APOD: Two Planet Opposition (2010 Oct 08)

[APOD Robot]

Two Planet Opposition

Explanation: In late September, two planets were opposite the Sun in Earth's sky, Jupiter and Uranus. Consequently closest to Earth, at a distance of only 33 light-minutes and 2.65 light-hours respectively, both were good targets for telescopic observers. Recorded on September 27, this well-planned composite of consecutive multiple exposures captured both gas giants in their remarkable celestial line-up accompanied by their brighter moons. The faint greenish disk of distant planet Uranus is near the upper left corner. Of the tilted planet's 5 larger moons, two can be spotted just above and left of the planet's disk. Both discovered by 18th century British astronomer Sir William Herschel and later named for characters in Shakespeare's A Midsummer Night's Dream, Oberon is farthest left, with Titania closer in. At the right side of the frame is ruling gas giant Jupiter, flanked along a line by all four of its Galilean satellites. Farthest from Jupiter is Callisto, with Europa and Io all left of the planet's disk, while Ganymede stands alone at the right.

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[orin stepanek]

Portia is quite difficult to see. http://apod.nasa.gov/apod/ap030115.html great photography though. Jupiter looks like a sun with the light being emitted around it.

[Ann]

That's a great double exposure of Jupiter, which shows us the overwhelming brightness of the King of the Planets as well as His non-overexposed, striped royal atmosphere-cloak!

I also love the aqua color of Uranus, which is exactly what I expect it to be. But Art recently claimed here that Uranus is actually light blue, the same hue as Neptune but less saturated. Maybe, but it doesn't look like that in almost any picture you see of it.

I love that you can see two of Uranus' moons lined up next to it!

I wonder if anyone can identify that intensely orange star pretty much in the middle of the picture for me?

Ann

[Chris Peterson]

I wonder if anyone can identify that intensely orange star pretty much in the middle of the picture for me?

It looks to be Hipparcos 117881, a V=7.6 K5 star.

[owlice]

My favorite Oberon (who refers to himself as an alto, despite what nonsense might be in print!), though the moon is a close second.

[León]

Moves the image of the planets Uranus, the sky, His equivalent in Roman mythology was Caelus, whose year eighty-four years hard ground, with the axis of rotation to ninety degrees presents the satellite spinning at right angles to the satellites of Jupiter, which each land forty-two years, the planet has continued successive eclipses its 27 satellites face the sun.

The four Galilean satellites, always presents the same face to Jupiter.

[emc]

I like today’s image… I get an “other-worldly” inspired emotion from space portraits such as this one. I like to imagine that I have my own little space craft, able to traverse the universe in mere minutes without obliterating me and itself due to the tremendous reality equations that those dream buffering physicists quibble about. I especially like the exposure phenomena giving Jupiter a sun-like appearance as Orin and Ann mention. Outstanding examples of mixing art and science these APODs…

[Lostinspace]

Spectacular photograph. On my MAC (and probably Windows PCs too) I have a feature that lets me zoom into any area on the screen. The features of Jupiter are very clear, but what causes that corona effect that partially obscures IO? The highest resolution view is truly amazing. Again and again congratulations on this site. I get my "astronomy fix" every morning.

[Ann]

I wonder if anyone can identify that intensely orange star pretty much in the middle of the picture for me?

It looks to be Hipparcos 117881, a V=7.6 K5 star.

Thanks, Chris! I would have called it HD 224037 myself, since I'm used to the HD catalogue, but fortunately my astronomy software can handle the Hipparcos catalogue, too.

HD 224037 is a quite red star, almost as red as Betelgeuse. But it is a far cry from the really red stars, the carbon stars. When I observed Betelgeuse, I thought it's color wasn't even orange, but golden. So the color balance in today's APOD may be slightly red. On the other hand, it is interesting to note that the brighter stars in the image almost all seem slightly red, while the fainter stars seem to be neutral-colored. Either this is a photographic effect, or else we are in a part of the sky where the brighter-looking stars are almost all red giants and the fainter-looking stars are more neutral main sequence stars. The latter scenario is definitely a possibility.

Ann

[Chris Peterson]

HD 224037 is a quite red star, almost as red as Betelgeuse. But it is a far cry from the really red stars, the carbon stars. When I observed Betelgeuse, I thought it's color wasn't even orange, but golden. So the color balance in today's APOD may be slightly red. On the other hand, it is interesting to note that the brighter stars in the image almost all seem slightly red, while the fainter stars seem to be neutral-colored. Either this is a photographic effect, or else we are in a part of the sky where the brighter-looking stars are almost all red giants and the fainter-looking stars are more neutral main sequence stars. The latter scenario is definitely a possibility.

Other considerations: the image was made with a DSLR, so it is likely to be a bit color challenged to begin with. When the exposure was made, this region was at an altitude of only 35° above the horizon, which is low enough that atmospheric extinction effects were present, including some reddening.

[Abused]

Stupidest shot so far this year

[Ann]

HD 224037 is a quite red star, almost as red as Betelgeuse. But it is a far cry from the really red stars, the carbon stars. When I observed Betelgeuse, I thought it's color wasn't even orange, but golden. So the color balance in today's APOD may be slightly red. On the other hand, it is interesting to note that the brighter stars in the image almost all seem slightly red, while the fainter stars seem to be neutral-colored. Either this is a photographic effect, or else we are in a part of the sky where the brighter-looking stars are almost all red giants and the fainter-looking stars are more neutral main sequence stars. The latter scenario is definitely a possibility.

Other considerations: the image was made with a DSLR, so it is likely to be a bit color challenged to begin with. When the exposure was made, this region was at an altitude of only 35° above the horizon, which is low enough that atmospheric extinction effects were present, including some reddening.

Well, I checked the stars with my astronomy software. Many of them are faint enough that my software has no information about them, but of the faint ones which had had their "vital statistics" taken, all had color indexes between 0.25 and 0.55. Those are all non-red stars. They are in fact blue enough that they may be early A-type stars that suffer some reddening, or they may be unreddened late A-type stars or F-type stars. The reddish K5 star that you identified for me had a luminosity of 85 times the Sun (plus/minus 50 Suns or so), and despite the uncertainty this shows quite well that HD 224037 is no brighter than Arcturus, which is 110 times brighter than the Sun. So HD 224037 is no supergiant star. Since it is redder than Arcturus and of a later spectral class but no brighter, I take it that HD 224037 is, if anything, less massive than Arcturus, or when it was less massive than Arcturus when both were main sequence stars.

But all the brighter stars in the vicinity of HD 224037 that are of a slightly similar distance from us (about a thousand light years) are all of spectral class K, although none are as red or have a similarly late spectral type as HD 224037. I find it quite interesting that this photograph might be showing us a few red giants and a larger number of A and F-type main sequence stars at moderately the same distance.

Ann