The Swan flies as the „Northern Cross“ along the Milky Way, its tail star Deneb is one of the stars of the Summer Triangle. Deneb is a 1,800 light-years distant supergiant with the 17,000-fold luminosity of our Sun. When we are looking into the Swan, we look deep into our spiral arm of the Milky Way, the Orion-Cygnus arm.
β Cygni (Albireo) is one of the most impressive binary stars for telescopes, as you can see the color contrast between the yellow, 3.1m bright main star and its 4.6m bright, bluish companion very nicely. Sadly, the two 34 arcseconds apart standing star cannot be separated in binoculars. Both stars are 380 light-years away and 4400 AE apart, which is about 55 times the diameter of the solar system. Whether they form a physical binary star system or not, is still unclear. The brighter star is also a spectroscopic binary.
Between α and δ Cygni lies ο¹ Cygni (31 Cygni). It is an optical triple star, which like Albireo shows a nice color contrast. In the center is the orange 31 Cygni, a 3.8 to 4.2m bright eclipsing binary at a distance of 1,350 light-years. Its invisible companion completes its orbit once every 10.42 years. 107 minutes of arc south of it shines a 7.0m bright star that appears bluish. It is 1,720 light-years away. 5,6 arcmins north of 31 Cygni is another 4.8m bright star that appears in turquoise color. It is only 720 light-years away.
61 Cygni is a rather inconspicuous double star of two orange dwarf stars. With at least 10x magnification, you can see a 5.2 and a 6.0m bright star. They circle each other probably once in 653 years. A brown dwarf star also belongs to the system.
61 Cygni is mainly of historical interest – in 1838 Friedrich Bessel succeeded here in measuring the first parallax. Within half a year, 61 Cygni’s position shifts against the more distant background stars by 0.3 arc-seconds. The reason for this is the movement of the Earth around the Sun, which results in a shift in perspective. Bessel was able for the first time to use this shift to determine the distance to a star. Bessel calculated a distance of 10.3 light-years, modern measurements yield a value of 11.4 light-years. This makes 61 Cygni the fourth closest star which can be observed with the naked eye.
Harrington 10 is a 3 × 10° large dark nebulae, which can be seen with the naked eye as a straight, dark line 7° north of Deneb. In binoculars, showing far more Milky Way stars, it looks more impressive, but you need giant binoculars to see details on its edge.
M 39 is an open cluster at a distance of 830 light-years. About 25 stars form a wide triangle 10° northeast of Deneb, which offers a beautiful sight in front of the weaker field stars. The brightest star shines at 7.0m, the overall brightness of the 200 million year old group is 4.6m. M 39 is visible to the naked eye as a small nebula – the oldest record dates from Aristotle in the year 325 B.C.
The North America Nebula (NGC 7000) with a size of 2.5 × 3° is much too extensive for most telescopes, while it can be clearly visible in binoculars. However, it has a low surface brightness so that it is difficult to distinguish it from the sky background and the Milky Way stars. If the sky is dark and you know where it is, you may even find it with the naked eye. It was only discovered in 1786 by William Herschel. Its shape is reminiscent of the North American continent. The emission nebula is probably 2,000 light-years away, its fluorescence may be excited by the 3° distant Deneb.
The Northern Coal Sack (Lynds 906) is the largest dark nebula in the northern sky and corresponds to the 2.5° wide northern end of the Great Rift of our Milky Way.