Three 'super-Earths' discovered
Are planets found orbiting in nearby solar system capable of
supporting human life?
A nearby solar system is packed with up to seven planets including
three "super-Earths" that may be capable of supporting life, say
The planets orbit Gliese 667C, one of three stars bound together in a
triple system 22 light years away in the constellation of Scorpius.
Astronomers believe they fill up the star's "habitable zone" - the
orbital region just the right distance away to permit mild temperatures
and liquid water.
Three of the new worlds are categorised as "super-Earths", meaning
they have between one and 10 times the mass of the Earth.
If like the Earth they are rocky and possess atmospheres and watery
lakes or oceans, they could conceivably harbour life.Because Gliese 667C
is part of a triple system, anyone standing on one of the planets would
see its two companions as very bright daylight stars. At night, the
companion stars would shine as brightly as the full moon on Earth.
Previous studies had identified three planets orbiting the star,
including one in the habitable zone.
The other planets were discovered after astronomers revisited
previous data and made new observations using a range of telescopes.
Lead scientist Dr Guillem Anglada-Escuda, from the University of
Gottingen in Germany, said: "We identified three strong signals in the
star before, but it was possible that smaller planets were hidden in the
data. "We re-examined the existing data, added some new observations,
and applied two different data analysis methods especially designed to
deal with multi-planet signal detection. Both methods yielded the same
answer: there are five very secure signals and up to seven low-mass
planets in short-period orbits around the star."
Gliese 667C is smaller, fainter and cooler than the Sun, having just
over a third of its mass. As a result its habitable zone - where
conditions are warm but not scalding hot - is relatively close in.
This is helpful to astronomers because the limits of current
technology make it hard to detect smaller Earth-like planets in more
distant orbits.The astronomers believe the star's habitable zone is full
- there are no more stable, long-lived orbits available within it that
could contain other planets.
If the Earth circled the Sun at the same distance it would be far too
hot to support life. But much milder conditions may exist on planets
orbiting close to dimmer, cooler stars such as Gliese 667C. Since
low-mass stars make up around 80 percent of the stars in our galaxy, the
Milky Way, astronomers hope they might provide a rich harvest of other
potentially habitable close-orbiting planets.
"The number of potentially habitable planets in our galaxy is much
greater if we can expect to find several of them around each low-mass
star," said co-researcher Dr Rory Barnes, from the University of
Washington. "Instead of looking at 10 stars to look for a single
potentially habitable planets, we now know we can look at just one star
and find several of them."
The findings, released by the European Southern Observatory, are to
appear in Astronomy and Astrophysics.
Although the planets are far too small to see with a telescope, they
could be detected by looking for the effect of their gravity on the
The gravitational "tug" of an orbiting planet makes a star "wobble"
which in turn causes its light wavelength to fluctuate. By measuring
these tiny changes astronomers can calculate the planet's orbit and
- The Independent