Messier Objects - M40

Messier 40 is probably the least exciting of any object on the entire catalogue.  American astronomer Robert Burnham Jr. is quoted as saying that M40 is "one of the few real mistakes in the Messier Catalog."

Messier 40, also known as Winnecke 4 is merely an optical double star.  Two stars completely unrelated gravitationally but appear close to each other as viewed from Earth.  There are many examples of this throughout the sky.

The most popular theory as to why this was added to the catalog was based on an observation made by the famous Polish astronomer, Johannes Hevelius.  Hevelius described the pair of stars as a nebula on the back of Ursa Major.  This was probably due to the quality of his telescope at the time as the two stars are quite close to each other.  Messier was able to split the two stars and included it in his list because those with small apertures may confuse it for a comet.  In the 21st century, telescopes are of a quality that it is quite easy to split these two stars at 51.7" apart.  They may have been even closer in Messier's day.

M40 is located approximately 80' from Delta Ursae Majoris, thus seemingly making it easy to find.  I went into the observation with expectations of easily uncovering a double star after moving the telescope in the correct direction.  I was quickly proven wrong.  I found my way to 70 Ursae Majoris which was about 1° away from δ UMa.  I knew M40 must be in the same field so I searched intently around the field of view.  There was a faint pair of stars about a quarter of the field of view away from 70 UMa.  This was the Messier object?  It turned out it was and it was the most spectacularly unimpressive sight I have ever seen.  The map below can help you locate this pair of stars if you are ever working on a Messier Certificate.

M40 Map

There are several other deep sky objects within the same 1° field of view as M40.  NGC's 4284, 4290, 4335, and 4358 are all faint galaxies that were likely too dim for Messier's day.  With a bright waxing gibbous and urban light pollution I would have no hope in my 8".  Perhaps in an extremely dark site during a new Moon with a 16" I could perhaps pick them out.

The observation record is shown below.

M40 Observation Record

This object is basically a checklist item on your way to observing all of the Messier objects.  There is no other real reason to head in this direction unless of course you want to catch those four NGC galaxies with a large aperture telescope.  Good luck if you intend to seek it as it is much dimmer than you would expect.