Astronomers find batch of 'super-Earths'
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- Date: Sun, 6 Jul 2008 00:27:12 -0700 (PDT)
Source:
http://www.bigpond. com/news/ technology/ content/20080616 /2276584.
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Astronomers find batch of 'super-Earths'
June 16, 2008 - 10:36PM
Source: ABC
European researchers say they have discovered a batch of three "super-
Earths" orbiting a nearby star, and two other solar systems with small
planets as well.
They say their findings, presented at a conference in France, suggest
that Earth-like planets may be very common.
"Does every single star harbour planets and, if yes, how many?" asked
Michel Mayor of Switzerland' s Geneva Observatory.
"We may not yet know the answer but we are making huge progress
towards it."
The trio of planets orbit a star slightly less massive than our Sun,
42 light-years away towards the southern Doradus and Pictor
constellations.
A light-year is the distance light can travel in one year at a speed
of about 300,000 km a second, or about 9.5 trillion km.
The planets are bigger than Earth - one is 4.2 times the mass, one is
6.7 times and the third is 9.4 times.
They orbit their star at extremely rapid speeds - one whizzing around
in just four days, compared with Earth's 365 days, one taking 10 days
and the slowest taking 20 days.
Professor Mayor and colleagues used the High Accuracy Radial velocity
Planet Searcher or HARPS, a telescope at La Silla observatory in
Chile, to find the planets.
More than 270 so-called exoplanets have been found. Most are giants,
resembling Jupiter or Saturn. Smaller planets closer to the size of
Earth are far more difficult to spot.
None can be imaged directly at such distances but can be spotted
indirectly using radio waves or, in the case of HARPS, spectrographic
measurements.
As a planet orbits, it makes the star wobble very slightly and this
can be measured.
"With the advent of much more precise instruments such as the HARPS
spectrograph ... we can now discover smaller planets, with masses
between 2 and 10 times the Earth's mass," said Stephane Udry, who also
worked on the study.
The team also say they have found a planet 7.5 times the mass of Earth
orbiting the star HD 181433 in 9.5 days.
This star also has a Jupiter-like planet that orbits every three
years.
Another solar system has a planet 22 times the mass of Earth, orbiting
every four days, and a Saturn-like planet with a 3-year period.
"Clearly these planets are only the tip of the iceberg," said
Professor Mayor.
"The analysis of all the stars studied with HARPS shows that about one
third of all solar-like stars have either super-Earth or Neptune-like
planets with orbital periods shorter than 50 days."
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