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The Zone of Avoidance (ZOA, ZoA), or Zone of Galactic Obscuration (ZGO), [1] [2] is the area of the sky that is obscured by the Milky Way. [ 3 ] The Zone of Avoidance was originally called the Zone of Few Nebulae in an 1878 paper by English astronomer Richard Proctor that referred to the distribution of " nebulae " in John Herschel 's General ...
A nebula that is visible to the human eye from Earth would appear larger, but no brighter, from close by. [6] The Orion Nebula, the brightest nebula in the sky and occupying an area twice the angular diameter of the full Moon, can be viewed with the naked eye but was missed by early astronomers. [7]
The temperatures observed in HH objects are typically about 9,000–12,000 K, [22] similar to those found in other ionized nebulae such as H II regions and planetary nebulae. [23] Densities, on the other hand, are higher than in other nebulae, ranging from a few thousand to a few tens of thousands of particles per cm 3 , [ 22 ] compared to a ...
Examples of astronomical objects include planetary systems, star clusters, nebulae, and galaxies, while asteroids, moons, planets, and stars are astronomical bodies. A comet may be identified as both a body and an object: It is a body when referring to the frozen nucleus of ice and dust, and an object when describing the entire comet with its ...
Ja — Jacoby (planetary nebulae) (for example: Jacoby 1 at 15:23 / +52°14' in Boötes) JaFu — Jacoby-Fullton (planetary nebulae) JAn — John A. Anderson (double stars) Jc — William Stephen Jacob (double stars) Jef — H.M. Jeffers (double stars) Jn — Jones (planetary nebulae) (for example: Jones 1 at 23:36 / +30°28' in Pegasus)
Based on the expansion rate, the estimated age of the nebula is 3,080 years. [5] The central star of the planetary nebula is a subdwarf O star with a spectral type of sdO. [7] The best fit model for this star gives an effective temperature of 100 kK, with 5,250 times the luminosity of the Sun [5] and 60.5% of the Sun's mass. [6]
The brightest, most massive and most luminous object among those 131 is Sirius A, which is also the brightest star in Earth's night sky; its white dwarf companion Sirius B is the hottest object among them. The largest object within the 20 light-years is Procyon.
The overall nebula with smaller hole shown in context. NGC 1999, also known as The Cosmic Keyhole, [1] [2] is a dust-filled bright nebula with a vast hole of empty space represented by a black patch of sky, as can be seen in the photograph. It is a reflection nebula, and shines from the light of the variable star V380 Orionis.