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NGC 4651: The Umbrella Galaxy

Explanation: Spiral galaxy NGC 4651 is a mere 35 million light-years distant, toward the well-groomed constellation Coma Berenices. About 50 thousand light-years across, this galaxy is seen to have a faint umbrella-shaped structure (right) that seems to extend some 50 thousand light-years farther, beyond the bright galactic disk. The giant cosmic umbrella is now known to be composed of tidal star streams. The streams themselves are extensive trails of stars gravitationally stripped from a smaller satellite galaxy that was eventually torn apart. Placing your cursor over the image will superimpose a simulation of the satellite galaxy's path as it was disrupted and absorbed into NGC 4651. Recent work by a remarkable collaboration of amateur and professional astronomers to image faint structures around bright galaxies suggests that even in nearby galaxies, such tidal star streams are common. The result is predicted by models of galaxy formation, including the formation of our Milky Way.

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Really nice!! However, i think it looks more like the Galaxy is in a 'bubble' rather than being under an umbrella.

If the 'bubble' was more defined it would look like a "snow globe". It would be fun to shake it and see all the stars and things swirling around and around and around and then see if they all fell back into place again or would just leave a BIG mess on the bottom which would mean that you broke it - and if you broke it, you bough it!

Lets see - how much are Galaxys going for now-a-days??

is it me or is there a similar structure coming out of the galaxies left ?

I ran the java applet that was supposed to simulate 2 galaxies interacting.
The final result didn't look anything like the way galaxies look today. Was a jumble of stars moving every which way, with no order.
Let alone show me how such "tidal star streams" could form.

What are the probabilities that galaxies would actually collide so near head on?
If we cannot even come up with gravitational theories for the way galaxies currently exist (only 5% or less of the matter seems to be there...), I would put no confidence in any of these models.
I would put our real understanding of galaxies at very near the 0% range.

Bart, have you ever tried to model two elliptical galaxies coming close together to form a spiral galaxy? Do you experiment with different masses for the center of the galaxy?

Doug Ettinger
Pittsburgh, PA

workgazer wrote:is it me or is there a similar structure coming out of the galaxies left ?

"Placing your cursor over the image will superimpose a simulation of
the satellite galaxy's path as it was disrupted and absorbed into NGC 4651."

Imagine the night view from one of these far flung stars.

I go to the Astronomy Picture of the Day as soon as I fire up my computer, first thing every morning, before I check the weather and read the newspaper. As a guy who was a history major in college and now works primarily with language and the law all day, it helps me put things in perspective, if I start the day thinking about other galaxies and the unknowns of space.

On today's photo, my comment is WOW, is that COOL. Not deep philosophy, but ---- thanks, guys. What a treat.

Brujo wrote:I go to the Astronomy Picture of the Day as soon as I fire up my computer, first thing every morning, before I check the weather and read the newspaper. As a guy who was a history major in college and now works primarily with language and the law all day, it helps me put things in perspective, if I start the day thinking about other galaxies and the unknowns of space.

On today's photo, my comment is WOW, is that COOL. Not deep philosophy, but ---- thanks, guys. What a treat.

APOD does that!

jbkuma wrote:Imagine the night view from one of these far flung stars.

Or just close your eyes.

Workgazer wrote
"is it me or is there a similar structure coming out of the galaxies left ?"

You're right. There's some sort of structure coming out of the lower left part of the galaxy that isn't shown or explained in the overlay.

jbkuma wrote:Imagine the night view from one of these far flung stars.

Probably not as impressive as you might imagine. In fact, not much different from our own night sky.

Bart wrote:I ran the java applet that was supposed to simulate 2 galaxies interacting.
The final result didn't look anything like the way galaxies look today. Was a jumble of stars moving every which way, with no order.
Let alone show me how such "tidal star streams" could form.

You are working with a simple model only, and it's probably extremely sensitive to the initial conditions you set up.

If we cannot even come up with gravitational theories for the way galaxies currently exist (only 5% or less of the matter seems to be there...), I would put no confidence in any of these models.

Current numerical models (which are complex monsters running on supercomputers) actually do a very good job at producing galaxies with the same morphologies we observe. That's why most researchers have a reasonable level of confidence that the foundations of knowledge in this area are solid, even if there is much that remains to be discovered.

Is the very large, bright object visually located near the end of the "umbrella" handle locate in or near the glactic planeof NGC 4651? If so, it suggests to me, granted without accredation, that at least some of the "umbrella" may have been formed by extremely large radiant torrents generated by my mystery object.

Maybe the black hole at the center of the galaxy burped. Just kidding, but really, on the universal scale, GRAVITY RULES!. In college I developed a n-body simulation that took forever to run (with small time steps) to get a significant duration with only a few bodies. I was modeling orbits of extrasolar planets around binary stars using C (code). Imagine keeping track of a couple billion bodies in 3-D--every body interacts with every other body--probably a black hole at the center. Huge task! This must be simplified, yet I imagine that it is possible to get valid results. Can anyone point me to the logistics of these simulations? Does one incorporate dark mass into the simulation?

If a person lived on the planet of one of these Tidal Stream stars, would he see his whole galaxy spread out before him in his night sky, or would the starlight be so dim that it wouldn't be visible?

Dan wrote:If a person lived on the planet of one of these Tidal Stream stars, would he see his whole galaxy spread out before him in his night sky, or would the starlight be so dim that it wouldn't be visible?

Dense regions would look about like the Milky Way appears to us. Depending on the planet's position, an observer might see that kind of glow over most of the sky, or only in streams or regions.

My 6 year old daughter would like to rename this galaxy "The Unicycle Galaxy." You just posted the photo sideways.

ALeary wrote:My 6 year old daughter would like to rename this galaxy "The Unicycle Galaxy." You just posted the photo sideways.

Oh? If I owned a unicycle, that is probably the orientation I would most likely see it in.

Chris Peterson wrote:

Dan wrote:If a person lived on the planet of one of these Tidal Stream stars, would he see his whole galaxy spread out before him in his night sky, or would the starlight be so dim that it wouldn't be visible?

Dense regions would look about like the Milky Way appears to us. Depending on the planet's position, an observer might see that kind of glow over most of the sky, or only in streams or regions.

But what a site they would have given the proper filters and photographic equipment.

BMAONE23 wrote:But what a site they would have given the proper filters and photographic equipment.

Well, since they would be closer, they could achieve higher spatial resolution in their images. But otherwise, there would be little difference. The resolution would be useful for scientific analysis, but simply in terms of the aesthetics of wide field images... I don't think their results would be substantially different than what we can see in images from here.