This picture is of the shells around galaxy NGC 474, near the constellation Pisces. Astronomers aren't certain if the shells are tidal tails or density waves. Tidal tails happen when a galaxy enters another galaxy's gravity and one gets slung around the other, causing the gravity to rip some stars and planets out of a galaxy's gravity and giving it a tail like appearance. Density waves, on the other hand, look more like shells around the galaxy and happen when one galaxy merges or attacks or crashes into or whatever another galaxy. Either way, the shells are probably caused by galaxy on galaxy contact. Whatever the reason, this picture supports the idea that large galaxies have halos created by interactions with smaller galaxies. This suggests the origins of the halo around our own Milky Way galaxy.
Friday, October 12, 2007
APOD 1.7
This picture is of the shells around galaxy NGC 474, near the constellation Pisces. Astronomers aren't certain if the shells are tidal tails or density waves. Tidal tails happen when a galaxy enters another galaxy's gravity and one gets slung around the other, causing the gravity to rip some stars and planets out of a galaxy's gravity and giving it a tail like appearance. Density waves, on the other hand, look more like shells around the galaxy and happen when one galaxy merges or attacks or crashes into or whatever another galaxy. Either way, the shells are probably caused by galaxy on galaxy contact. Whatever the reason, this picture supports the idea that large galaxies have halos created by interactions with smaller galaxies. This suggests the origins of the halo around our own Milky Way galaxy.
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