Starship Asterisk*

Massive Nearby Spiral Galaxy NGC 2841

Explanation: It is one of the more massive galaxies known. A mere 46 million light-years distant, spiral galaxy NGC 2841 can be found in the northern constellation of Ursa Major. This sharp view of the gorgeous island universe shows off a striking yellow nucleus and galactic disk. Dust lanes, small, pink star-forming regions, and young blue star clusters are embedded in the patchy, tightly wound spiral arms. In contrast, many other spirals exhibit grand, sweeping arms with large star-forming regions. NGC 2841 has a diameter of over 150,000 light-years, even larger than our own Milky Way and captured by this composite image merging exposures from the orbiting 2.4-meter Hubble Space Telescope and the ground-based 8.2-meter Subaru Telescope. X-ray images suggest that resulting winds and stellar explosions create plumes of hot gas extending into a halo around NGC 2841.

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Nice presentation, like a B25 doing a low pass over the field ( I like B25's ). So the far end of this galaxy takes more than 150000 years longer than the closest end to get here. Hard to wrap your mind around the enormity of this place called the Universe.

Massive... and busy! I got a chuckle out of tomorrow's APOD. This just might be a big week of massive things.

I like B-52's. That's a tad more than twice B-25's.

NGC 2841 is a typical flocculent galaxy. It is also a galaxy that is "settling down" and producing few new stars. Compare NGC 2841 with this ESA/NASA picture of vigorously starforming galaxy M101. Compare the very "disturbed" shape of M101 with the almost perfectly round shape (oval from our perspective) of NGC 2941. Note the presence of large bright "knots" or "splotches" in M101, and note the absence of them in NGC 2841. Note, too, that NGC 2841 is "peppered" with little pink emission nebulas, whereas the color pink is completely absent in the picture of M101. Why is that? The answer is that a Ha filter was used for the image of NGC 2941, while no Ha filter was used for the ESA/NASA picture of M101. Why? Well, simply because there is so little star formation in NGC 2841, those who made the original image of this galaxy wanted to see if there were any emission nebulas there at all. But in M101, there is so much star formation there, and so many emission nebulas that are so well known, that those who commissioned the original image chose to concentrate on the stars rather than on the nebulas in this galaxy.

Today's APOD looks good. Robert Gendler has done a fine job of processing the data.

Ann

I am 74 and have always been an astronomer, first amateur, then professional. So you can imagine how many times in my life I have looked at a picture of a galaxy! And yet when I looked at this picture, a moment ago, a thought came into my mind that had never before come into my mind on looking at a picture of a galaxy: it was, "And I know I am looking at a picture of billions of Earth-sized planets." I know that now, of course, from the Kepler mission results. I still don't know what fraction of Earth-sized planets have water oceans, or have life, or have life that is bigger than single-cell organisms....or have .... people.... But I can never look again at a photo of a galaxy and not explicitly wonder how many "people" I am looking at! Thank you, Kepler mission!

ta152h0 wrote: So the far end of this galaxy takes more than 150000 years longer than the closest end to get here. Hard to wrap your mind around the enormity of this place called the Universe.

Me too- it's mind boggling

plumes of hot gas extending into a halo

The halo is not unresolved stars, but is hot gas from the core?

Just Awesome...

:---[===] *

Psnarf wrote:

X-ray images suggest that resulting winds and stellar explosions create plumes of hot gas extending into a halo

The halo is not unresolved stars, but is hot gas from the core?

You left out an important part of the statement, which I have added back in. This is a visible light image so all that you see glowing here is stars, except for the red bits which are H-alpha. The halo of gas mentioned is visible in X-rays, seen here: http://chandra.harvard.edu/photo/2006/n2841/

...how many "people" I am looking at

Ahh, the old Fermi Paradox vs Drake Equation ploy!
Intelligent critters showed up after some five major extinction events occurring at serendipitous periods of Earth's history. It is difficult to detect all such events because the majority of diversity and biomass on Earth is microbial. All we can detect are events affecting complex life. In addition to the five major extinction events (each eliminating at least 50% of complex species), there are lesser extinction events which could be the result of sampling bias, so we don't talk much about those.
Each major extinction event created conditions for different species to flourish. I submit that in order for intelligent life to form (able to communicate with future generations via the written and spoken word), those extinction evens must occur at approximately the same epoch in other worlds. Intelligent species did not gradually evolve from single-celled organisms in the oceans. We cannot trace human life back to single-celled organisms because each extinction event eliminated different species. At best, we can compare pre- and post- Cretaceous–Paleogene extinction to conclude that some 90% of the pre-K/T species left no evidence of their existence after the K/T event. That event is not taken into account in the Drake equation. Consider the types of organisms that survived and flourished after each major extinction event. It may be the case that such a sequence is necessary for primates to show up. The SETI folks could be trying to communicate with sauropods. Contrawise, there is such an enormous number of habitable planets in each of an enormous number of galaxies that such a sequence of events could be commonplace in at least one, if not countless other galaxies. That's Bob and his family waving at us from the third planet of the gazillionth star to the right.

Oustanding

Recommend red wine and camembert cheese and gentle violin sonata as a study aid.

By now NASA and ESA will have developed mathematical models to describe individual planetary systems similar to the Earth and Moon. A unique type of planetary system which deserves attention is one in which both primary and secondary are locked in synchronous orbit - the same side of each planet facing the other. The Pluto - Charon system appears to be such an example. The difference would be that attributes such as mass and diameter and gravity would be on a larger scale. A day on such a system would also equal one month.
What are the attributes of such a system? That is what the mathematical model must attempt to describe. Imagination would complete the picture.

ta152h0 wrote:Nice presentation, like a B25 doing a low pass over the field ( I like B25's ). ...

Beyond wrote: ... I like B-52's. ...

I would guess that neither of you gentlemen have ever been on the receiving end of a bombing raid.

Another stunning image by Robert Gendler. Thank you APOD for bringing such beauty to our living room.

Enjoying the comments today as well.

Psnarf wrote:

...how many "people" I am looking at

Ahh, the old Fermi Paradox vs Drake Equation ploy!

........The SETI folks could be trying to communicate with sauropods......


More likely they are trying to communicate with bacteria. For roughly 85% of the history of life on earth......that's all there was.

hoohaw wrote:I am 74 and have always been an astronomer, first amateur, then professional. So you can imagine how many times in my life I have looked at a picture of a galaxy! And yet when I looked at this picture, a moment ago, a thought came into my mind that had never before come into my mind on looking at a picture of a galaxy: it was, "And I know I am looking at a picture of billions of Earth-sized planets." I know that now, of course, from the Kepler mission results. I still don't know what fraction of Earth-sized planets have water oceans, or have life, or have life that is bigger than single-cell organisms....or have .... people.... But I can never look again at a photo of a galaxy and not explicitly wonder how many "people" I am looking at! Thank you, Kepler mission!

When I was fifteen, I looked at a galaxy (Andromeda, of course) for the first time. I used a pair of binoculars, and I couldn't hold my arms steady, so I lay down on the ground. Suddenly I was aware of planet Earth below me. When I found Andromeda in my binoculars and knew that I was looking at billions of stars all at once, I felt absolutely sure that I was looking at "people" in Andromeda! Indeed, I even thought I might be looking at people there, beings very similar to myself. Although I didn't let go of my binoculars, I waved at them in my mind and imagined that I was communicating with them. It was a rush of a feeling!

Nowadays I don't believe for a moment that there are people in Andromeda, although there might certainly be intelligent species there. As for communicating with them... Personally I don't believe that humans will be around by the time Andromeda and the Milky Way collide with one another, but just maybe there will be other species from the Milky Way and Andromeda that can communicate with one another when our two galaxies merge in a gravitational embrace.

There may certainly be intelligent species in NGC 2841, but we will never know. We can, of course, imagine their presence when we look at pictures like today's APOD.

Ann

Ann wrote:

hoohaw wrote: ... But I can never look again at a photo of a galaxy and not explicitly wonder how many "people" I am looking at! Thank you, Kepler mission!

... There may certainly be intelligent species in NGC 2841, but we will never know. ...
Ann

Ann -- There are lots of solid reasons to make that statement.
But I can still hope that for some as-yet-unforeseen reason, you're wrong about that.

Another way to put your statement, is that the Universe's design allows for life, but also tends to give that life a good deal of privacy.
P.S. I am using "design" here in a theologically-neutral way.

Ann wrote:Nowadays I don't believe for a moment that there are people in Andromeda, although there might certainly be intelligent species there. As for communicating with them... Personally I don't believe that humans will be around by the time Andromeda and the Milky Way collide with one another, but just maybe there will be other species from the Milky Way and Andromeda that can communicate with one another when our two galaxies merge in a gravitational embrace.

Of course, even when we are colliding most of our galaxy and most of Andromeda will be as much separated as different parts of ours right now. If there is intelligent life in Andromeda (or any other galaxy), so too is there in the Milky Way. And we already know how impractical communication is (indeed, two-way communication is impractical to the point of impossibility).

Is it known how long it would take for a star to move from 0 degrees on the approximate perimeter of the galaxy to 180 degrees?

robolt wrote:Is it known how long it would take for a star to move from 0 degrees on the approximate perimeter of the galaxy to 180 degrees?

This galaxy probably has a similar orbital period to our own, 200-300 million years.