Comments on: The Great … Black Spots?

By: Class science project grade 6 B>>>>>>>>>>>>>>>>>>>>>>>>>>K>>>>>>>>>>>>>>>>>>>>>>>>>hizzee

Fri, 12 Jan 2007 04:41:58 +0000

Wow I thought that there was only a red spot amazing!! (ã…‡ã…—ã…‡)

By: Srinivasa Ramanujam

Srinivasa Ramanujam — Wed, 02 Aug 2006 14:31:20 +0000

The red spot is bigger than earth, but it looks very small in this photo, when compared with jupiter!

By: mikewong

mikewong — Wed, 02 Aug 2006 07:05:48 +0000

alright… i hope this response isn’t TMI…

this one shows the spectrum around 5 microns (for bright regions):

and this one shows jupiter’s whole thermal and reflected spectrum:

you were right when you said jupiter doesn’t act like a blackbody. since it has so many gases (mainly CH4, NH3, H2) that absorb/emit in the infrared, you end up looking at a different level of the atmosphere at every wavelength… and since temperature increases with depth, the spectrum is more complicated than a smooth blackbody spectrum.

i see how you got 300 C tho. this looks like a misapplication of wein’s law. the wavelength in wein’s law is the wavelength at which a blackbody emits the most radiation. a blackbody at 300 C would have the peak of its spectrum at 5 microns, like you calculated. but a blackbody at 300 K would also radiate at 5 microns, even though it would radiate even more at 0.29 / 300 or about 10 microns.

i guess it might have seemed like we picked 5 microns because that’s where the peak of the thermal spectrum was, but the real reasons are 1) earth’s atmosphere is relatively transparent at 5 microns and 2) jupiter’s atmosphere is relatively transparent at 5 microns.

By: The Bad Astronomer

The Bad Astronomer — Wed, 02 Aug 2006 04:22:16 +0000

Mike:

I used Wien’s law to get 300 C.

T(Kelvin) = .29 / wavelength (cm)

5 microns = 5×10^-4 cm so

T = .29 / 5×10^-4 = 580 K

and subtract 273 to convert to C to get 580 – 273 = 307 C.

This is assuming Jupiter acts like a blackbody, which it probably doesn’t even at those wavelengths. I don’t have a thermal IR spectrum of Jupiter handy. If you have one, link to it here! I’d be curious to see it, actually.

By: mikewong

mikewong — Wed, 02 Aug 2006 03:05:28 +0000

hi, i was one of the observers who took these images at keck, and i put together the final graphics. so i’m pretty stoked that this is being blogged about. i have a few comments:
it’s 300 K not 300 C. although we haven’t finished the calibration of the data, the brightest pixels in the thermal IR image are probably closer to 300 K, which is like room temperature.
why jupiter is hot: heat is still coming out of the planet from when it formed. so over time jupiter is cooling off, partly by radiating its heat through holes in the clouds like in the picture. but the deeper you go into jupiter’s atmosphere, the hotter it gets. it’s just like how temperatures are nice at sea level here, but at the tops of mountains, the air is much colder. i think this is the effect that berlie was talking about.
no one of consequence’s third spot: if you look closely at the big (reflected sunlight) picture, you can see that the bottom corner of the outline is falling on brighter clouds. these clouds block the thermal radiation from below and appear dark in the 5-micron image. i think it just LOOKS like a spot in the thermal image because there’s a little clearing in this band of clouds, and the border of the image cuts off the rest of the band. so there’s no 3rd spot, at least, none as big as the GRS and oval BA.

By: Blake Stacey

Blake Stacey — Tue, 01 Aug 2006 15:52:51 +0000

I see someone has already made the obvious 2010: The Year We Make Contact wisecrack, so I’ll just shut up now. (-;

By: Irishman

Irishman — Tue, 01 Aug 2006 13:44:28 +0000

No One, I’m not sure what “third spot” you mean. There’s a fair amount of dark swirled in the bright. I don’t see any more spots per se, but looking at the bigger image on the Keck page, the brighter areas on the IR are the bluer elements on the color image.

http://www.keckobservatory.org/images/article_pictures/88_215.jpg

I think you’re just seeing darkness where the hotter skies below are obscured by clouds.

By: Moonage Spacedream

Moonage Spacedream — Tue, 01 Aug 2006 12:49:05 +0000

The Star Child is coming…

Phil Platt over at Bad Astronomy goes to great lengths to explain this in great detail: In essence, if you look at the entire planet at 300 centigrade, the black spot is much cooler, therefore appearing black. I think there’s…

By: No One of Consequence

No One of Consequence — Tue, 01 Aug 2006 12:06:29 +0000

In the infra-red image, it looks like there is a third spot below the other two that I don’t see in the color picture. Any clue as to what that is?

By: Berlie

Berlie — Tue, 01 Aug 2006 12:02:58 +0000

Those are really cool pictures. I like the black and red one, it adds to the mystique of the gas giant.

Merovingian, I might be wrong, and if I am someone please correct me, but Jupiter’s so dense that the pressure probably heats up the gases it’s made from. And since heat has to go somewhere, it escapes the surface and that’s what gives such great pictures in IR. That’s just a hypothesis, on my part. Not a theory, though. Can anyone verify (or villify) this?

By: Merovingian

Merovingian — Tue, 01 Aug 2006 10:31:51 +0000

300 Centigrade? How can Jupiter be so warm?

By: Navneeth

Navneeth — Tue, 01 Aug 2006 08:18:52 +0000

Amazing stuff!