pending planets

Last week we had an inaugural meeting for our new "Center for Exoplanets and Habitable Worlds".

There were some interesting talks and new planets aplenty

Mayor was there and presented some preliminary results, and hinted at upcoming, but as yet unpublished results.

Current radial velocity sensitivity is better than 1 m/sec on the HARPS instrument, over a 4 year baseline, so far.
They are doing a survey of a sub-sample of 200 stars from the CORALIE survey, with high cadence - doing frequent observing over several nights and then longer intervals, but adapting to hints of signals. This gets a lot of discoveries, but makes it very hard to model post facto the completeness of the survey since sampling is not uniform.

There are tens of candidate planets with masses less than 50 times the mass of the Earth, including many multiplets.
More than 40 candidate objects with mass less than 30 Earth masses and orbital periods less than 50 days. Including objects on significantly eccentric orbits.

There is a hint of a a peak towards shorter periods in this range, and that the mass function is rising towards lower masses.

Interestingly, the fraction of stars with planets in this mass range does not show the sensitivity to metallicity seen for the hot, short orbital periods, giant planets.
Which would be an extremely interesting result if it holds up as more data is gathered.

They're looking at some bright nearby star and getting sensitivity down to 0.4 m/sec, with very well identified sources of noise on different timescales. It does not seem unlikely that the next generation spectrographs, with laser comb frequency standars and on 10 m telescopes, will get to precision of 10 cm/sec over multi-year timescales.

At current levels, the data extrapolates to detection of earth mass planets with short orbital periods by 2010 or 2011. And suggests the sensitivity will be there to followup low mass transiting planets for Kepler, if the host star is not too faint.
The HARPS data strongly suggest that Kepler can expect to see a lot of "super-Earths", and around K-stars they might well be within the habitable zone.
K stars are looking very interesting, might have rushed too much over to the M stars...

The hopefully-soon-to-be-published COROT detection-that-is-extremely-interesting was flashed up on the screen.

The radius is clearly less than 2 earth radii, and (radial velocity?) confirmation is being pursued. One infers a mass of at least 2 earth masses and no more than 8 earth masses or so. Depends a bit on what one believes about theoretical predictions of phase transitions at very high pressures and abundance of ice VII, X and XI. Or so I am told.
Hence one also infers it cannot be a neptunian, but must be a true rocky or icy planet (well, melted ice...).

Interesting... COROT clearly has the sensitivity so where are the other candidates?
Could be they have issue with systemic calibration over long time periods???
Which means a lot of candidate small planets may pop out of the data if and when they sort that out.
I expect a lot more from COROT, but they may take their time and do it properly, especially if there is concern about systematics in the relative photometry. The short term relative photometry looks exquisite.

Interesting times.

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So where is the new Center ? is there an URL?

CoRoT teases a lot with hints of new planets; any pointers to more details on this Super-Earth (for someone who's thesis is on Ocean planets ...)

I'm confused by your comments on the COROT planet. If the radius was 1.7 Earth radii, then we'd expect a mass of about 10 Earth masses if the composition was similar to that of the Earth. If the mass was as small as 2 Earth masses, then I would think that it must be mostly water or have a significant amount of H and He. So, I would think that a Neptune-like composition would certainly be a possibility.

By David Bennett (not verified) on 04 Oct 2008 #permalink

At 1.7 Earth radii, I'd expect mass of 5-8 earth masses or so, maybe a bit higher if there is a phase transition to a denser rocky state.
A water world might allow masses in the 2-6 earth mass range, I think if you allow any significant H/He the photosphere would be larger than 2 earth radii for any mass.

This is from eyeballing phase graphs, not doing formal calculation.