Starship Asterisk*

by **neufer** » Sat Jan 07, 2017 2:27 pm

montycash@hotmail.com wrote:
Im brand new.

Just want to know
how yall getting these pictures.

Plz send me info

by **montycash@hotmail.com** » Sat Jan 07, 2017 8:48 am

Im brand new.Just want to know how yall getting these pictures.Plz send me info

by **Chris Peterson** » Fri Dec 02, 2016 11:34 pm

neufer wrote:For blue supergiants with luminosities a million times the Sun (but masses only 100 times that of the Sun) the radiation pressure exceeds the gravitational attraction by a factor of 10,000 for 1 µm dust grains. A 1 µm dust grain sitting one light year from such a blue supergiant could be pushed out to two light years in about 10,000 years.

Yes. And every energetic photon that hits that particle has the possibility of dissociating an atom from it. Most won't, but it's a process that will occur. High energy charged particles even more so.

by **neufer** » Fri Dec 02, 2016 7:14 pm

neufer wrote:
Dust grains may have icy coatings that "cook" and evaporate in the normal sense of those words.

Dust grain cores are made of refractory materials that only "evaporate" by being blown away due to radiation pressure.

Chris Peterson wrote:
neufer wrote:
Chris Peterson wrote:
The refractory material also evaporates via spallation due to collisions with energetic particles, which is an important source of some elements in dust-rich regions.

On what sort of time scale
Pretty slow, I imagine. It certainly isn't the dominant component of "evaporation" in these sorts of clouds, not by a long shot. But the process exists. Even hard UV knocks atoms off the surface of refractory dust grains (as opposed to spallation, which creates material with a different atomic number).

For our solar system, radiation pressure exceeds the gravitational attraction for (zodiacal light) dust grains smaller than 1 µm (i.e., those containing a million atoms or less).

For blue supergiants with luminosities a million times the Sun (but masses only 100 times that of the Sun) the radiation pressure exceeds the gravitational attraction by a factor of 10,000 for 1 µm dust grains. A 1 µm dust grain sitting one light year from such a blue supergiant could be pushed out to two light years in about 10,000 years.

by **geckzilla** » Fri Dec 02, 2016 6:33 am

MarkBour wrote:I looked around a bit and found some references that said a giant molecular cloud can have up to about 10^6 solar masses of material, but this is dispersed with typical average densities of only about 100 molecules per cm^3. These numbers, though, are not helping my understanding very much, by themselves. I don't think I have any intuitive grasp of them, since I don't have much intuitive grasp of gravity in general.

https://en.wikipedia.org/wiki/Vacuum

Ultra-high vacuum chambers, common in chemistry, physics, and engineering, operate below one trillionth (10⁻¹²) of atmospheric pressure (100 nPa), and can reach around 100 particles/cm³.

So, there you go. The best vacuums we can make here in a lab on Earth are on par with a molecular cloud in space.

(Chris has posted about this here a number of times now; that's the only reason I knew to look at vacuum quality.)

by **MarkBour** » Fri Dec 02, 2016 3:17 am

geckzilla wrote:
MarkBour wrote:The question I'm wondering about, is: "Would passing through this cloud have any significant effect on the orbits of the planets? Could any of them get stripped away, or would there be any other alteration, less drastic, but still significant?"
No. You may as well expect to have your clothes stripped off by the gravitational pull of a passing water cloud here on Earth.

I really like this answer! (and Art's, too). I think I've been on this direction of thinking for a while. I look at images like today's APOD and my earth-life-trained mind says "that's a whole lot of mass, like a giant strawberry milkshake spilled all over the place". I need to re-train myself that what is shown here is the miracle of modern astronomical imaging and processing to show something that is quite sparse.

I looked around a bit and found some references that said a giant molecular cloud can have up to about 10^6 solar masses of material, but this is dispersed with typical average densities of only about 100 molecules per cm^3. These numbers, though, are not helping my understanding very much, by themselves. I don't think I have any intuitive grasp of them, since I don't have much intuitive grasp of gravity in general.

I understand that the Solar system is travelling through a cloud even now, though I doubt our velocity through it is comparable to AE Aurigae's through the Flame, and this region is evidently even less dense in material than the flame nebula region, only about 0.3 atoms per cm^3.

Oh, while I was composing this reply, I see Chris posted a reply that really helps. It says some things I was just beginning to guess.

Our distant descendants (if there are any) can be comforted that this is one danger they won't have to worry about.

by **Chris Peterson** » Fri Dec 02, 2016 2:12 am

MarkBour wrote:Today's APOD serendipitously illustrates just the kind of encounter I was asking about. We happen to have a star passing through a large cloud. Some basic questions are:

What is the typical mass density of the cloud forming the Flaming Star nebula? and

What would that come out to as a total mass?
Now, suppose, hypothetically, that AE Aurigae has a planetary system, much like our own. The question I'm wondering about, is: "Would passing through this cloud have any significant effect on the orbits of the planets? Could any of them get stripped away, or would there be any other alteration, less drastic, but still significant?"

Geck's comparison to a water cloud on Earth is good, although such a cloud would probably have many orders of magnitude greater impact on you (and your clothes) than these stellar clouds would have on stars and planets. Their density is only high with respect to the interstellar background. In absolute terms, these regions of space are still hard vacuums. The total mass may be quite large, measured in many solar masses, but the degree to which they will gravitationally perturb a stellar system is a function of the sort of tidal force or gravitational gradient they exert. The cloud is so large compared with a planetary system that every part of the system feels essentially the same force. So there is no disruption. Given a large enough cloud, the orbit of the star within the galaxy could be perturbed, but all its planets would be taken along for the ride.

by **Ann** » Thu Dec 01, 2016 11:41 pm

MarkBour wrote: Today's APOD serendipitously illustrates just the kind of encounter I was asking about. We happen to have a star passing through a large cloud. Some basic questions are:

What is the typical mass density of the cloud forming the Flaming Star nebula? and

What would that come out to as a total mass?
Now, suppose, hypothetically, that AE Aurigae has a planetary system, much like our own. The question I'm wondering about, is: "Would passing through this cloud have any significant effect on the orbits of the planets? Could any of them get stripped away, or would there be any other alteration, less drastic, but still significant?"

I did a quick googling of "Flaming Star Nebula mass" and came up empty.

I think there can be no doubt that the nebula is tenuous. There seems to be agreement that the nebula is about 5 light years across. Obviously the nebula is not a flat disk but an irregular sphere, and its depth might well be 5 light years, too.

If AE Aurigae had not been there, there would have been no Flaming Star Nebula. Also we would not have seen a dark nebula against the background sky. (All right... infrared photography would definitely have detected dust in the region of the Flaming Star Nebula, but only cutting-edge visual photography would have spotted it.) I agree that AE Aurigae might act as a snowplow, piling up gas and dust in front of it, so that the nebula has become thicker because of AE Aurigae's effect on it than it would otherwise have been. Nevertheless, it is still very thin.

So while AE Aurigae has a great impact on its surroundings, its surroundings have little influence on AE Aurigae or on any planets it might have. The greatest danger to those planets would be AE Aurigae itself, at least if we are considering planets bearing life forms on their surfaces.

Jim Kaler wrote:

...AE's temperature measured at 36,500 Kelvin (anomalously high for its class; 33,000 might be better). In either case, the star is very luminous, between 26,000 and 33,000 times the luminosity of the Sun (depending on the temperature and the allowance for ultraviolet radiation) and massive (at least 17 times solar...

AE Aurigae can be expected to go supernova in, oh, twenty million years? In either case, you wouldn't want to be in orbit around such a monster star.

Ann

by **neufer** » Thu Dec 01, 2016 10:16 pm

geckzilla wrote:
MarkBour wrote:
The question I'm wondering about, is: "Would passing through this cloud have any significant effect on the orbits of the planets? Could any of them get stripped away, or would there be any other alteration, less drastic, but still significant?"
No. You may as well expect to have your clothes stripped off by the gravitational pull of a passing water cloud here on Earth.

Neptunians might notice a change in their auroras.

https://en.wikipedia.org/wiki/Heliosphere wrote:
<<The heliosphere is the bubble-like region of space dominated by the Sun, which extends far beyond the orbit of Pluto. Plasma "blown" out from the Sun, known as the solar wind, creates and maintains this bubble against the outside pressure of the interstellar medium, the hydrogen and helium gas that permeates the Milky Way Galaxy. The solar wind flows outward from the Sun until encountering the termination shock, where motion slows abruptly. The Voyager spacecraft have actively explored the outer reaches of the heliosphere, passing through the shock and entering the heliosheath, a transitional region which is in turn bounded by the outermost edge of the heliosphere, called the heliopause. The overall shape of the heliosphere is controlled by the interstellar medium through which it is traveling, as well as the Sun, and is not perfectly spherical.>>

by **geckzilla** » Thu Dec 01, 2016 9:23 pm

MarkBour wrote:The question I'm wondering about, is: "Would passing through this cloud have any significant effect on the orbits of the planets? Could any of them get stripped away, or would there be any other alteration, less drastic, but still significant?"

No. You may as well expect to have your clothes stripped off by the gravitational pull of a passing water cloud here on Earth.

by **mee** » Thu Dec 01, 2016 9:17 pm

Anyone else notice the small black dot at the top of the image in the center?

by **MarkBour** » Thu Dec 01, 2016 9:14 pm

I lifted a quote from the Starship Asterisk discussion of the 2016-11-28 APOD. I was asking about non-stellar objects in a galactic merger having any effect on planetary systems. An excerpt from the reply Chris Peterson gave, is:

Chris Peterson wrote: ... Molecular clouds, dust clouds, gas clouds, dark matter- these things don't disrupt planetary systems because they're too diffuse. Disrupting stellar system requires tiny, dense bodies- stars or very large planets.

Hopefully, Chris, you don't mind my transplanting it here. Today's APOD serendipitously illustrates just the kind of encounter I was asking about. We happen to have a star passing through a large cloud. Some basic questions are:

What is the typical mass density of the cloud forming the Flaming Star nebula? and
What would that come out to as a total mass?

Now, suppose, hypothetically, that AE Aurigae has a planetary system, much like our own. The question I'm wondering about, is: "Would passing through this cloud have any significant effect on the orbits of the planets? Could any of them get stripped away, or would there be any other alteration, less drastic, but still significant?"

I'm thinking that this question is essentially the same as my question from 11/28. If so, then I guess that Chris (and Art, who had made a statement on the 11/28 discussion that brought up my question) may simply agree that the already-given answer would apply (i.e. "No, no significant effect.") But, lest I put words in your mouths, I welcome any replies you wish to add.

by **bls0326** » Thu Dec 01, 2016 8:09 pm

"Ann wrote
I think the Flaming Star Nebula pretty much is the bow shock."

thanks for the info. The Flaming Star Nebula does look like the bow shock in your picture.

Brian

by **Chris Peterson** » Thu Dec 01, 2016 6:40 pm

neufer wrote:
Chris Peterson wrote:
neufer wrote: Dust grains may have icy coatings that "cook" and evaporate in the normal sense of those words.

Dust grain cores are made of refractory materials that only "evaporate" by being blown away due to radiation pressure.
The refractory material also evaporates via spallation due to collisions with energetic particles, which is an important source of some elements in dust-rich regions.

On what sort of time scale :?:

Pretty slow, I imagine. It certainly isn't the dominant component of "evaporation" in these sorts of clouds, not by a long shot. But the process exists. Even hard UV knocks atoms off the surface of refractory dust grains (as opposed to spallation, which creates material with a different atomic number).

(There's a heck of lot of dust in the Universe for it to be as vulnerable to destruction as you suggest.)

And a significant amount of the light metals (Li, Be, B) we observe in the Universe probably comes from just that kind of cosmogenic nucleosynthesis stemming from spallation by energetic particles.

by **starsurfer** » Thu Dec 01, 2016 6:36 pm

Ann wrote:I'm always glad to see a fine RGB image

Ann

I'm always glad to see a fine HaOIIIRGB image of planetary nebulae or supernova remnants or other ionized nebulae.

Also this image is amazing, one of the very best of this colourful nebulae!!!

by **starsurfer** » Thu Dec 01, 2016 6:35 pm

Click to play embedded YouTube video.

by **neufer** » Thu Dec 01, 2016 5:59 pm

Chris Peterson wrote:
neufer wrote:
Ann wrote:
Ordinarily, a hot star like AE Aurigae would "cook" the dust grains in its vicinity to smaller sizes, thereby virtually destroying the chances for a dusty reflection nebula to form. But just because AE Aurigae is a runaway star and just passing through, it hasn't had time to evaporate the dust grains. So the blue tendrils in today's APOD are indeed dusty features,
Dust grains may have icy coatings that "cook" and evaporate in the normal sense of those words.

Dust grain cores are made of refractory materials that only "evaporate" by being blown away due to radiation pressure.
The refractory material also evaporates via spallation due to collisions with energetic particles, which is an important source of some elements in dust-rich regions.

On what sort of time scale

(There's a heck of lot of dust in the Universe for it to be as vulnerable to destruction as you suggest.)

by **Chris Peterson** » Thu Dec 01, 2016 3:58 pm

neufer wrote:
Ann wrote:
Ordinarily, a hot star like AE Aurigae would "cook" the dust grains in its vicinity to smaller sizes, thereby virtually destroying the chances for a dusty reflection nebula to form. But just because AE Aurigae is a runaway star and just passing through, it hasn't had time to evaporate the dust grains. So the blue tendrils in today's APOD are indeed dusty features,
Dust grains may have icy coatings that "cook" and evaporate in the normal sense of those words.

Dust grain cores are made of refractory materials that only "evaporate" by being blown away due to radiation pressure.

The refractory material also evaporates via spallation due to collisions with energetic particles, which is an important source of some elements in dust-rich regions.

by **Asterhole** » Thu Dec 01, 2016 3:27 pm

Boomer12k wrote:I half expected to see ELVIS...

What a spectacular image!!!
Flaming and firing up the nebula..."Hunka, Hunka Burnin' LOVE...."

:---[===]*

I was wondering if anyone else was going to make the "Elvis" reference. Hm - with AE Aurigue's apparent velocity, perhaps one day it will have left the Nebula...?

by **Ann** » Thu Dec 01, 2016 2:18 pm

bls0326 wrote:Is there a "bow shock wave" with AE Aurigae? Other articles indicate these speedy stars produce them if there is material in the way. I do not see it, but maybe I am missing it.

Any idea which way the star is moving in this picture (left, right, up, down, in out?)

I think the Flaming Star Nebula pretty much is the bow shock.

: Click to view full size image

IC 405 and IC 410 (Flaming Star Nebula).
Photo: Gerald Rhemann.

In Gerald Rhemann's image, where north is to the left, AE Aurigae would have come zipping in from the right.

In reality, the star came from the south (or south by southeast) and is moving north (north by northwest).

Ann

by **RJN** » Thu Dec 01, 2016 2:08 pm

ManInFla wrote:I think some of the links on the nav bar at the bottom are messed up today...

Sorry. Fixed now.

by **bls0326** » Thu Dec 01, 2016 1:50 pm

Is there a "bow shock wave" with AE Aurigae? Other articles indicate these speedy stars produce them if there is material in the way. I do not see it, but maybe I am missing it.

Any idea which way the star is moving in this picture (left, right, up, down, in out?)

by **neufer** » Thu Dec 01, 2016 1:15 pm

Ann wrote:
Ordinarily, a hot star like AE Aurigae would "cook" the dust grains in its vicinity to smaller sizes, thereby virtually destroying the chances for a dusty reflection nebula to form. But just because AE Aurigae is a runaway star and just passing through, it hasn't had time to evaporate the dust grains. So the blue tendrils in today's APOD are indeed dusty features,

Dust grains may have icy coatings that "cook" and evaporate in the normal sense of those words.

Dust grain cores are made of refractory materials that only "evaporate" by being blown away due to radiation pressure.

by **geckzilla** » Thu Dec 01, 2016 12:10 pm

ManInFla wrote:I think some of the links on the nav bar at the bottom are messed up today...

Yeah. Thanks. Bystander let the editors know earlier this morning. It will get fixed.

by **ManInFla** » Thu Dec 01, 2016 12:02 pm

I think some of the links on the nav bar at the bottom are messed up today...

Starship Asterisk*

APOD: Flaming Star Nebula (2016 Dec 01)

Post a reply

Expand view Topic review: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)

Re: APOD: Flaming Star Nebula (2016 Dec 01)