M 97

Right Ascension	11 : 14.8 (h:m)
Declination	+55 : 01 (deg:m)
Distance	2.6 (kly)
Visual Brightness	9.9 (mag)
Apparent Dimension	3.4x3.3 (arc min)

The Owl Nebula M97 is one of the fainter objects in Messier's catalog, discovered by Pierre Mechain. In the description of this object, Messier also mentions two other nebulous objects that he (or Mechain) have seen at the same time, but which he had not added in his printed catalog version of 1781 (in the Connaissance des Temps for 1784); as the description is obvious and he added positions by hand in his personal copy, we now know that he had observed the objects M108 and M109.

M97 is one of the more complex planetary nebulae. Its appearance has been interpreted as that of a cylindrical torus shell (or globe without poles), viewed oblique, so that the projected matter-poor ends of the cylinder correspond to the owl's eyes. This shell is enveloped by a fainter nebula of lower ionization. The mass of the nebula has been estimated to amount 0.15 solar masses, while the 16 mag central star is believed to be of about 0.7 solar masses. Its dynamical age is about 6,000 years. (from Stephen J. Hynes, Planetary Nebulae).

As often for planetary nebulae, the Owl is significantly brighter visually (Machholz: 9.7 mag, Hynes: 9.9 mag) than photographically (about 12.0 mag), as most light is emitted in one green spectral line (see our Planetary Nebulae page). Its distance is uncertain; the Sky Catalog 2000 has 1,300 light years (400 pc), I.S. Shklovsky 1,430, O'Dell and Kohoutek independently found 1,600 in the early 1960s, Cudworth (1974) 2,600 (our value), Becvar's Atlas Coeli Catalog 7,460, Voroncov-Vel'jaminov published 8,150, Kenneth Glyn Jones gives 10,000, and Kaufmann has 12,000 light years (some of these values quoted from Burnham).

Amateur images of M97

The DSSM image of M97 reveals that in the background of this nebula, there are several small nebulous objects, most probably very distant galaxies, the brightest of these objects being superimposed by the brighter star above and slightly left of M97. This brightest background object can be found on many larger-field exposures of the Owl Nebula (also is some of the amateur images in our collection).

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