Starship Asterisk*

[quote="Skylark53"]
Instead of coming up with a new theory of gravity that fits the data, we've continually propped GR up by proposing the existence of forms of matter ('dark matter') and energy ('dark energy') for which there is no theoretical understanding and no observational evidence, despite decades of searching. [/quote]

A lot of professional astronomers [i]hate[/i] dark matter and dark energy. A lot of stuff they thought they had figured out was screwed up by these effects. They'd be happy to find a way to explain them away.

But despite trying hard to accomplish what you suggest, none have come up with a solid alternative explanation. Theories of Modified Newtonian Dynamics (MOND) may come close for dark matter, but they run into serious problems of its own such as an inability to explain observations like the apparently contradictory distributions of mass and matter in the Bullet Cluster.

Simply tossing out General Relativity does absolutely nothing to explain dark matter, and while I'm less well-versed in the implications of dark energy on GR, I'm not aware of any way dismissing GR helps explain increased distant red-shift. It seems to me getting rid of GR only makes the red-shift problem more acute.

[quote]zerro1 wrote:
Ann: You never cease to amaze me at your extensive knowlege of all things space. not just comments but background info![/quote]

Thank you so much, zerro1! But my knowledge is not so extensive as you think. There are many areas of astronomy that I'm not knowledgeable about at all - ask me about the crew of Apollo 15, the third largest telescope in the world, the number of moons of Uranus, the meaning of the expression "sidereal day", the highest temperature of the poles of Mercury, what the large Hadron Collider is really looking for apart from the supposed mass-endowing Higgs boson etcetera etcetera, and I will come up short. (Of ocurse I could try to google!) :wink:

I love galaxies, though, I really like stars - at least if they are [b][color=#0040FF]blue![/color][/b], :wink: and I'm extremely fascinated by dark energy ! :D (Plus I'm too fond of talking sometimes.) :blah:

Ann

[quote="orin stepanek"]Ann! In the explantion it is called a spiral! So that is why I called it a spiral! Besdes the galaxy is full of dust clouds. :?[/quote]
Really, you are both right- or maybe it would be better to say that your views are not in opposition. Lenticular galaxies are almost certainly on the evolutionary path between spirals and ellipticals, and as such, many show a degree of spiral structure- including NGC 4526. Indeed, this galaxy's classification of SAB(s)0 formally identifies it as a spiral (S) with loosely wound arms (AB), no ring (s), and as lenticular (0) based probably on stellar population and disc-to-bulge ratio. That is, the very classification scheme used recognizes lenticular galaxies as a form of spiral galaxy.

In the case of edge-on or near edge-on galaxies, it can be difficult or impossible to accurately distinguish between spiral, lenticular, and elliptical forms, and the classifications in these cases are often uncertain. Most people would consider it acceptable to refer to NGC 4526 as either lenticular or spiral, and I've seen both terms in the professional literature.

[quote="APOD Robot"] The [url=http://www.cfa.harvard.edu/supernova//highz/figures/pictures.html]above picture[/url] of a supernova that occurred in [url=http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998AGM....14..P95D]1994[/url] on the outskirts of a [url=http://apod.nasa.gov/apod/spiral_galaxies.html]spiral galaxy[/url] was taken by one of these collaborations. [/quote][quote="Ann"][quote="orin stepanek"]What a beautiful spiral! When I first looked at the photo I thought that the star in the foreground was a star in our own galaxy. Upon reading the explanation I see that it was a supernova just outside the spiral. 8-) 8-) 8-)[/quote]
That's not correct, Orin. The galaxy is a so called lenticular galaxy of type SB0, meaning it isn't actually a spiral.
Ann[/quote]
Ann! In the explantion it is called a spiral! So that is why I called it a spiral! Besdes the galaxy is full of dust clouds. :?

[quote="Skylark53"]I hate to put the dampers on the recent Nobel Prize announcement, but let's not forget that supernova studies of cosmology are all based on a theory (Einstein's General Relativity) that has huge problems - as demonstrated by Zwicky in the 1930s, Rubin [i]et al[/i] in the 1970s, and continually since. [/quote]
You display an appalling lack of knowledge about the current state of physics and cosmology. In fact, GR has never been on more solid ground. New types of observations continue to demonstrate its accuracy and relevance, and confidence continues to grow that the current cosmological model is substantially correct.

GR doesn't even have much that could be considered small problems, let alone huge ones.

Big Bang Cosmology...the kind from several decades ago has been replaced; or rather is being developed on a quantum level by professional astronomers. Not by groupies found in so many internet Cafes. These three astronomers wrote a beautiful article on a model for space. Space itself, that quantum vacuum we might think of when considering virtual particles. It is found in the July issue of Scientific American and is titled "[url=http://www.signallake.com/innovation/SelfOrganizingQuantumJul08.pdf]The Self Organizing Quantum Universe[/url]". It isn't about the universe of stars and telescopes, it is about the container which has no center or shape and so will be pretty hard visualize.

The skill with which they assemble and present their ideas is remarkable and appealing.

[quote="Ann"][quote="orin stepanek"]What a beautiful spiral! When I first looked at the photo I thought that the star in the foreground was a star in our own galaxy. Upon reading the explanation I see that it was a supernova just outside the spiral. 8-) 8-) 8-)[/quote]

That's not correct, Orin. The galaxy is a so called lenticular galaxy of type SB0, meaning it isn't actually a spiral. What you are seeing is the small circumnuclear dust ring and the supernova very close this tiny dust ring, deep inside the galaxy's disk. I have already posted a link to the picture of NGC 4526, the host galaxy of Supernova 1994D, but now I'm posting the actual picture of the galaxy here.

Ann[/quote]
Wich to me, (taking an image/picture of a structure deep inside another galaxy), makes it an even more spectacular image!

Ann: You never cease to amaze me at your extensive knowlege of all things space. not just comments but background info!

[quote="orin stepanek"]What a beautiful spiral! When I first looked at the photo I thought that the star in the foreground was a star in our own galaxy. Upon reading the explanation I see that it was a supernova just outside the spiral. 8-) 8-) 8-)[/quote]

[float=left][img2]http://cosmo.nyu.edu/hogg/rc3/NGC_4526_UGC_7718_VCC_1535_irg.jpg[/img2][/float]
That's not correct, Orin. The galaxy is a so called lenticular galaxy of type SB0, meaning it isn't actually a spiral. What you are seeing is the small circumnuclear dust ring and the supernova very close this tiny dust ring, deep inside the galaxy's disk. I have already posted a link to the picture of NGC 4526, the host galaxy of Supernova 1994D, but now I'm posting the actual picture of the galaxy here.






Ann

I hate to put the dampers on the recent Nobel Prize announcement, but let's not forget that supernova studies of cosmology are all based on a theory (Einstein's General Relativity) that has huge problems - as demonstrated by Zwicky in the 1930s, Rubin [i]et al[/i] in the 1970s, and continually since.

Instead of coming up with a new theory of gravity that fits the data, we've continually propped GR up by proposing the existence of forms of matter ('dark matter') and energy ('dark energy') for which there is no theoretical understanding and no observational evidence, despite decades of searching.

Present-day workers make the assumption that the model is correct, and merely obtain best-fit parameter values. I find it jaw-dropping that the astronomy community continues to do this. We're all so busy admiring the metric's exotic garments that we've failed to notice how badly they fit.

In short, it's time for one of Thomas Kuhn's paradigm shifts. Ironically, were he still with us, Einstein would be the first to try on the inverting lenses.

What a beautiful spiral! When I first looked at the photo I thought that the star in the foreground was a star in our own galaxy. Upon reading the explanation I see that it was a supernova just outside the spiral. 8-) 8-) 8-)

It is great the see SN 1994D again - long ago the picture of the Day. To clarify, this picture was actually taken as part of Vera Ruben's HST program and was colourised by High-Z Team member, Pete Challis, who deserves full credit for the image's visual impact. The supernova was not intentionally imaged as part of Vera's program, but, none-the-less, it remains the poster child for type Ia supernovae, and the accelerating Universe. Thank you Vera, thank you Pete, and thank you to the High-Z team for all of their hard work over the years.

Supernovae type Ia are incredibly interesting because they give us crucial information about the large-scale expansion (and acceleration) of the universe. The type Ia supernovae are so much more predictable and alike than supernovae of type II, those that originate in massive, core-collapse supernovae. Many people know that [url=http://www.cbc.ca/gfx/images/news/photos/2009/07/30/betelgeuse-cp-w7097650.jpg]Betelgeuse[/url] will go supernova one day, but Betelgeuse is too massive to ever become a supernova type Ia. Instead, it will explode as a supernova type II, whose brightness will be a lot more unpredictable.

Well-known supernova [url=http://outreach.atnf.csiro.au/education/senior/astrophysics/images/binvar/aatsn1887albl.jpg]SN 1987A[/url] in the nearby [url=http://www.spacetelescope.org/static/archives/images/large/heic0411d.jpg]Large Magellanic Cloud[/url] was a supernova of type II, and it was faint as supernovae go. By contrast, ongoing supernova [url=http://astrobob.areavoices.com/files/2011/09/SN2011fe-September-telefinderS2-343x400.jpg]SN 2011fe in the Pinwheel Galaxy, M101,[/url] is of type Ia, and it is just as bright as can be expected from this kind of supernova.

Supernovae of type Ia are typically visually brighter than supernovae of type II, because they release more of the energy they generate as optical light.

Supernovae of type Ia are also found in a wider variety of galaxies than supernovae of type II. The type II supernovae are generally found in obviously starforming galaxies with a large population of young massive stars. The Large Magellanic Cloud is a typical example of a starforming galaxy with a large population of young massive stars.

By contrast, the supernova that can be seen in today's APOD, Supernova 1994D, was found in a galaxy that has mostly shut down its star formation. The galaxy in question is [url=http://cosmo.nyu.edu/hogg/rc3/NGC_4526_UGC_7718_VCC_1535_irg.jpg]NGC 4526[/url]. If you follow the link, you can see that this galaxy is strongly dominated by a smooth and yellow low-mass old population. You can see the very small central dust lane that is so prominent in today's APOD. It is probably no coincidence that the supernova exploded so close to the central dust lane, where star formation can be expected to have kept going the longest.

It seems possible that galaxies with a large population of young massive stars (such as M101) may produce type Ia supernovae that are, on average, a little brighter than the supernovae Ia that originate in galaxies like NGC 4526. A [url=http://spiff.rit.edu/richmond/ritobs/sep11_2011/sn2011fe_comp94d.png]comparison[/url] between supernova 1994D (the one in today's APOD) and Supernova 2011fe (the ongoing one in M101) suggests that SN 2011fe may have been a little brighter than Supernova 1994D, at least in blue light. It is suspected that supernovae type Ia are produced by white dwarf stars, and while such stars exist in all galaxies, there could be a larger population of relatively massive and possibly binary white dwarfs in starforming galaxies than there are in mostly "dead" galaxies like NGC 4526.

Ann

That was fun! A beautifully dense APOD post. Thanks.

[url=http://apod.nasa.gov/apod/ap111009.html][img]http://apod.nasa.gov/apod/calendar/S_111009.jpg[/img] [size=150]Nobels for a Strange Universe[/size][/url]

[b] Explanation: [/b] Thirteen years ago [url=http://adsabs.harvard.edu/abs/1998AAS...193.3904A]results[/url] were [url=http://adsabs.harvard.edu/abs/1998AJ....116.1009R]first presented[/url] indicating that most of the energy in our universe is not in stars or galaxies but is tied to space itself. In the language of cosmologists, a large [url=http://super.colorado.edu/~michaele/Lambda/lambda.html]cosmological constant[/url] is directly implied by new distant [url=http://imagine.gsfc.nasa.gov/docs/science/know_l2/supernovae.html]supernova[/url] observations. Suggestions of a [url=http://en.wikipedia.org/wiki/Cosmological_constant]cosmological constant[/url] (lambda) were [url=http://relativity.livingreviews.org/Articles/lrr-2001-1/]not new[/url] -- they have existed since the advent of [url=http://www.astro.ucla.edu/~wright/cosmolog.htm]modern relativistic cosmology[/url]. Such claims were not usually popular with astronomers, though, because lambda is so unlike known [url=http://adsabs.harvard.edu/abs/2008ApJ...685.1297P]universe components[/url], because lambda's value appeared limited by other observations, and because less-[url=http://apod.nasa.gov/apod/ap071021.html]strange cosmologies[/url] without lambda had previously done well in explaining the data. What is noteworthy here is the seemingly direct and reliable method of the observations and the good reputations of the [url=http://cfa-www.harvard.edu/oir/Research/supernova/highz/members.html]scientists conducting[/url] [url=http://panisse.lbl.gov/public/]the investigations[/url]. Over the [url=http://apod.nasa.gov/apod/ap980302.html]past thirteen years[/url], independent teams of astronomers have continued to accumulate data that appears to [url=http://apod.nasa.gov/apod/ap050925.html]confirm[/url] the existence of [url=http://en.wikipedia.org/wiki/Dark_energy]dark energy[/url] and the unsettling result of a presently [url=http://en.wikipedia.org/wiki/Accelerating_universe]accelerating universe[/url]. This year, the team leaders were [url=http://www.nytimes.com/2011/10/05/science/space/05nobel.html]awarded the Nobel Prize in Physics[/url] for their work. The [url=http://www.cfa.harvard.edu/supernova//highz/figures/pictures.html]above picture[/url] of a supernova that occurred in [url=http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998AGM....14..P95D]1994[/url] on the outskirts of a [url=http://apod.nasa.gov/apod/spiral_galaxies.html]spiral galaxy[/url] was taken by one of these collaborations.

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