Starship Asterisk*

VdB 152: A Ghost in Cepheus

Explanation: Described as a "dusty curtain" or "ghostly apparition", mysterious reflection nebula VdB 152 really is very faint. Far from your neighborhood on this Halloween Night, the cosmic phantom is nearly 1,400 light-years away. Also catalogued as Ced 201, it lies along the northern Milky Way in the royal constellation Cepheus. Near the edge of a large molecular cloud, pockets of interstellar dust in the region block light from background stars or scatter light from the embedded bright star giving parts of the nebula a characteristic blue color. Ultraviolet light from the star is also thought to cause a dim reddish luminescence in the nebular dust. Though stars do form in molecular clouds, this star seems to have only accidentally wandered into the area, as its measured velocity through space is very different from the cloud's velocity. This deep telescopic image of the region spans about 7 light-years.

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BOO!! It's that time of year again. Apparently in space, also.

Eek!!!!

You scared me!!!!

BOO!!!!!! Gotchya.....ooooh....somebody already did that....


:---[===] *

This item brings back a question I've asked before but never got an answer that didn't seem contrived or avoiding the issue.

We are told we are in an expanding universe, with all parts moving away from all other parts, an effect of the Big Bang.
So how do stars move though dust clouds going different directions and speeds? How can galaxies collide (and there are so many that do...) if we are all moving apart, driven by the same starting influence? Collisions should be nearly impossible, it would seem. What am I missing?

bay area john wrote:This item brings back a question I've asked before but never got an answer that didn't seem contrived or avoiding the issue.

We are told we are in an expanding universe, with all parts moving away from all other parts, an effect of the Big Bang.
So how do stars move though dust clouds going different directions and speeds? How can galaxies collide (and there are so many that do...) if we are all moving apart, driven by the same starting influence? Collisions should be nearly impossible, it would seem. What am I missing?

Dark energy isn't strong enough to make galaxies fly apart. Inside galaxies, gravity dominates over dark energy. Between galaxies that are close together, such as the Milky Way and Andromeda (~2 million light-years), gravity also dominates over dark energy. Between galaxy clusters, such as the Local Group (where we belong) and the Virgo Cluster (~60 million light-years) dark energy usually dominates over gravity, and always if the clusters are not extremely massive and are, say, 100 light-years apart.

Inside galaxies, various "currents" and "eddies" form, which make objects move in different directions.

Ann

Ann wrote:

bay area john wrote:This item brings back a question I've asked before but never got an answer that didn't seem contrived or avoiding the issue.

We are told we are in an expanding universe, with all parts moving away from all other parts, an effect of the Big Bang.
So how do stars move though dust clouds going different directions and speeds? How can galaxies collide (and there are so many that do...) if we are all moving apart, driven by the same starting influence? Collisions should be nearly impossible, it would seem. What am I missing?

Dark energy isn't strong enough to make galaxies fly apart. Inside galaxies, gravity dominates over dark energy. Between galaxies that are close together, such as the Milky Way and Andromeda (~2 million light-years), gravity also dominates over dark energy. Between galaxy clusters, such as the Local Group (where we belong) and the Virgo Cluster (~60 million light-years) dark energy usually dominates over gravity, and always if the clusters are not extremely massive and are, say, 100 light-years apart.

Inside galaxies, various "currents" and "eddies" form, which make objects move in different directions.

Ann

i think dark energy is hard vacuum , just ABSOLUTE NOTHING ! and galaxies skids off their gravitational path due to ENTROPY i mean energy driving them diffuse to energy-less areas ie vacuum

Yay my prediction was wrong!!!

could there be something like this preventing us from seeing beyond the 'edge' of the known universe?

Another stunning image. APOD is on a roll. I am taken by the embedded wandering star and the loops that surround it. Are the loops caused by the bright star's movement through the cloud? Could the loops be created by the smaller star which seems to lineup with the loops or is that coincidental? Are the two stars even related?

Beyond wrote:BOO!! It's that time of year again. Apparently in space, also.

Reminded me of an old knock knock joke!
Knock knock1
Who's there?
Boo!
Boo who?
Why are you crying?
Argh!

APOD Robot wrote: Explanation: Described as a "dusty curtain" or "ghostly apparition", mysterious reflection nebula VdB 152 really is very faint.

When I read the first sentence of this explanation I thought to myself, from our vantage point this nebula seems to be blocking much more light than it is reflecting. I would say it is more of a 'dark nebula' than a 'reflection nebula'. At least a 90-10 ratio..
Though I suppose one could call it either.

bay area john wrote:
This item brings back a question I've asked before but never got an answer that didn't seem contrived or avoiding the issue.

We are told we are in an expanding universe, with all parts moving away from all other parts, an effect of the Big Bang.
So how do stars move though dust clouds going different directions and speeds? How can galaxies collide (and there are so many that do...) if we are all moving apart, driven by the same starting influence? Collisions should be nearly impossible, it would seem. What am I missing?

1) Big Bang expansion itself canNOT do work against gravity such that it has no affect on gravitationally bound objects.

Shortly after the big bang, galactic clusters started to condense around concentrations of dark matter. Thereafter, the expansion "momentum" effects of the big bang itself had no further affect on anything inside the individual galactic clusters. Galaxies within any cluster were free to interact irrespective of the initial big bang expansion that separates clusters from one another.

2) Dark energy expansion CAN do work against gravity but...
it currently amounts to only a fraction of the Hubble expansion:

"As of 3rd Oct 2012 the Hubble constant, as measured by NASA's Spitzer Telescope
and reported in Science Daily, is 74.3 ± 2.1 (km/s)/Mpc"

Where Mpc = one million parsecs ~ 3,260,000 light-years.

At 1,400 light-years away (today's APOD) the hypothetical Hubble expansion amounts to just 32 m/s or ~72 mph.

At 2.54 Mly to M31 the hypothetical Hubble expansion amounts to ~58 km/s.

However, the Andromeda Galaxy is approaching the Milky Way at about 100 to 140 km/s.
This exceeds the dark energy expansion fractional component of the ~58 km/s hypothetical Hubble expansion.

Wadsworth wrote:

APOD Robot wrote: Explanation: Described as a "dusty curtain" or "ghostly apparition", mysterious reflection nebula VdB 152 really is very faint.

When I read the first sentence of this explanation I thought to myself, from our vantage point this nebula seems to be blocking much more light than it is reflecting. I would say it is more of a 'dark nebula' than a 'reflection nebula'. At least a 90-10 ratio..
Though I suppose one could call it either.

vdB152 only refers to the small blue reflection nebula. The dusty dark nebula is catalogued as B175 and was discovered in a photographic plate nearly 100 years ago by the famous astronomer Edward Emerson Barnard, who published a well known catalogue of dark nebulae. The whole catalogue is available online here: http://www.library.gatech.edu/barnard/

Awwwwwwwwwww its a blue eyed ghost

neufer wrote:...
However, the Andromeda Galaxy is approaching the Milky Way at about 100 to 140 km/s.
This exceeds the dark energy expansion fractional component of the ~58 km/s hypothetical Hubble expansion.

Thanks, that's interesting but somehow unsatisfying as to explain how galaxies expanding from a common origin can be crossing paths at such speeds billions of years later. I'm being simplistic in the extreme, but imagining an infinity large pool table with a hellava break. With no bumpers to direct the balls back "in", they scatter, and keep scattering, and never change course to cross each other's paths, especially long after the break. Saying that "gravity is stronger" may be true but gravity would not change the direction of a single moving object, only interacting objects... so how do they START to cross paths?

starsurfer wrote:

Wadsworth wrote:

APOD Robot wrote: Explanation: Described as a "dusty curtain" or "ghostly apparition", mysterious reflection nebula VdB 152 really is very faint.

When I read the first sentence of this explanation I thought to myself, from our vantage point this nebula seems to be blocking much more light than it is reflecting. I would say it is more of a 'dark nebula' than a 'reflection nebula'. At least a 90-10 ratio..
Though I suppose one could call it either.

vdB152 only refers to the small blue reflection nebula. The dusty dark nebula is catalogued as B175 and was discovered in a photographic plate nearly 100 years ago by the famous astronomer Edward Emerson Barnard, who published a well known catalogue of dark nebulae. The whole catalogue is available online here: http://www.library.gatech.edu/barnard/

So, though it is one 'grouping' of gas and dust, it can be cataloged under multiple different names and titles. This makes sense.

old guy wrote:could there be something like this preventing us from seeing beyond the 'edge' of the known universe?

How far we can see is directly related to the speed of light and the age of the universe. We can only see as far as the light/photons have traveled since the Big Bang (the ones that travelled toward us that is). That's the simple answer at least, this gets much more complicated when you take into account our position within the universe and our relative motion. Our edge is only what we can see, which is limited, of course there is something beyond that but we'll never be able to see it unless we somehow move significantly closer to it, thereby altering everything else we see. Lol! Fun to contemplate though.


Love this picture, perfect for today. Does anyone else see those red lines/apparitions to the right of the nebula? Any idea what they are??? Camera artifacts? Or something creepier?

bay area john wrote:

neufer wrote:...
However, the Andromeda Galaxy is approaching the Milky Way at about 100 to 140 km/s.
This exceeds the dark energy expansion fractional component of the ~58 km/s hypothetical Hubble expansion.

Thanks, that's interesting but somehow unsatisfying as to explain how galaxies expanding from a common origin can be crossing paths at such speeds billions of years later. I'm being simplistic in the extreme, but imagining an infinity large pool table with a hellava break. With no bumpers to direct the balls back "in", they scatter, and keep scattering, and never change course to cross each other's paths, especially long after the break. Saying that "gravity is stronger" may be true but gravity would not change the direction of a single moving object, only interacting objects... so how do they START to cross paths?

Hi John. I'll take a shot at your pool table analogy. Each individual pool ball is an entire galaxy cluster. Within each pool ball are galaxies, stars, dust clouds, planets, life forms, poached eggs on toast, atoms, and subatomic particles. The eight ball (and all the other balls) absorbed some energy from the break (nice shot, by the way!), but the force of gravity is much greater over the short distances within the eight ball than over the longer (and expanding) distances between the different pool balls, and thus gravity holds the innards of the pool ball together even as all the balls are scattering over the table. How does that work for you?

Anthony Barreiro wrote:

bay area john wrote:

neufer wrote:...
However, the Andromeda Galaxy is approaching the Milky Way at about 100 to 140 km/s.
This exceeds the dark energy expansion fractional component of the ~58 km/s hypothetical Hubble expansion.

Thanks, that's interesting but somehow unsatisfying as to explain how galaxies expanding from a common origin can be crossing paths at such speeds billions of years later. I'm being simplistic in the extreme, but imagining an infinity large pool table with a hellava break. With no bumpers to direct the balls back "in", they scatter, and keep scattering, and never change course to cross each other's paths, especially long after the break. Saying that "gravity is stronger" may be true but gravity would not change the direction of a single moving object, only interacting objects... so how do they START to cross paths?

Hi John. I'll take a shot at your pool table analogy. Each individual pool ball is an entire galaxy cluster. Within each pool ball are galaxies, stars, dust clouds, planets, life forms, poached eggs on toast, atoms, and subatomic particles. The eight ball (and all the other balls) absorbed some energy from the break (nice shot, by the way!), but the force of gravity is much greater over the short distances within the eight ball than over the longer (and expanding) distances between the different pool balls, and thus gravity holds the innards of the pool ball together even as all the balls are scattering over the table. How does that work for you?

I would go one further: Imagine that instead of a vigorous break, you have a table from the middle of a game with the balls spread out more or less at random. Now imagine the pool table itself is getting larger, but the pool balls are staying in their locations relative to the pockets. it looks like they're flying apart, but they're actually just riding the overall expansion of the table without moving at all. The influence of gravity will start rolling them towards each other, but except for where balls are particularly close to each other the table's expansion will dominate and carry them further and further apart.

by bay area john » Wed Oct 31, 2012 5:54 pm

neufer wrote:
...
However, the Andromeda Galaxy is approaching the Milky Way at about 100 to 140 km/s.
This exceeds the dark energy expansion fractional component of the ~58 km/s hypothetical Hubble expansion.
Thanks, that's interesting but somehow unsatisfying as to explain how galaxies expanding from a common origin can be crossing paths at such speeds billions of years later. I'm being simplistic in the extreme, but imagining an infinity large pool table with a hellava break. With no bumpers to direct the balls back "in", they scatter, and keep scattering, and never change course to cross each other's paths, especially long after the break. Saying that "gravity is stronger" may be true but gravity would not change the direction of a single moving object, only interacting objects... so how do they START to cross paths?

------
There is also the theory that there have been several "Big Bangs" that have created many "Bubble Universes." As the different bubbles expand, they bump into other bubbles, and then their collective universe poskets interact with each other.---Very simplified explination by a non-scientist.

Diana

Reflection Nebula in blue
Not only has a ghost, I see one big and two small
The ghost family!