Search results
Results from the WOW.Com Content Network
Starlight overcast moonless night sky [1] 140 microlux: Venus at brightest [1] 200 microlux: Starlight clear moonless night sky excluding airglow [1] 10 −3: 1 millilux: 2 millilux: Starlight clear moonless night sky including airglow [1] 10 −2: 1 centilux: 1 centilux: Quarter Moon 10 −1: 1 decilux: 2.5 decilux: Full Moon on a clear night ...
Rho Cassiopeiae (/ ˌ r oʊ k æ s i ə ˈ p iː aɪ,-s i oʊ-,-iː /; ρ Cas, ρ Cassiopeiae) is a yellow hypergiant star in the constellation Cassiopeia.It is about 8,150 light-years (2,500 pc) from Earth, yet can still be seen by the naked eye as it is over 300,000 times brighter than the Sun.
Luminosity is an absolute measure of radiated electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. [1] [2] In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a star, galaxy, or other astronomical objects. [3] [4]
Apparent magnitude, the brightness of an object as it appears in the night sky. Absolute magnitude, which measures the luminosity of an object (or reflected light for non-luminous objects like asteroids); it is the object's apparent magnitude as seen from a specific distance, conventionally 10 parsecs (32.6 light years).
A preliminary description of the three areas of this diagram was made in 2003 by Eric F. Bell et al. from the COMBO-17 survey [1] that clarified the bimodal distribution of red and blue galaxies as seen in the analysis of Sloan Digital Sky Survey data [2] and even in de Vaucouleurs's 1961 analyses of galaxy morphology. [3]
Several emission lines are dominant: a green line from oxygen at 557.7 nm, a yellow doublet from sodium at 589.0 and 589.6 nm, and red lines from oxygen at 630.0 and 636.4 nm. The sodium emissions come from a thin sodium layer approximately 10 km thick at an altitude of 90–100 km, above the mesopause and in the D-layer of the ionosphere. The ...
A truly dark sky has a surface brightness of 2 × 10 −4 cd m −2 or 21.8 mag arcsec −2. [9] [clarification needed] The peak surface brightness of the central region of the Orion Nebula is about 17 Mag/arcsec 2 (about 14 milli nits) and the outer bluish glow has a peak surface brightness of 21.3 Mag/arcsec 2 (about 0.27 millinits). [10]
It was observed in 1866 by Angelo Secchi, the first star ever observed with emission lines. [12] [13] It is now considered a Be star. Gamma Cassiopeiae is also a variable star and a multiple star system. Based upon parallax measurements made by the Hipparcos satellite, it is located at a distance of roughly 550 light-years from Earth.