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Blue Snowball Nebula
__NOTOC__ NGC 7662 (also known as the Blue Snowball Nebula, Snowball Nebula, and Caldwell 22) is a planetary nebula located in the constellation Andromeda. NGC 7662 is a popular planetary nebula for casual observers. A small telescope will reveal a star-like object with slight nebulosity. A 6" telescope with a magnification around 100x will reveal a slightly bluish disk, while telescopes with a primary mirror at least 16" in diameter may reveal slight color and brightness variations in the interior. The central star of the planetary nebula is an subdwarfO star with a spectral type of sdO. Image gallery File:NGC_7662_"Blue_Snowball".jpg See also * NGC 2022, which resembles NGC 7662 * NGC 2392 * NGC 3242 * List of NGC objects The following is a list of NGC objects, that is objects listed in the New General Catalogue (NGC). It is one of the largest comprehensive astronomical catalogues for deep sky objects such as star clusters, nebulae, and galaxies. * List of NGC objec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primary Mirror
A primary mirror (or primary) is the principal light-gathering surface (the objective) of a reflecting telescope. Description The primary mirror of a reflecting telescope is a spherical or parabolic shaped disks of polished reflective metal ( speculum metal up to the mid 19th century), or in later telescopes, glass or other material coated with a reflective layer. One of the first known reflecting telescopes, Newton's reflector of 1668, used a 3.3 cm polished metal primary mirror. The next major change was to use silver on glass rather than metal, in the 19th century such was with the Crossley reflector. This was changed to vacuum deposited aluminum on glass, used on the 200-inch Hale telescope. Solid primary mirrors have to sustain their own weight and not deform under gravity, which limits the maximum size for a single piece primary mirror. Segmented mirror configurations are used to get around the size limitation on single primary mirrors. For example, the Gia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NGC Objects
The ''New General Catalogue of Nebulae and Clusters of Stars'' (abbreviated NGC) is an astronomical catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including galaxies, star clusters and emission nebulae. Dreyer published two supplements to the NGC in 1895 and 1908, known as the ''Index Catalogues'' (abbreviated IC), describing a further 5,386 astronomical objects. Thousands of these objects are best known by their NGC or IC numbers, which remain in widespread use. The NGC expanded and consolidated the cataloguing work of William and Caroline Herschel, and John Herschel's '' General Catalogue of Nebulae and Clusters of Stars''. Objects south of the celestial equator are catalogued somewhat less thoroughly, but many were included based on observation by John Herschel or James Dunlop. The NGC contained multiple errors, but attempts to eliminate them were made by the ''Revised New General Catalogue'' (RNGC) by Jack W. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planetary Nebulae
A planetary nebula (PN, plural PNe) is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives. The term "planetary nebula" is a misnomer because they are unrelated to planets. The term originates from the planet-like round shape of these nebulae observed by astronomers through early telescopes. The first usage may have occurred during the 1780s with the English astronomer William Herschel who described these nebulae as resembling planets; however, as early as January 1779, the French astronomer Antoine Darquier de Pellepoix described in his observations of the Ring Nebula, "very dim but perfectly outlined; it is as large as Jupiter and resembles a fading planet". Though the modern interpretation is different, the old term is still used. All planetary nebulae form at the end of the life of a star of intermediate mass, about 1-8 solar masses. It is expected that the Sun will form a planetary nebul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of NGC Objects
The following is a list of NGC objects, that is objects listed in the New General Catalogue (NGC). It is one of the largest comprehensive astronomical catalogues for deep sky objects such as star clusters, nebulae, and galaxies. *List of NGC objects (1–1000) *List of NGC objects (1001–2000) * List of NGC objects (2001–3000) *List of NGC objects (3001–4000) *List of NGC objects (4001–5000) * List of NGC objects (5001–6000) *List of NGC objects (6001–7000) *List of NGC objects (7001–7840) Superlative entries NGC objects of superlative significance include: * NGC 2573 - Polarissima Australis, the closest NGC object to the south celestial pole * NGC 3172 - Polarissima Borealis, the closest NGC object to the north celestial pole Stars Some objects originally thought to be deep sky objects and listed in the NGC have been subsequently shown to be ordinary stars, so their inclusion in the catalog is now considered erroneous. This list of stars is based on the 'NGC ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NGC 3242
NGC 3242 (also known as the Ghost of Jupiter, eye nebula or Caldwell 59) is a planetary nebula located in the constellation Hydra. William Herschel discovered the nebula on February 7, 1785, and catalogued it as H IV.27. John Herschel observed it from the Cape of Good Hope, South Africa, in the 1830s, and numbered it as h 3248, and included it in the 1864 General Catalogue as GC 2102; this became NGC 3242 in J. L. E. Dreyer's '' New General Catalogue'' of 1888. This planetary nebula is most frequently called the ''Ghost of Jupiter'', or '' Jupiter's Ghost'' due to its similar shape to the planet, but it is also sometimes referred to as the ''Eye Nebula''. The nebula measures around two light years long from end to end, and contains a central white dwarf with an apparent magnitude of eleven. The inner layers of the nebula were formed some 1,500 years ago. The two ends of the nebula are marked by FLIERs, lobes of fast moving gas often tinted red in false-color pictures. NGC 32 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NGC 2392
The Eskimo Nebula (NGC 2392), also known as the Clown-faced Nebula, Lion Nebula, or Caldwell 39, is a bipolar double-shell planetary nebula (PN). It was discovered by astronomer William Herschel in 1787. The formation resembles a person's head surrounded by a parka hood. It is surrounded by gas that composed the outer layers of a Sun-like star. The visible inner filaments are ejected by a strong wind of particles from the central star. The outer disk contains unusual, light-year-long filaments. NGC 2392 lies about 6500 light-years away, and is visible with a small telescope in the constellation of Gemini. At the center of NGC 2392, there is an O-type star with a spectral type of O(H)6f. Historic data The nebula was discovered by William Herschel on January 17, 1787, in Slough, England. He described it as "A star 9th magnitude with a pretty bright middle, nebulosity equally dispersed all around. A very remarkable phenomenon." NGC 2392 WH IV-45 is included in the Astronomical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NGC 2022
NGC 2022 is a planetary nebula in the equatorial constellation of Orion, located at a distance of from the Sun. It was first observed by William Herschel on December 28, 1785, who described it as: considerably bright, nearly round, like a star with a large diameter, like an ill-defined planetary nebula. In medium-sized amateur telescopes it looks like a small grayish patch of light. It is not very bright but it is still easy to spot it in the eyepiece. Even in a telescope as small as 80mm it can just be seen using a narrowband filter such as an OIII filter as a 'fuzzy' star. The object has the shape of a prolate spheroid with a major to minor axis ratio of 1.2, an apparent size of , and a halo extending out to , which is about the angular diameter of Jupiter as seen from Earth. This is a double-shell planetary nebula with a wind-compressed inner shell and a more nebulous second shell. The linear radius of the inner shell is estimated at . It is expanding with a velocity of . T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectral Type
In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colors interspersed with spectral lines. Each line indicates a particular chemical element or molecule, with the line strength indicating the abundance of that element. The strengths of the different spectral lines vary mainly due to the temperature of the photosphere, although in some cases there are true abundance differences. The ''spectral class'' of a star is a short code primarily summarizing the ionization state, giving an objective measure of the photosphere's temperature. Most stars are currently classified under the Morgan–Keenan (MK) system using the letters ''O'', ''B'', ''A'', ''F'', ''G'', ''K'', and ''M'', a sequence from the hottest (''O'' type) to the coolest (''M'' type). Each letter class is then subdivide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subdwarf
A subdwarf, sometimes denoted by "sd", is a star with luminosity class VI under the Yerkes spectral classification system. They are defined as stars with luminosity 1.5 to 2 magnitudes lower than that of main-sequence stars of the same spectral type. On a Hertzsprung–Russell diagram subdwarfs appear to lie below the main sequence. The term "subdwarf" was coined by Gerard Kuiper in 1939, to refer to a series of stars with anomalous spectra that were previously labeled as "intermediate white dwarfs". Cool subdwarfs Like ordinary main-sequence stars, cool subdwarfs (of spectral types G to M) produce their energy from hydrogen fusion. The explanation of their underluminosity lies in their low metallicity: these stars are unenriched in elements heavier than helium. The lower metallicity decreases the opacity of their outer layers and decreases the radiation pressure, resulting in a smaller, hotter star for a given mass. This lower opacity also allows them to emit a higher pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnification
Magnification is the process of enlarging the apparent size, not physical size, of something. This enlargement is quantified by a calculated number also called "magnification". When this number is less than one, it refers to a reduction in size, sometimes called ''minification'' or ''de-magnification''. Typically, magnification is related to scaling up visuals or images to be able to see more detail, increasing resolution, using microscope, printing techniques, or digital processing. In all cases, the magnification of the image does not change the perspective of the image. Examples of magnification Some optical instruments provide visual aid by magnifying small or distant subjects. * A magnifying glass, which uses a positive (convex) lens to make things look bigger by allowing the user to hold them closer to their eye. * A telescope, which uses its large objective lens or primary mirror to create an image of a distant object and then allows the user to examine the im ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hubble Space Telescope
The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versatile, renowned both as a vital research tool and as a public relations boon for astronomy. The Hubble telescope is named after astronomer Edwin Hubble and is one of NASA's Great Observatories. The Space Telescope Science Institute (STScI) selects Hubble's targets and processes the resulting data, while the Goddard Space Flight Center (GSFC) controls the spacecraft. Hubble features a mirror, and its five main instruments observe in the ultraviolet, visible, and near-infrared regions of the electromagnetic spectrum. Hubble's orbit outside the distortion of Earth's atmosphere allows it to capture extremely high-resolution images with substantially lower background light than ground-based telescopes. It has recorded some of the most ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
