Comments on: Getting closer: Super-Earth found in a star’s habitable zone

By: Matt B.

Matt B. — Mon, 12 Nov 2012 23:03:35 +0000

@4 Andrew Smith – I believe it means a planet can be habitable with that much cloud cover, not that it does have that much.

By: Messier Tidy Upper

Messier Tidy Upper — Sat, 10 Nov 2012 04:05:48 +0000

@49. andy : Thanks for that.

@36. Anders asked : “Phil, or anyone really… If there are no other planets outside this super-Earth, wouldn’t that make it more vulnerable to asteroids?”

Plus comets, yeah, I’d imagine it could well do so although it would depend on whether and what sort of asteroid and cometary belts /disks / clouds the host star(s) have, naturally.

@ The Bad Astronomer, Dr Phil Plait : Please can you answer the question I’ve asked in comment 33 here? Please?

By: Peter Davey

Peter Davey — Fri, 09 Nov 2012 22:38:45 +0000

As the scientists, Jack Cohen (who has provided aid and advice to a number of science fiction writers) and Ian Stewart, have said: “Life exists everywhere it can, and everywhere it can’t.”

As Arthur C Clarke once pointed out, if it turned out that there is life on Titan, and that the life reached the point of intelligence, and developed a religion, it would probably thank its Deity for creating such a hospitable world.

Each to their own – whether their style of clothing. or choice of atmosphere.

By: andy

andy — Fri, 09 Nov 2012 22:30:34 +0000

Incidentally @Phil Plait I don’t know how much control you have over the spam filter here, but if possible it might be worth whitelisting a few sites so that they don’t get held up in the moderation queue: being able to link arXiv and ADS abstracts without incurring the moderation queue penalty would be really useful! Maybe something to consider in the blog’s new home?

By: andy

andy — Fri, 09 Nov 2012 22:24:11 +0000

Incidentally, thinking possibly habitable exoplanets has anyone heard any further news on the question of whether Gliese 581 g exists or not?

Well the last two papers to come out on arXiv both came to the conclusion that it doesn’t exist:

Baluev (arXiv:1209.3154) investigates the system taking into account red noise and comes to the conclusion that only three planets are well-supported (b,c and e)

Tuomi & Jenkins (arXiv:1211.1280) come to the conclusion that the system only contains 4 planets using Bayesian analysis, they also consider the issue of red noise.

My own investigations using the Systemic console seem to show that the 32-day period (“planet g”) disappears when the HARPS and HIRES datasets are combined, furthermore it is only present if the planetary orbits are assumed to be circular. Note that the latest claim by Vogt et al. for the planet’s existence (arXiv:1207.4515) only takes the HARPS dataset into account rather than the combination of HARPS and HIRES.

The claimed period of planet g (32.129 days) also matches the following alias relationship suspicously well:

1/(claimed period g) ≈ 1/(lunar month) – 1/(1 year)

Both of the frequencies on the right hand side are relevant to the observation schedules. Taking this into account and also considering the apparent disappearance of the period in the combined dataset, I regard “Gliese 581 g” as a systematic effect in the HARPS data rather than a genuine planet candidate.

By: Andrei

Andrei — Fri, 09 Nov 2012 20:57:39 +0000

That’s a hell of a HDR illustration for this article…. And usually, the “artist’s conceptions” with these topics are all done the same – the planet is seen as a crescent or maybe as a third quarter phase, illuminated by another light source than it’s primary (point observed also by others on this very blog), a dark sky full of stars, half the times with the Milkyway in the background, and a spherical star, without diffraction spikes or light bleeding. And half the times with the Milkyway behind it. And la cerise sur le gateau – star spots or maybe planetary transits! The dynamic range in the picture is more than millions (more than 6 orders of magnitude) but yet, somehow, we see all this in a picture with a dynamic range less than 500 – well, about half of that – i.e. 8 bits of intensities….
I know this illustration is just CGI, but unfortunately, the digital photo revolution flooded the web with HDR photos that mimic the appearance of CGIs (and viceversa) that HDRs lost their original artistic appearance and became hip and kitsch. And viceversa, the CGIs are now only kitsch and hip….

By: ctj

ctj — Fri, 09 Nov 2012 20:41:05 +0000

MaDeR @46:

that’s my whole point. i keep hearing astronomers talking about stellar habitable zones as if it’s something we actually know.

By: MaDeR

MaDeR — Fri, 09 Nov 2012 15:52:25 +0000

@ctj: problem is that some definitions of habitable zone does not take atmosphere in account. Obviously, it is hard to take it in account, as we do not have full knowledge about full range of possible atmospheres for all possible worlds. Knowledge about atmosphere is critical to know about HZ of given planet. For example, without accounting for atmosphere, we would be a little outside HZ (minus 17C or something like that).

This leave only experimental science. In other words we have to detect atmosphere and its chemical composition, temperature, pressure etc empirically. Thankfully, in next decade or two out technology should be up to this challenge.

By: Nigel Depledge

Nigel Depledge — Fri, 09 Nov 2012 13:17:13 +0000

Jeff S (27) said:

Life is a type of biochemical process, and if you want to generalize biochemical processes to call them life, then maybe life does exist outside earth.

This is a bit tricky, because biochemistry means “the chemistry of life”. We need a definition of life that does not risk entering a circular argument.

By: Nigel Depledge

Nigel Depledge — Fri, 09 Nov 2012 13:14:11 +0000

Randy A (18) said:

An ocean deep enough so the tide wasn’t always a shallow water wave? What would that be like?

We don’t need to imagine, because tidal range does not depend on depth of water.

The tidal range depends on the strength of the tidal forces that cause it. Shortly after the Earth and Moon had solidified, the moon orbited very much closer to Earth than it does now, and the tides were several metres (or was that tens of metres) high.