by neufer » Wed Apr 29, 2009 10:10 pm
orin stepanek wrote:Can you imagine how scientists; who may live on a planet in one of these galaxies; may react to this collision? It would be a great study in progress; except for the eons it would take to complete the merge of these galaxies.
http://antwrp.gsfc.nasa.gov/apod/ap081127.html
http://antwrp.gsfc.nasa.gov/apod/ap080619.html
http://antwrp.gsfc.nasa.gov/apod/ap050529.html
http://antwrp.gsfc.nasa.gov/apod/ap071104.html
http://en.wikipedia.org/wiki/Canis_Major_Dwarf_Galaxy wrote:
<<The Canis Major Dwarf galaxy is located in the same part of the sky as the constellation Canis Major. The galaxy contains a relatively high percentage of red giant stars, and is thought to contain an estimated one billion stars in all.
The Canis Major dwarf galaxy is classified as an irregular galaxy and is now thought to be the closest neighbouring galaxy to our location in the Milky Way, being located about 25,000 light-years away from our Solar System and 42,000 light-years from the Galactic Center. It has a roughly elliptical shape and is thought to contain as many stars as the Sagittarius Dwarf Elliptical Galaxy, the previous contender for closest galaxy to our location in the Milky Way.
The galaxy was first discovered in November 2003. Although closer to the Earth than the centre of the galaxy itself, the Canis Major Dwarf galaxy was difficult to detect as it is located behind the plane of the Milky Way, where concentrations of stars, gas and dust are densest. This, along with its small size, explains why it was not discovered sooner.
Astronomers believe that the Canis Major Dwarf Galaxy is in the process of being pulled apart by the gravitational field of the more massive Milky Way galaxy. The main body of the galaxy is extremely degraded. Tidal disruption causes a long filament of stars to trail behind it as it orbits the Milky Way, forming a complex ringlike structure sometimes referred to as the Monoceros Ring which wraps around our galaxy three times. The stream of stars was first discovered in the early 21st century by astronomers conducting the Sloan Digital Sky Survey. It was in the course of investigating this ring of stars, and a closely spaced group of globular clusters similar to those associated with the Sagittarius Dwarf Elliptical Galaxy, that the Canis Major dwarf galaxy was discovered.
Globular clusters thought to be associated with the Canis Major Dwarf galaxy include NGC 1851, NGC 1904, NGC 2298 and NGC 2808, all of which are likely to be a remnant of the galaxy's globular cluster system before its accretion, or swallowing, into the Milky Way. NGC 1261 is another nearby cluster, but its velocity is different enough from that of the others to make its relation to the system unclear. The Canis Major Dwarf galaxy may also have associated open clusters, including Dol 25 and H18, and possibly AM 2. It is thought that the open clusters may have formed due to the dwarf galaxy's gravity perturbing material in the galactic disk and stimulating star formation.
The discovery of the Canis Major Dwarf Galaxy and subsequent analysis of the stars associated with it has provided some support for the current theory that galaxies may grow in size by swallowing their smaller neighbors. Martin et al. believe that the preponderance of evidence points to the accretion of a small satellite galaxy of the Milky Way which was orbiting roughly in the plane of the galactic disk.
A new study by Yazan Momany using 2MASS data casts doubts on the nature of the dwarf galaxy. The data suggests that the trail of stars is actually part of the warped galactic disc. This conclusion, however, is still being challenged and the true nature of the overdensity in Canis Major remains unknown
http://en.wikipedia.org/wiki/Andromeda-Milky_Way_collision wrote:
<<The Andromeda-Milky Way collision is a predicted galaxy collision that is due to take place in approximately 3 billion years' time between the two largest galaxies in the Local Group – the Milky Way and the Andromeda Galaxy.
It is often used as an example of the kind of phenomena associated with such collisions in simulations. As with all such collisions, it is unlikely that objects such as stars contained within each galaxy will actually collide, as galaxies are in fact very diffuse—the nearest star to the Sun is in fact almost thirty million solar diameters away from the Earth. (If the sun were scaled to the size of an American quarter, 24.26 mm (0.955 in), the next closest quarter/star would be 700 km (475 miles) away.) If the theory is correct, the stars and gas contained in Andromeda will be visible to a naked-eye viewer in approximately 2 billion years. If the collision occurs, the galaxies will likely merge into one larger galaxy. Various names have been proposed for the resulting merged galaxy, the most dominant being Milkomeda.
There is, as yet, no way to know whether the possible collision is definitely going to happen or not. The radial velocity of the Andromeda galaxy with respect to the Milky Way can be measured by examining the Doppler shift of spectral lines from stars in the galaxy, but the transverse velocity (or "proper motion") cannot be directly measured. Thus, while it is known that the Andromeda galaxy is getting closer to the Milky Way by about 120 km/s, there is no way to tell whether it is going to collide, or miss. The best indirect estimates of the transverse velocity indicate that it is less than 100 km/s. This suggests that the dark matter halos, although possibly not the actual disks, of the galaxies will collide. A future European Space Agency spacecraft, the Gaia mission, expected to launch around 2011, is intended to measure the positions of stars in the Andromeda galaxy with sufficient precision to pin down the transverse velocity.
Frank Summers of the Space Telescope Science Institute has created a CGI visualization of the predicted event, based on research by Professors Chris Mihos of Case Western Reserve University and Lars Hernquist of Harvard University.
Such collisions are relatively common—Andromeda, for example, is believed to have collided with at least one other galaxy in the past. It is possible, but not certain, that our Solar System may be ejected from the new galaxy some time during the collision. Such an event would have no adverse effect on the system and chances of any sort of disturbance to the Sun or planets themselves are remote.>>
[quote="orin stepanek"]Can you imagine how scientists; who may live on a planet in one of these galaxies; may react to this collision? It would be a great study in progress; except for the eons it would take to complete the merge of these galaxies. :shock: [/quote]
[b] http://antwrp.gsfc.nasa.gov/apod/ap081127.html
http://antwrp.gsfc.nasa.gov/apod/ap080619.html
http://antwrp.gsfc.nasa.gov/apod/ap050529.html
http://antwrp.gsfc.nasa.gov/apod/ap071104.html[/b]
[quote=" http://en.wikipedia.org/wiki/Canis_Major_Dwarf_Galaxy"]
<<The Canis Major Dwarf galaxy is located in the same part of the sky as the constellation Canis Major. The galaxy contains a relatively high percentage of red giant stars, and is thought to contain an estimated one billion stars in all.
The Canis Major dwarf galaxy is classified as an irregular galaxy and is now thought to be the closest neighbouring galaxy to our location in the Milky Way, being located about 25,000 light-years away from our Solar System and 42,000 light-years from the Galactic Center. It has a roughly elliptical shape and is thought to contain as many stars as the Sagittarius Dwarf Elliptical Galaxy, the previous contender for closest galaxy to our location in the Milky Way.
The galaxy was first discovered in November 2003. Although closer to the Earth than the centre of the galaxy itself, the Canis Major Dwarf galaxy was difficult to detect as it is located behind the plane of the Milky Way, where concentrations of stars, gas and dust are densest. This, along with its small size, explains why it was not discovered sooner.
Astronomers believe that the Canis Major Dwarf Galaxy is in the process of being pulled apart by the gravitational field of the more massive Milky Way galaxy. The main body of the galaxy is extremely degraded. Tidal disruption causes a long filament of stars to trail behind it as it orbits the Milky Way, forming a complex ringlike structure sometimes referred to as the Monoceros Ring which wraps around our galaxy three times. The stream of stars was first discovered in the early 21st century by astronomers conducting the Sloan Digital Sky Survey. It was in the course of investigating this ring of stars, and a closely spaced group of globular clusters similar to those associated with the Sagittarius Dwarf Elliptical Galaxy, that the Canis Major dwarf galaxy was discovered.
Globular clusters thought to be associated with the Canis Major Dwarf galaxy include NGC 1851, NGC 1904, NGC 2298 and NGC 2808, all of which are likely to be a remnant of the galaxy's globular cluster system before its accretion, or swallowing, into the Milky Way. NGC 1261 is another nearby cluster, but its velocity is different enough from that of the others to make its relation to the system unclear. The Canis Major Dwarf galaxy may also have associated open clusters, including Dol 25 and H18, and possibly AM 2. It is thought that the open clusters may have formed due to the dwarf galaxy's gravity perturbing material in the galactic disk and stimulating star formation.
The discovery of the Canis Major Dwarf Galaxy and subsequent analysis of the stars associated with it has provided some support for the current theory that galaxies may grow in size by swallowing their smaller neighbors. Martin et al. believe that the preponderance of evidence points to the accretion of a small satellite galaxy of the Milky Way which was orbiting roughly in the plane of the galactic disk.
A new study by Yazan Momany using 2MASS data casts doubts on the nature of the dwarf galaxy. The data suggests that the trail of stars is actually part of the warped galactic disc. This conclusion, however, is still being challenged and the true nature of the overdensity in Canis Major remains unknown
[/quote]
[quote=" http://en.wikipedia.org/wiki/Andromeda-Milky_Way_collision"]
<<The Andromeda-Milky Way collision is a predicted galaxy collision that is due to take place in approximately 3 billion years' time between the two largest galaxies in the Local Group – the Milky Way and the Andromeda Galaxy.
It is often used as an example of the kind of phenomena associated with such collisions in simulations. As with all such collisions, it is unlikely that objects such as stars contained within each galaxy will actually collide, as galaxies are in fact very diffuse—the nearest star to the Sun is in fact almost thirty million solar diameters away from the Earth. (If the sun were scaled to the size of an American quarter, 24.26 mm (0.955 in), the next closest quarter/star would be 700 km (475 miles) away.) If the theory is correct, the stars and gas contained in Andromeda will be visible to a naked-eye viewer in approximately 2 billion years. If the collision occurs, the galaxies will likely merge into one larger galaxy. Various names have been proposed for the resulting merged galaxy, the most dominant being Milkomeda.
There is, as yet, no way to know whether the possible collision is definitely going to happen or not. The radial velocity of the Andromeda galaxy with respect to the Milky Way can be measured by examining the Doppler shift of spectral lines from stars in the galaxy, but the transverse velocity (or "proper motion") cannot be directly measured. Thus, while it is known that the Andromeda galaxy is getting closer to the Milky Way by about 120 km/s, there is no way to tell whether it is going to collide, or miss. The best indirect estimates of the transverse velocity indicate that it is less than 100 km/s. This suggests that the dark matter halos, although possibly not the actual disks, of the galaxies will collide. A future European Space Agency spacecraft, the Gaia mission, expected to launch around 2011, is intended to measure the positions of stars in the Andromeda galaxy with sufficient precision to pin down the transverse velocity.
Frank Summers of the Space Telescope Science Institute has created a CGI visualization of the predicted event, based on research by Professors Chris Mihos of Case Western Reserve University and Lars Hernquist of Harvard University.
Such collisions are relatively common—Andromeda, for example, is believed to have collided with at least one other galaxy in the past. It is possible, but not certain, that our Solar System may be ejected from the new galaxy some time during the collision. Such an event would have no adverse effect on the system and chances of any sort of disturbance to the Sun or planets themselves are remote.>>[/quote]