by Chris Peterson » Fri Sep 30, 2016 4:40 pm
FLPhotoCatcher wrote:The description says that the Nebula is "drifting above the plane of our Milky Way galaxy." But wouldn't it be orbiting the Milky Way like our solar system is? In other words, wouldn't it move "up" and "down" through the plane of the galaxy?
Indeed, it is in orbit around the center of the Milky Way. Virtually everything making up our galaxy is either above or below the galactic plane. LDN 1251 is approximately 250 ly above the plane, which means it is well inside the thin stellar disk of the galaxy. Not above the galaxy, just above the central plane (as is the Sun, which could be as much as 100 ly above it).
So this nebula is on a very slightly inclined ellipical orbit which over more than 200 million years would take it around the Milky Way, half of the time above the plane and half of the time below. Of course, the lifetime of nebulas like this is only a fraction of a galactic year, so this one will spend its entire life above the galactic plane. But as you say, orbiting, not drifting.
[quote="FLPhotoCatcher"]The description says that the Nebula is "drifting above the plane of our Milky Way galaxy." But wouldn't it be orbiting the Milky Way like our solar system is? In other words, wouldn't it move "up" and "down" through the plane of the galaxy?[/quote]
Indeed, it is in orbit around the center of the Milky Way. Virtually everything making up our galaxy is either above or below the galactic plane. LDN 1251 is approximately 250 ly above the plane, which means it is well inside the thin stellar disk of the galaxy. Not above the galaxy, just above the central plane (as is the Sun, which could be as much as 100 ly above it).
So this nebula is on a very slightly inclined ellipical orbit which over more than 200 million years would take it around the Milky Way, half of the time above the plane and half of the time below. Of course, the lifetime of nebulas like this is only a fraction of a galactic year, so this one will spend its entire life above the galactic plane. But as you say, orbiting, not drifting.