The Frequency of Planets around M Dwarfs

http://www.space.com/19655-alien-planets-discovery-wednesday.html

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But two out of the three terrestrial candidates are bigger than the 20 percent limit to be an earth analog.

Taking this fact into account it will lowers their results and maybe only 2% of the M stars has an earth analog in their HZs.

0.9,1.4 and 1.7 earth radius .1.4 earth radius is not bad as kepler 36 b has high density.Considering mass loss for kepler 36 b and no mass loss like in case this candidate this potentially habitable planet can have easily density over 5 g/cm3.Planet with radius 0.9 surely is similar in density to earth.Planet with radius 1.7 earth is mystery(as we have no similar planets with mass determined outside mass loss zone but the closest two kepler 32 b and c with 2.2 and 2.0 earth radius have density 1,7 and 2.6 g/cm3) but considering some data could have density around 3.7-4.2 g/cm3

Very good. When infrared spectrographs like CARMENES or HPF will start operations in the next few years, they will already know a handful of interesting targets to weigh or costrain.

Galzi wrote:

Very good. When infrared spectrographs like CARMENES or HPF will start operations in the next few years, they will already know a handful of interesting targets to weigh or costrain.

Yes! It is certainly frustrating not to have density values for the various potentially-habitable planets, what with the whole mini-Neptunes issue!

Minineptune? Very unlikely the candidate with 1.7 R in the worst case will have density 3.0 g/cm3 so if even planet contains hydrogen surely not enough to be even partly liquid so only gaseous with sharp transition to planet surface(rock or water)

Hey guys, I'm a newbie here. Amateur astronomer and tech geek. Just wanted to weigh in based on what we know about the Kepler program already.

I think that we have to remember two things here. First, this new data is all dependent upon that study group's re-interpretation of the radii of the M-dwarfs in question. Second, the eta_earth percentage drawn from this data may in fact be a low estimate, due to the fact that the Kepler mission is only half complete (or a high one, since the planets are still candidates!).

Kepler is continuing to discover small planets in short orbits and those small planets (especially on longer period orbits!) are the toughest to detect The census of these small stars can't possibly be complete at that level. Couldn't 2 to 6 percent be considered a minimum baseline? What I think is cool is that the study shows that it's possible that 60 percent of them have planets of varying types! What do you folks think? I can't wait till they release the actual study.

I think it's probably safe to say that most, if not all, of the transiting Earths around the M-dwarf target stars Kepler is observing have already been found. The 6% may not actually be a lower limit. It's well-established that eta_Earth would be easier to measure around M dwarfs, and it seems this is what that is. The transit depths of Earths around M dwarfs will be much higher than around G-type stars, so the completeness factor should be quite a bit higher. This is on top of the ability to stack transits quickly due to their short orbital periods. I would not expect eta_earth to be revised significantly for M dwarfs based on future Kepler data.

I disagree. The problem with this data is that it is not clear what is the real size of the stars, and as a consequence, we don' t actually know the sizes of the planets neither the habitability zones extente. Changing some assumptions or parameters you obtein different planets in different HZs, in the same data.

We will have to wait until 2022, when Gaia paralaxes of the Kepler stars will be complete. Then we will obtain real sizes and luminosities.

On the other hand, the number of red dwarfs is low compared with G stars (in the Kepler field). So it lacks good great numbers for good statistics.

Pity they don't seem to be taking the transit duration into account. Do the new stellar parameters result in a reasonable eccentricity distribution for the planets?

Now on arXiv.
http://arxiv.org/abs/1302.1647

Good news! The possible habitable planet around a M dwarf at 13 light-years can be imaged for the E-ELT

It's seems that with E-ELT ever no-transit Earth-size planets in HZ of Red Dwarf at 10 pc will be imaged

Abstract:
Direct Imaging of Habitable Exoplanets with ELTs

http://ao4elt2.lesia.obspm.fr/sites/ao4elt2/IMG/pdf/077guyon.pdf

and

How ELTs will acquire the first spectra of rocky habitable planets

http://adsabs.harvard.edu/abs/2012SPIE.8447E..1XG

I have to point out a significant typo in either these Kepler papers.

Steffen et al. (2013) (eprint August 2012) Kepler-50 was referred to Kepler Object of Interest KOI-262 with a 2-planets solution. Today Huber et al. (2013) assigns Kepler-50 to KOI-85 with utterly another 3-planets solution, whereas former 2-planets one is referred to KOI-262 or Kepler-65.

Moreover we come to know something more about missing Kepler-37 (KOI-245) - hosting three small planets, two of which with very small radius (0.8 and 0.36 R_E) - and Kepler-65 too, of course.

The estimate for the occurrence rate of Earth-sized planets in the HZ of M dwarf stars has increased to 15%.

http://arxiv.org/abs/1302.1647

Quote :

We corrected an error in the code that calculates the number of stars for which a given planet could have been detected. The stellar parameters, planet parameters, and fraction of stars with planets did not change significantly. However, our estimate of the occurrence rate of habitable-zone, Earth-sized planets increased. Accepted for publication in ApJ. Machine readable tables in right sidebar

Sirius_Alpha wrote:

The estimate for the occurrence rate of Earth-sized planets in the HZ of M dwarf stars has increased to 15%.

So the estimate of the nearest transiting habitable planet has dropped from within 29 parsecs to within 21 parsecs (95% confidence), and the estimate of the nearest non-transiting habitable planet has dropped from within 7 parsecs to within 5 parsecs.

The most probable values have changed from 18 parsecs to 13 parsecs for the nearest transiting habitable planet, and 4 to 3 parsecs for the nearest transiting habitable planet.

(4 parsecs = 13 light years, the figure quoted in the press release. 3 parsecs = 10 light years)

I hope life likes flare stars...

A revised estimate of the occurrence rate of terrestrial planets in the habitable zones around kepler m-dwarfs
http://arxiv.org/abs/1303.2649

Using the new HZ limits given by Kopparapu et al, they increase the estimate for the frequency of M dwarf HZ planets.

So a 50% occurrence rate... that ought to bring the distance estimates for the nearest habitable planet even closer...

This New Scientist article gives the estimate of the average distance to the nearest habitable planet of about 6.5 to 7 light years.

Hmmm. That's a pretty good match for that WISE Jlotsofnumbers binary brown dwarf.

Don' t forget about Proxima... 50% possibilities of having a terrestrial planet in its HZ, if we can extrapolate this results to smaller M dwarfs.

Proxima is quite an active flare star... maybe not such a good target.

Been a while since I looked it up, but if I remember correctly, you could pretty much count the number of stars within seven light years on your fingers - M class or otherwise.

Also...M dwarfs are FAINT. Even the brighter ones have around 1% of Sol's luminosity, and most are substantially fainter. A habitable planet around a fainter M dwarf would pretty much have to be orbiting so close to the star it would get roasted by even 'normal' solar flares.

I'm not disputing the presence of the planets themselves - that seems fairly likely.

I'm pointing out that the mere existence of a planet of the right size in an M dwarfs hab zone does not make that planet habitable.

ThinkerX wrote:

A habitable planet around a fainter M dwarf would pretty much have to be orbiting so close to the star it would get roasted by even 'normal' solar flares.

Eh. That only really gets a problem towards the end of M, at about M5V. Early-mid M dwarfs have ~0.1-0.3 AU habitable zones, giving fairly long periods for HZ planets (~four weeks as seen for Gliese 667 C and Gliese 163). These are short enough that they are going to tidally lock their habitable zone planets, but by the time they're a billion years old or so activity shouldn't be especially problematic (particularly considering M dwarfs get so very quiet!)