top of page

M40 - Photographing One of Charles Messier's Mistakes

Messier 40, also known as Winnecke 4 is just... two regular stars... that were cataloged by Charles Messier as a Deep Sky Object as he was trying to find a nebula. M40 is in fact not a deep sky object and was added in Messier's catalog as a mistake! It became known as "Winnecke 4" after German astronomer Friedrich August Theodor Winnecke added it in fourth place in its Winnecke Catalogue of Double Stars, in 1863.

M40 is in fact what we call an optical double star, two stars that are not related in any way but look like they are gravitationally attracted due to their close distance and similar size and brightness.

Object Designation: M40

Also Known as: Winnecke 4

Constellation: Ursa Major

Object Type: Optical Double Star

Distance: 1,142 & 457 light-years away

Magnitude: 9.6 & 10.1

Discovered in: 1777

Messier 40 and surrounding galaxies
Messier 40 by Wikisky (top left)

It is important to note that Charles Messier did know that what he found was a double star and not a deep sky object when he entered it in his catalog. He simply could not find anything else around the area so he decided to add M40.

Messier was trying really hard to locate a "nebula" found by Polish astronomer Johannes Hevelius.

What Hevelius found was likely either NGC 4290 or NGC 4284. It was impossible for Messier to spot either one of these galaxies due to the small telescope he was using.

We imaged Messier 40 for just a couple of hours after being done with a different target one night. While sleeping in the car, I made sure to wake up around 3 AM to ensure SGP properly slewed the telescope to M40 automatically.

Below is our full image of M40! We are not super happy with it mostly because for some reason it still looks grainy despite our attempts at reducing the noise in several ways, but it still is a beautiful image overall.

Our image of Messier 40

Messier 40 Double Star in Ursa Major Astrophotography