Perseus Cluster of Galaxies, green stars? (APOD 20 May 2008)

[orin stepanek]

http://apod.nasa.gov/apod/ap080520.html


http://apod.nasa.gov/apod/ap030505.html

Nice view! Interesting mixture of two galaxies merging. When two galaxies merge does the two black holes tend to orbit each other and become the core of the combination? Seems as the concentration of stars in the combined galaxy would bring them closer together; or maybe the newly formed galaxy would just be larger!
Orin

[Animation]

Which objects in the image are part of the Perseus cluster?

I know the small stars are in our galaxy.

I'm not sure about the circular shapes with the lens flare (or whatever that is) on them. Are they also stars in our galaxy that are close or that are aligned in such a way to make the "lens flare" or whatever? As an example, I'm talking about the bright blue flared object in the upper left.

Anyway, then there are the smudgy things. I can tell these are obviously galaxies, but which ones are part of the Perseus cluster? There are fuzzy/blobby galaxies, and more distinct spiral ones. Some seem "close" but some appear distant as if they probably arent in the cluster. For example there are a couple on the top of the image, one 40% from left and one about 35% rrom right, that look quite distant or unrelated to the other shapes.

This is one of those apod images I wish had been done with a mouse-over. If an astronomer could have circled the galaxies that ARE in the cluster with a red line, and circled the non-perseus ones with a blue line, and then digitally removed all the stars from our galaxy, such that a mouse-over would show you ... that would have ruled.

Lewis

[orin stepanek]

The spiked ones (blue) are stars in the Milky-way; the gold globs are galaxies; than there are the spiral galaxies.
Orin

[harry]

G'day

Nice links Orin

Just imagine the full scope of what we can see. Over 100 billion galaxies with the tools at hand.

But! down under, in the land of ozzzz, we see them upside down.

[orin stepanek]

G'day

Nice links Orin

Just imagine the full scope of what we can see. Over 100 billion galaxies with the tools at hand.

But! down under, in the land of ozzzz, we see them upside down.

Hey Harry! Depends on what you call upside down. Any more; up is away from and down is toward.
Orin

[CharlieNNC]

Has anybody gone to the trouble of redoing this pic and others like it such as the Hubble Deep Field, and removing all the Milky Way stars so that you could get a view representative of being outside of this galaxy and looking out?

[BMAONE23]

G'day

Nice links Orin

Just imagine the full scope of what we can see. Over 100 billion galaxies with the tools at hand.

But! down under, in the land of ozzzz, we see them upside down.

Hey Harry! Depends on what you call upside down. Any more; up is away from and down is toward.
Orin

Sometimes you just can"t tell about those South is Up people
G-day back atya

[crodom]

Several of the foreground stars in the photo are green (have green halos). I'm familiar with the general explanation of why we do not see green stars. Are the green stars the result of too much green level in the composite?

[NoelC]

http://antwrp.gsfc.nasa.gov/apod/ap080520.html

I believe the colored halos around the bright stars to be an artifact from secondary filter reflections. In other words, light coming in bounces off the imager, up to the back side of whatever filter they used, then back down to the imager.

Assuming it's an image constructed from separate exposures taken through red, green, and blue filters, it looks as though the secondary reflections while the blue channel was being exposed were stronger than those from other channels, except for when the light was primarily yellow-red, causing strong secondary reflections in the red and green channels as well, which mixed with the stronger blue secondary reflections and yielded green.

It takes some effort, but secondary reflections can usually be mostly removed digitally.

I don't mean to be critical, but the data processing in that image leaves something to be desired. Things don't really look the way they are portrayed in there. Though the exposure appears to be quite deep, the black point has been clipped quite badly and the colors have been turned way up.

This is a more realistic looking image: http://www.rc-astro.com/photo/id1156.html

-Noel

[harry]

G'day

That is why we won the Americas Cup with a down under thing.

But! that was a few years ago.

[orin stepanek]

Has anybody gone to the trouble of redoing this pic and others like it such as the Hubble Deep Field, and removing all the Milky Way stars so that you could get a view representative of being outside of this galaxy and looking out?

I think I recall a picture where the frontal stars have been removed of blocked out. Maybe it can be found.
Orin

[orin stepanek]

This is the one I remembered!
http://apod.nasa.gov/apod/ap050926.html
I don't recall any other ones though.
Orin

[Animation]

Orin,

That is a cool pic with the stars removed, but its too bad there isnt one like it that is zoomed in so much. I wish the APOD image associated with this thread had a version with the stars removed. It'd be cool to see what percentage of the "specks" and "blobs" on the sky were actually galaxies. The "zoom" on the link you provided kinda took that aspect away since it was zoomed up as far as possible on the Virgo galaxies.

Lewis

[CharlieNNC]

Yes, that is the idea, removing the Milky Way stars, and I agree with Animation that example is zoomed in too much. Would seem in this day of data processing, it would not be hard to ID and blank out our galaxy's stars, backfilling the space with something other than a black dot, to get a good idea of how it would look.

Charlie in NC