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Hubble brings galaxies out of coma ...NASA’s Hubble Space Telescope has captured the magnificent starry population of the Coma Cluster galaxies, one of the densest known galaxy stockpiles in the Universe...

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Successful first test of high speed Moon penetrator

...high speed penetrators that could one day be used to breach the surface of planets, moons and asteroids have successfully passed their first test in the UK...

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Pluto assigned 'plutoid' tag in new IAU classification

...the term 'plutoid' has been introduced to describe "Pluto-like transneptunian dwarf planets"...

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Video archive

STS-120 day 2 highlights

Flight Day 2 of Discovery's mission focused on heat shield inspections. This movie shows the day's highlights.


STS-120 day 1 highlights

The highlights from shuttle Discovery's launch day are packaged into this movie.


STS-118: Highlights

The STS-118 crew, including Barbara Morgan, narrates its mission highlights film and answers questions in this post-flight presentation.

 Full presentation
 Mission film

STS-120: Rollout to pad

Space shuttle Discovery rolls out of the Vehicle Assembly Building and travels to launch pad 39A for its STS-120 mission.


Dawn leaves Earth

NASA's Dawn space probe launches aboard a Delta 2-Heavy rocket from Cape Canaveral to explore two worlds in the asteroid belt.

 Full coverage

Dawn: Launch preview

These briefings preview the launch and science objectives of NASA's Dawn asteroid orbiter.

 Launch | Science

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Trio of super-Earths discovered

Posted: June 16, 2008

A harvest of low mass planets has been discovered with the High Accuracy Radial Velocity Planet Searcher (HARPS) at the ESO La Silla Observatory, and 45 other candidate planets with masses below 30 Earth masses have also been identified.

The announcement was made by a team of European astronomers at the three day international conference ‘Extra-solar Super-Earths’ which began today.

The team made very precise measurements of the velocities of many stars over the last five years, which revealed the planets by inducing a wobble in the star’s motion. “The perturbations induced by the planets are really tiny – the mass of the smallest planets is one hundred thousand times smaller than that of the star – and only the high sensitivity of HARPS made it possible to detect them," says Francois Bouchy of the Institut d'Astrophysique de Paris.

"With the advent of much more precise instruments such as the HARPS spectrograph on ESO's 3.6 metre telescope at La Silla, we can now discover smaller planets, with masses between 2 and 10 times the Earth's mass," adds Stephane Udry from Geneva Observatory.

Artist impression of the new 'triple-Earth' system discovered by European astronomers using the HARP instrument at ESO's La Silla Observatory. The system orbits a star known to astronomers as HD 40307. Image: ESO.

The three super-Earths, which have masses 4.2, 6.7 and 9.4 times the mass of the Earth, orbit a star only slightly less massive than our own Sun with periods of 4.3, 9.6 and 20.4 days respectively. The system is located 42 light years away towards the southern Doradus and Pictor constellations.

In a second system, one 7.5 Earth mass planet orbits its parent star HD 181433 in 9.5 days and has a Jupiter-like companion orbiting at a relatively leisurely pace of 3 years. Yet another system highlighted by the research team is reported to have a 22-Earth mass planet orbiting with a period of 4 days and a Saturn-like planet orbiting with a three year period.

"Does every single star harbour planets and, if yes, how many? We may not yet know the answer but we are making huge progress towards it." Michel Mayor, Geneva Observatory.

More remarkably, analysis of all the stars studied so far with HARPS shows that about one third of all solar-like stars have either super-Earth of Neptune-like planets with orbits shorter than 50 days. It is even possible that more planets are lurking in these identified systems, awaiting discovery, because a planet in a tight, short period orbit is easier to find than one in a wide, long-period orbit.

"It is most probable that there are many other planets present: not only super-Earth and Neptune-like planets with longer periods, but also Earth-like planets that we cannot detect yet. Add to it the Jupiter-like planets already known, and you may well arrive at the conclusion that planets are ubiquitous," says Udry.