The Swiss-French planet hunter team have a new interesting discovery.
A low mass "super Earth" in a potential habitable zone.
UPDATE: Details are up on the Extrasolar Planet Encyclopedia
and Udry's web page
and here is the actual preprint (PDF)
Hm, interesting, the full solution gives a finite eccentricity to the middle planet, which is interesting, but it could still be very small. Dynamically, looking at formation it makes a big difference if the middle planet has e << 0.1 or e ~ 0.1-0.2
Interestingly the numbers in the submitted paper are slightly different from those in the press release - someone been doing some last minute re-analysis of additional data points?!
this is where the ESO press release will be, but as of midnight EST it is not up yet
It is an interesting system - a low metallicity ( about half of solar) M3 dwarf (1/3 mass of the Sun) in the solar neighbourhood.
And it has THREE planets, all relatively low mass.
We should be careful not to exagerate the prospects for habitability. The planet is probably less than 10 Earth masses, and quite likely close to the minimmum 4.8 Earth masses.
Given the stellar luminosity, the expected mean temperature of the planet is in the 270-310K range which is comfortably in the liquid water range, but that is with some simple assumptions about the albedo and atmospheric thickness.
It is also quite possible that the planet is tidally locked to its parent star, which makes habitability a trickier issue. (Although people tend to forget that tidal locking can be in 3:2 rotation rather than 1:1 rotation, which would be fine).
With tidal locking you need substantial atmosphere to redistribute heat, in which case you are also vulnerable to runaway greenhouse heating.
We have no idea if the planet is volatile rich - it _could_ be a bare metal/rock ball, although since it is in orbit around a low metallicity low mass star, I'd guess that it is more likely to be a "failed" Neptune - a volatile rich rock core planet, possibly with an ice or liquid out layer of substantial depth.
We see systems like this - with the more massive interior planet, and outer super Earth - in simulations although you can only trust those || this far. So far. The annoying thing about simulations is that physics is robust, and you often get the right answer even with incomplete microphysics.
You ain't heard nothing yet, going to be an interesting year for planets...
Knowledgable people have reiterated to me that we should look for some potentially Very Interesting planet news next week. Stay posted.
The HARPS instrument is absolutely astonishing by the way. And the very large amount of telescope time the team gets helps. The US is falling behind in this game. More observations would be useful.
Greg has very interesting things at systemic - y'all join the hunt there
(h/t busy Chad)
This was supposed to be embargoed until wednesday, to be published in Nature this week, submitted to A&A, but somebody broke the embargo here is the NYT coverage - it is all over Google News.
Looks like the Malaysia Sun broke the embargo. Bastards.
Statutory artist conception. From ESO (who are still embargoing this as of this minute).
The parent star is a nearby low mass M dwarf, Gliese 581, already known to have a close orbiting Neptune mass planet.
The new discover is 5 earth masses (or a little bit more depending on the inclination)
There are hints of a third planet in the system, further out, at 8 earth masses.
The new planet has a 13 day orbital period, a little bit close for comfort.
Gliese 581 is only about 6pc (20 lightyears away).
Extrapolating from a single data point, the inference is that rocky planets, certainly super Earths, and probably, by continuity, regular Earths, are like dead common.
This is a more robust inference than it sounds. There are more exciting currently embargoed results out there. I expect at least three major announcements in the next few weeks, leading into the conference season.
Next up, the first results from the COROT initial anti-galactic center observing run.
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If this is supposed to be in this week's Nature, why do the stories say this has been submitted to A&A?
Interesting question.
You are right, it is listed as "A&A submitted" - so presumably fast tracked in the A&A letters.
I was told Nature, this thursday - now it could be they meant the News & Views, but I am puzzled because I was also told under embargo conditions and A&A doesn't usually do embargoes, the timing was right for a Nature associated press release.
It could be there is a second story coming out, there is one in the pipeline but I thought it was for next week - I'll do some digging.
Seriously amazing. Just detecting something this size, potentially habitable or not, is incredible.
I'm curious about the dynamics of this system. There's at least one other massive body involved (the Neptune-sized planet closer in). I'm strictly an amateur astronomer, so I don't have much sense of whether this extra massive body seriously destabilizes the climate of an Earthlike planet nearby. Are there any good references (even rough rules of thumb) for this sort of analysis?
Lots of references, wikipedia is quite robust on extrasolar planets and the two encyclopedia are very informative - both the european one I point to and the UC Berkeley run one. They do get technical quite quickly.
In short, the planet configuration is stable and the inner Neptune mass should have neglibible influence on the middle planet (other than being a spectacular evening/morning star) - only way it would affect the climate on the middle planet is if it affected tidal locking process - the middle planet is just outside a 2:1 orbital resonance with the inner planet - hm, in fact it might be in the 12:5 resonance which is a bit weird - but their final orbital configuration might have been dynamically coupled, this could influence whether the middle planet locked to its orbital period in 1:1 rotation resonance.
If it is in 1:1 rotation resonance, then it always faces the star the same way, no apparent rotation, and prospects for habitability are poor. If it is not tidally locked, or locked in at 3:2 rotation (like Mercury) then the odds are better.
Be very hard to find out. But we'll think of something.
CNN article on this discovery is up, and has a mistake in the 8th paragraph. And just Monday I was letting my students know about confusion between stars and galaxies, often in the media...
http://www.cnn.com/2007/TECH/space/04/25/habitable.planet.ap/index.html
Why do you think that it is a "failed Neptune", and what's the difference between a "failed Neptune" and a terrestrial planet? The amount of volatiles?
Well, to the extent we know anything about disks, it is hard to see a 0.3 solar mass star having a very massive protoplanetary disk.
So... I'm thinking the "hot Neptune" is analogous to a "hot Jovian" - that it formed right at the snowline and migrated, and the two outer planets formed beyond the snowline in the region that would be the trans-Jovian in the solar system - ie where we think the ice giants formed.
So the two outer pair would be analogous to Uranus/Neptune in that they formed with rocky cores but a high ice fraction and then migrated in with the hot Jovian (or formed post migration in radially mixed debris).
It is just hard to see it as a true terrestrial (iron core, rocky mantle, sparse volatiles) because there just couldn't have been that much mass in this system to begin with.
All speculation of course. But that is what we theorists live for...
The temperature estimates look like simple radiation balance results. So while we can say that the planet emits IR at a temperature between -3 and 40C, if it is indeed a rocky planet with an atmosphere, the surface temperature will be much warmer. Say somewhere between 30 and 1000C, depending on the thickness of the atmosphere. And the lower end requires a Venus type albedo without much of a greenhouse effect.
Given the optical properties of water vapour, I'd say the only way there could be liquid water is if there isn't any liquid water.
William Hyde
yeah, it is an "astronomer's temperature" the effective mean photospheric temperature given an albedo ~ 0.5 as I recall. NOT the plausible surface temperature.
I did say it was a "bit close for comfort" - the formal habitable zone is actually a little bit further out, starting at 0.08 AU
Tidal locking is also a major issue.
Actually, looks like the habitable planet in the Gliese 581 system is the third planet. The second planet looks too close for comfort, especially once greenhouse effect is taken into account (the 0 degrees C limit looks like Venus albedo, whereas equilibrium temperature on the real Venus is somewhere between minus 10 and minus 20 degrees C). Scaling the habitable zone of our Sun (I'm taking it to be 0.95-1.65 AU) to Gliese 581 gives 0.13-0.23 AU, which means the third planet dives into the habitable zone at periastron.
The first and second planets, if ocean worlds, likely have supercritical oceans which merge smoothly into their atmospheres, rather than having a liquid/gaseous surface.
Dear Chad,
Is it possible for a planet to be big enough to accumulate Ne and/or He during formation, while H can still escape? Would these 5-8 mass planets be large enough to do that?
Also, do you know if the metallicity dudes report C/O ratios, or just assume solar and scale using the Fe content?
One last thing:
How do you get a late veneer without any outlying gas giants to deflect icy bodies? Or is the H2O supposed to be primeval?
cheers,
LL
Has anyone contemplated what would happen when a gas giant, similar in ratio of mass elements to Jupiter, were to "hit" a star the size of the sun? Aside from instantaneously dissintegrating its outer gasses, couldn't a massive planet have risidual glowing-hot radioactive bits of mass escape the star's gravity if the speed and angle of the collision were just right?
Could not such a theoretical "starchip" then attain a slower, outward-bound orbit? And could not said starchip then collide with a terrestial planet, say the size of Earth before it was hit by a Mars-size planet, forming our moon?
Could starchips help explain the early abundance of radioactivity on Earth, adding longevity to its vulcanism?
Great! Makes me wish that I were still an Adjunct Professor of Astronomy. Hmmmm. I've currently taken a pay cut to teach Chemistry, Biology, Anatomy, and Physiology to underserved teenagers in a nearby high school. I think I'll be lecturing Monday on the Chemistry of neptune (I coincidently put up some JPL Voyager photos of Neptune and Triton this week), the Biology of the Habitable Zone, and the possible Anatomy, and Physiology of organisms on failed Neptunes.
Professor: I'm sorry, you fell below the minimum on this final exam. I am, by law, unable to award you your Trident.
Demigod: So I'm a... failed Neptune?