Two other Canis Major galaxies worth mentioning are NGC 2207 and IC 2163, located 144 million light years from Earth.
Vast gravitational forces emanating from NGC 2207 are stretching and contorting IC 2163. As a result, IC 2163 is in the process of flinging streams of plasma and dust 200,000 light years into space. Both galaxies will continue this slow motion head-on collision for millions, perhaps billions of years. When the collision stops-and the titanic event will eventually come to rest-both galaxies will cease to exist as separate entities. The afterbirth will form a completely new galaxy, a galaxy that will incorporate the stars and planets from the original structures.
Visit the Internet and check out the Hubble Site's stunning NASA Hubble Space Telescope image of this colliding pair of Canis Major. It's a "jaw dropper" that is best viewed by opening the 28.7 kB image file. The URL is: http://hubblesite.org/gallery/album/entire/pr2004045a.
What's in the Sky: Check out the constellation Canis Major this weekend in the southeast before dawn (see this week's sky map). If you have a telescope, see if you can locate some of the deep sky objects mentioned in this week's Seeing Stars.
Correction: A typo last week skewed my note about the percentages of Jupiter's atmospheric hydrogen and helium. The correction: 88-92 percent hydrogen and 8-12 percent helium. Thanks to reader Mark Boivin for pointing it out.
Louis Varricchio, M.Sc., is a former NASA science writer. He is a NASA-JPL Solar System Ambassador in Vermont.