The MEarth project

The MEarth project: searching for transiting habitable super-Earths around nearby M-dwarfs

A description of the survey, plus some preliminary results. While no planets are reported (yet), a new M-dwarf+M-dwarf eclipsing binary has been discovered.

It seems they're able to detect only that...

So far...

I remember reading about this at around the beginning of the year.

The authors of the paper write that they've only got a few of their telescopes up and running, and they'll have a few more in September(? -- It's been a while since I read it... ~3 hours). So, it isn't fully operational yet.

Identity of the eclipsing binary is GJ 3236

http://www.astro.ex.ac.uk/esp09/presentations/Irwin_Tuesday.pdf

Quote :

Largest data-set spans October 2008 – June 2009 (inclusive)
- 20 minute cadence, 715nm long-pass filter
- Targets M3 or later, high proper motion selection and < 33pc
- 355 well-observed (> 100 data points over > 10 nights)
– 52 reasonably solid detections of rotation periods
– Very few not variable at level to which we are sensitive
– Majority of the rest are clearly variable but difficult to determine period (spot evolution? systematics? not enough data yet?)

http://www.astro.ex.ac.uk/esp09/presentations/Berta_Monday.pdf

Quote :

find 3 candidates from these criteria
+ high-cadence follow-up with the MEarth observatory confirmed all three to be true
astrophysical transits/eclipses
+ criteria should be taken as conservative (pure but not necessarily complete!)
+ use them to simulate current sensitivity to believable transits

I.e. they have studied around (355/2000)< 20% sample and there is three good candidates in planets.

3 planets in 20%? So perhaps 15 planets total? If I recall, the yield from the MEarth project was expected to be much smaller than this. This is great news.

http://www.eso.org/sci/observing/visas/lp/lpsummary/180.C-0886.html

Quote :

Title: "New habitable planets around M dwarfs, and 1st radius measurement of a 1-30 M exoplanet"

Scientific program:
"With HARPS observations, we propose to detect:
− 20−30 new very-low mass planets (typically 4 − 16M),
− among which  2 − 3 habitable planets
− and at least one transit of a low-mass planet.
This goal will be achieved by observing 250 M dwarfs with high-frequency observations (one measurement per night during 10 nights). After each observing campaign of 10 nights, the few best candidates will be followed with HARPS during 10 more nights, to i) confirm the discoveries and ii) refine the ephemeris for a photometric transit search.
Such a major increase of the still small sample of very-low-mass planets and/or the first radius measurements of such objects will obviously put unprecedented constraints on our understanding of planetary structure and formation.
The observational effort described in the present proposal ask for half the time required to reach that goal (i.e. 80 nights a needed in total, and 40 nights are asked for P80 and P81)"

I.e. Geneva group assesses the frequency of small planets orbiting red dwarfs in 10%. If we take the probability of transit at 10%, this is 1 of transiting planets in the 100 red dwarfs.

No new Mearth candidates since Gj 1214 b?

http://arxiv.org/abs/1307.3178

Constraints on Planet Occurrence around Nearby Mid-to-Late M Dwarfs from the MEarth Project

The MEarth Project is a ground-based photometric survey to find planets transiting the closest and smallest main-sequence stars. In its first four years, MEarth discovered one transiting exoplanet, the 2.7 Earth radius planet GJ1214b. Here, we answer an outstanding question: in light of the bounty of small planets transiting small stars uncovered by the Kepler mission, should MEarth have found more than just one planet so far? We estimate MEarth's ensemble sensitivity to exoplanets by performing end-to-end simulations of 1.25 million observations of 988 nearby mid-to-late M dwarfs, gathered by MEarth between October 2008 and June 2012. For 2-4 Earth radius planets, we compare this sensitivity to results from Kepler and find that MEarth should have found planets at a rate of 0.05 - 0.36 planets/year in its first four years. As part of this analysis, we provide new analytic fits to the Kepler early M dwarf planet occurrence distribution. When extrapolating between Kepler's early M dwarfs and MEarth's mid-to-late M dwarfs, we find that assuming the planet occurrence distribution stays fixed with respect to planetary equilibrium temperature provides a good match to our detection of a planet with GJ1214b's observed properties. For larger planets, we find that the warm (600-700K), Neptune-sized (4 Earth radius) exoplanets that transit early M dwarfs like Gl436 and GJ3470 occur at a rate of <0.15/star (at 95% confidence) around MEarth's later M dwarf targets. We describe a strategy with which MEarth can increase its expected planet yield by 2.5X without new telescopes, by shifting its sensitivity toward the smaller and cooler exoplanets that Kepler has demonstrated to be abundant.