Astronomy Picture of the Day 9-24-03

Explanation: The small constellation Triangulum in the northern sky harbors this magnificent face-on spiral galaxy, M33. Its popular names include the Pinwheel Galaxy or just the Triangulum Galaxy. M33's diameter spans over 50,000 light-years, making it third largest in the Local Group of galaxies after the Andromeda Galaxy (M31), and our own Milky Way. About 3 million light-years from the Milky Way, M33 lies very close to the Andromeda Galaxy and observers in these two galaxies would likely have spectacular views of each other's grand spiral star systems. As for the view from planet Earth, this sharp 27 frame mosaic of M33 nicely shows off blue star clusters and pinkish star forming regions which trace the galaxy's loosely wound spiral arms. In fact, the cavernous NGC 604 is the brightest star forming region seen here, visible along an arm arcing above and to the right of the galaxy center. Like M31, M33's population of well-measured variable stars have helped make this nearby spiral a cosmic yardstick for establishing the distance scale of the Universe.

If you haven't been there before, be sure to visit Rob Gendler's website. This amateur astrophotographer is GOOD.

M33 "Triangulum Galaxy"

Right Ascension	01 : 33.9 (h:m)
Declination	+30 : 39 (deg:m)
Distance	3000 (kly)
Visual Brightness	5.7 (mag)
Apparent Dimension	73x45 (arc min)

For the observer, this galaxy can be glanced (averted vision) with the naked eye under exceptionally good conditions; for most people, it is the most distant object visible to the naked eye (there are rare reports that some eagle-eyed stargazers managed to see M81 under exceptional conditions, but this is exceptional with all respects). It is outstanding in good binoculars, but as its considerable total brightness is distributed quite evenly over an area of nearly four times that covered by the full Moon, its surface brightness is extremely low. Therefore, it is difficult to impossible to view this galaxy in telescopes which do not allow low magnification - lowest is best for this object !

I have never been able to see M33 without magnification, even in high-altitude desert skies. But then my vision is not perfect even when corrected.

Below is the constellation Triangulum.

Below is a wide-angle chart of Triangulum and the surrounding region.

AND...

What do we find in M33 (among a host of interesting objects)? A giant star-forming region! It's got its own designation, NGC 604.

And a close-up of the nebula and its stars:

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.