Comments on: A hot hot Neptune

By: systemic - 6 Gigabytes. Two Stars. One Planet.

systemic - 6 Gigabytes. Two Stars. One Planet. — Fri, 14 Dec 2007 02:31:15 +0000

[...] It will likely take a month or so before we’re finished with the analysis and the interpretation of the data. The IRAC instrument produces a gradually increasing sensitivity with time (known to the cognescenti as “the ramp”). This leads to a raw photometric light curve that slopes upward during the first hours of observation. For example, here’s the raw photometry from our Gliese 436 observations that Spitzer made last Summer. The ramp dominates the time series (although the secondary eclipse can also be seen): [...]

By: tacitus

tacitus — Thu, 26 Jul 2007 06:54:19 +0000

A brief update from COROT:

“A complete set of twelve thousand exoplanet lights curves, corresponding to one month of observation, has already been generated.”

http://smsc.cnes.fr/COROT/GP_actualite.htm

Mmmm, light curves.

By: luis

luis — Wed, 25 Jul 2007 09:47:05 +0000

The HAT team just got an accepted paper in ApJ Letters. Looks like they have an interesting , metal-rich hot-Jupiter around a K-dwarf. No preprint yet :(

A web search got this:

HAT-P-3b: A Transiting Planet with a Rocky Core. Rp = 0.89 +/- 0.05 RJup. Mp = 0.61 +/- 0.03 MJup. r = 1.1 +/- 0.2 g cm-3

from a presentation by Charbonneau.
Looks very interesting. Any more info on this anyone ? Identity of the star ?

Cheers,

Luis

By: andy

andy — Mon, 23 Jul 2007 09:58:04 +0000

It’s rather pale isn’t it. In fact, I’m seeing a rather good approximation to that colour looking out of my window at a dismally overcast sky.

My script generates an RGB colour of #3A78FF for Rayleigh scattering around a Sunlike star, which if you check it is a much deeper and bluer shade.

So maybe a clear sunny day on a habitable planet orbiting a red dwarf looks a bit gray and grim.

By: pvanes

pvanes — Mon, 23 Jul 2007 04:24:42 +0000

Out of curiosity, how does that color compare to the day-side sky of earth?

By: greg

greg — Fri, 20 Jul 2007 16:30:16 +0000

It would be nice to have the perl script.

For those following the discussion, here’s #D9EDFF:

Doesn’t quite have Mauve’s decade-nostalgia panache, but I think Oscar Wilde would likely have approved of D9EDFF as well.

By: andy

andy — Fri, 20 Jul 2007 15:36:38 +0000

Colour I get for Rayleigh scattering of a 3500 K blackbody is #D9EDFF. If you like, I could send you the Perl script I used to generate it.

By: greg

greg — Fri, 20 Jul 2007 15:17:05 +0000

Hi andy,

Interesting. Could you take a screenshot of the resulting color or send a link?

Greg

By: andy

andy — Fri, 20 Jul 2007 15:08:40 +0000

Hi, I did a simulation of Rayleigh scattering with various blackbody spectra (basically multiplied the blackbody spectrum by 1/lambda^4), then integrated the resultant spectrum. Result I got for illumination by a ~3500 K red dwarf is very pale blue, not mauve.

Perhaps for hotter planets (like HD 209458 described in the post you linked), the red glow from the planet becomes more important and starts tinting it mauve, I’m not sure…

By: greg

greg — Fri, 20 Jul 2007 15:02:29 +0000

Hi mckinstry,

I’m extrapolating down in temperature from the HD 209458b models of Jonathan Fortney and collaborators. The idea is that you have selective absorbtion of red by molecules in the largely cloud-free atmosphere accompanied by Raleigh scattering which preferentially sends back the blue light from the star to the observer. Check out this oklo post from last year:

http://oklo.org/?p=96

John Moores created Fortney’s optical spectrum in an integrating sphere, and it appears quite close to Mauve.

best,

Greg