55 Cancri e is the densest and most solid planet ever found

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  • It has a surface temperature close to 2,700C
  • A year there last just 18 hours

The discovery of an ‘exotic super-Earth’ that is as dense as lead and where a year lasts just 18 hours could be the most significant breakthrough yet in the study of planet evolution and survival.
The remarkable find – named 55 Cancri e – is the densest and most solid planet ever uncovered and is so close to Earth that stargazers can view its sun with the naked eye.
The rocky ‘exoplanet’, meaning it’s out of our solar system, is 13,000miles in diameter or 60 per cent larger than Earth but is eight times as massive and twice as dense.

Two planetary systems: A simulation of planet 55 Cancri e passing in front of its parent star, compared to Earth and Jupiter transiting our Sun. The MOST telescope detected the tiny dip in starlight caused when the super-Earth planet blocked a small portion of the disk of the star 55 Cancri A, which is nearly a twin to the sun (

And despite a surface temperature close to 2,700C (4,900F), some astronomers believe the planet may retain an atmosphere thanks to its strong gravity.
Super-Earths, which are up to ten times larger than our own planet, hold a special interest for scientists because they have the potential to be solid or have liquid oceans.
That means if other conditions, such as temperature, are right, they may be a potential home for alien life forms.
‘It’s so exotic, it’s like the poster child for rocky super-Earths,’ mission scientist Jaymie Matthews, of the University of British Columbia, said.
‘It’s the densest solid planet found anywhere so far, in the solar system or beyond – you would weigh three times heavier than you do on Earth.’
Making the discovery even more remarkable, the planet was found using a bargain-basement space telescope from the University of British Columbia.
The data collected by the suitcase-sized telescope called MOST (Microvariability and Oscillations of STars) shows the new planet orbits a star, called 55 Cancri A, so closely that a year lasts just 17 hours and 41 minutes.
‘By day, the sun would look 60 times bigger and shine 3,600 times brighter in the sky,’ Professor Matthews said. ‘You could set dates on this world by your wrist watch, not a calendar.’
Approximately 40 light years away, the planet’s host star – a G-type star, or yellow dwarf like our own sun – is visible to the naked eye for the next two months in the constellation of Cancer.
Cancri e is part of a system of four planets that have been under surveillance by scientists since 1997 but the latest find stands out because it’s so dense and so close to Earth.
The group was discovered using the ‘Doppler technique’ that measures wobbles in stars caused by the gravitational pull of their unseen planets.
Although the inferno-like heat means life on 55 Cancri e is all but impossible, it is the type of planet scientists are desperate to ‘visit’ with their telescopes.
‘The brightness of the host star makes many types of sensitive measurements possible, so 55 Cancri e is the perfect laboratory to test theories of planet formation, evolution and survival,’ lead study author Josh Winn of the Massachusetts Institute of Technology said.
‘It’s wonderful to be able to point to a naked-eye star and know the mass and radius of one of its planets, especially a distinctive one like this.’
The discovery also excites Jaymie Matthews: ‘That’s the kind of thing Captain Kirk would do in an old episode of Star Trek.
‘We’re finally catching up with – maybe starting to surpass – the science fiction I dreamed about as a kid.’
MOST is a micro-satellite that orbits the Earth as part of a Canadian Space Agency mission and carries a telescope that feeds into a photometer, an instrument that measures the intensity of light from distant stars.
It was launched by the Canadian Space Agency in 2003 to study 10 stars in a mission that was expected to last just a year. But almost eight years later, MOST is still going strong and has observed more than 2,000 stars.
‘We’ve had a big bang for the buck,’ Professor Matthews said of the $10million device.

Size of a suitcase: Canada's space telescope MOST detected the transits of 55 Cancri e as it orbited its star (

The discovery team included astronomers from the Massachusetts Institute of Technology, the University of British Columbia, the Harvard-Smithsonian Center for Astrophysics and the University of California at Santa Cruz.

Written by physicsgg

May 2, 2011 at 10:25 am


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