Cygnus, The Swan.

The constellation Cygnus the Swan, also known as the Northern Cross, stretches across 804 square degrees of one of the richest areas of the Summer Milky Way. It reaches from almost 19 hours in the west to 22 hours in the east and runs from +27 degrees to +60 degrees north declination. The stars that make up the main figure of Cygnus are first, second and third magnitude gems that stand out easily against the ethereal glow of the Milky Way back drop.

Alpha Cygni is known as Deneb, from Al Dhanab al Dajajah (the Hen's Tail). It marks the tail of the swan. This is a supergiant (more than a hundred times the diameter of the Sun) with a very high luminosity. Since it is so far away (3200 light years) its real brilliance is lost in space.

Beta Cygni is called Albireo, which is really a mistake. The words written in a sixteen-century edition of Ptolemy's Almagest, had been "ab ireo" (the meaning of which rests a mystery). The Arabs called it "Al Minhar al Dajajah", the Hen's Beak. This is a magnificent binary with a nice colour contrast.

Gamma Cygni is "Sadr", from Al Sadr al Dajajah, "The Hen's Breast". Between gamma and beta Cygni is the Cygnus Star Cloud, a vast region of exceptional beauty.
Epsilon Cygni is "Gienah", from Al Janah, "The Wing".

The constellation has several superb visual binaries as well as one of the more intriguing Mira-type variables. Several faint deep sky objects are also found in Cygnus, but it seems surprising that, while the constellation lies in the heart of the Milky Way, it has no truly outstanding clusters, nebulae, or galaxies.

Things to Check Out in Cygnus

Multiple Star Systems

Albireo, Beta Cygni, STF43, ADS 12540

RA (J2000): 19h 30m 43.29s dec: +27d 57m 34.9s
Included in the Astronomical League's certificate list of 100 double stars.
Included in the Saguaro Astronomy Club's list of 110 best multiple stars.
Components show no relative motion.
Colorful double star.
Distance: 380 light-years
Component A: magnitude +3.1
Component B: magnitude +5.1
Separation AB: 34.4" at position angle 54 degrees
Discovered by Struve in 1832.
Despite the wide separation, the two stars are thought to be physically associated.
The best-known of all colored double stars, and considered by many to be the finest in the sky.
The colors are yellow or "topaz" for the primary, and blue or greenish for the companion.

61 Cygni, STF2758, ADS 14636
61 Cygni is another fine binary of two orange stars: 5.2, 6.0. The 2000.0 values are PA 150º, and separation 30.3". 61 Cygni also holds the distinction of being the first star to have its parallax measured. This occurred in 1838, by Friedrich Wilhelm Bessel, a German astronomer.

RA (J2000): 21h 06m 52.19s dec: +38d 44m 03.9s
Included in the Astronomical League's certificate list of 100 double stars.
Included in the Saguaro Astronomy Club's list of 110 best multiple stars.
Visual binary star.
Distance: 11.4 light-years
Component A: magnitude +5.4
Component B: magnitude +6.0
Separation AB: 30.3" at position angle 150 degrees
The famous "Flying Star". Its unusually large proper motion (5.22" a year at PA 52) was first noticed by Piazzi in 1792, although the first measurement as a double was by Struve in 1830.
Bessel chose 61 Cygni in 1838 for the first successful measurement of the distance of a star using its annual parallax. At 11.4 light-years, this is the fourth nearest star to the Sun, only Alpha Centauri, Sirius, and Epsilon Eridani being closer.
Sometimes said to look yellowish or orange, which fits the spectral classes. The system consists of two orange dwarfs.
There is a dark third component known as 61 Cygni C, with a mass only 8 times that of Jupiter.

31 (Omicron) Cygni and 30 Cygni, STF50, ADS 13554

RA (J2000): 20h 13m 37.90s dec: +46d 44m 28.8s
Included in the Astronomical League's certificate list of 100 double stars.
Included in the Saguaro Astronomy Club's list of 110 best multiple stars.
Optical double, colorful double star.
Distance: A 1350 light-years B 1700ly C 720ly
Component A: magnitude +3.8
Component B: magnitude +6.7
Component C: magnitude +4.8
Separation AB: 101" at position angle 173 degrees
Separation AC: 338" at position angle 323 degrees
An interesting triple group, although the stars are certainly not physically associated. Star C in this data is actually numbered 30 Cygni in Flamsteed's catalogue.
31 Cygni A has a noticeable yellow color, while B and C (30 Cygni) are bluish.
31 Cygni A is an eclipsing binary of the Algol type numbered V695 Cygni. It ranges between magnitudes 4.9 and 5.3, with a period of 10.4 years. The orbit is very nearly edge-on to us, so that the eclipse of the companion is almost total. It is preceded and followed by a period of partial eclipse as the companion passes behind the extended atmosphere of the primary. Each atmospheric eclipse lasts for 2.5 months, and the total phase for 63 days. The next atmospheric eclipse is due to begin in mid-October 2003.

Delta Cygni, STF2579, ADS 12880

RA (J2000): 19h 44m 58.44s dec: +45d 07m 50.5s Visual binary star.
Distance: 171 light-years
Component A: magnitude +2.9
Component B: magnitude +6.5 variable
Separation AB: 2.5" at position angle 221 degrees
First observed by Struve in 1826 (WDS) or 1830 (Burnham).
This is a particularly tricky double for a small telescope because the secondary lies on the first diffraction ring of the primary.
Muirden (1988) says some people suggest looking during twilight.
Star B is variable between magnitudes 6.5 and 8.5 (approximately).

Mu Cygni
is another visual binary (4.8, 6.1) with a long orbit, 789 years. For the next fifty years the orbit will continue to appear to approach the primary (as seen from the earth). The 2000.0 values are: 309º, 1.85".

Tau Cygni
is a visual binary with a 49.9 year orbit: 3.9, 6.8. The 2000.0 year values are PA 328º, separation 0.8".

Variable stars in Cygnus:

Cygnus has many variable stars, most of which are too slight to notice without high-tech equipment.
Alpha Cygni is the prototype for a variable class of pulsating supergiants. These variables have a spectral type of A or B and very high absolute magnitudes.
Some fifteen supergiants are members of this group (including kappa Cas). The period ranges from five to ten days and the amplitude is less than 0.1 magnitude. For alpha Cygni, the range is 1.21 to 1.29.

Tau Cygni is a delta Scuti type variable, ranging from 3.65 to 3.75.
Upsilon Cygni is a gamma Cas type variable: 4.28-4.50.
Chi Cygni is by far the most interesting variable of the constellation. This is a Mira-type variable with period of 408.05 days. It takes several months to reach its maximum, then several more before it disappears from sight, at a minimum of 14.2.
The maximum varies, mostly it winds up in the 4.3-4.5 range, although it has been known to achieve third-magnitude status. Burnham has a finder's chart, but if it is in the fifth or fourth magnitude range, you should have no difficulty in finding it: it has a bright red colour, and is located about two degrees SW of eta Cygni (or about one quarter the distance from eta to beta Cygni).

Deep Sky Objects

The area of the sky we are looking into is also known as the Cygnus Star Cloud and is one of the most visually beautiful parts of the northern Milky Way. When you examine this area you are looking down the length of our spiral arm where is begins to curve around the center of our galaxy. So, you might expect to see clusters and nebulae of all types and that is exactly what you find, here are some of my favorites.
NGC 6819

R. A. 19h41.3000m Dec: +40d 10.99'
Angular diameter: 5.0 arc minutes
Distance: 2200 parsecs
Age 3,400,000,000 years
Open cluster, very large, very rich in stars, stars
150 stars (11-15 mag).
Brightest star is magnitude 11.0

NGC 6866

J2000 RA: 20h03.7m dec: +44 00'
Angular diameter: 6.0 Arc minutes
Distance: 1200 parsecs
Age 230,000,000 years
Open Cluster, large, very rich in stars, considerably compressed
50 stars (10 - 13mag)
Brightest star is magnitude 10.0

NGC 6826, Blinking Planetary, PK83+12.1

J2000 RA: 19h44.8m dec: +50 31'
Planetary nebula, bright, pretty large, round.
Star in middle of image is 11th magnitude
Angular diameter 27"X24"
Visual magnitude, integrated over entire object: 9.8

IC5146, Cocoon Nebula

J2000 RA: 21h53.4m dec: +47 16'
Maximum diameter: 540 arcseconds
Distance: 1000 parsecs
Age 230,000,000 years
Brightness level: 1 (1=brightest, ..., 6=faintest)
Emission nebula, pretty bright, very large, irregular figure
A 9.5mag star is located in the middle of the image.

NGC 6910

J2000 RA: 20h23.1m dec: +40 47'
Angular diameter: 7.0 Arc minutes
Distance: 1650 parsecs
Age 10,000,000 years
Open Cluster, pretty bright, pretty small in angular size, poor, pretty compressed
20 stars (10-12 mag)

NGC6913, M29

J2000 RA: 20h23.9m dec: +38 32'
Distance: 1250 parsecs
Age 10,000,000 years
Open Cluster, poor, little compressed, stars large and small in angular size
About 20 stars (mags 9-12), brightest star is magnitude 9.0
Angular diameter 7.0'

NGC 6960, Veil Nebula (western part), Supernova Remnant

J2000 RA: 20h45.7m dec: +30 43'
Angular diameter 70'X6'
Magnitude: 7.0
Brightness level: 4 (1=brightest, ..., 6=faintest)
Reflection nebula, very much remarkable, pretty bright, considerably large, extremely irregular figure
52 Cygni involved

NGC 6992 and NGC 6995, Veil Nebula (eastern part), Supernova Remnant

(NGC 6992 left and NGC 6995 right)

J2000 RA: 20h56.4m dec: +31 43'
Angular diameter 60'X8'
Magnitude: 7.0
Brightness level: 4 (1=brightest, ..., 6=faintest)
Reflection nebula, very much remarkable, extremely faint, extremely large, extremely extended, extremely irregular figure, bifurcated

NGC 7000, North America Nebula

J2000 RA: 20h58.8m dec: +44 20'
Angular diameter 120'X10'
Magnitude: 4.0
Brightness level: 4 (1=brightest, ..., 6=faintest)
Reflection nebula, faint, most extremely large, diffused nebulosity
Open Cluster NGC 6997 involved

NGC 7092, M39

J2000 RA: 21h32.2m dec: +48 26'
Distance: 270 parsecs
Age 270,000,000 years
Open Cluster, very large, very poor, very little compressed
(7-10 mag) Brightest star is 7.0mag
Angular diameter: 31.0'