This colour image, captured in both visible and infrared light by the Digitised Sky Survey and Spitzer Space Telescope, shows Caldwell 20, also known as the North American Nebula. Caldwell 20 is an emission nebula composed of clouds of ionised gas that emit energy at various wavelengths and glow in bright colours.

You might think it's called the North American Nebula because of its shape, but where does the name Caldwell 20 come from?

In the 18th century, French astronomer Charles Messier compiled a list of more than 100 cosmic objects that could mislead comet seekers, known as Messier's Catalogue. In the 1980s, British astronomer Sir Patrick Moore compiled an additional list to highlight more cosmic wonders for amateur astronomers to observe. Moore's middle name was Caldwell, and he preferred the name Caldwell because the letter ‘M’ was already used by Messier. This nebula is the 20th object in the Caldwell Catalogue, consisting of 46 star clusters, 35 galaxies, and 28 nebulae.

If you want to observe Caldwell 20, you should scan the sky in autumn in the Northern Hemisphere and in spring in the Southern Hemisphere. This nebula is located in the constellation Cygnus and appears three times larger than the full moon. Although it is not very bright, through binoculars it can be seen shining elegantly against the galactic background.

Image description:

From the upper left corner to the centre of the image, the background is bright blue and the rest of the image is red. Gas clouds swirl across the image, and clusters of stars millions of years old shine between them.