Additional Planets at Gliese 581

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.

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!)

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."

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

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.

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

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?

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.

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:

Quote :

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.

"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

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

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

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

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

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

tommi59 wrote:

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

That's… not how aliases work.

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

Keep the flame alive!

The Once-canceled Habitable-zone Super-Earth Gliese 581d Might Indeed Exist!
Manfred Cuntz, et al. Published Jan 2024.
https://iopscience.iop.org/article/10.3847/2515-5172/ad1de4

Quote :

Recent studies indicate that Gliese 581d, a proposed habitable zone (HZ) super-Earth planet, does not exist, as the respective data denote that the planet is an artifact of stellar activity. Here we report evidence to the contrary considering that those studies were based on inaccurate spectroscopic measurements of the stellar rotation period regarding the planet's inactive host star (dM3). Gliese 581d, if real, is of particular interest as it constitutes the first planet identified to be in a stellar HZ outside of the solar system based on studies in 2007. If confirmed as a true planet, at 20.5 lt-yr, it would also be one of the nearest potentially habitable super-Earths.

Never give up. I was (almost) certain that it was actually hiding out there. Same for Rho1 Cancri, the room between Rho1 Cnc e and b cannot be empty, in my opinion.

Might exist and g also but this is not transiting and is not as significant like in past especially d is very likely minineptune with minimum radius 1.8 earth. We have some transiting earthsize planets we can follow