Charles Messier and his fuzzy objects...

Messier Objects

Some of the most interesting objects in our galaxy are examples of either the very early stages of star formation, or the very end stages. In this section of the course, you will look at some of the beautiful Messier objects,and see how they fit in the scheme of stellar evolution -- denizens of the Milky Way. Because many of them look like small fuzzy clouds, they have often been mistaken for comets, but in fact they are much farther away than anything inside the solar system.  
Comet Hale-Bopp -- HOU image
HOU Image of Comet Hale Bopp
Note: This is not a Messier object—it is a comet.
[click on image for larger version, with HOU FITS header info]
Distances to comets seen in our solar system can be most conveniently stated in
  • millions of kilometers,
  • astronomical units (average distance from the Earth to the Sun),
  • light-seconds (the distance light travels in a second),
  • light-minutes (the distance light travels in a minute), or
  • light-hours (the distance light travels in an hour)

    By contrast, distances to the Messier Objects are all most conveniently measured in light-years. A light-year, the distance light travels in a year, is about 10 trillion kilometers (about 6 trillion miles).

    • Charles Messier

    It was actually the appearance of a bright comet in 1744 that triggered the first real survey of objects in the sky that are not single stars. That comet so fired the imagination of Charles Messier, in France, that he became a life-long comet-hunter and astronomer. In his comet searches, Messier came across many "comet masqueraders" -- fuzzy patches that looked like comets, but did not move at all against the background stars. The lack of movement indicated the masqueraders were not in orbit around the Sun, and so were not in the solar system.
    Charles Messier portrait
    Portrait of Charles Messier
    from Bulletin de la Societe Astronomique de France, 1929.

    The Messier catalog, with objects named with "M" numbers such as M42 (Great Nebula in Orion) and M32 (Great Galaxy in Andromdea), is not the only catalog of interesting objects. You may come across objects with NGC numbers, such as NGC 4565, a really cool looking spiral galaxy seen nearly perfectly edge-on. NGC stands for "New General Catalog".

    		Image of comet Tempel-Tuttle
    In this image of Comet 55P/Tempel-Tuttle, taken 1/27/98, the telescope was made to track the comet. Since the comet moved with respect to the background stars, those stars appear as streaks in this image. Planets, asteroids, and any object in the solar system, including comets, will show this characteristic. Incidentally, this is the comet related to the Leonid meteor showers and storms. Copyright © 1998 by Akimasa Nakamura (Kuma Kogen Astronomical Observatory, Japan).
    Image from Gary W. Kronk's comet page
    (http:/ /comets.amsmeteors.org/).
     
    HOU Image: M80
    A globular cluster observed by Charles Messier in 1871