Starship Asterisk*

vmorand wrote:
This image looks wrong to me. Judging by the angle of the terminator, a line to the sun must be perpendicular to the equator and rings of Neptune. In other words, Neptune appears to be tipped over on its side, with its pole pointing to the Sun. Uranus does this, but Neptune has an axial tilt similar to the Earth, with its poles pointing at a high angle to the ecliptic plane.

http://www.azlyrics.com/lyrics/katiemelua/blameitonthemoon.html wrote:

• Now that it's gone too far to call for a halt,
  I'll blame it on the moon
  'Cause it's not my fault;
  I didn't think that this would happen so soon
  So I'll blame it on the moon.

http://en.wikipedia.org/wiki/Voyager_2#Encounter_with_Neptune wrote:

[url=http://physicsworld.com/cws/article/news/2011/dec/05/voyager-sets-sights-on-milky-way]Voyager sets sights on Milky Way[/url]

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<<Voyager 2's closest approach to Neptune occurred on August 25, 1989. Since this was the last planet of our Solar System that Voyager 2 could visit, the Chief Project Scientist, his staff members, and the flight controllers decided to also perform a close fly-by of Triton, the larger of Neptune's two originally known moons, so as to gather as much information on Neptune and Triton as possible, regardless of Voyager 2's departure angle from the planet. This was just like the case of Voyager 1's encounters with Saturn and its massive moon Titan.

Since the plane of the orbit of Triton is tilted significantly with respect to the plane of the ecliptic, through mid-course corrections, Voyager 2 was directed into a path several thousand miles over the north pole of Neptune. At that time, Triton was behind and below (south of) Neptune (at an angle of about 25 degrees below the ecliptic), close to the apoapsis of its elliptical orbit. The gravitational pull of Neptune bent the trajectory of Voyager 2 down in the direction of Triton. In less than 24 hours, Voyager 2 traversed the distance between Neptune and Triton, and then observed Triton's northern hemisphere as it passed over its north pole. The net and final effect on the trajectory of Voyager 2 was to bend its trajectory south below the plane of the ecliptic by about 30 degrees. Voyager 2 is on this path permanently, and hence, it is exploring space south of the plane of the ecliptic, measuring magnetic fields, charged particles, etc., there, and sending the measurements back to the Earth via telemetry.

While in the neighborhood of Neptune, Voyager 2 discovered the "Great Dark Spot", which has since disappeared, according to observations by the Hubble Space Telescope. Originally thought to be a large cloud itself, the "Great Dark Spot" was later hypothesized to be a hole in the visible cloud deck of Neptune.>>

Nitpicker wrote:

BDanielMayfield wrote:

Nitpicker wrote: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.

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?

I don't know if they are still viable as possibilities. I've read that the "current thinking" is, because of Triton's strange orbit and similar composition to Pluto, that Triton might have been captured, after escaping from the Kuiper Belt.

BDanielMayfield wrote:

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?

geckzilla wrote:

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.

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.

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...

the interplanetary perspective looks back toward the Sun

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?

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.

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;

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;

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.

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.

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.