by Ann » Tue Oct 27, 2020 5:17 am
VictorBorun wrote: ↑Mon Oct 26, 2020 8:20 pm
wow
Went to read on
Herbig-Haro objects and
bow shocks.
If the jet is 1000 years old and is flowing at 300 km/s = 1/1000 c, then the jet should be 1 light years long, quite plausible here.
And the Dust Pillar of the Carina Nebula is a beauty and a model for two-eyed dusty head interpretation.
On the other hand, if the star at the vertex of the bow shock were the culprit, it should move away from us uncanny fast. And that movement would show as an uncanny red shift, wouldn't it?
Actually, I don't believe that the star seemingly at the vertex of the bow shock in the Ghost Nebula is anything else than a background object, and I don't believe that it has plunged through the nebula.
I think that the nebula would be very disturbed, full of shocks and eddies, if a star had plunged right through it. Look at the picture at right. Speeding runaway star AE Aurigae has run straight into a molecular cloud during its rush through space. As it entered the cloud, hot O9.5-type star AE Aurigae ionized hydrogen in the cloud, turning it into a red emission nebula. But AE Aurigae also lit up dusty regions in the cloud, making them reflect the blue light of AE Aurigae itself.
But note how disturbed the nebula surrounding AE Aurigae is, and how "calm" the Ghost Nebula is. I don't think the Ghost Nebula has had a star run right through it.
But take a look at this nebula, NGC 1999, at left, one of the weirdest nebulas in the sky. Astronomers long thought that the pitch-black thing located right next to the illuminating star, multiple star V380 Orionis, was a so called Bok globule. A Bok globule is an evaporating dust cloud floating around in a nebula, usually inside a red emission nebula near very hot stars. In the picture at right, you can see several Bok globules floating around inside nebula IC 2944. This nebula is ionized by several very hot O-type stars with temperatures well over 30,000 K.
Yes, but the pitch-dark spot right next to the blue star illuminating blue reflection nebula NGC 1999 doesn't look like a dust cloud, does it? It looks like a hole that has been punched right through the nebula. And astronomers now agree that it
is a hole.
Wikipedia wrote about nebula NGC 1999:
NGC 1999 is a dust-filled bright nebula with a vast hole of empty space represented by a black patch of sky, as can be seen in the photograph. It is a reflection nebula, and shines from the light of the variable star V380 Orionis.
It was previously believed that the black patch was a dense cloud of dust and gas which blocked light that would normally pass through, called a dark nebula. (...)
With support from ground-based observations done using the submillimeter bolometer cameras on the Atacama Pathfinder Experiment radio telescope (November 29, 2009) and the Mayall (Kitt Peak) and Magellan telescopes (December 4, 2009), it was determined that the patch looks black not because it is an extremely dense pocket of gas, but because it is truly empty.
The exact cause of this phenomenon is still being investigated, although
it has been hypothesized that narrow jets of gas from some of the young stars in the region punctured the sheet of dust and gas (...)
So my best guess is that the strange "wake" and hole in the Ghost Nebula have also been caused by a jet.
Ann
[quote=VictorBorun post_id=307591 time=1603743609 user_id=145500]
wow
Went to read on [i]Herbig-Haro objects[/i] and [i]bow shocks[/i].
If the jet is 1000 years old and is flowing at 300 km/s = 1/1000 c, then the jet should be 1 light years long, quite plausible here.
And the Dust Pillar of the Carina Nebula is a beauty and a model for two-eyed dusty head interpretation.
On the other hand, if the star at the vertex of the bow shock were the culprit, it should move away from us uncanny fast. And that movement would show as an uncanny red shift, wouldn't it?
[/quote]
[float=left][img3="Reflections of the Ghost Nebula. Image Credit & Copyright: Bogdan Jarzyna."]https://apod.nasa.gov/apod/image/2010/GhostNebula_Jarzyna_960.jpg[/img3][/float][float=right][img3="The Flaming Star Nebula, surrounding hot star AE Aurigae (near center) that has plunged straight into it. The nebula looks strongly disturbed because a star has plunged straight into it. Photo: Rolf Geissinger."]https://apod.nasa.gov/apod/image/1103/IC405FlamingstarDetail_geissinger900.jpg[/img3][/float]
Actually, I don't believe that the star seemingly at the vertex of the bow shock in the Ghost Nebula is anything else than a background object, and I don't believe that it has plunged through the nebula.
I think that the nebula would be very disturbed, full of shocks and eddies, if a star had plunged right through it. Look at the picture at right. Speeding runaway star AE Aurigae has run straight into a molecular cloud during its rush through space. As it entered the cloud, hot O9.5-type star AE Aurigae ionized hydrogen in the cloud, turning it into a red emission nebula. But AE Aurigae also lit up dusty regions in the cloud, making them reflect the blue light of AE Aurigae itself.
But note how disturbed the nebula surrounding AE Aurigae is, and how "calm" the Ghost Nebula is. I don't think the Ghost Nebula has had a star run right through it.
[float=left][img3="Nebula NGC 1999 with a keyhole-shaped hole in it. NASA and The Hubble Heritage Team. (STScI)"]https://upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Ngc1999.jpg/800px-Ngc1999.jpg[/img3][/float] [float=right][img3="Bok globules, evaporating dark dust clouds, in emission nebula IC 2944. Photo: ESO."]https://upload.wikimedia.org/wikipedia/commons/thumb/9/9d/The_Very_Large_Telescope_Snaps_a_Stellar_Nursery_and_Celebrates_Fifteen_Years_of_Operations.jpg/1200px-The_Very_Large_Telescope_Snaps_a_Stellar_Nursery_and_Celebrates_Fifteen_Years_of_Operations.jpg[/img3][/float]
But take a look at this nebula, NGC 1999, at left, one of the weirdest nebulas in the sky. Astronomers long thought that the pitch-black thing located right next to the illuminating star, multiple star V380 Orionis, was a so called Bok globule. A Bok globule is an evaporating dust cloud floating around in a nebula, usually inside a red emission nebula near very hot stars. In the picture at right, you can see several Bok globules floating around inside nebula IC 2944. This nebula is ionized by several very hot O-type stars with temperatures well over 30,000 K.
Yes, but the pitch-dark spot right next to the blue star illuminating blue reflection nebula NGC 1999 doesn't look like a dust cloud, does it? It looks like a hole that has been punched right through the nebula. And astronomers now agree that it [b][i]is[/i][/b] a hole.
[quote][url=https://en.wikipedia.org/wiki/NGC_1999]Wikipedia[/url] wrote about nebula NGC 1999:
[b][color=#0040FF]NGC 1999 is a dust-filled bright nebula with a vast hole of empty space[/color][/b] represented by a black patch of sky, as can be seen in the photograph. It is a reflection nebula, and shines from the light of the variable star V380 Orionis.
It was previously believed that the black patch was a dense cloud of dust and gas which blocked light that would normally pass through, called a dark nebula. (...)
With support from ground-based observations done using the submillimeter bolometer cameras on the Atacama Pathfinder Experiment radio telescope (November 29, 2009) and the Mayall (Kitt Peak) and Magellan telescopes (December 4, 2009), it was determined that the patch looks black not because it is an extremely dense pocket of gas, but because it is truly empty.
The exact cause of this phenomenon is still being investigated, although [b][color=#FF0000]it has been hypothesized that narrow jets of gas from some of the young stars in the region punctured the sheet of dust and gas[/color][/b] (...)[/quote]
So my best guess is that the strange "wake" and hole in the Ghost Nebula have also been caused by a jet.
Ann