There is some exciting news today regarding exoplanets – for the first time, multiple planets have been found orbiting within the habitable zone of their star, the region where temperatures can allow liquid water to exist on planets with rocky surfaces, like Earth. The news release was published this morning by the European Southern Observatory (ESO).
The star, Gliese 667C, is only about 22 light-years away, right next door in cosmic terms, and is part of a three-star system called Gliese 667 (or GJ 667) in the constellation Scorpius. Gliese 667C is smaller and dimmer than our own sun. Astronomers already knew that there were at least three planets orbiting this star, but now new observations from the ESO’s HARPS telescope and Very Large Telescope, the W.M. Keck Observatory and the Magellan Telescopes have shown that there are at least six and possibly seven.
What’s most intriguing however, is that three of those planets are orbiting within the star’s habitable zone. Moreover, all three planets, Gliese 667C c, f and e, are super-Earths, planets which are larger than Earth but smaller than Uranus or Neptune in our own solar system.
“We knew that the star had three planets from previous studies, so we wanted to see whether there were any more,” said Mikko Tuomi of the University of Hertfordshire, UK. “By adding some new observations and revisiting existing data we were able to confirm these three and confidently reveal several more. Finding three low-mass planets in the star’s habitable zone is very exciting!”
The actual surface conditions of the three super-Earth planets are not known yet, but generally, these kinds of planets are thought to most likely be rocky, with perhaps quite thick atmospheres. Kind of like Earth on steroids.
These new results are separate from the findings of the Kepler space telescope, which has found thousands of confirmed and candidate exoplanets so far, including many super-Earths. All of Kepler’s target stars, however, are much farther away than Gliese 667C. This is exciting because it shows that similar worlds are everywhere in the galaxy, not just in Kepler’s field of view. Other data from Kepler has shown that smaller worlds, like Earth or Mars are also probably quite common, maybe even more than larger planets. How many of those are also in their stars’ habitable zones?
This also now brings the total number of confirmed exoplanets so far to about 900, with thousands of other candidates awaiting confirmation!