|
Dark Nebulae
A dark nebula or absorption nebula is a type of interstellar cloud, particularly molecular clouds, that is so dense that it obscures the visible wavelengths of light from objects behind it, such as background stars and emission or reflection nebulae. The extinction of the light is caused by interstellar dust grains located in the coldest, densest parts of molecular clouds. Clusters and large complexes of dark nebulae are associated with Giant Molecular Clouds. Isolated small dark nebulae are called Bok globules. Like other interstellar dust or material, things it obscures are only visible using radio waves in radio astronomy or infrared in infrared astronomy. Dark clouds appear so because of sub-micrometre-sized dust particles, coated with frozen carbon monoxide and nitrogen, which effectively block the passage of light at visible wavelengths. Also present are molecular hydrogen, atomic helium, C18O (CO with oxygen as the 18O isotope), CS, NH3 (ammonia), H2CO (formaldehyde), c-C3 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interstellar Cloud
An interstellar cloud is generally an accumulation of gas, plasma, and dust in our and other galaxies. Put differently, an interstellar cloud is a denser-than-average region of the interstellar medium, the matter and radiation that exists in the space between the star systems in a galaxy. Depending on the density, size, and temperature of a given cloud, its hydrogen can be neutral, making an H I region; ionized, or plasma making it an H II region; or molecular, which are referred to simply as molecular clouds, or sometime dense clouds. Neutral and ionized clouds are sometimes also called ''diffuse clouds''. An interstellar cloud is formed by the gas and dust particles from a red giant in its later life. Chemical compositions The chemical composition of interstellar clouds is determined by studying electromagnetic radiation that they emanate, and we receive – from radio waves through visible light, to gamma rays on the electromagnetic spectrum – that we receive from them. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diazenylium
frameless, right Diazenylium is the chemical N2H+, an inorganic cation that was one of the first ions to be observed in interstellar clouds. Since then, it has been observed for in several different types of interstellar environments, observations that have several different scientific uses. It gives astronomers information about the fractional ionization of gas clouds, the chemistry that happens within those clouds, and it is often used as a tracer for molecules that are not as easily detected (such as N2). Its 1–0 rotational transition occurs at 93.174 GHz, a region of the spectrum where Earth's atmosphere is transparent and it has a significant optical depth in both cold and warm clouds so it is relatively easy to observe with ground-based observatories. The results of N2H+ observations can be used not only for determining the chemistry of interstellar clouds, but also for mapping the density and velocity profiles of these clouds. Astronomical detections N2H+ was f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LDN 1768 , Gwynedd, Wales (by National Rail station code)
{{disambig ...
LDN is usually contractional slang for London, UK. LDN may also refer to: Arts and media * London Daily News, former newspaper * BBC London (formerly ''BBC LDN''), broadcasting body * "LDN" (song), a 2006 single by Lily Allen Language * Láadan, a feminist, sci-fi conlang (by ISO 639-3 code) Science and technology * Low dose naltrexone * Day-night average sound level, Ldn or DNL * Linked Data Notifications, a communications protocol Transport * Llandanwg railway station Llandanwg railway station is in the village of Llandanwg in Gwynedd, Wales. It is an unstaffed halt on the Cambrian Coast Railway with direct passenger services to Harlech, Porthmadog and Pwllheli to the north and west, and Barmouth, Machynlleth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regioni Celesti Scelte - Osc B
The regions of Italy ( it, regioni d'Italia) are the first-level administrative divisions of the Italian Republic, constituting its second NUTS administrative level. There are twenty regions, five of which have higher autonomy than the rest. Under the Italian Constitution, each region is an autonomous entity with defined powers. With the exception of the Aosta Valley (since 1945) and Friuli-Venezia Giulia (since 2018), each region is divided into a number of provinces (''province''). History During the Kingdom of Italy, regions were mere statistical districts of the central state. Under the Republic, they were granted a measure of political autonomy by the 1948 Italian Constitution. The original draft list comprised the Salento region (which was eventually included in Apulia); ''Friuli'' and ''Venezia Giulia'' were separate regions, and Basilicata was named ''Lucania''. Abruzzo and Molise were identified as separate regions in the first draft, but were later merged into ''Abruz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regioni Celesti Scelte - Osc A
The regions of Italy ( it, regioni d'Italia) are the first-level administrative divisions of the Italian Republic, constituting its second NUTS administrative level. There are twenty regions, five of which have higher autonomy than the rest. Under the Italian Constitution, each region is an autonomous entity with defined powers. With the exception of the Aosta Valley (since 1945) and Friuli-Venezia Giulia (since 2018), each region is divided into a number of provinces (''province''). History During the Kingdom of Italy, regions were mere statistical districts of the central state. Under the Republic, they were granted a measure of political autonomy by the 1948 Italian Constitution. The original draft list comprised the Salento region (which was eventually included in Apulia); ''Friuli'' and ''Venezia Giulia'' were separate regions, and Basilicata was named ''Lucania''. Abruzzo and Molise were identified as separate regions in the first draft, but were later merged into ''Abruz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrophysical Maser
An astrophysical maser is a naturally occurring source of stimulated spectral line emission, typically in the microwave portion of the electromagnetic spectrum. This emission may arise in molecular clouds, comets, planetary atmospheres, stellar atmospheres, or various other conditions in interstellar space. Background Discrete transition energy Like a laser, the emission from a maser is stimulated (or ''seeded'') and monochromatic, having the frequency corresponding to the energy difference between two quantum-mechanical energy levels of the species in the gain medium which have been pumped into a non-thermal population distribution. However, naturally occurring masers lack the resonant cavity engineered for terrestrial laboratory masers. The emission from an astrophysical maser is due to a single pass through the gain medium and therefore generally lacks the spatial coherence and mode purity expected from a laboratory maser. Nomenclature Due to the differences between en ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the earliest constellations likely go back to prehistory. People used them to relate stories of their beliefs, experiences, creation myth, creation, or mythology. Different cultures and countries adopted their own constellations, some of which lasted into the early 20th century before today's constellations were internationally recognized. The recognition of constellations has changed significantly over time. Many changed in size or shape. Some became popular, only to drop into obscurity. Some were limited to a single culture or nation. The 48 traditional Western constellations are Greek. They are given in Aratus' work ''Phenomena'' and Ptolemy's ''Almagest'', though their origin probably predates these works by several centuries. Constellation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Great Rift (astronomy)
In astronomy, the Great Rift (sometimes called the Dark Rift or less commonly the Dark River) is a dust lane, dark band caused by interstellar clouds of cosmic dust that significantly obscure (extinction (astronomy), extinguish) the Galactic Center, center and most radial sectors of the Milky Way galaxy from Earth's perspective. In dark, clear night sky, night skies, the rift appears as clear as the bright galactic bulge, bulge of stars around the Galactic Center does to the naked eye or binoculars. The rift is largely between the Solar System (which is close to the inner edge of the Orion Arm) and the next arm, inward, the Sagittarius Arm. The clouds are an obstruction to millions of the galaxy's stars detected at visible spectrum, visible wavelengths, which compose a bright hazy band appearing angular diameter, 30° wide and arching through the night sky. The clouds within our radial sector of the galaxy span about from Earth. The clouds are estimated to contain about 1 millio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coalsack Nebula
The Coalsack Nebula (Southern Coalsack, or simply the Coalsack) is a prominent dark nebula in the skies, being easily visible to the naked eye as a dark patch obscuring a brief section of Milky Way stars as they cross their southernmost region of the sky, east of Acrux (Alpha Crucis) which is the bright, southern pointer star of the southern cross. It dominates and overspills the southeast corner of what is considered the extent of the constellation Crux at a little less than twice the distance of Acrux, away from Earth. General information The Coalsack Nebula covers nearly 7 ° by 5° and overlaps somewhat with the neighbor constellations Centaurus and Musca. The first observation was reported by Vicente Yáñez Pinzón in 1499. It was named "''il Canopo fosco''" (the dark Canopus) by Amerigo Vespucci and was also called "''Macula Magellani''" (Magellan's Spot) or "''Black Magellanic Cloud''" in opposition to the Magellanic Clouds. The Coalsack is omitted in most of today's sta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
