Densest known rocky planet: Astronomers unveil portrait of 'super-exotic super-Earth'

Apr 29, 2011
Family portraits of two planetary systems: A simulation of the silhouette of planet 55 Cancri e passing in front of (“transiting”) its parent star, compared to the Earth and Jupiter transiting our Sun, as seen from outside the Solar System. The MOST space 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. (Credit: Jason Rowe, NASA Ames and SETI Institute and Prof. Jaymie Matthews, UBC)

(PhysOrg.com) -- An international team of astronomers today revealed details of a "super-exotic" exoplanet that would make the planet Pandora in the movie Avatar pale in comparison.

The planet, named 55 Cancri e, is 60 per cent larger in diameter than but eight times as massive. Twice as dense as Earth – almost as dense as lead – it is the densest solid planet known, according to a team led by astronomers from the Massachusetts Institute of Technology (MIT), the University of British Columbia (UBC), the Harvard‑Smithsonian Center for Astrophysics and the University of California at Santa Cruz (UCSC).

The research, based on observations from Canada's MOST (Microvariability & Oscillations of ) space telescope, was released online today at arXiv.org and has been submitted for publication in The Astrophysical Journal Letters. MOST is a Canadian Space Agency mission.

Approximately 40 light years from Earth, 55 Cancri e orbits a star – called 55 Cancri A – so closely that its year is less than 18 hours long. "You could set dates on this world by your wrist watch, not a calendar," says UBC astronomer Jaymie Matthews.

The temperature on the planet's surface could be as high as 2,700 degrees Celsius. "Because of the infernal heat, it's unlikely that 55 Cancri e has an atmosphere," says lead author Josh Winn of MIT. "So this is not the type of place where exobiologists would look for life."

However, 55 Cancri e is the type of place exoplanetary scientists will be eager to "visit" with their telescopes, says Winn. "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."

While the planet isn't visible, even through a telescope, its host star, 55 Cancri A, can be observed with the naked eye for the next two months on a clear dark night.

"On this world – 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. By day, the sun would look 60 times bigger and shine 3,600 times brighter in the sky," says Matthews, MOST Mission Scientist and second author on the paper.

How to point to an alien world tonight: Amateur exoplanet hunters in North America and Europe can go outside, away from city lights, and see the star 55 Cancri A for themselves. Around 10 pm local time, look southwest, below the Big Dipper, near the northern tip of the brightest stars in the constellation Cancer (the Crab). This view of the sky shown is from Vancouver, Canada, on the night of 28 April 2011, but the view will be similar for all mid-northern latitudes Stellarium and Prof. Jaymie Matthews, UBC.)

The first planet discovered around 55 Cancri A – designated "b" – was found by a California-based team in 1997. Over the next five years, two more planets ("c" and "d") were found by the same team around the star. In 2004, a Texas-based team found 55 Cancri e, the subject of the latest paper and (a fifth planet, f, was discovered in 2008.)

All five planets were detected using the Doppler technique, where a star's "wobbles" due to the gravities of its unseen planets are measured in the shifting wavelengths of the spectra of the starlight.

Last year, Rebekah Dawson, an astronomy PhD student at Harvard and Daniel Fabrycky, a Hubble Fellow at UCSC, re-analyzed the data and proposed that the orbital period of 55 Cancri e could be much shorter than others had assumed.

MIT's Winn, along with Smithsonian astronomer Matt Holman, brought the problem to Matthews, who ordered the astronomical equivalent of a police stakeout using MOST, which was able to detect subtle dips in the brightness of star 55 Cancri A as planet e passed in front of it during each orbit.

The research team found that these "transits" occur like clockwork every 17 hours and 41 minutes, just as Dawson and Fabrycky predicted. The starlight is dimmed by only 1/50th of a per cent during each transit, telling the astronomers that the planet's diameter is about 21,000 km – only 60 per cent larger than Earth.

Canada's space telescope, MOST, which detected the transits of the super-Earth exoplanet 55 Cancri e. (Credit: Canadian Space Agency and the MOST Team.)

"It's wonderful to be able to point to a naked-eye star and know the mass and radius of one of its , especially a distinctive one like this," says Winn.

Matthews agrees. "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."

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User comments : 22

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Mercury_01
1.6 / 5 (11) Apr 29, 2011
This writing is crazy. I had to wade through three paragraphs of media- pandering, pseudo- sensationalist crap cake to finally get to the point: A planet was detected with a very high density and close orbit.
Mercury_01
3.2 / 5 (9) Apr 29, 2011
"Super exotic Super earth"? Seriously?
omatumr
1.4 / 5 (15) Apr 29, 2011
This writing is crazy. I had to wade through three paragraphs of media- pandering, pseudo- sensationalist crap cake to finally get to the point: A planet was detected with a very high density and close orbit.


Yes, a planet with a very high density and close orbit was observed because such planets consist almost entirely of Fe-Ni produced near the core of the supernova.

Just like the event that produced dense planets near the Sun:

http://www.omatum...igin.htm

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
delemming
4.7 / 5 (9) Apr 29, 2011
how can it be 'super' exotic while no planet found till now is anything like our own?
Husky
4.5 / 5 (10) Apr 29, 2011
a miners wet dream, a huge blob of liquid metal waiting to be scooped up, a bit far away though...
Jeddy_Mctedder
2 / 5 (8) Apr 29, 2011
someone needs to push mercury directly into the sun. jeeeeezus.
LKD
4.1 / 5 (13) Apr 29, 2011
astronomers today revealed details of a "super-exotic" exoplanet that would make the planet Pandora in the movie Avatar pale in comparison.


Well seeing Pandora couldn't exist exactly what is your point?

This is the remnant of a gas giant that had its atmosphere burned off. We should be celebrating how we can get details about the core. This is a great chance for exceptionally revealing science.
GreyLensman
4.3 / 5 (7) Apr 29, 2011
Was thinking the same thing, LKD. Could be - but we just don't know enough to say for sure. Our sample of exoplanets is subject to such a huge bias.
TopherTO
5 / 5 (10) Apr 29, 2011
As a Canadian, it is nice to see Canada providing direct contributions to the exoplanet field. The Perimeter Institute, MOST, and earlier with the Canadarm 1,2 are examples of why we need to pressure for continued and strengthened public support for astronomy/physics.
DigiMc
4.8 / 5 (17) Apr 29, 2011
Pandora was not a planet, but a moon (orbiting a planet named Polyphemus).

Yes I should get a life instead of nitpicking :-)
pokerdice1
2.5 / 5 (8) Apr 29, 2011
This planet sucks!
that_guy
1.7 / 5 (7) Apr 29, 2011
As a Canadian, it is nice to see Canada providing direct contributions to the exoplanet field. The Perimeter Institute, MOST, and earlier with the Canadarm 1,2 are examples of why we need to pressure for continued and strengthened public support for astronomy/physics.

It's about time Canada got into the game. Us Americans are tired of carrying all the scientific weight for north america. Ever since you guys made that space shuttle robot arm, you all started acting like Canada is tha man, and get credit for anything he wants. Yeah, I went there. jk
Pratyeka
4.2 / 5 (6) Apr 29, 2011
to "that guy":
the landing gears of the LEMs were canadian made, which makes us the first on the moon, you ignorant.
unknownorgin
1 / 5 (4) Apr 30, 2011
Canada should look at the picture of the space telescope because it looks like a plywood box in need of a paint job. The gold foil and lack of gold color give it a wood look but it is a bad joke on canada. A planet so close to its sun must be colliding with particles emmited by the star so it will slow down until it falls into its sun.
braindamage
not rated yet Apr 30, 2011
Lets not fight, there's plenty of toys for everyone. If one does not like what the Canadians have accomplished, come up with something better.
that_guy
2.7 / 5 (3) Apr 30, 2011
Wow, I am amazed at how little sense of humor some of you guys have. It's one thing to maybe think it's not funny, another thing altogether to be like pratyeka and call me ignorant without even understanding that it's not serious. at all. and explicitly indicates that it's a joke.

Pratyeka, for Canada's sake, I hope you're not canadian.
Shootist
1.8 / 5 (5) Apr 30, 2011
Oh Canada!, Oh Canada!,
with their squinty little eyes,
flapping heads all full of lies
Oh Canada!, Oh Can-a-daaaa-a!,
It's not a real country anyway.
jamesrm
1 / 5 (1) Apr 30, 2011
""visit" with their telescopes"

Please stop torturing the English language.
unknownorgin
3 / 5 (4) Apr 30, 2011
I am sure the canadian telescope is a fine scientific instrument but the photograph at least on my monitor makes it look like a plywood box. No insult intended.
frajo
not rated yet May 01, 2011
I am sure the canadian telescope is a fine scientific instrument but the photograph at least on my monitor makes it look like a plywood box. No insult intended.
Seems to be an artefact of photoediting. When you download the image and play around a bit with RGB colours, brightness, and contrast, it begins to look more real. Only those two large white patches on the front I can't make look real.
d_robison
5 / 5 (3) May 02, 2011
"Nationalism is an infantile sickness. It is the measles of the human race." -Albert Einstein

That being said, who cares what country did what, we should be happy with any scietific discoveries no matter where they come from.
Paljor
not rated yet May 03, 2011
I am suprised that canada was looking for extra solar planets. Do we know if it has an atmosphere? What is it made of?

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