Salt Lake Community College Cygnus: The Swan Kristine Pataray Elementary Astronomy, Physics 1040. 008




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Salt Lake Community College

Cygnus:


The Swan

Kristine Pataray

Elementary Astronomy, Physics 1040.008

Professor J. Harrison

24 November 2014

Cygnus:


The Swan


Figure 1. Cygnus the swan from Cygnus. Digital image. PBS. PBS, n.d. Web. 22 Nov. 2014.
Once upon a Greek lore, two dear friends Cycnus, son of Ares, and Phaeton, son of Apollo, challenged one another to a race across the sky. The competitors accepted the dare and the match was on. Chariot chased chariot through the heavens, on the path to round the Sun then be the first to return to Earth. Both Cycnus and Phaeton undoubtedly wanted to gain the upper hand. In an attempt to do just that, the charioteers neared too close to the fiery rays as they bolted toward the star. Their rides went up in flames. They fell unconscious and plummeted to the Earth. When Cycnus awoke, he exhaustingly searched the lands for his friend. He finally discovered Phaeton's lifeless body arrested by the roots of a tree at the bottom of the Eridanus River. Cycnus relentlessly dove into the river in desperate attempts to reach his friend, each time more useless than the last. As he sat mourning on the river bank, he pleaded for help from Zeus. In response, the god of the sky said that if he were to change Cycnus into the form of a swan, then he would gain the ability to dive to the depths where his friend lays. Then he can rescue the body and give it a proper burial so that Phaeton's soul can journey into the afterlife. The catch? If Cycnus were transformed, then he would be relinquishing his immortality to live the rest of his life as and die a regular swan. He agreed. Touched by this selfless sacrifice, Zeus fixed the image of Cycnus in the sky (“Cygnus Constellation;” McCarter).

The Constellation




Figure 2. Cygnus and neighboring constellations from Cygnus Constellation Chart. Digital image. International Astronomical Union. IAU, n.d. Web. 22 Nov. 2014.
With its soaring wings and extending neck, the guise of the swan is one of the most distinguished patterns in the northern sky (see figure 1). It was first documented in the 2nd century A.D. by Greek astronomer Claudius Ptolemy, along with 47 other constellations. It wouldn't be until several centuries later that European astronomers add to the previously listed discoveries and redefine them by specific boundaries rather than ambiguous shapes (“The Constellations”). Flying along the Milky Way, Cygnus spans an area of 804 square degrees as the 16th largest constellation charted on our celestial sphere (“Cygnus Constellation”). The constellations Cepheus, Draco, Lacerta, Lyra, Pegasus, and Vulpecula lie on the outskirts of the region (see figure 2). Centered at approximately 20h 45m 39.7s right ascension and +30° 43' 11'' declination (“Cygnus”), Cygnus is fully observable from latitudes greater than 28°S and lower than 90°N. It is viewed highest in the sky at 10:00 PM in the late summer and early fall months of August and September (Dinwiddie et al. 366). A couple meteor showers that are identified with the constellation include the October Cygnids and the Kappa Cygnids (“Cygnus Constellation”).

The Northern Cross

Found within the swan is the unmistakable asterism commonly known as the Northern Cross. It traces the five brightest stars in the constellation (see table 1). Deneb is Cygnus' brightest star and the 19th brightest in the sky. At about 1,400 light-years distant, it is also the farthest 1st-magnitude star. The supergiant symbolizes the tail of the swan and the head of the cross. It also marks the vertex of another prominent asterism called the northern Summer Triangle. Sadr is the next brightest star. It makes the heart of Cycnus and the junction of the Northern Cross. On either side of this supergiant are Gienah and Rukh forming the wings of the bird and the arms of the cross. Lastly, representing the beak of the swan and the foot of the cross is Albireo. It is a double star visibly separable through just a regular pair of binoculars. Albireo B is the dimmer star at 5.1 magnitude while Albireo A has a magnitude of 3.1 (Dinwiddie et al. 366). Although it received the designation Beta (β), Albireo A is only the fifth brightest star in the constellation (“Northern Cross”).
Table 1

List of the 20 brightest stars in the Cygnus Constellation by descending apparent magnitude



Designation

(Name)


Right

Ascension



Declination

Distance(ly)

Visual

Magnitude



Spectral

Classification



α Cyg (Deneb)

20h 41m 25.91s

+45° 16' 49.2''

1400

1.25

A2 Ia

γ Cyg (Sadr)

20h 22m 13.70s

+40° 15' 24.1''

1800

2.23

F8 Iab

ε Cyg (Gienah)

20h 46m 12.43s

+33° 58' 10.0''

72

2.48

K0 III

δ Cyg (Rukh)

19h 44m 58.44s

+45° 07' 50.5''

171

2.86

B9 III

Table 1 continued...

Designation

(Name)


Right

Ascension



Declination

Distance(ly)

Visual

Magnitude



Spectral

Classification



β¹ Cyg (Albireo A)

19h 30m 43.29s

+27° 57' 34.9''

385

3.05

K3 III

ζ Cyg

21h 12m 56.18s

+30° 13' 37.5''

151

3.21

G8 III

ξ Cyg

21h 04m 55.86s

+43° 55' 40.3''

1177

3.72

K5 Ib

τ Cyg

21h 14m 47.35s

+38° 02' 39.6''

68

3.74

F1 IV

ι Cyg

19h 29m 42.34s

+51° 43' 46.1''

122

3.76

A5 V

κ Cyg

19h 17m 06.11s

+53° 22' 05.4''

123

3.80

K0 III

ο¹ Cyg

20h 13m 37.90s

+46° 44' 28.8''

1353

3.80

K2 II

η Cyg

19h 56m 18.40s

+35° 05' 00.6''

139

3.89

K0 III

ν Cyg

20h 57m 10.41s

+41° 10' 01.9''

356

3.94

A1 V

ο² Cyg

20h 15m 28.32s

+47° 42' 51.1''

1109

3.96

K3 Ib

ρ Cyg

21h 33m 58.87s

+45° 35' 31.4''

124

3.98

G8 III

41 Cyg

20h 29m 23.73s

+30° 22' 06.8''

758

4.01

F5 II

52 Cyg

20h 45m 39.76s

+30° 43' 10.8''

206

4.22

K0 III

σ Cyg

21h 17m 24.95s

+39° 23' 40.9''

4528

4.22

B9 Ia

π² Cyg (Pennae Caudalis)

21h 46m 47.61s

+49° 18' 34.5'

1156

4.23

B3 III

33 Cyg

20h 13m 23.80s

+56° 34' 03.1''

152

4.28

A3 IV


Source: “Cygnus Constellation.” Constellation Guide. Constellation Guide, n.d. Web. 30 Oct. 2014.

List of Stars in Cygnus.” Wikipedia. Wikimedia Foundation, 29 Oct. 2014. Web. 30 Oct. 2014.


The Deep Sky


Figure 3. The radio lobes of Cygnus A from Cygnus A. Digital image. Black Holes: Gravity's Relentless Pull. Hubble Site, n.d. Web. 22 Nov. 2014.
The eminent constellation also accommodates the spectacular, spiral Fireworks Galaxy (NGC 6946). It was discovered by Sir Frederick William Herschel, a German-born British astronomer, on 9 September 1798. With a 9.6 apparent visual magnitude, it is situated near the border with Cepheus at about 22.5 million light-years away (“Cygnus Constellation”). Cygnus A (3C 405) is an elliptical, robust radio galaxy probably resulting from the collision of two galaxies. Located approximately 600 million light-years away, its tremendous remoteness raises questions about the powerful radio source, as shown in figure 3 (Dinwiddie et al. 324).

Cygnus contains the North America Nebula (NGC 7000), identified by Herschel on 24 October 1786, years before his discovery of the Fireworks Galaxy. The emission nebula coincides with the continent but lies 1,600 light-years away with an apparent visual magnitude of 4. In the interstellar Mexico and Central America is an area named the Cygnus Wall, where star forming activity is highest. Adjacent is the emission Pelican Nebula that more or less resembles a pterodactyl. It has an apparent visual magnitude of 8.0 and is a little more distant from the Earth than it is from the North America Nebula. Located in the chest of the hen is another emission nebula, the Sadr Region (IC 1318). Then there is the Veil Nebula (see figure 4), the visible portion of the Cygnus Loop (Sharpless 103). The loop consists of remnants from a long ago supernova explosion around 90 light-years across and 1,470 light-years away. Finally there's the Crescent Nebula (NGC 6888): an emission nebula about 5,000 light-years distant, 7.4 apparent visual magnitude, and looks nothing like a crescent (“Cygnus Constellation”).




Figure 4. Western portion of the Veil Nebula from Uncovering the Veil Nebula. Digital image. Hubble. Space Telescope, 31 July 2007. Web. 22 Nov. 2014.

Cygnus contains two Messier objects and 10 stars with detected exoplanets. Found near Gamma (γ) Cygni, Messier 29 (NGC 6913) is an open cluster visible through binoculars with an apparent visual magnitude of 7.1, about 4,000 light-years away. Found south of Pi-2 (π²) Cygni, Messier 39 (MGC 7092) is also an open cluster where all observed stars are on the main sequence. M39 has an apparent magnitude of 5.5 and is approximately 800 light-years distant. Both were discovered in 1764 by French astronomer Charles Messier.

One of the first x-ray sources to be discovered, Cygnus X-1 (see figure 5) is pinpointed near the neck of the swan—Eta (η) Cygni. With a mass around 15 times that of the Sun, the stellar-mass black hole spins at a rate over 800 times a second. It is calculated to be about 6,070 light-years away (Dunbar).


Figure 5. An optical image (left) and artist's rendition (right) of the stellar-mass black hole. Source: (Dunbar).

Works Cited

The Constellations.” International Astronomical Union. IAU, n.d. Web. 30 Oct. 2014.

Cygnus.” Top Astronomer. N.p., n.d. Web. 9 Nov. 2014.



Cygnus Constellation.” Constellation Guide. Constellation Guide, n.d. Web. 30 Oct. 2014.

Dinwiddie, Robert, et al. Universe. Ed. Martin Rees. Revised ed. New York: DK 2012. Print.

Dunbar, Brian. “Cygnus X-1: A Stellar Mass Black Hole.” NASA. Ed. Brooke Boen. NASA, 17 Nov. 2011. Web. 22 Nov. 2014.

McCarter, Norm. Constellation Legends. N.p.: Tulare County Office of Education, n.d. PDF.

Northern Cross.” Constellation Guide. Constellation Guide, 10 Aug. 2014. Web. 30 Oct. 2014.


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