Starship Asterisk*

peter_from_nyc wrote:Hi:

I assume the "halo" of the Milky Way is a sphere the surrounds the flattened, spiral disk that is the Milky Way. As opposed to a 2-dimensional halo around the spiral.

It would be good if we could see the image projected upon a solid sphere (or upon a transparent sphere that showed where the sun was).

I understand that some programs have been written for planetariums and other museums to project earth data upon a sphere so you can see it in 3-D.

Can that be done for this picture, which I take is a flat representation of a spherical view, much like a 2-D map is a representation of a 3-D earth?

Here's an example of showing the earth in 3-D:
http://www.earth3d.org/

and here's a video (as opposed to a user controlled image) of a 3-D Milky Way:

Click to play embedded YouTube video.

If the Milky Way were in 3-D under user control, one could see it from the point of view of Earth, and from that of an intergalactic visitor.

Peter

http://www.csiro.au/news/mediarel/mr1998/mr98194.html wrote:
CAUGHT RED-HANDED: OUR GALAXY IS DESTROYING ITS NEIGHBOURS

<<Astronomers using CSIRO's Parkes radio telescope have made a picture that shows our Galaxy ripping apart its nearest neighbours.

The two nearest neighbouring galaxies, the Large and Small Magellanic Clouds, are less than a tenth of our Galaxy in size. They are close by, only twice as far from the starry edge of our Galaxy as that edge is from the Galaxy's centre. And they orbit our Galaxy, in thrall to its gravitational pull. That pull is now tearing them apart, by tugging harder on their near side than on their far side. Hydrogen gas stripped from the Clouds by this process is now streaming out ahead and behind them. The dismemberment was imaged by the new 'multibeam' instrument on the Parkes telescope, which detects the hydrogen gas in galaxies - the 'bones' underlying their starry 'flesh'.

Developed by CSIRO, it is the most powerful instrument of its kind in the world. Most of its work is searching for faint and hidden galaxies that can't be detected any other way. The new picture has settled a long-standing controversy sparked by a much earlier finding made with the Parkes telescope. In 1973 Dr (later Professor) Don Mathewson from Mount Stromlo Observatory used the Parkes telescope to discover a trail of gas flowing behind the Magellanic Clouds. This trail, called the Magellanic Stream, is more than twice as long as the diameter of our Galaxy. Astronomers have argued for decades about the Stream's origin. "But over the years we've whittled it down to two choices," said CSIRO's Dr Lister Staveley-Smith, lead scientist on the multibeam project.

"One was a process called ram-pressure stripping - gas being swept out of the Magellanic Clouds as the Clouds travelled through our Galaxy's outskirts."

"The other was so-called tidal forces from our Galaxy. That idea predicted we'd find material coming off the leading edge of the Clouds - and we have," said Dr Staveley-Smith.

"People have looked before for this stuff but haven't found it because they sampled the sky rather coarsely, whereas we've been searching with a fine-toothed comb," said Ms Mary Putman, the PhD student at Mount Stromlo Observatory who made the key picture. "We are interested in how galaxies interact, because it's an important aspect of how they evolve over time. We are still trying to understand how important interactions are in creating new stars, for instance," said Mt Stromlo Observatory's Dr Brad Gibson, Ms Putman's thesis supervisor.>>

<<Barack Obama stated that his health care plan has “run into a bit of a buzz saw.”>>

Artist's impression: our Galaxy's gravity claws at the fabric of two neighbouring galaxies,
the Large and Small Magellanic Clouds, pulling out streams of hydrogen gas.
The letters X, Y and Z label the axes, to indicate positions in 3D space.
Picture: Dallas Parr, CSIRO.>>

peter_from_nyc wrote:This is some thanks to Art Neuendorffer for the illustration which shows that the "halo" is 2-D, and that it is perpendicular to the plane of our spiral galaxy.

DonAVP wrote:I was reading another thread in "The Asterisk Cafe" and found this link http://www.skyandtelescope.com/news/81035932.html. It sure seems to be the same thing.

mark swain wrote:Yes it is. but the topic is different. There is no mention of DE/DM on this thread.

Chris Peterson wrote:

mark swain wrote:Yes it is. but the topic is different. There is no mention of DE/DM on this thread.

Dark energy is not discussed and is irrelevant to the topic. Dark matter is very relevant to the discussion, and is mentioned if you follow some of the links.

mark swain wrote:Until now you mean.

Chris Peterson wrote:

mark swain wrote:Until now you mean.

Not sure what you mean. My point was that dark matter has previously been discussed, and is very relevant to the thread. Dark energy is not. The S&T article discusses both, and is interesting and topical even though its discussion of dark energy really has nothing to do with this particular discussion.

A key to this revelation was the ability to measure the distances of far galaxies by the apparent brightnesses of Type-Ia supernovae within them, independently of a galaxy's redshift. This distance can then be matched with the redshift — which tells how much the universe expanded while the light was in transit. In this way, astronomers were able to see how the expansion rate has changed over long stretches of cosmic time.

Since then, astronomers have found a wealth of other evidence that some force is causing the expansion to speed up — and how much of it there is, and the crucial fact that it seems to be neither weakening nor strengthening as space enlarges. It was named "dark energy" for lack of anything better.

Now an international team has teased out the effects of dark energy in our own Local Group of galaxies. The Local Group includes the Milky Way, the Andromeda Galaxy, M33, and about 50 dwarf galaxies identified so far.

The team analyzed recent Hubble Space Telescope observations of Local Group galaxy motions (radial velocities), made by a team led by Russian astronomer Igor Karachentsev. By studying how galaxies move with respect to the gravitational center of the Local Group, they could find the boundary where the Local Group’s gravity gives way to dark energy’s “antigravity” effect on larger scales. Dwarf galaxies beyond this boundary are moving outward and will be lost.

mark swain wrote:What part of this do you not understand mate?

mark swain wrote:What part of this do you not understand mate?

By studying how galaxies move with respect to the gravitational center of the Local Group, they could find the boundary where the Local Group’s gravity gives way to dark energy’s “antigravity” effect on larger scales. Dwarf galaxies beyond this boundary are moving outward and will be lost.

It would be good if we could see the image [as] a transparent sphere that showed where the sun was ....

Can that be done for this picture [of The Magellanic Stream], which I take is a flat representation of a spherical view, much like a 2-D map is a representation of a 3-D earth?

The model can be visualized as a big meatball in a bowl of spaghetti. The meatball is the Milky Way, and spaghetti strands winding away in all different directions represent ripped apart small galaxies.

Juanko wrote:I entered the astrology world few weeks ago

beyond wrote:Hmmm....seems to me that Astrology & Astronomy both deal with the same thing(space)but in two different ways.