Lista obiektów NGC (4001–5000)
Lista obiektów Nowego Katalogu Ogólnego (NGC) o numerach 4001-5000. Ten katalog astronomiczny obejmuje głównie gromady gwiazd, mgławice i galaktyki.
4001 – 4100
4101 – 4200
4201 – 4300
4301 – 4400
4401 – 4500
4501 – 4600
4601 – 4700
4701 – 4800
4801 – 4900
4901 – 5000
Bibliografia
- The NGC/IC Project (ang.)
- Courtney Seligman: New General Catalog (NGC) Objects (ang.). W: Celestial Atlas [on-line]. 2014. [dostęp 2014-09-03].
- Wolfgang Steinicke: Revised NGC and IC Catalog (ang.). W: The Interactive NGC Catalog Online [on-line]. SEDS. [dostęp 2014-09-03].
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This is a mosaic image, one of the largest ever taken by NASA's Hubble Space Telescope, of the Crab Nebula, a six-light-year-wide expanding remnant of a star's supernova explosion. Japanese and Chinese astronomers recorded this violent event in 1054 CE, as did, almost certainly, Native Americans.
The orange filaments are the tattered remains of the star and consist mostly of hydrogen. The rapidly spinning neutron star embedded in the center of the nebula is the dynamo powering the nebula's eerie interior bluish glow. The blue light comes from electrons whirling at nearly the speed of light around magnetic field lines from the neutron star. The neutron star, like a lighthouse, ejects twin beams of radiation that appear to pulse 30 times a second due to the neutron star's rotation. A neutron star is the crushed ultra-dense core of the exploded star.
The Crab Nebula derived its name from its appearance in a drawing made by Irish astronomer Lord Rosse in 1844, using a 36-inch telescope. When viewed by Hubble, as well as by large ground-based telescopes such as the European Southern Observatory's Very Large Telescope, the Crab Nebula takes on a more detailed appearance that yields clues into the spectacular demise of a star, 6,500 light-years away.
The newly composed image was assembled from 24 individual Wide Field and Planetary Camera 2 exposures taken in October 1999, January 2000, and December 2000. The colors in the image indicate the different elements that were expelled during the explosion. Blue in the filaments in the outer part of the nebula represents neutral oxygen, green is singly-ionized sulfur, and red indicates doubly-ionized oxygen.