M40 – Winnecke 4, or the Astronomer's Mistake
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The first to document the discovery of this object was Charles Messier in 1764. While searching, Messier relied on the notes of Johannes Hevelius, which suggested the presence of a nebula in a specific region of the constellation Ursa Major. Despite the absence of a nebular object in that area of the celestial sphere, Messier cataloged one of the double stars found there, assigning it the number 40 to maintain order in his list. This story is fascinating for both astronomers and other astronomy enthusiasts, as it illustrates the challenges faced by early astronomers (and sometimes even today) in searching for and cataloging cosmic objects.
Just over a century later, in 1863, Friedrich Winnecke, while searching for multiple star systems, independently discovered the same double star and included it in his catalog.
Winnecke measured the angular separation between the components as 49.2". In 1966, measurements yielded a value of 51.7", and by 1991, it had increased to 52.8". It is now known that Messier 40 is an optical double star—its components are not gravitationally bound.
Observations
May 5, 2024, around 10:30 PM – Jaworzno (Poland), garden
urban conditions, high level of light pollution
This double star system cannot be visually resolved into its individual components without optical instruments. In fact, even spotting it with the naked eye is impossible, even under the best conditions, as their apparent magnitudes are 9m and 9.3m, with spectral types close to G0 and F8, respectively.
In 2018, based on measurements from the Gaia space probe, the parallax values of both stars were published. Using these data, the distances of the two components from Earth were determined to be 317.1 parsecs (1,034 light-years) and 145.8 parsecs (476 light-years).
Even in a photograph with such a short exposure time, two distant galaxies—NGC 4290 and NGC 4284—can be observed as faint, blurred patches of light.
Photo 1 Parameters:
Photo 1 Parameters:
- Total exposure time: 3 minutes (stack of 18 RAW frames at 10s each, using an appropriate number of dark, bias, and flat frames)
- ISO: 800
- Newton telescope (150/750), prime focus exposure
- A filter was used to reduce the effects of artificial light pollution and atmospheric glow
- Mount: equatorial mount with tracking, aligned using the drift method and controlled by a custom-built system.
Further readings:
- Mallas J. H., Letter to the Editor, Sky and Telescope, 32(2), 1966, str. 83
- Winnecke F. A. Th., Doppelsternmessungen, Astronomische Nachrichten, 1869
- Nugent R. L., The Nature of the Double Star M40, Journal of the Royal Astronomical Society of Canada, 96, 2002, str. 63-65
Marek Ples