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Super-earth confirmed, first of many? February 3, 2009

Posted by Sarah in science.
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Today with much to-do and under heavy embargoes, scientists have announced the discovery of an extrasolar planet with a mass diameter of just 1.7 times that of the Earth. That’s very very small. With a mass of It whizzes around its host star, Exo-7, in around 20 hours and with a temperature of over 1,000 degrees, is incredibly hot. Using data from the satellite CoRoT (Convection Rotation and planetray Transits), the German-led French-led team of scientists detected the minute dip in the light coming from the host star from the planet passing in front of it. The discovery was confirmed with observations at a number of ground-based observatories, including VLT, the Canada-France-Hawaii telescope, McDonald Observatory.

In case you hadn’t noticed: exoplanet news is coming hard and fast. Every year since 1995, when Mayor & Queloz reported the discovery of 51 Peg b, has seen a number of “major breakthroughs” (see here, here, and many more) in the detection and characterisation of planets around other stars in our Galaxy.  Scientists have pushed the boundaries of our knowledge to a massive extent, and the rapid progress is just fantastic. But brace yourself for more.

While the CoRoT Exo-7b discovery is clearly an exciting result and I certainly wouldn’t want to detract from the team’s accomplishments, let’s keep this in perspective. After all, CoRoT was designed specifically to detect planetary companions or seismic-like activity below the stellar surface. To do this, it stares at stars and records their light intensity to a high precision for an unprecedented amount of time. Since its launch in December 2006 and first light early in 2007, it has measured many thousands of stellar light curves; over the mission lifetime, it will look at over 120,000 stars!

The CoRoT mission was planned from the late 90s, soon after the first exoplanet discovery, and is one of the first major exoplanet surveys of its kind. The satellite is working a treat, so the number of known exoplanets will go through the roof in coming years. And NASA’s planet hunting Kepler mission is set for launch in March of this year.

In fact, the rate of discovery at this stage is most likely limited by how quickly people can actually examine the data.

Like with stars and galaxies, which we now know to come in every imagineable size, colour and flavour, the parameter space of the planets’ physical properties is likely to increase by orders of magnitude as well. This raises a bit of a PR question, as announcing every single one of these outliers could quickly become very boring indeed. I hope the media folks at ESA and CNRS have given this some thought and devised a strategy to give proper credit to scientists’ and engineers’ accomplishments with the CoRoT mission without causing major media (and public) exoplanet fatigue.

I presume the results were presented at the CoRoT science symposium that is taking place this week in Paris. Read the press release from Paris-Meudon Observatory here, from ESA here. The paper by Léger et al. will soon be submitted to a special edition of A&A dedicated to CoRoT science.

Image credit: CNRS



1. Vagueofgodalming - February 3, 2009

It’s exciting, but I think it’s the diameter that’s about 1.7 times Earth’s. The mass seems to be from 5 to 11 times Earth’s. Gliese 581c (for which we admittedly only have a minimum mass) is probably lighter.

http://exoplanet.eu/planet.php?p1=CoRoT-Exo-7&p2=b .

2. Pierre BARGE - February 3, 2009

I agree with your comment.

3. Pierre BARGE - February 4, 2009

The science team of CoRoT is not led by a German!

Please check your information. This is possibly a first sign of the Exoplanet fatigue but possibly also of a more standard illness.

Anyway, I think that the fatigue will increase when Kepler will be launched with a lot of exoplanet discoveries.

Sarah - February 4, 2009

Thanks for the comments and corrections all. I’ll check everything and update asap!

4. JT - February 5, 2009

I can’t believe there are no bloggers at the COROT science symposium giving a daily recap! 300+ exo-solar planets and counting, yet this is still exciting because each one is somehow always different from all that came before!

5. Pierre BARGE - February 5, 2009

Please note that what is equal to 1.7 Earth radius is the radius of this planet and not its diameter!

Thanks to check on the official press release, for example at:

6. Sarah - February 5, 2009

Pierre – if the radius is 1.7 times that of the Earth then so is the diameter. In any case, the Paris-Meudon press release says: “This new object, named CoRoT-Exo-7b, is very different: its diameter is only 1.8 that of the Earth. ” [NB – I heard it was 1.75 so should be ok to state both 1.7 and 1.8]. Or did I misunderstand your comment?

JT – yes on the one hand it would be great to get “live updates” from a conference like that, and some meetings like the UK National Astronomy Meeting last year had a pretty lively blog (http://orbitingfrog.com/nam/). But scientists present a lot of early results at such meetings, that are perhaps unconfirmed and often unpublished. Widely publicising these on the internet is just not a good idea. It’s important that these symposia remain places where scientists can exchange results and information with scrutiny only from their peers, not the interweb-at-large, politicians etc.

This exoplanet discovery hasn’t been published in a peer-reviewed journal yet, in fact no paper has even been submitted. So I thought carefully first about whether I even wanted to say something about it. In the end the large amount of ground-based data that has been collected by the team convinced me that they have gathered enough data to support their findings, and that the result will stand. But it would have been much nicer to read a paper than a bunch of press releases.

7. Vagueofgodalming - February 6, 2009

Sarah, thanks for taking the time to post this.

Sorry to come over all nitpicky in my first comment there – I was a bit annoyed with the ESA press people because I thought the way the release was worded (‘size’) was designed to encourage misunderstandings over mass and diameter, and to make it hard to do comparisons with other well-known small exoplanets.

Interestingly, the DPS 08 conference was streamed as live video on the internet, and then turned into downloadable movies. When what was streamed was things like Michael Mumma saying “Don’t tell anyone yet, but we’ve mapped methane on Mars”, it gets kind of interesting (I only found that after the public announcement myself).

8. Sarah - February 6, 2009

Vague – ah thanks, nice to hear. And nitpicking is good, diameter and mass of a planet are not exactly interchangeable quantities! I found out about the exoplanet discovery at a meeting 2 weeks ago too when a scientist said exactly the same thing about this discovery…. I think it’s best if those things don’t get streamed live personally.

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