronomers recorded the movements of orbiting planets, and their effect on the trajectory of the star they orbited. When a planet spins around a star, it can make the star shake. The size of the shake can tell astronomers whether there are planets orbiting around the star and what size they might be.

Once they discovered Gliese 581g, they found that it sat close enough to its sun to have liquid water on its surface. Two planets that sat on either side of Gliese 581g were previously thought to be habitable, but their temperatures were found to be too extreme. Gliese 581g’s temperature, what astronomers and the media have called the ‘goldilocks’ planet, is just right.

Why is this planet a big find in astronomy?

Astronomers around the world are very excited about this latest find by the Carnegie-California Planet Search. “It’s a pretty big step,” says Bayliss, who is part of a planet searching project at Mt Stromlo Observatory. “We don’t know whether planets like earth are rare or common in our galaxy. Up till now it’s been guesses. This is the first time where we can actually start getting a quantative idea of whether (planets like) earth (are) rare or common.”

John Huchra from the Harvard-Smithsonian Centre for Astrophysics said “the first astronomer who can prove they found an Earth-like planet around an Earth-like star will win many kudos and prizes.” It’s what all of this research has been leading to, according to Bayliss and “the ultimate push has always been to find out whether there are habitable planets.”

What are Australian Astronomers doing in this field?

Australian astronomers have been involved in planetary searches for many years, not all in search for habitable planets however. Many projects look for planets a lot larger than Earth, which according to Bayliss, may not result in finding habitable planets.

One of the main planetary exploration projects is HAT-South, a search for planets larger than earth. Telescopes in Namibia, Chile and in Siding Springs near Coonabarabran in Australia watch the sky for 24 hours a day, searching for planets like Jupiter.

Scientists have also been working on similar projects to the one that found Gliese 581g. Australian astronomers, with both the University of California and the Carnegie Institution of Washington, have been working on an extension to their program called the Anglo-Australian Planet Search. For this project, a specially built Anglo-Australian Telescope searches for radial velocities, the same technique used to find Gliese 581g. This partnership has existed for more than 10 years and puts Australia in the thick of it regarding planetary exploration.

What is planned for the future?

The report released by Vogt, Butler, and their team has pointed out that this type of work is slow and difficult. To improve our ability to find new planets like earth, they have suggested two new telescopes be built in the northern and southern hemispheres specifically using radial velocities to find planets a similar size to earth.

Australian institutions, along with others around the world, are also investing in a new project called the Giant Magellan Telescope (GMT). This telescope, marked for completion in 2018, will give astronomers a much better chance of finding new planets. Its site, in Chile, is the highest and driest in the southern hemisphere and will give astronomers a better chance at finding more habitable planets.

Bayliss is optimistic about the future of astronomy, saying that over the next 10 years there is going to be a greater demand for the sort of technology that will tell us if stars have planets orbiting around them. Whatever the outcome, we can look forward to learning a lot more about our universe and what sort of planets exist within it.