CoRoT Results

If I´m not mistaken, the original presentation:

"The smallest CoRoT planet", D. Rouan

was changed to:

"Has CoRoT discovered the first transiting super-earth around a main sequence star ?" D. Rouan, A. Léger, J. Schneider et al.

in the final program.

The fact they are not talking about a Corot-Exo-7b may mean that they are not 100% confident that this is a bona-fide planet. I don´t particularly like that final question mark in the later title...

Title also begs the question of why you'd have to qualify "first transiting super-Earth" with "around a main sequence star", but that's almost certainly reading too much into it...

Well I guess we just wait and find out. And in any case, judging by some of the titles, there will be some good stuff in there even if the super-Earth detection isn't entirely solid. Certainly they have something, and it's probably quite interesting, maybe more in the kind of way that CoRoT-Exo-3b was for being a transiting object in the brown dwarf desert, rather than being (super?)Earth shattering. I doubt anyone could get away with partying like it's 1995 over a single hot Jupiter detection anymore, though some of the CoRoT announcements have had a pretty good shot at it...

(All puns intentionally horrible)

If you download the program (a PDF) the file contains the abstracts for the presentations. More info is comming on Corot-exo-4b /5b and also this apparent detection of a deep secondary eclipse of Corot-exo-2b, apparently another member of the pM class of Pegasids. There indeed seems to be a lot of cool stuff in there...

Poster presentations
P-V-58
ATMOSPHERIC STUDY OF THE YOUNG COROT-EXO-2B
PLANET WITH SPITZER
B.-O. Demory (1), M. Gillon (1), D. Queloz (1), J. Schneider
(2), J. Harrington (3), M. Deleuil (4)
1 Geneva Observatory, Geneva, Switzerland; 2 Paris Observatory,
Meudon, France; 3 UCF, Orlando, USA; 4 OAMP,
Marseille, France

Hi!

CoRoT-Exo-7b comes :Super-Earth found! The smallest extrasolar planet ever discovered

Bye!

More info here:

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

Fascinating. It's finally here. CoRoT's 7th planet is a superEarth. That is better than I was expecting. Note that this planet breaks the records. Smallest known tranisiting planet, least massive transiting planet, lowest orbital period (0.85d!).

The interesting thing is that, assuming a maximum mass of 11 Mearth and a minimum radius of 1.75 Rearth, the maximum possible density can be calculated at around 2.7, about half that of the Earth. So it may be an silicate and ice (water) planet.

Plus a brown dwarf in tight orbit (30 Mj P=8.6 d e=0).

No hint of Corot-exo-6b yet.

Excuse me, but if the mass is 11 times that of Earth, and the radius is 1.75 times, the volume of Corot-exo-7b should be 1.75^3 that of Earth, and therefore, its density is 11 (mass) / 1.75^3 * 5.5 g/cm3 (Earth density) .
So, the value is 2.05 times Earth density, or aprox. 11.3 g/cm3, a lot different from Earth's.

You are absolutely correct. I forgot to leave the 4/3 pi factor out.

So, if its density is 11.3 g/cm3, what kind of planet should we expect?

From what I've read so far, it should have a lot of water in its interior, and its surface might be superheated.

The composition of the planet would be determined by where it formed. If it formed beyond the snow line and migrated inward, it'll have a lot of water content. If not, it could be quite dry.

At 11 Earth masses, I would expect any atmosphere to be rather thick. Hot water vapour atmosphere?

Space.com is reporting it as an "Earth-like planet orbiting a sun-like star." From that I'd expect continents and oceans and jungle vegetation and smiling flowers and dancing unicorns trailing rainbows behind them in blissful paradise.

Edasich wrote:

No hint of Corot-exo-6b yet.

All we know is it's a "giant planet in a 9 day orbit".

I don't suppose it's possible that CoRoT-Exo-7b is a mini-Neptune? (i.e. perhaps like the planets HD 40307).

With a hot water vapor atmosphere that close to the star, wouldn't it be expected that a lot of water would dissociate in the upper atmosphere and produce an hydrogen tail similar to that observed in HD209458 ?

Now this is weird. Extrasolar Planets Encyclopaedia's COROT-Exo-7 page lists a COROT-Exo-7c, which is listed as a 30 Jupiter mass planet in an 8.6 day orbit! You'd think such a weird planetary configuration would be at least mentioned in the press release. (First double transit system and all that)

Unless 8.6 days is rounded to 9, and the listing for "COROT-Exo-7c" is actually COROT-Exo-6b.

Wow that's really interesting. 30 M_j is a brown dwarf IMHO though. i've a hard enough time rationalising why a 20 M_j object should be called a planet, but a 30 M_j one?

CoRoT-Exo-6b being the 30 M_j object would make sense, and be easier to rationalise away as a brown dwarf. If the two planets are really in the same system, in such close orbits, then it's going to be very interesting indeed...

exoplanet wrote:

With a hot water vapor atmosphere that close to the star, wouldn't it be expected that a lot of water would dissociate in the upper atmosphere and produce an hydrogen tail similar to that observed in HD209458 ?

Mars lost a great lot of its water due to photodissociation (by ultraviolet light?), and Mars is very far from the sun, compared to Corot-exo-7b. So, wouldn´t this new planet have lost all water long ago, since the estimated age of its star is nearly 1 billion years (form Extrasolar Planets Encyclopedia)? The greater mass of the planet could limit the loss of water ?

30 M_J is pushing the use of the term "planet", it's pretty much right in the middle of the "brown dwarf desert". On the other hand, if such an object is in a non-hierarchical system, who knows.

Incidentally I partially retract the comment about double transits - working out the semimajor axis from the period ratio and taking the inclination of 70 degrees, the star would have to be at least 5.8 solar radii for the brown dwarf/superplanet to transit, assuming coplanarity, which is not particularly plausible for a K0V star. Plugging in values of 60 and 80 degrees for the ends of the error bars yields 3-8.5 solar radii, again not plausible. A double transit in such a configuration is therefore not guaranteed. Nevertheless even without the transit the configuration would almost certainly be worthy of mention as it would pose severe challenges to planet formation theories, so I'm guessing this is an error in the EPE database.

(Or another alternative, the value of 30 is actually meant to be Earth masses and this is a super Earth + hot Neptune system, but again this has the problem of not being mentioned in the press release.)

I'll e-mail Jean Schneider and ask him if indeed it is supposed to be 30 M_e, and while I'm at it, I'll ask where he got that planet from. After that, I'll plug in the values of the planets as given in the EPE into gravity simulator and check for stability.

Edit:
From the orbital parameters provided by the EPE, I calculate a stellar mass of 0.91 solar masses. Not unreasonable for K0V star. I calculated a semi-major axis of this "CoRoT-Exo-7 c" to be ~0.08 AU.

All in all, it looks pretty stable, if indeed there is a 30 M_j object at 0.08 AU.

Edit2:
Does anyone by chance know, or can calculate the radius of CoRoT-Exo-7 (the star itself)?

Edit3: On the Russian astronomy.ru forum, this was posted (after being translated into English)

Byran wrote:

When I first looked at the link Schroeder It said that the first mass of the planet in the vicinity of 5-11 J, and the second 30 J. So there probably a typo.

I've noticed the 30 Mj object has vanished indeed.

Sorry if I'm being slow but can someone clarify this for me:

The ~20hr period planet is Corot 7c? If so, what of 7b? Is there a Corot 7b?

Cheers.

Corot-Exo-7b is the 20hr period planet. The "super-Earth".

Corot-Exo-7c was likely a mistaken entry in the database.

We are still waiting on the announcement of another planet Corot-Exo-6b in this conference.

http://exoplanet.eu/star.php?st=CoRoT-Exo-7

I got a reply from Jean Schneider.

Jean Schneider wrote:

It is a mistake (an unconfirmed planet).
I have suppressed it.

Any news of Corot-Exo-6b ? Should have been announced by now...

According to the latest comment on the oklo.org post about this, there are apparently hints of an additional Neptune-mass planet with a period 4 times that of the super-Earth.

In the same post, regarding density:

"T = 1100-2000 K depending on albedo. If M > 6 M_earth, rocky - solid
or liquid lava? ocean if M < 5 M_earth. Atmosphere?? Would escape in
< 1 Gyr."

(this answers a previous question by Anarres)

"So, wouldn´t this new planet have lost all water long ago, since the
estimated age of its star is nearly 1 billion years (form Extrasolar
Planets Encyclopedia)? The greater mass of the planet could limit the
loss of water ?"