The Frequency of Planets around M Dwarfs

View previous topic View next topic Go down

Re: The Frequency of Planets around M Dwarfs

Post by Led_Zep on 6th February 2013, 6:03 am

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

« …Scientists Unveiling Exoplanet Discovery Wednesday: How to Watch Live … »

bounce
avatar
Led_Zep
Jovian
Jovian

Number of posts : 529
Location : France
Registration date : 2011-09-09

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by Stalker on 6th February 2013, 12:06 pm


_________________
avatar
Stalker
Jovian
Jovian

Number of posts : 529
Age : 26
Location : Paris, France
Registration date : 2008-06-16

View user profile http://exoplanetes.wetpaint.com/

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by pochimax on 6th February 2013, 12:18 pm

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.
avatar
pochimax
Planetary Embryo
Planetary Embryo

Number of posts : 89
Location : Torrejon, Spain
Registration date : 2011-09-09

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by tommi59 on 6th February 2013, 12:47 pm

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
avatar
tommi59
Jovian
Jovian

Number of posts : 548
Age : 39
Location : Baile Atha Cliath
Registration date : 2010-07-31

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by Galzi on 6th February 2013, 3:47 pm

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
Planetary Embryo
Planetary Embryo

Number of posts : 86
Age : 31
Location : Venetia et Histria
Registration date : 2012-06-03

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by Lazarus on 6th February 2013, 4:16 pm

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!
avatar
Lazarus
dG star
dG star

Number of posts : 2845
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by tommi59 on 6th February 2013, 4:58 pm

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)
avatar
tommi59
Jovian
Jovian

Number of posts : 548
Age : 39
Location : Baile Atha Cliath
Registration date : 2010-07-31

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by tachyonic on 6th February 2013, 7:50 pm

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.

tachyonic
Hydrogen Atom
Hydrogen Atom

Number of posts : 3
Registration date : 2010-01-01

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by Sirius_Alpha on 6th February 2013, 7:54 pm

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.

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3494
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by pochimax on 7th February 2013, 5:32 pm

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.
avatar
pochimax
Planetary Embryo
Planetary Embryo

Number of posts : 89
Location : Torrejon, Spain
Registration date : 2011-09-09

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by Lazarus on 7th February 2013, 5:45 pm

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?
avatar
Lazarus
dG star
dG star

Number of posts : 2845
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by Sirius_Alpha on 7th February 2013, 9:36 pm


_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3494
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by Daniel on 9th February 2013, 11:31 am

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
avatar
Daniel
SuperEarth
SuperEarth

Number of posts : 238
Registration date : 2009-11-14

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by Edasich on 13th February 2013, 6:45 am

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 RE) - and Kepler-65 too, of course.
avatar
Edasich
dM star
dM star

Number of posts : 1517
Location : Tau Ceti g - Mid Latitudes
Registration date : 2008-06-02

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by Sirius_Alpha on 25th February 2013, 9:19 am

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
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

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3494
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

The Frequency of Planets around M Dwarfs

Post by Lazarus on 25th February 2013, 5:41 pm

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...
avatar
Lazarus
dG star
dG star

Number of posts : 2845
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by Sirius_Alpha on 11th March 2013, 8:24 pm

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.

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3494
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by Lazarus on 12th March 2013, 2:22 pm

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

Number of posts : 2845
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by Lazarus on 13th March 2013, 2:26 pm

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. Razz
avatar
Lazarus
dG star
dG star

Number of posts : 2845
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by pochimax on 14th March 2013, 7:14 am

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.
avatar
pochimax
Planetary Embryo
Planetary Embryo

Number of posts : 89
Location : Torrejon, Spain
Registration date : 2011-09-09

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by Lazarus on 14th March 2013, 2:11 pm

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

Number of posts : 2845
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by ThinkerX on 14th March 2013, 5:51 pm

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
Rock
Rock

Number of posts : 39
Age : 54
Location : Alaska
Registration date : 2013-02-22

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by Shellface on 15th March 2013, 12:08 pm

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!)

Shellface
Neptune-Mass
Neptune-Mass

Number of posts : 282
Location : g2 17.∞ 997 t
Registration date : 2013-02-14

View user profile

Back to top Go down

Re: The Frequency of Planets around M Dwarfs

Post by Sponsored content


Sponsored content


Back to top Go down

View previous topic View next topic Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum