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Pogson's original 1856 paper defined magnitude 6.0 to be the faintest star the unaided eye can see, [11] but the true limit for faintest possible visible star varies depending on the atmosphere and how high a star is in the sky. The Harvard Photometry used an average of 100 stars close to Polaris to define magnitude 5.0. [12] Later, the Johnson ...
For example, the binary star system Alpha Centauri has the total or combined magnitude of −0.27, while its two component stars have magnitudes of +0.01 and +1.33. [3] New or more accurate photometry, standard filters, or adopting differing methods using standard stars can measure stellar magnitudes slightly differently. This may change the ...
Stars in the night sky. The first star catalogue in Greek astronomy was created by Aristillus in approximately 300 BC, with the help of Timocharis. [10] The star catalog of Hipparchus (2nd century BC) included 1,020 stars, and was used to assemble Ptolemy's star catalogue. [11] Hipparchus is known for the discovery of the first recorded nova ...
Venus is often called the Evening Star or Morning Star because, when it is prominent, it appears like the brightest "star" in the sky. More astronomical delights are expected this new year, as ...
Note that the brighter the star, the smaller the magnitude: Bright "first magnitude" stars are "1st-class" stars, while stars barely visible to the naked eye are "sixth magnitude" or "6th-class". The system was a simple delineation of stellar brightness into six distinct groups but made no allowance for the variations in brightness within a group.
The bright star at top center is Alhena, which forms a cross-shaped asterism with the Winter Triangle. With an apparent magnitude of −1.46, Sirius is the brightest star in the night sky, almost twice as bright as the second-brightest star, Canopus. [72]
For example, 3C 273 has an average apparent magnitude of 12.8 (when observing with a telescope), but an absolute magnitude of −26.7. If this object were 10 parsecs away from Earth it would appear nearly as bright in the sky as the Sun (apparent magnitude −26.744).
Some of the brightest stars in the night sky, such as Rigel and Antares, are in the list. While supergiants are typically defined as stars with luminosity classes Ia, Iab or Ib, other definitions exist, such as those based on stellar evolution. [1] Therefore, stars with other luminosity classes can sometimes be considered supergiants.