Astronomy Picture of the Day -- Earth...

Astronomy Picture of the Day -- Earth at Night

There are 3 comments on the Free Republic story from Dec 8, 2012, titled Astronomy Picture of the Day -- Earth at Night. In it, Free Republic reports that:

Explanation: This remarkably complete view of Earth at night is a composite of cloud-free, nighttime images.

Join the discussion below, or Read more at Free Republic.

“Geologist [I'm Climate Change]”

Since: Mar 07

formerly Nuneaton

#1 Dec 10, 2012
This one showed up on CNN and drew some favourable comments.

There looks to be an upside to the telescope view blocking light pollution that gets in the way of amateur astronomers.

Have a nice day: Ag
litesong

Lynnwood, WA

#2 Dec 10, 2012
The lights of Las Vegas attract human gamblers to Nevada. Whether we shuffle cards or not, all humans now gamble for much bigger stacks..... that aliens from other parts of the Universe, attracted by our lights, will be......... friendly.
Adrian..... have you noted the two little lights in the bottom left hand corner of your avatar, showing galaxy M104? They aren't two stars. They are two spiral galaxies, I'm assuming have what?...... 100+ billion stars each!
I wonder if they may be gravitationally orbiting one another, or separated by millions of light-years.

“Geologist [I'm Climate Change]”

Since: Mar 07

formerly Nuneaton

#3 Dec 17, 2012
litesong wrote:
The lights of Las Vegas attract human gamblers to Nevada. Whether we shuffle cards or not, all humans now gamble for much bigger stacks..... that aliens from other parts of the Universe, attracted by our lights, will be......... friendly.
Adrian..... have you noted the two little lights in the bottom left hand corner of your avatar, showing galaxy M104? They aren't two stars. They are two spiral galaxies, I'm assuming have what?...... 100+ billion stars each!
I wonder if they may be gravitationally orbiting one another, or separated by millions of light-years.
Difficult.

The info for redshift for the 2 small background galaxies is not available in the ngc info (they are too faint).

The galaxies may be aligned by line of sight as in the NGC55 versus sculptor group (NGC55 is 3 million light years closer than ngc253 which is the core galaxy of the sculptor group, where both galaxies appear similar sizes due to distance).
Then again the galaxies may constitute a gravitationally bound pair in a small group.

The answer is difficult to give unless you happen to be there.

Ah almost forgot. about 1/4 of galaxy interaction pictures are line of sight overlaps where a similar sized foreground galaxy is superimposed over a background system. They can however on occasions be very odd superimpositions. One example being the giant elliptical galaxy M60 and a blue spiral in the background, still part of the virgo cluster, seen through the outer layers of the giant E, and entirely within the globular cluster halo of the foreground M60.

Have a nice day: Ag

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