When it comes to galactic objects and clusters, the constellation Canis Major has a lot to offer. This constellation includes a variety of island universes; it even contains a stunning example of two colliding galaxies famously photographed by the Hubble Space Telescope.
Below is a lineup of a few of the galaxies and star clusters lurking within Canis Major. We have provided magnitude numbers in parentheses for telescope and binocular observers.
According to SUNY Stony Brook astronomer Aaron Evans' Internet article on magnitude: "Very bright objects have negative magnitudes. For example, Sirius, the brightest star of the celestial sphere, has an apparent magnitude of -1.4. The modern scale includes the Moon and the Sun; the full Moon has an apparent magnitude of -12.6 and the Sun has an apparent magnitude of -26.73. The Hubble Space Telescope has located stars with magnitudes of +30 at visible wavelengths and the Keck telescopes have located similarly faint stars in the infrared."
Here's a sampling of Canis Major's deep sky objects: Basel 11A (+8.2), Cr 121 (+2.6), Cr 132 (+3.6), Cr 140 (+3.5), Haffner 6 (+9.2), Haffner 8 (+9.1), M 41 (+4.5), NGC 2204 (+8.6), NGC 2243 (+9.4), NGC 2345 (+7.7), NGC 2354 (+6.5), NGC 2360 (+7.2), NGC 2362 (+4.1 naked eye in a very dark sky), NGC 2367 (+7.9), NGC 2374 (+8.0), NGC 2383 (+8.4), NGC 2384 (+7.4), NGC 2396 (+7.4), Ru 18 (+9.4) Ru 20 (+9.5), Tr 6 (+10.0).
Most observed of Canis Major's objects is the open cluster M41 (aka NGC 2287)-it's the only "M" or Charles Messier object in the constellation. M41 is located south of the star Sirius and is approximately 195 million years old. Most of M41's approximately 100 stars are aging from the main sequence growth stage to the red-giant stage. If you'd like to try your hand at deep-sky astrophotography, M41 is a good target; its red-giant stars provide rich colors with long-exposure photography.
See STARS, page 7
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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: Seen in the evening western sky this weekend are many galaxies in Pisces, but only one is worth gazing through a modest telescope-galaxy M74, approximately one degree east of Eta Piscium.
Lou Varricchio, M.Sc., is a member of the NASA-JPL Solar System Ambassador Program (Vermont). His website is located at www2.jpl.nasa.gov/ambassador/profiles/Louis_Varricchio.htm. You can e-mail him at email@example.com. He is available for school assemblies and classroom chats about astronomy and the future of space travel.