DAMGEM wrote: ↑Sun Mar 18, 2018 5:14 am
I like the image and can visualize their references.What caught my attention were the two spheres at top centre.
They seem so out of place. Perfect super-dense Ort cloud like objects.
Or could they be super novae remnants.
IC 2177, the Seagull Nebula. Note the purple "orbs" at top.
Photo: Strongmanmike. Large picture here.
The "two orbs" are reflection nebulas, not supernova remnants or Oort Cloud objects. I'm posting another picture of the Seagull Nebula here, because I find the colors of the APOD rather weird.
In the picture at left, you can clearly see the color difference between "the two orbs" at upper center-left and most of the Seagull Nebula itself. The Seagull Nebula is mostly magenta-pink. The color is a combination of red hydrogen alpha emission and blue-green hydrogen beta emission.
"The two orbs" at upper center-left look mostly purple. That is because the orbs are produced by normal but hot and bright stars, whose ultraviolet light ionizes hydrogen gas in the vicinity and makes it glow red, and their blue light is reflected in dust surrounding the stars. The stars in question are GU Canis Majoris (GU CMA, or HD 52721) and FZ Canis Majoris (FZ CMa, or HD 52942).
GU CMa is a star of spectral class B2Vne, hot enough to ionize some hydrogen gas and make it glow red, but cool enough to not to blow all the dust away, so that the dust can remain centered on the star and reflect its blue light. FZ CMa is a star of spectral class B3n. It is barely hot enough to ionize any hydrogen, but it could be that much of the ionizing of the gas around FZ CMa (and
the gas around GU CMa) is actually done by the combined ultraviolet light of many hot stars in or near the Seagull Nebula.
I'd like to repeat that strongmanmike's picture makes the purple (red + blue) color of the "orbs" obvious, which in turn makes it easy for us to identify the "orbs" as nebulas made up of one emission (red) component and one reflection (blue) component. The "orb" centered on GU CMa is called vdB 88, and the "orb" centered on FZ CMa is called vdB 90. The orbs are named for their "reflection components", so they are named as reflection nebulas.
It is interesting that vdB 88 and vdB 90 are so round and so perfectly centered on the stars. They look like they are the products of some kind of outbursts of the stars themselves, where the gas and dust that was "cast off" during the outbursts have stayed centered on the stars, not unlike the cast-off shells of gas and dust in planetary nebulas
. But GU CMa and FZ CMa are not scorchingly hot but "dead" little white dwarfs that have cast off all of their "outer atmospheres" and have stopped all energy-generating fusion processes. GU CMa and FZ CMa are normal stars, but hot and bright.