APOD: Voyager's Neptune (2014 May 15)

Comments and questions about the APOD on the main view screen.
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APOD: Voyager's Neptune (2014 May 15)

Post by APOD Robot » Thu May 15, 2014 4:05 am

Image Voyager's Neptune

Explanation: Cruising through the outer solar system, the Voyager 2 spacecraft made its closest approach to Neptune on August 25, 1989, the only spacecraft to visit the most distant gas giant. Based on the images recorded during its close encounter and in the following days, this inspired composited scene covers the dim outer planet, largest moon Triton, and faint system of rings. From just beyond Neptune's orbit, the interplanetary perspective looks back toward the Sun, capturing the planet and Triton as thin sunlit crescents. Cirrus clouds and a dark band circle Neptune's south polar region, with a cloudy vortex above the pole itself. Parts of the very faint ring system along with the three bright ring arcs were first imaged by Voyager during the fly-by, though the faintest segments are modeled in this composited picture. Spanning 7.5 degrees, the background starfield is composed from sky survey data centered on the constellation Camelopardalis, corresponding to the outbound Voyager's view of the magnificent Neptunian system.

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Re: APOD: Voyager's Neptune (2014 May 15)

Post by sgwmunro » Thu May 15, 2014 4:33 am

Is it just me, or does that south polar region look very similar to Saturn's Hexagon?

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Re: APOD: Voyager's Neptune (2014 May 15)

Post by Nitpicker » Thu May 15, 2014 4:52 am

sgwmunro wrote:Is it just me, or does that south polar region look very similar to Saturn's Hexagon?
It is certainly tempting to think so. But this modified colour image of Neptune: Source: http://uanews.org/story/clocking-neptunes-spin

... would seem to suggest it is a circular pattern.

This APOD is spectacular. Thank you Mr Olsen.

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Re: APOD: Voyager's Neptune (2014 May 15)

Post by owlice » Thu May 15, 2014 8:01 am

Nitpicker wrote:This APOD is spectacular. Thank you Mr Olsen.
This! Yes!
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Re: APOD: Voyager's Neptune (2014 May 15)

Post by prh » Thu May 15, 2014 9:20 am

I'm having trouble with the perspective here. Either Triton is inside the rings, which I didn't think possible, or else it's at least 30 degrees off the equatorial plane, which also seems impossible.

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Re: APOD: Voyager's Neptune (2014 May 15)

Post by RedFishBlueFish » Thu May 15, 2014 9:42 am

OH!

My.

Speechless.

The most amazing photo I have ever seen.

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Re: APOD: Voyager's Neptune (2014 May 15)

Post by Boomer12k » Thu May 15, 2014 10:19 am

And it is STILL an awesome photo....


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Re: APOD: Voyager's Neptune (2014 May 15)

Post by Indigo_Sunrise » Thu May 15, 2014 10:42 am

I second the replies here: this is a spectacular image!
Fabulous job, Mr. Olson!


:saturn: <--we need one of these for Neptune!


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Re: APOD: Voyager's Neptune (2014 May 15)

Post by Nitpicker » Thu May 15, 2014 11:07 am

prh wrote:I'm having trouble with the perspective here. Either Triton is inside the rings, which I didn't think possible, or else it's at least 30 degrees off the equatorial plane, which also seems impossible.
Triton has an unusual orbit. It is inclined about -23&deg; (or +157&deg;) to Neptune's equator and ring system, indicating that it orbits in the opposite direction to Neptune's axial rotation. Triton's orbit is more than five times further out than the outer-most Adams ring.

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Re: APOD: Voyager's Neptune (2014 May 15)

Post by orin stepanek » Thu May 15, 2014 11:29 am

Love this photo of Neptune! :yes: :clap: :thumb_up:
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Re: APOD: Voyager's Neptune (2014 May 15)

Post by TimGregg » Thu May 15, 2014 11:53 am

I too came here to suggest that that polar structure reminded me strongly of Saturn's polar hexagon. Remembering that convection in a fluid will form hexagonal cells, has anybody ever discussed the possibility that both could be convection phenomena?

But the more I look at the photograph, the more I think it looks, uhh, shall we say a bit ribald.

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Re: APOD: Voyager's Neptune (2014 May 15)

Post by Nitpicker » Thu May 15, 2014 12:25 pm

TimGregg wrote:I too came here to suggest that that polar structure reminded me strongly of Saturn's polar hexagon. Remembering that convection in a fluid will form hexagonal cells, has anybody ever discussed the possibility that both could be convection phenomena?

But the more I look at the photograph, the more I think it looks, uhh, shall we say a bit ribald.
I would have thought that all the weather in all planetary atmospheres are largely convection phenomena.

I suppose the south pole area is a bit areola-like, or maybe just aureola-like. I'm certainly not thinking about Neytiri, the Na'vi from planet Pandora.

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Re: APOD: Voyager's Neptune (2014 May 15)

Post by CURRAHEE CHRIS » Thu May 15, 2014 12:36 pm

That blue at the southern pole is very pretty.

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Re: APOD: Voyager's Neptune (2014 May 15)

Post by Tszabeau » Thu May 15, 2014 1:16 pm

Nitpicker wrote:
TimGregg wrote:, .

But the more I look at the photograph, the more I think it looks, uhh, shall we say a bit ribald.
I suppose the south pole area is a bit areola-like, or maybe just aureola-like. I'm certainly not thinking about Neytiri, the Na'vi from planet Pandora.
I was thinking the capture scene in Woody Allen's "Everything You Wanted to Know About Sex..."

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Re: APOD: Voyager's Neptune (2014 May 15)

Post by Ann » Thu May 15, 2014 1:37 pm

This is a truly superb image. Thank you so much, Rolf Wahl Olsen, for this splendid effort as well as for previous ones! :D

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Re: APOD: Voyager's Neptune (2014 May 15)

Post by ro_star » Thu May 15, 2014 3:19 pm

is this image to scale? I mean especially the rings, if that is their proper scale and shape; if it is, that means the center ring is at about 1 planetary radius distance from the cloudtops of Neptune;

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Re: APOD: Voyager's Neptune (2014 May 15)

Post by geckzilla » Thu May 15, 2014 4:13 pm

ro_star wrote:is this image to scale? I mean especially the rings, if that is their proper scale and shape; if it is, that means the center ring is at about 1 planetary radius distance from the cloudtops of Neptune;
Rolf went through some painstaking efforts to ensure accuracy but there's always a chance he's off somewhere. Here's a real photo from Voyager 2 of Neptune's ring system: http://en.wikipedia.org/wiki/File:Rings ... A01997.png

There is more information on how exactly he created the image at his website, here: http://www.rolfolsenastrophotography.co ... /i-vjMHSxz
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Re: APOD: Voyager's Neptune (2014 May 15)

Post by Chris Peterson » Thu May 15, 2014 4:42 pm

ro_star wrote:is this image to scale? I mean especially the rings, if that is their proper scale and shape; if it is, that means the center ring is at about 1 planetary radius distance from the cloudtops of Neptune;
Looks like the scaling is quite accurate. When I measure the ring radiuses in units of planetary diameter, I get the standard published values.
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Re: APOD: Voyager's Neptune (2014 May 15)

Post by ta152h0 » Thu May 15, 2014 5:12 pm

never get tired at looking at this image, and I am guessing we will have more from the " vault "
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Re: APOD: Voyager's Neptune (2014 May 15)

Post by Jim Leff » Thu May 15, 2014 8:37 pm

Here's what I don't get. The illuminated side is bright and radiant. And we've also seen the full-on (non-crescent) shots where Neptune is that brilliant shade of blue. Yet the sun from there (as confirmed in the photo) is just a feeble little flicker in the far distance, only a few times brighter than the background stars.

Can someone explain? Did Voyager 2's cameras just carry a heckuva flash?

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Re: APOD: Voyager's Neptune (2014 May 15)

Post by BDanielMayfield » Thu May 15, 2014 9:22 pm

Nitpicker wrote:
prh wrote:I'm having trouble with the perspective here. Either Triton is inside the rings, which I didn't think possible, or else it's at least 30 degrees off the equatorial plane, which also seems impossible.
Triton has an unusual orbit. It is inclined about -23&deg; (or +157&deg;) to Neptune's equator and ring system, indicating that it orbits in the opposite direction to Neptune's axial rotation. Triton's orbit is more than five times further out than the outer-most Adams ring.
I was going to second prh's comment/question, but you answered it well Nitpicker. Your point about Triton's unusual orbit reminded me of something from an old astronomy textbook about a theory that way back in wilder, younger day's of our solar system a close encounter with another planet sized body may have flipped Triton's orbit. The idea also suggested that the same near miss may have also torn former Neptunian moons loose, forming today's Plutonian system. Are these ideas still viable as possibilities?
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Re: APOD: Voyager's Neptune (2014 May 15)

Post by geckzilla » Thu May 15, 2014 9:37 pm

Jim Leff wrote:Here's what I don't get. The illuminated side is bright and radiant. And we've also seen the full-on (non-crescent) shots where Neptune is that brilliant shade of blue. Yet the sun from there (as confirmed in the photo) is just a feeble little flicker in the far distance, only a few times brighter than the background stars.

Can someone explain? Did Voyager 2's cameras just carry a heckuva flash?
That's an accurately simulated star background using DSS data for the stars themselves and Voyager 2 imagery to obtain the correct positioning of the stars. The sun is not in the picture at all and nor should it be.
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Re: APOD: Voyager's Neptune (2014 May 15)

Post by Jim Leff » Thu May 15, 2014 10:38 pm

Geckzilla, I guess I misinterpreted this:
the interplanetary perspective looks back toward the Sun
....to mean that the brightish star in the photo was the sun.

But I'm still surprised the surface of Neptune is so well-illuminated in photos when it's at that distance from the sun...

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Re: APOD: Voyager's Neptune (2014 May 15)

Post by Chris Peterson » Thu May 15, 2014 10:54 pm

Jim Leff wrote:Geckzilla, I guess I misinterpreted this:
the interplanetary perspective looks back toward the Sun
....to mean that the brightish star in the photo was the sun.

But I'm still surprised the surface of Neptune is so well-illuminated in photos when it's at that distance from the sun...
You can't tell what the actual illumination is, because the intensity range is stretched so pixels display between white and black. However, the actual intensity at Neptune is still as bright as what we have on Earth on an overcast day. No artificial lighting would be required by humans walking around during the day on any planet in the Solar System.
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Re: APOD: Voyager's Neptune (2014 May 15)

Post by geckzilla » Thu May 15, 2014 11:25 pm

Jim Leff wrote:Geckzilla, I guess I misinterpreted this:
the interplanetary perspective looks back toward the Sun
....to mean that the brightish star in the photo was the sun.
Yeah, it would be less confusing to say that the perspective is looking back toward the inner solar system. We are looking up at Neptune from below, though, so the sun and planets aren't in the frame at all. If the sun were in the frame Neptune would appear nearly totally black with only the thinnest sliver of crescent visible. If Neptune were occulting the sun, the rings would be brilliantly illuminated and details never before seen would be revealed. We'd need to send a new probe out to do that, though. I bet it would be an astonishing view, much like the two backlit Saturn portraits we have from Cassini.
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