List of extremes in the sky

This article describes some extremes in the sky as a textual addition to the list of star extremes page.

Brightness

The brightest star in the sky as to be observed from Earth is the Sun with a stellar magnitude of −26.7. When counting objects outside the solar system it is Sirius in the constellation of the Greater Dog with magnitude −1.45 and lies in the celestial southern hemisphere.

The brightest star in the northern celestial hemisphere is Arcturus in Bootes with a magnitude of −0.03.

The faintest stars visible to the naked eye are of magnitude +6.3 in good conditions but may vary from +3 in heavily light polluted city centers to +7.5 in excellent Bortle 0 skies and good visual acuity.

The brightest star in absolute magnitude is S Doradus with an absolute magnitude of −9.9 which is about 700 000 times brighter than the Sun. Of the first magnitude stars (brighter than +1.5) it is Deneb with −8.4 which equals 170 000 Suns.

All stars in the sky added together are as bright as a single star of magnitude −6.5. From 11500 AU (0.18 ly) the Sun won't outshine all other stars in the sky. [1]

Location

The northernmost first magnitude star is Capella with a declination of 46 degrees north and brightness of +0.2. The northernmost second magnitude star is the current Pole star of +2.0 at declination 89 degrees North and is the closest naked eye star to the North Pole.

The southernmost first magnitude star is Acrux with a declination of 63 degrees south and brightness of +0.8. The southernmost second magnitude star is Beta Hydri of +2.8 at declination 77 degrees South. Sigma Octantis of magnitude 5.6 is the closest star to the South Pole (89 South) visible by the naked eye.

The southern hemisphere consists of more 1st magnitude stars (mv brighter than +1.6) (12) than the northern (11).

Due to precession this will change over the centuries, by AD 13800, Vega will be only 4 degrees from the North Pole, at the same time Canopus will be 10 degrees from the South pole. At that time, the number of bright stars in the northern hemisphere will be only 6 while 17 in the southern. Moreover, due to proper motion some nearby stars like Arcturus or Alpha Centauri will be displaced several degrees. About AD 6400 Alpha Centauri will pass 1 degree from Beta Centauri.[2]

At BC 3400, Achernar was only 8 degrees from the South Pole.[2]

The greatest concentration of bright stars is around Orion. Within a circle of 60 degrees degrees radius around a point in Monoceros at RA 6:30, DE 5ºS, 11 stars of magnitude +1.6 or brighter occur: Capella, Pollux, Castor, Regulus, Procyon, Sirius, Adhara, Canopus, Rigel, Betelgeuse and Aldebaran. No other part of the sky consists of so many bright stars. The entire sky consists of 23 such stars. Narrowing the circle to 50 degrees and moving the center to the midway point of Capella and Canopus (a few degrees east of Orion's belt) will still consist of 9 stars leaving out only Regulus.

Within a much smaller circle of 10 degrees radius from Alnilam, the center Orion belt star, 5 stars of mag +2.2 or brighter occur of which 70 are available in the entire sky.

The most 'remote' 1st magnitude star from another 1st magnitude star is Fomalhaut which is nearest to Achernar (39 degrees) and Antares which is nearest to Alpha Centauri (also 39 degrees). All other 1st magnitude stars are closer than that angular distance to another 1st magnitude star.

See also

Notes

    References

    1. ↑ http://www.oocities.org/aa_spaceagent/ahads_sphere.htm, Ahad's constant
    2. 1 2 calculated by Stellarium 0.13, an open source sky mapping app. http://www.stellarium.org
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