Comments on: Peek-a-moon!

By: quasidog

quasidog — Sat, 20 Dec 2008 22:07:48 +0000

Unreal. The detail in Ganymede (not that I was aware it was) was the first thing that I noticed. An amazing shot.

By: Autumn

Autumn — Sat, 20 Dec 2008 06:39:41 +0000

Thanks, Phil. I guess I was just making basic mistakes in trying to scale objects according to my preconceptions. After so many years of math, I still overestimate the relative diameters of spheres with regard to their volume.

By: Peek-a-movie! | Bad Astronomy | Discover Magazine

Peek-a-movie! | Bad Astronomy | Discover Magazine — Fri, 19 Dec 2008 17:23:01 +0000

[...] was just informed by Twitterer karabaic that the picture of Ganymede going behind Jupiter that I posted yesterday also comes with a very cool [...]

By: Phil Plait

Phil Plait — Fri, 19 Dec 2008 17:09:46 +0000

Autumn, swan: the GRS changes its size over time a bit. A quick look at wikipedia has a comparison of it and the Earth that makes the scale of this image look about right: http://en.wikipedia.org/wiki/Great_Red_Spot#Great_Red_Spot

By: swan

swan — Fri, 19 Dec 2008 17:01:07 +0000

Like Autumn, I’m a bit befuddled by the apparent size of Ganymede compared to Jupiter. I even scaled this to a stock picture to make sure this wasn’t the Less Spot of Jupiter.

By: My-Name-is-Kenneth

My-Name-is-Kenneth — Fri, 19 Dec 2008 16:04:55 +0000

What’s that growing black spot in Jupiter’s atmosphere? Is the planet losing its chemical stain?

By: Autumn

Autumn — Fri, 19 Dec 2008 05:56:30 +0000

Has the Great Red Spot shrunk recently? I thought that the GRS was about two or three Earth diameters across, but if Ganymede is behind Jupiter in this image, Ganymede appears to me to be nearly Earth-sized. I am just remembering stuff off the top of my head, so I’m probably wrong about this, but I assumed that the moon was in front of Jupiter when I initially looked at the picture. Seems too big.

By: Blizno

Blizno — Fri, 19 Dec 2008 05:55:18 +0000

“Wouldn’t Galileo have been impressed…………..”

I can imagine Galileo passing his terminal house arrest with delighted hour after hour of studying the images we’ve obtained of the solar system that he could barely see through his tiny telescope.

By: The Mad LOLScientist, FCD

The Mad LOLScientist, FCD — Fri, 19 Dec 2008 04:29:24 +0000

=sw000000000000n= i has n00 wallpaparz! =^..^=

By: IVAN3MAN

IVAN3MAN — Fri, 19 Dec 2008 03:20:48 +0000

I can’t believe nobody has bothered to “Digg” this article already! Well, I just “dugg” it several minutes ago.

By: Gary Ansorge

Gary Ansorge — Fri, 19 Dec 2008 00:56:00 +0000

Sean: You’re right on,,,that’s exactly what we do.

So, GAnymede has a significant mag field? Wouldn’t that imply a very low rate of H2 loss due to energetic particle bombardment?
Granted, at that distance from Sol, it would likely be particles(electrons, mainly) from interaction with the Jupiter ionosphere. Too far from Sol for the Solar wind effect?
Well, maybe not.

GAry 7

By: YoJimbo

YoJimbo — Thu, 18 Dec 2008 23:42:10 +0000

That’s no Moon, That’s a space station!

By: Gordan

Gordan — Thu, 18 Dec 2008 21:51:59 +0000

Oh, my… This is absolutely *wicked*! One of the best planetary images Hubble ever captured!

By: sean hogge

sean hogge — Thu, 18 Dec 2008 21:23:32 +0000

A layperson’s spectroscopy question:

If we were to sample the light filtering through the Jovian atmosphere, Ganymede’s spectrum would contribute, correct? I assume we correct this by “subtracting” in some form the Ganymedian spectrum from the Jovian spectrum for light from that source. Or is that a foolish guess?

By: Chris A.

Chris A. — Thu, 18 Dec 2008 21:06:52 +0000

@Phil:
Umm, I’m not convinced the red color is due to Jupiter’s atmosphere. Remember that Hubble can’t take R, G, and B images simultaneously, and Ganymede moves a wee bit between shots while the filter is being changed.

By: American Voyager

American Voyager — Thu, 18 Dec 2008 20:49:13 +0000

That’s incredible! To think we had to wait for the Voyager flyby to get any kind of detail at all on these moons. Now we can pull it in from Earth using Hubble. WOW!! I remember “far encounter” pictures that weren’t that good! Does anybody know how close Voyager had to be to top this kind of detail? Another question: if we are so good at taking objects like Ganymede, why can’t we get closeups of the asteroids like this? The best ones I’ve seen are fuzzy. Still, it’s an awesome picture! One of those jaw droppers. Wouldn’t Galileo have been impressed…………..

By: Sili

Sili — Thu, 18 Dec 2008 20:41:49 +0000

Presumably Ganymede was one of the moons that let Rømer to discover that the speed of light is finite.

By: jdporter

jdporter — Thu, 18 Dec 2008 20:36:49 +0000

FAKE! Shooped!

And the word is “embiggen”.

By: Mang

Mang — Thu, 18 Dec 2008 20:36:30 +0000

Oooooooo …. and I don’t say that often.

By: Phil Plait

Phil Plait — Thu, 18 Dec 2008 20:27:56 +0000

Sorry about comments being turned off; they’re on again now.