If you go to the APOD archive and Click on Feb 13' you can cut the http and you will have the right link.Indigo_Sunrise wrote:http://antwrp.gsfc.nasa.gov/apod/astropix.html
Now, reading the description, I am wondering what the "fascinating background galax[y]" is at about the nine o'clock position, on the far left....? What a beautiful galaxy! *Of course, the entire image is gorgeous, but that galaxy really leaps out at me!
Anyway, another great image - keep up the great work, PTB!
[P.S. I'm not too good with inserting links, so I hope that I did it right. Apologies in advance if not.]
The nice thing is that if you make a mistake; you can click the edit button and correct them. I try to preview and proof read before submitting; but once in a while, one still slips past me.Indigo_Sunrise wrote:Thank you, orin, for the tutorial on link-inserting! As you can tell, I had just copied/pasted the address from the webpage!
And as for looking at it under magnification, I only looked at the hi-res image by clicking on the image itself, but it's definitely worth further investigation - so I guess that means I'm off to follow more links!
Aren't you yourself arguing against black hole "dust panning" interstellar space due to a general lack of cool gas.henk21cm wrote:What puzzles me, why an old elliptical system is emitting so much X-ray radiation. In an elliptical system there is hardly any cold gas left for new stars to be formed (http://heritage.stsci.edu/2008/07/caption.html)
If there isn't much cold gas, then where does all the hot gas come from?
X-rays are associated with rather violent phenomena in the universe: accretion disks around pulsars, small parasitic stars which suck matter from larger stars, black holes "dust panning" interstellar space. Generally spoken, these kind of processes, in which cool gas spirals inbound towards a havy object. Due to concentration of flow, the gas is heated up to temperatures which allow for X-ray emission. Such processes usually do not last for long times (compared to the lifetime of a star).
The X-rays seem to come from the outer regions of the galaxy, where the concentration of gas is likely to be less than in the inner regions of the galaxy. Is the galaxy still dust panning?
Thats right, i never forget that my concepts can be wrong, so approach it from the opposite direction: "suppose its true, then X and Y must be valid, but since we see the opposite of X and Y happen, the assumption is not true" (reductio ad absurbum type of proof)Aren't you yourself arguing against black hole "dust panning" interstellar space due to a general lack of cool gas.
Yes, that is a valid argument. The argument leads to the result that X-ray emission and elliptical galaxies should be abundant. I did not know that. Google reports over 100k hits for "elliptical galaxies" and "X ray". I read only some (articles); they support your argument.An old galaxy should have lots of old stars in their last stages expanding into red giants whose shells can be sucked into neighboring neutron stars or black holes.
And what about the Cooling Flow Problem?
Don't retreat. Stay engaged and learn. While the existence of dark matter may be unproven, it is the best fit the astronomers can come up with to explain the behavior of the galaxies they observed and measured. If you can come up with a better explanation, with supporting evidences based on direct observations, data and calculations, please do let us know. In other words, do your homework first. Just remember that the astronomers have access to very expensive instruments, including gigabucks worth of space telescopes that you and I can never hope to have. If we poor under-privileged amateurs can't come up with alternative explanations, then we should accept what the professionals say, with of course a little bit of skepticism.triastro wrote:OK, fair enough, they only mention 'likely', but I'm getting weary of this 'instant' science where pictures are said to depict things that are only conjecture or at best unproven theory such as dark matter.
I'll retreat to the background on this. No further replies are necessary.
