Alpha Centauri, the hunt for planets.

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Alpha Centauri, the hunt for planets.

Post by Sirius_Alpha on 7th June 2009, 6:56 pm

A well written article has appeared in Seed. In it, it is revealed that HARPS has been examining Alpha Centauri B since 2003.

http://seedmagazine.com/content/article/the_long_shot/

Since 2003, Mayor and his team have used HARPS to search for planets around Alpha Centauri B. Last August, they began observing the star every available night in a strategy similar to Fischer’s.

In a recent [HARPS] survey, the team showed that one-third of about 200 nearby Sun-like stars harbor rocky, terrestrial worlds several times more massive than Earth in short-period orbits. They’re called “super-Earths.”

“These objects aren’t exactly like our Earth, but they may very well be habitable,” Mayor said. “We’re discovering them everywhere we look.

Greg Laughlin goes more in depth in his post at oklo.org
http://oklo.org/?p=337


Last edited by Sirius_Alpha on 8th June 2009, 12:42 pm; edited 2 times in total

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Alpha Centauri

Post by tesh90 on 8th June 2009, 2:23 am

As there are threads on Corot and Kepler maybe we should start to keep one on Alpha Centauri???

http://oklo.org/

Greg has been a keen pusher on this theory and lately it seems to have caught on a bit more...

Let's hope to hear something later than sooner!

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Re: Alpha Centauri, the hunt for planets.

Post by Sirius_Alpha on 8th June 2009, 12:40 pm

A post has already been started in the detection projects forum about this. I'll merge the two.

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Re: Alpha Centauri, the hunt for planets.

Post by Sirius_Alpha on 23rd August 2009, 6:11 pm

Greg Laughlin discusses the possibility of terrestrial planet formation at Alpha Centauri.

http://oklo.org/2009/08/22/keep-hope-alive/

Payne, Wyatt and Thebault suggest that outward migration of planetary embryos in the Alpha Cen B protoplanetary disk can provide a mechanism for circumventing the problems associated with habitable planet formation in the binary environment. In the second paper (posted to astro-ph earlier this year) Xie and Zhou argue that a modest inclination between Alpha Cen A’s proptoplanetary disk and Alpha Cen B’s orbit can also tip the balance quite significantly in favor of terrestrial planet accretion around A (and with similar logic applying to planet formation around B).

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Re: Alpha Centauri, the hunt for planets.

Post by Sirius_Alpha on 29th August 2009, 11:35 pm

According to this okly entry, it turns out HARPS is doing more like 25 radial velocity measurements a year on Alpha Centauri instead of 100.

Since signal-to-noise increases as the root of the number of observations, this means that the minimum mass threshold for Alpha Cen Bb at any given time is approximately doubled relative to my estimates at the beginning of the Summer. Instead of arriving at 2.5 Earth masses in the habitable zone a bit more than a year from now, they’ll be at roughly 5 Earth masses.
Greg Laughlin wrote:I would advocate two fully p-mode averaged velocities per night, 50 nights per year. I know that because Alpha Cen B is so bright, the duty cycle isn’t great. I know that there are a whole panoply of other interesting systems calling for time. It is indeed a gamble, but from the big-picture point of view, there’s a hugely nonlinear payoff in finding a potentially habitable planet around Alpha Centauri in comparison to any other star.


Last edited by Sirius_Alpha on 29th August 2009, 11:36 pm; edited 2 times in total (Reason for editing : Formatting.)

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Also from oklo.org ...

Post by tesh90 on 31st August 2009, 1:58 am

Greg's comment (#6) is very interesting

greg
August 31st, 2009 at 4:34 am
Hi Coolstar,
Debra Fischer (with Geoff Marcy as a collaborator) is indeed running a competing program on Alpha Cen from the southern hemisphere. From what I hear, it’s progressing quite well — I think it’s important though, for a discovery of this importance, to have two competing teams.
You can read the details in both the Seed article, as well as in the google translation of the FAZ article.
cheers,
Greg


Let us hope for more news later rather than sooner!

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Re: Alpha Centauri, the hunt for planets.

Post by Borislav on 1st September 2009, 8:41 am

Sirius_Alpha wrote:According to this okly entry, it turns out HARPS is doing more like 25 radial velocity measurements a year on Alpha Centauri instead of 100.

http://archive.eso.org/eso/eso_archive_main.html
Title "Searching for Earth analogs around nearby stars with HARPS"
Wink

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Re: Alpha Centauri, the hunt for planets.

Post by Sirius_Alpha on 1st September 2009, 8:48 am

From what I can tell, "Searching for Earth analogs around nearby stars with HARPS" was just a poster for an astronomy conference early last month.

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Re: Alpha Centauri, the hunt for planets.

Post by Sirius_Alpha on 2nd December 2009, 5:12 pm

A third team sets out to find planets at Alpha Centauri

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Re: Alpha Centauri, the hunt for planets.

Post by philw1776 on 4th December 2009, 10:39 am

Here's an interview with Debra Fischer on her CTIA 1.5 meter scope focused search on Alpha Centauri A and B for terrestrial planets inside the 2 AU dynamical limit.

http://marketsaw.blogspot.com/2009/10/eyes-on-alpha-centauri-hunt-for-pandora.html

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Re: Alpha Centauri, the hunt for planets.

Post by Sirius_Alpha on 4th December 2009, 10:59 am

Michael: The Hubble recently directly imaged the first extrasolar planet...
Prof. Fischer: That was around HR 8799...

Wasn't Fischer one of the people who made the press release about the discovery, with HST, of the planet orbiting Fomalhaut? Surely, that's what Michael is talking about.

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Re: Alpha Centauri, the hunt for planets.

Post by Borislav on 18th December 2009, 11:25 pm








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Re: Alpha Centauri, the hunt for planets.

Post by Borislav on 18th December 2009, 11:27 pm

Picture take http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=46020

With the chosen strategy, for a quiet K V star like α Cen B, we would be able to detect planets with masses a few times the mass of Earth with an orbital period of 200-300 days, which corresponds to the habitable region of this type of stars. These estimates are still including HARPS instrumental limitations (with centring and guiding effects) and a contribution from photon noise. Improvements are then expected with more stable instruments as ESPRESSO and longer exposure times to better average the stellar oscillations.

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Re: Alpha Centauri, the hunt for planets.

Post by Borislav on 16th January 2010, 4:21 pm

http://www.astro.yale.edu/smarts/schedules/15m10A.txt
Planned to redouble the search for Alpha Centauri Debra Fischer in 2010?

For comparison
http://www.astro.yale.edu/smarts/schedules/sched15m2008b.txt
http://www.astro.yale.edu/smarts/schedules/sched15m2008b.txt
http://www.astro.yale.edu/smarts/schedules/sched15m2009a.txt
http://www.astro.yale.edu/smarts/schedules/sched15m2009b.txt

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Re: Alpha Centauri, the hunt for planets.

Post by Sirius_Alpha on 17th January 2010, 9:53 pm

Planetesimal Accretion in Binary Systems: Could Planets Form Around Alpha Centauri B ?
http://arxiv.org/abs/1001.2614

Abstract wrote:Stellar perturbations affect planet-formation in binary systems. Recent studies show that the planet- formation stage of mutual accretion of km-sized planetesimals is most sensitive to binary effects. In this paper, the condition for planetesimal accretion is investigated around CenB, which is believed to be an ideal candidate for detection of an Earth-like planet in or near its habitable zone(0.5-0.9 AU). A simplified scaling method is developed to estimate the accretion timescale of the planetesimals em- bedded in a protoplanetary disk. Twenty-four cases with different binary inclinations(iB=0, 0.1o 1.0o, and 10o), gas densities(0.3,1,and 3 times of the Minimum Mass of Solar Nebula, MMSN hereafter), and with and without gas depletion, are simulated. We find: (1) re-phasing of planetesimals orbits is independent of gas depletion in CenB, and it is significantly reached at 1 − 2 AU, leading to accretion-favorable conditions after the first  105 yrs, (2)the planetesimal collision timescale at 1-2 AU is estimated as: TB col  (1 + 100iB) × 103 yrs, where 0 < iB < 10o, (3)disks with gas densities of 0.3-1.0 MMSN and inclinations of 1o-10o with respect to the binary orbit, are found to be the favorable conditions in which planetesimals are likely to survive and grow up to planetary embryos, (4)even for the accretion-favorable conditions, accretion is significantly less efficient as compared to the single-star case, and the time taken by accretion of km-sized planetesimals into planetary embryos or cores would be at least several times of TB col, which is probably longer than the timescale of gas depletion in such a close binary system. In other words, our results suggest that formation of Earth-like planets through accretion of km-sized planetesimals is possible in CenB, while formation of gaseous giant planets is not favorable.

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