Additional Planets at Gliese 581

Page 6 of 6 Previous  1, 2, 3, 4, 5, 6

View previous topic View next topic Go down

Re: Additional Planets at Gliese 581

Post by Shellface on 7th July 2014, 3:35 pm

Mm. I refrained from posting my thoughts before seeing the paper because this is a rather tall claim, but after looking at it it is very convincing.

I think the most important thing to take from this is how absurdly important the activity indicators are. The discovery of planets orbiting this star predate "proper" analyses of the activity indicators by a few years, so this is the first time they have been analysed at all for Gliese 581… almost a shame, considering that the correlation could quite possibly have been picked up by Forveille et al. had they checked the biswidth. But, that does mean something of this scale will likely not happen again, as use of the activity indicators is becoming more common for M-dwarfs.

Also important to take from this result is that Baluev was actually right! I was …skeptical, to say the least, of these red noise models that have popped up over the last few years - that result being the most outlandish - but with this study in hand it seems it is actually, somehow, sensible. Even if I have no idea how you constrain the model. I guess I have to take it for Gliese 667 C now too - perhaps that 91-day signal is akin to Gliese 581's 67-day one? I'd certainly like to see a similar analysis for Mr. HZ.

So, I think that wraps up the four-year fiasco concerning g, and takes d with it. Not exactly the preferable result, but accuracy takes precedent! After I finish writing up my next post in the modeling subforum, I think I'm gonna attempt the herculean task of fixing the wikipedia article. Though that might take a week, there's like 20 papers concerning the star's RVs…

But yeah. Definitely a shocking result. Gonna be on people's minds for a while.

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: Additional Planets at Gliese 581

Post by Lazarus on 7th July 2014, 5:02 pm

Talking of the Forveille et al. paper, I have to wonder what the chances are of it finally getting published? (Not that being arXiv-only has prevented it from being cited a fair few times!)
avatar
Lazarus
dG star
dG star

Number of posts : 2822
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: Additional Planets at Gliese 581

Post by Led_Zep on 23rd July 2014, 6:32 pm


Xavier Delafosse (HARPS team) speak for a french website

http://www.futura-sciences.com/magazines/espace/infos/actu/d/exoplanetes-doute-exoplanete-gliese-581-d-astronome-xavier-delfosse-repond-54529/


In regards to the announcement of the team which challenged the detection of Gliese 581 d, I find one of their fairly convincing curve, at least enough for me to also doubt the existence of this planet. I do not say that the story is complete but that doubt is allowed for the time being. On our side, we also often rejected candidates for the title of extrasolar planet for the same reasons, namely that the stellar activity could be the cause of the radial speed variation.
For Gliese 581 the situation is similarly complex because the signs to suspect that its activity is at the origin of the observed variations exist only at certain times, and they weren't particularly visible when we published results on the discovery of the extrasolar planet. "We'll have to continue to try to understand what is happening around this star with longer periods... data."
avatar
Led_Zep
Jovian
Jovian

Number of posts : 517
Location : France
Registration date : 2011-09-09

View user profile

Back to top Go down

Re: Additional Planets at Gliese 581

Post by Sirius_Alpha on 6th March 2015, 3:27 pm

"'Habitable' planet GJ 581d previously dismissed as noise probably does exist"
http://phys.org/news/2015-03-habitable-planet-gj-581d-previously.html

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

Number of posts : 3468
Location : Earth
Registration date : 2008-04-06

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

Back to top Go down

Re: Additional Planets at Gliese 581

Post by Lazarus on 6th March 2015, 6:21 pm

It's worth reading both of the linked articles in the press release. In particular, the press release does not discuss the response to this comment from Robertson et al, even though it links it.
avatar
Lazarus
dG star
dG star

Number of posts : 2822
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: Additional Planets at Gliese 581

Post by ThinkerX on 6th March 2015, 7:52 pm

Ok, now I'm having visions of the whole planet fading in and out of sight like something from an SF movie.

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: Additional Planets at Gliese 581

Post by tommi59 on 7th March 2015, 5:15 am

I wonder if anyone of 3 closest planets in this system b,c,or e would be transiting would it help to solve the problem with d, or g?
avatar
tommi59
Jovian
Jovian

Number of posts : 546
Age : 39
Location : Baile Atha Cliath
Registration date : 2010-07-31

View user profile

Back to top Go down

Re: Additional Planets at Gliese 581

Post by Lazarus on 7th March 2015, 11:21 am

Actually I really don't think the press release is valid at this stage at all, and ignoring the response from the original authors in the text of the press release is extremely suspect.

If they want to question the methods then fair enough, but until you have demonstrated that the planet is there while taking into account the stellar activity, then don't go putting out press releases. Especially when the question is not whether the signal is there, but whether the signal is due to a planet or stellar activity.

Gliese 581 has had more than enough "science by press release" already.
avatar
Lazarus
dG star
dG star

Number of posts : 2822
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: Additional Planets at Gliese 581

Post by Shellface on 8th March 2015, 1:15 pm

I am in strong agreement with Lazarus' point of view. If you read the relevant text, Escudé and Tuomi question the statistical rigor of how Robertson et al. reached their result - which is, ultimately, valid -, but do not actually improve on it, and only make conjecture of how such an improved analysis would go - which is practically meaningless. As said in the response:

Although we agree that improvements in multiparametric radial velocity (RV) modeling are necessary for the detection of Earth-mass planets, the key physical points we raised were not challenged.

The creation of this criticism, or whatever it is suitable to refer to it by, was excessively premature. Though I have no doubt that Escudé and Tuomi - who have made it clear they are capable statisticians - could produce a sound result of some sort on this matter, this attack on Robertson et al.'s work is frankly immature. I see it unfit to believe that the latter's extensive and highly plausible work can be invalidated by sub-par analysis.

Perhaps most frustrating of this is that the relevant party could undeniably foresee how this announcement would be taken by the media, or the common person, despite there being no proper analysis involved. I maintain that this action was an inexcusably aggressive and counter-productive one.

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: Additional Planets at Gliese 581

Post by Sirius_Alpha on 8th March 2015, 8:29 pm

"Comment on ”Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581”" is on arXiv now.

http://arxiv.org/abs/1503.01976

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

Number of posts : 3468
Location : Earth
Registration date : 2008-04-06

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

Back to top Go down

Re: Additional Planets at Gliese 581

Post by Sirius_Alpha on 9th March 2015, 8:27 pm

And the response to it.
Response to Comment on "Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581"
http://arxiv.org/abs/1503.02565

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

Number of posts : 3468
Location : Earth
Registration date : 2008-04-06

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

Back to top Go down

Re: Additional Planets at Gliese 581

Post by Lazarus on 17th May 2015, 11:40 am

Guillem Anglada-Escudé has an article on the Centauri Dreams blog including some discussion of the GJ 581 situation.
avatar
Lazarus
dG star
dG star

Number of posts : 2822
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: Additional Planets at Gliese 581

Post by Lazarus on 4th December 2015, 1:55 pm

It's been a while. Let the Gliese 581 wars continue! Razz

Artie P. Hatzes, "Periodic Halpha variations in GL 581: Further evidence for an activity origin to GL 581d"
http://arxiv.org/abs/1512.00878
avatar
Lazarus
dG star
dG star

Number of posts : 2822
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: Additional Planets at Gliese 581

Post by tommi59 on 4th December 2015, 3:01 pm

So we should go back to the period of 82 days then
avatar
tommi59
Jovian
Jovian

Number of posts : 546
Age : 39
Location : Baile Atha Cliath
Registration date : 2010-07-31

View user profile

Back to top Go down

Re: Additional Planets at Gliese 581

Post by Shellface on 4th December 2015, 4:36 pm

tommi59 wrote:So we should go back to the period of 82 days then
That's… not how aliases work.

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: Additional Planets at Gliese 581

Post by Sirius_Alpha on 4th December 2015, 6:09 pm

It might be worth reviewing this article on the Oklo blog about aliases.
http://oklo.org/2010/05/31/de-aliased/

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

Number of posts : 3468
Location : Earth
Registration date : 2008-04-06

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

Back to top Go down

Re: Additional Planets at Gliese 581

Post by Sponsored content


Sponsored content


Back to top Go down

Page 6 of 6 Previous  1, 2, 3, 4, 5, 6

View previous topic View next topic Back to top


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