I always thought it was the Silver Dollar because it looked flat (no central bulge) compared with other spiral galaxies.APOD wrote:Some call it the Silver Dollar Galaxy for its appearance in small telescopes
Whatta you mean "flat" !apodman wrote: http://antwrp.gsfc.nasa.gov/apod/ap091121.html
I always thought it was the Silver Dollar because it looked flat (no central bulge) compared with other spiral galaxies.
The Sculptor Galaxy as seen at near-infrared wavelengths. Credit: 2MASS. North is up.http://www.goldprice.org/buy-silver/2006/04/us-silver-dollar-coin.html wrote:
<<Probably the most famous US silver dollar coin is the 1804 United States, Draped Bust, Heraldic Eagle. This is so rare that not long ago one was sold at auction for over 4 million US dollars. There are a few 1804 silver dollars but none were actually minted in 1804. They were actually minted in 1834 and in the 1850s also. They were not meant for circulation. This was because the value of silver rise so much that the silver dollars in circulation were being melted down and being moved out of the country. The US government acted on this by ceasing production of silver coins by 1803. However several presentation sets were required as diplomatic gifts and a silver dollar dated 1804 was included in those sets. These were referred to as ‘original’ 1804 silver dollars and they were a severely minted mintage. It is thought by some that the King of Siam (Thailand) had ten sets but now only 8 of these coins are considered to exist.>>
http://antwrp.gsfc.nasa.gov/apod/ap081002.htmlESO wrote:
<<NGC 253 is one of the brightest spiral galaxies in the sky, and also one of the dustiest. The whole galaxy is shown here as observed with the WFI instrument, while the insert shows a close-up of the central parts as observed with the NACO instrument on ESO's Very Large Telescope and the ACS on the NASA/ESA Hubble Space Telescope. This unique set of observations has allowed a team of astronomers from the Instituto de Astrofísica de Canarias (Spain) to study the galaxy in great detail, uncovering many young, massive and dusty stellar nurseries. They also found that the centre of this galaxy appears to harbour a twin of our own Milky Way's supermassive black hole.>>
My question is that, when I take a closer look at many galaxies, it seems that they are not flat at their center but instead I see some kind of denivellation such as a turning water whirpool leading matter and gaz to the center black hole...am I right or it's just an illusion?apodman wrote:http://antwrp.gsfc.nasa.gov/apod/ap091121.html
I always thought it was the Silver Dollar because it looked flat (no central bulge) compared with other spiral galaxies.APOD wrote:Some call it the Silver Dollar Galaxy for its appearance in small telescopes
Spiral galaxies have a central bulge (probably always, even when the viewpoint might make it not apparent). The whirlpool effect you describe is an illusion. Material is not spiraling into the center of these galaxies, and the central black holes are only absorbing a tiny amount of matter from their surrounds, and those surrounds are far too small to be visible at the scale where you can see the entire galaxy.Run wrote:My question is that, when I take a closer look at many galaxies, it seems that they are not flat at their center but instead I see some kind of denivellation such as a turning water whirpool leading matter and gaz to the center black hole...am I right or it's just an illusion?
What?Chris Peterson wrote:Spiral galaxies have a central bulge (probably always, even when the viewpoint might make it not apparent). The whirlpool effect you describe is an illusion. Material is not spiraling into the center of these galaxies, and the central black holes are only absorbing a tiny amount of matter from their surrounds, and those surrounds are far too small to be visible at the scale where you can see the entire galaxy.
We are seeing a spiral shape. The brain tries to interpret spirals as material flowing into the center (or out of it), but that isn't usually what's going on. The Sun has orbited the Milky Way many times since it was formed, but our distance from the center hasn't changed. Likewise for all the stars you see in any spiral galaxy- each is orbiting in an approximately elliptical orbit (it's a little more complex than simple Keplerian orbit dynamics, because the mass is distributed), and each is staying about the same distance from the center over time. There is no inward flow of material in a spiral galaxy.mark swain wrote:What?
So can you please explain what we are seeing?
Chris Peterson wrote: We are seeing a spiral shape. The brain tries to interpret spirals as material flowing into the center (or out of it), but that isn't usually what's going on. The Sun has orbited the Milky Way many times since it was formed, but our distance from the center hasn't changed. Likewise for all the stars you see in any spiral galaxy- each is orbiting in an approximately elliptical orbit (it's a little more complex than simple Keplerian orbit dynamics, because the mass is distributed), and each is staying about the same distance from the center over time. There is no inward flow of material in a spiral galaxy.
Nice applet, but alas, it's YAASWBBAWT (Yet Another Astronomy Site With Black Background And White Text). Do astronomy geeks think that because the sky is dark, their sites have to be dark? (That is, of course, a rhetorical {and off-topic} question. Just ignore me when I'm being grumpy.)geckzilla wrote:My favorite thing that helped me understand, at least partially, how spiral galaxies might get their spiral formation was this little Java applet. Here is a link for you. Just click "Applet" on the side menu and tinker away at it.
http://burro.cwru.edu/JavaLab/GalCrashWeb/
Many studies show that the majority of people have difficulty reading light colored text on a dark background. If you are designing a site with a high text content, it is a mistake to use a dark background because you exclude most of your audience from comfortable reading. However, people can easily read captions and headline text when it is light-against-dark, and images usually present better against a dark background. So image-heavy sites with only a little text are often best designed that way.geckzilla wrote:There's actually a good lot of us who find it more comfortable to read white text on a black background. We stay up late with the lights off and large blocks of bright white hurts our vampiric eyes. Well, that, and I just think it looks better. My favorite forum is almost all dark gray and grayscale text. I think it's more of a late-night geek thing than an astronomer thing.
1981 IBM PC 5150 with green monochrome monitorgeckzilla wrote:I have never been able to make sense of why some people strain to read white on black while others, like myself, find it much less straining. Actually, I find it easiest to read with two shades which aren't so distant from each other, like say a 40% difference in value. But if I have to choose black and white I choose black for the background.
neufer wrote:1981 IBM PC 5150 with green monochrome monitorgeckzilla wrote:I have never been able to make sense of why some people strain to read white on black while others, like myself, find it much less straining. Actually, I find it easiest to read with two shades which aren't so distant from each other, like say a 40% difference in value. But if I have to choose black and white I choose black for the background.
I'm not sure if you're trying to make some point or not.mark swain wrote:Oh Right.
For a minute , Taking a look at the image of the milky way, one would think of a very complex center .
I think in this case it's more about missing meds than missing dividers.apodman wrote:If I put more than one topic in a single post, I generally put a "---" dividing line between them to let the reader know I'm starting a separate thought. It is economical and effective.
If your angular velocity times your distance is enough (i.e., such that a simple non-relativistic angular momentum conservation calculation indicates that your angular velocity approaches the speed of light as you fell towards the Schwarzchild radius) then you probably won't be sucked up by the black hole. For the ~ 4 million solar mass black hole (such as that which lies at the center of our Milky Way) an angular velocity of 85 mph at 10 light years distance should be sufficient. (Loss of angular momentum due to gravitational radiation will doom you eventually, however.)Chris Peterson wrote:there is no significant inflow of material into the center of spiral galaxies, and black holes don't generally suck things up.
Certainly. Of course, the same is true whether or not a galaxy has a black hole at the center. Given long enough (and we're talking many, many times the age of the Universe) everything ends up in the center.neufer wrote:(Loss of angular momentum due to gravitational radiation will doom you eventually, however.)
We welcome any and all who comes to this forum wanting to learn more about what they see in the APODs, but not to push their personal anti-science agendas.PassionateBomba wrote: Science gave us abortion, and said it was good, after all we are either all atheists or fools. Now we see the most fervent opposition to abortion comes from those that have experienced it. Sometimes the soul, truth rears its ugly head at the wrong time.
You are bringing religion or moralities to the forum, which is not welcomed! Please take the matter up in the Cafe.
Even today, we are learning that the leading scientists on global warming are suddenly coming into doubt. The word fraud is even beginning to surface in some reports. WOW! And scientists in Australia were saying the Earth was cooling all along. They didn't get media attention though, and I would "guess" there wasn't much money to be made in cooling. But maybe if we get the temp down another degree or two, Al Gore won't sweat so much, and that will benefit us all.
Neither is political discussion welcomed here. Again take it up in the Cafe. This pro- and anti-global warming argument has gotten tiresome.
Maybe this was off topic, but was intended for background.
Why would anyone speak callously about Mark thinking black holes suck everything up. That's how they were represented to the public, and trust me on this one, most people are not reading the latest and greatest on scientific change of hearts. When science makes its public pitch, it never fails to claim absolute authoritative truth. Maybe that's the last Mark heard of it, I know it was the last I heard of it. Now this thing with so much gravity, even photons can't escape its pull, can only suck things up that happen to jump in to it. Hmmm. One thing about scientific truth is, if you live long enough, it will change with the next need to get a name in a scientific journal.
It is an outright falsehood that scientists claim "absolute authoritative truth", as you put it. They are forever revising their opinions based on latest findings and observations, and they are always arguing their hypotheses and theories with their peers. They are not doing it for money either as you seem to believe. If they are, they must be stupid for choosing a low paying career when they could use their smarts to get rich off Wall Street like those "brilliant" traders there who got multi-million dollar bonuses. No, they are doing it because they love making discoveries and coming up with possible explanations for them, based, of course, what make sense, not what fits their religious or ideological beliefs if any.
NASA gets a lot of money. Public perception and interest is absolutely critical. After all, its the public's money they get.
Now Enceladus is erupting ice. Ice? This conjures up visions of under ice oceans and of course, the trusty old purse puller, Life on another planet! We need billions. We need them now! Remember everybody, the Earth was once covered in ice too. Enceladus might be in birthing pains, ice blows all over the place! A whale might pop out at anytime. We must be there, give us billions!
Are you saying that the "billions" spent on scientific research and space exploration are a waste of money? If it weren't for those "billions", we wouldn't have all those fantastic pictures from Hubble Space Telescope and the robotic spacecrafts that explored the solar system. We wouldn't have either the necessary miniaturization of electronics that NASA funded to reduce spacecraft weight which eventually gave us all those wonderful gizmos that we can't live without today!
Mark, keep asking the questions buddy. You will get many answers that go deeper and deeper until you don't know what is being said. If you don't think so, you best brush up on your quantum physics. Reading other threads you see that's where it winds up if it needs to. I asked a question here once about why NASA feels the need to publicize these "doctored" photos. Just show us what we see, at least along side the the doctored one. You won't see many of these photos in your telescope. In the end, I thought I was at a lecture of the Einstein Guild.
These "doctored" photos were created for the benefits of scientific study of the chemical and electromagnetic signatures given off by the planets, stars, galaxies, and other space bodies, not for general public! They don't have the time to make the photos you want, They just happen to make them available to us for our enjoyment and wonder. If you want the pictures to be what your eyes would see, you will be disappointed and dissatisfied.
Don't get me wrong, I love space (APOD), always have. Always had a telescope too, but never much good at using it. Showed my friends some craters and moons and Orion's "star". Wasn't as pretty as those shown in APOD. Mine wouldn't have generated billions either.
Einstein once interpreted that gravity could bend light and was later "proven" by Eddington that could see stars behind the Sun in an eclipse. The Mayans used this principle thousands of years ago to travel all the way to 2012, by starring into desert thermals. Most of us can do this now by standing between two mirrors holding a candle. Don't try that at home until someone has learnt you how to get back! Hint: you're going to need a pyramid.
Your simple backyard telescope will never match what you can get from the "billion" dollar space- and land-based large telescopes, but if you are willing to spend a few thousands on a better telescope outfitted with an expensive camera and computer system and set it up in a dark sky site, you can get pretty good deep sky pictures.
Don't worry so much about the bulge in the galaxy center. A city from a distance appears to bulge into the night sky as well, but it doesn't. Just a process of living in a 3D universe.
And don't confuse knowledge with thinking. There is no such thing as absolute knowledge. In that case, the Earth would still be flat. A picture and/or an illegible mathematical equation will not gain us any knowledge on what's occurring in our own galaxy, let alone a distant one. That would be, theoretical. At 10 million light years away, the Silver Dollar Galaxy may not even exist now. The whole universe may have blown up (or jumped into a black hole), but it will take many millenniums for the light to reach us, or stop reaching us. BTW, a galaxy doesn't light up like its having its picture took at the corner studio. But, If you look at it long enough you can almost hear it roar. Sounds sort of like an approaching freight train doesn't it? Everything seems to sound like that. Must have something to do with chicken.
Some of the guys here know more than 1000 guys like me will ever know about these things. What they know is, the principles behind the theories. Its how the theories are often presented as knowledge that is the problem.
The question is, WHY? As they say in politics, follow the money, prestige, or power.
Sounds like you want your science to be simple and easy to understand, based mostly on what you can see or imagine. Sorry, that is not how science works. That may be how religion works, but religion is not science, which requires a rigorous examination of evidence, a lot of measurements and mathematical calculations and a great deal of discussions. There are people who have so-called alternative theories, for example, the "electric universe" proponents, who frequently pop up in this forum and are met with collective eye-rollings.
Again, I love space and its all consuming darkness, I love honesty and its all revealing light, more! The photos are lovely.
Keep asking questions, the all seeing eyes must render their replies. Sometimes, they are even right!
May Peace and Love bless you ALL, and light your universe beyond all understanding. Its worth more than all the universes combined.
PB
Unless your large star, is trying to get to the same place another 30,000 stars, also want to get to.Chris Peterson wrote:Certainly. Of course, the same is true whether or not a galaxy has a black hole at the center. Given long enough (and we're talking many, many times the age of the Universe) everything ends up in the center.neufer wrote:(Loss of angular momentum due to gravitational radiation will doom you eventually, however.)
