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Deneb main star in the constellation Cygnus, of magnitude 1.3, is the 19th among the 20 brightest stars in the sky. It belongs to the spectral class A2, it is from Earth 400 years-light, it is 4800 times brighter than the Sun.
Being boreal forms, your observation is favored in the northern hemisphere. It is a white supergiant of spectral class A2I, intrinsically very bright. If less than bright star appears as Sirius, Arcturus or Vega, this is due to its great distance, which however has not yet been precisely determined.
Deneb is in any case among the stars of the first magnitude that is farthest from the sun. Its name comes from the Arabic Dhaneb, meaning tail. Set against the backdrop of the Milky Way, Deneb can be easily identified in the night sky because of its brightness and because of membership in the most conspicuous asterism of the summer sky in the northern hemisphere, the summer triangle, formed not only by Deneb, Vega of Lyra and Aquila Altair.
Deneb, the less brilliant of the three stars, is 38 ° to 24 ° from Altair and Vega, while the angular distance between Vega and Altair is 34 °. Deneb with Vega then forms the basis of a nearly isosceles triangle, of which it constitutes the most northern summit.
It is also the northernmost star of the Northern Cross, the asterism that includes the brightest stars in the constellation Cygnus: together with Albireo, Deneb forms the longest of the cross arm. Having a + 45 ° angle around, his observation is privileged hemisphere northern hemisphere of the Earth, where north of latitude 45 ° North appears circumpolar, while the southern hemisphere is visible only to the north of latitude 45 ° South. The star so it is never visible from Argentina and southern Chile, the Falkland Islands, from the southernmost regions of New Zealand and the Antarctic continent.
The best time for your observation in the northern hemisphere is in the summer, although it is visible in the evening sky low on the horizon until late January, while in the Southern Hemisphere Deneb comes low on the horizon and the best time for the ‘ observation falls in the months of August and September.
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