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View Full Version : HD 5512b...a Habitable Planet around HD5512



trinitree88
2011-Aug-18, 02:13 PM
Thrown in with Gliese's potentially habitable planet, the authors reason this one is too if the cloud cover is ~ 50%:shifty:. SEE:http://arxiv.org/ftp/arxiv/papers/1108/1108.3561.pdf


pete oops HD85512...

BigDon
2011-Aug-18, 03:58 PM
I'm going to have to come back and read this at length.

Thanks Trin.

trinitree88
2011-Aug-18, 06:46 PM
I'm going to have to come back and read this at length.

Thanks Trin.

Me,too, Big Guy. I often scan and post for others, and then browse through them later when I'm less harried. This week, definitely harried. Enjoy

Hungry4info
2011-Aug-18, 08:52 PM
Thrown in with Gliese's potentially habitable planet
Gliese is a star catalogue. Star catalogues don't have planets of their own.
Perhaps you meant Gliese 581? :razz:

Bynaus
2011-Aug-19, 09:13 AM
potentially habitable planet

Its almost certainly a super-Venus, but we will not be able to know that for sure for at least another decade, or two (except if it transits).

trinitree88
2011-Aug-20, 02:59 PM
Gliese is a star catalogue. Star catalogues don't have planets of their own.
Perhaps you meant Gliese 581? :razz:

Hungry. Yep, I abbreviated that a bit. What with all the international media on Gliese 581's little companion, I figured most people would jump to the correct conclusion. :eek::shifty:pete

Kullat Nunu
2011-Aug-23, 09:02 AM
They monitored 10 chromospherically quiet stars... and found (http://arxiv.org/abs/1108.3447) five super-Earths! One for HD85512, two for HD192310, and three for HD20794. These planets must be very common! :eek:

PS. Interesting how low profile the HARPS team keeps. IMO this definitely is worth at least a press release. Or are we already in the situation where only genuine super-Earths are newsworthy? ;)

kzb
2011-Aug-23, 12:25 PM
Anyone else find this HDxxxx.... nomenclature distracting?

Anyway, on a skim read, what I noticed is that two of these stars have markedly lower metallicity than the sun. One of them (HD192310) is only slightly lower than the sun. Yet all three have potentially rocky worlds more massive than the Earth.

The other thing is their ages, given as 5.61, 5.76 and 7.81 billion years (the solstation website gives even larger ages for two of them). All substantially older than the sun. This means any ecosystems have had far longer to evolve intelligent life, and/or those intelligent lifeforms have had substantially longer to evolve technology. Jumping the gun perhaps.

Kullat Nunu
2011-Aug-23, 02:13 PM
Anyone else find this HDxxxx.... nomenclature distracting?

Well, if you like, you can call HD20794 "82 Eridani" instead. :D

kzb
2011-Aug-23, 05:47 PM
Well, if you like, you can call HD20794 "82 Eridani" instead. :D

Well yes I would like ! I am actually talking about the paper linked to in Post #7 I should add.

Two of the others on their list of 10 are Alpha Centauri B (HD 128621) and Tau Ceti (HD10700). Why can't they put another column in their tables to call them by these better known names?

Kullat Nunu
2011-Aug-23, 06:35 PM
Because in scientific literature the HD numbers (or Gliese) are preferred over traditional names, which include also Flamsteed/Bayer designations.

Same goes for deep sky objects, where NGC/IC catalog numbers are usually used by astronomers, Messier numbers nicknames in non-scientific literature.

kzb
2011-Aug-24, 11:36 AM
OK I've had my moan about the names. Point taken.

I've read a bit more now, and what got my attention this time is the section on Tau Ceti (HD10700). Long been a favourite of SF and SETI because it's a nearby single star, of the right spectral class to host an Earth-like world.

However they say they have detected no planetary signature whatsoever. They even use it as a calibrator to find what their noise level is for detections in other systems.

On the face of it that is a disappointing result. But perhaps we should take heart from the fact their detection limit seems firmly in the super-Earth mass range with current data. Possibly there is still room for an Earth mass planet orbiting Tau Ceti even given their negative result.

Does anyone have a better feeling for what these RV measurements mean for the probability or not of smaller planets around Tau Ceti?

Bynaus
2011-Aug-25, 02:00 PM
Does anyone have a better feeling for what these RV measurements mean for the probability or not of smaller planets around Tau Ceti?

If the planets are orbiting the star in the same plane as the surrounding disk (which seems plausible), then the limits on the planetary mass are indeed in the super-Earth range. However, it seems the star has a very low rotational velocity (vsini) which might imply that we see the star almost pole-on. If that is true, it could have very massive planets but there would be no way to detect them by radialvelocity measurements. However, the planets then should show up in astrometric measurements.

kzb
2011-Aug-25, 03:56 PM
If the planets are orbiting the star in the same plane as the surrounding disk (which seems plausible), then the limits on the planetary mass are indeed in the super-Earth range. However, it seems the star has a very low rotational velocity (vsini) which might imply that we see the star almost pole-on. If that is true, it could have very massive planets but there would be no way to detect them by radialvelocity measurements. However, the planets then should show up in astrometric measurements.

Thanks Bynaus, since I posted I have learned that Tau Ceti is indeed pole-on view to us, and that makes RV no good for detecting planets. Maybe this is why the authors chose it as kind of RV-background noise standard, and not because it has no planets?

However, quote from the paper:

<<....there is no significant planetary signal in the precise HARPS data available o date and we can set a higher limit for the masses of possible planets aroun Tau Ceti as a function of period. For a detailed analysis and discussion we refer to Lovis (2011).>>

So it seems they will be able to set upper limits for the Tau Ceti planetary system on the basis of their RV data. I looked for the Lovis (2011) paper "in press" and I can't see there is a pre-print available yet. Guess we just have to wait for that...