Northern Cross (asterism)
The Northern Cross is a prominent astronomical asterism in the northern hemisphere celestial sphere, corresponding closely with the constellation Cygnus The Swan. It is much larger than the more famous Southern Cross and consists of the brightest stars in Cygnus, Deneb, Sadr, Gienah, Delta Cygni and Albireo. The 'head' of the cross, Deneb, is also part of the Summer Triangle asterism.
Like the Summer Triangle, the Northern Cross is a prominent indicator of the seasons. Near midnight, the Cross lies virtually overhead at mid-northern latitudes during the summer months, it can also be seen during spring in the early morning to the East. In the autumn the cross is visible in the evening to the West until November. It never dips below the horizon at or above 45° north latitude, just grazing the northern horizon at its lowest point at such locations as Minneapolis, Montréal and Turin. From the southern hemisphere it appears upside down and low in the sky during the winter months .
In the 17th-century, German celestial cartographer Johann Bayer's star atlas the Uranometria, Alpha, Beta and Gamma Cygni form the pole of a cross, while Delta and Epsilon form the cross beam. The variable star P Cygni was then considered to be the body of Christ.[1]
The stars of the Northern Cross
| Name | Bayer designation | Apparent magnitude | Luminosity (× solar) |
Spectral type | Distance (light years) |
|---|---|---|---|---|---|
| Deneb | α Cygni | 1.25 | 7000 | A2 | 3230 |
| Gienah | ε Cygni | 0.03 | 52 | K0III-IV | 72 |
| Delta Cygni | δ Cygni | 2.87 | 76 | B9 III + F1 V | 170 |
| Sadr | γ Cygni | -2.45 | 33 | F8 Iab | 16.6 |
| Albireo | β Cygni | -2.45 | 1,200 | K2II | 430 |
See also
References
External links
- http://earthsky.org/favorite-star-patterns/the-northern-cross-backbone-of-the-milky-way
- http://www.seiyaku.com/customs/crosses/northern.html
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