Astronomy Picture of the Day

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lurch
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Astronomy Picture of the Day

Post by lurch »

Astronomy Picture of the Day

antwrp.gsfc.nasa.gov/apod/astropix.html


Everyday is a different pic and explanation of astronomy and or science interest..It has a calendar that goes back..so lots of neat pics..
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Post by CovenantJr »

Spectacular stuff! :o
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Post by aTOMiC »

As vast as the universe is I find it interesting that 2 galaxies would collide in this way. Since we're getting the picture of what was happening in the distant past I'm curious as to how this turned out. If we were nearby would the galaxies have combined after a long impact event?
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lurch
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Post by lurch »

aTOMiC wrote: If we were nearby would the galaxies have combined after a long impact event?
Generally,,no..They pass thru each other..and effect each other with each other's gravity. BUT...after repeated " collisions.."..two galaxies may actually become one..It takes numerous times before becoming one..if they ever do at all...thats my understanding anyway..
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Post by High Lord Tolkien »

lurch wrote:
aTOMiC wrote: If we were nearby would the galaxies have combined after a long impact event?
Generally,,no..They pass thru each other..and effect each other with each other's gravity. BUT...after repeated " collisions.."..two galaxies may actually become one..It takes numerous times before becoming one..if they ever do at all...thats my understanding anyway..
Is that where baby galaxies come from?

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lurch
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Post by lurch »

Ha!..close but no cigar..what is born from these collisions,,are stars. The interacting gravity waves from each galaxy, compress the gas and particules and these compressed zones heat up and stars are born as a result.
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Post by fragile granite »

Good job Lurch!

The Mice:

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antwrp.gsfc.nasa.gov/apod/ap090426.html
Explanation: These two mighty galaxies are pulling each other apart. Known as "The Mice" because they have such long tails, each spiral galaxy has likely already passed through the other. They will probably collide again and again until they coalesce. The long tails are created by the relative difference between gravitational pulls on the near and far parts of each galaxy. Because the distances are so large, the cosmic interaction takes place in slow motion -- over hundreds of millions of years. NGC 4676 lies about 300 million light-years away toward the constellation of Bernice's Hair (Coma Berenices) and are likely members of the Coma Cluster of Galaxies. The above picture was taken with the Hubble Space Telescope's Advanced Camera for Surveys which is more sensitive and images a larger field than previous Hubble cameras. The camera is scheduled to be serviced during the coming flight of Space Shuttle.
NGC 4676 is a favorite topic on APoD. As is the Whirlpool Galaxy:

Image
Explanation: The 51st entry in Charles Messier's famous catalog is perhaps the original spiral nebula - a large galaxy with a well defined spiral structure also cataloged as NGC 5194. Over 60,000 light-years across, M51's spiral arms and dust lanes clearly sweep in front of its companion galaxy (right), NGC 5195. Image data from the Hubble's Advanced Camera for Surveys has been reprocessed to produce this alternative portrait of the well-known interacting galaxy pair. The processing has further sharpened details and enhanced color and contrast in otherwise faint areas, bringing out dust lanes and extended streams that cross the small companion, along with features in the surroundings and core of M51 itself. The pair are about 31 million light-years distant. Not far on the sky from the handle of the Big Dipper, they officially lie within the boundaries of the small constellation Canes Venatici.
There is a growing amount of data which suggest the Milky Way has also had similar occurrences of collisions. Here's an interesting tutorial for those who want to see more...

hubblesite.org/explore_astronomy/cosmic_collision/cosmic_collision.swf
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Post by fragile granite »

re: data suggesting galactic collisions affecting the Milky Way

There seem to be two main areas of newly developing research (that I'm aware of) which support the hypothesis that the Milky Way Galaxy has (or maybe IS) undergoing collisions and cannibalism with small neighboring satellite galaxies.

The first is a relatively new discovery called the Sagittarius Dwarf Elliptical Galaxy.

Sag DEG: www.seds.org/messier/more/sagdeg.html

Image

From our earthly perspective, this small close galaxy is difficult to observe because it lies behind the galactic core making it hard to see. The main technique is to observe by using wavelengths of light which are longer and therefore bigger than interstellar dust grains.

Image

animation: www.astro.virginia.edu/~mfs4n/sgr/sgr.flyaround.mpg

The Two Micron All Sky Survey (2MASS) has yielded these amazing results. The sun is represented by the yellow dot. The 2 micron wavelength is in the infra-red part of the EM spectrum and is able to map the tidal stream of Sag DEG.

The second part is something called "Gould's Belt" which has a diameter of about 3000 ly and is tilted to the galactic plane by about 20. The sun is off-set from its center by about 650 ly.

map: galaxymap.org/detail_maps/gould.html

It would appear that Sag DEG (or some other culprit) has gone through the galactic plane in the not-so-distant past and caused shock waves which promoted generation of hot young blue stars which form Gould's Belt. So, in a manner of speaking, our solar system may very well be in a part of the galaxy which has already experienced a collision! Some have actually gone so far as to speculate that the sun doesn't originally come from the Milky Way at all but instead came from Sag DEG and was left in orbit in the Milky Way after the collision. I'm not too sure about that conclusion which isn't really supported by the data or the laws of physics. Still it does spark the imagination doesn't it?
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