Goldilocks Might Find New Planet ‘just Right’

This artist's conception shows the inner four planets of the Gliese 581 system and their host star. The large planet in the foreground is the newly discovered Gliese 581 g, which has a 37-day orbit right in the middle of the star's habitable zone and is only three to four times the mass of Earth, with a diameter 1.2 to 1.4 times that of Earth. Credit: Lynette Cook

Better watch out for the three bears, Goldilocks. A team of exoplanet hunters from University of California-Santa Cruz, and the Carnegie Institution of Washington announced their exciting discovery today of a potentially habitable planet around the star Gliese (GLEE-zeh) 581 in the constellation Libra the Scales. They used a high resolution spectrometer on the Keck I telescope in Hawaii over a period of 11 years to dig out the subtle gravitational tugs the new planet, named Gliese 581 g, exerted on its host star. After detailed analysis, the scientists determined the planet has a mass three to four times that of Earth and orbits within the “goldilocks” or habitable zone over a period of 37 days. Habitable in this case means it’s at the right distance from its sun for liquid water to exist on its surface. It’s also massive enough to hold onto an atmosphere. Both are key ingredients for life.

“Our findings offer a very compelling case for a potentially habitable planet,” said Steven Vogt, professor of astronomy and astrophysics at UC Santa Cruz and co-leader of the Lick-Carnegie Exoplanet Survey. “The fact that we were able to detect this planet so quickly and so nearby tells us that planets like this must be really common.”

The planetary orbits of the Gliese 581 system compared to those of our own solar system. The star is orbited by six planets labeled from b through g. G orbits fourth from the star. Image Credit: National Science Foundation.
The sun (left) and star Gliese 581. Credit: R.J. Hall/Kevin Heider

Gliese 581 is a red dwarf star with only 1/3 the mass of the sun and a much cooler surface temperature — 5300 degrees F vs. 11,000. Red dwarfs are ideal candidates for searching for extrasolar planets because with cooler temperatures, their habitable zones lie closer to the star. A planet orbiting close to a small sun exerts a stronger, more easily detectable tug than one orbiting within the more distant habitable zone of a massive, hotter star.

The planet’s gravitational pull causes the star to wobble a bit back and forth, and that’s what astronomers detect with sophisticated equipment. Gliese 581 g orbits just 14 million miles from Gliese 581, more than six times closer than Earth to the sun. Its close proximity has slowed the planet’s rotation so only one side faces the sun, while the other is in shadow. The team estimates that temperatures range from 160 above on the sunny side to 25 below on the back. In the twilight zone, along day-night border, it would be comfortable enough to stroll about without a coat.

Gliese 581 is well known among the exoplanet crowd – four previous planets have been discovered around it. The Lick-Carnegie team added two more, making it the most exoplanet-rich star of any thus far discovered. The total of extrasolar planets currently stands at 490 planets. Amazing!

Read more about the new discovery HERE.