|
Westerhout 49
In astronomy Westerhout 49 also known as W49, is a strong galactic thermal radio source characteristic of an HII region. It was discovered by Gart Westerhout in 1958. Its distance is estimated to be about 11.1 kpcs or 36,000 light years. and it lies in the galactic plane about the same distance from the Galactic Center as does the Sun. It has been compared to the giant HII region NGC 3603 which is about half as distant. Non-thermal radiation has been found which is believed to be from an old supernova remnant. Gaseous molecular outflows have been detected as well as H2O (water) masers . No optical counterpart has yet been discovered. While this is partly due to interstellar absorption, any tight clustering of stars at such a great distance in the galactic plane would be scarcely distinguishable from the general background. A study published in 2014, where the VLT has been used among other instruments, shows the presence of a very massive star in the central cluster of this star- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aquila (constellation)
Aquila is a constellation on the celestial equator. Its name is Latin for 'eagle' and it represents the bird that carried Zeus/Jupiter's thunderbolts in Greek-Roman mythology. Its brightest star, Altair, is one vertex of the Summer Triangle asterism. The constellation is best seen in the northern summer, as it is located along the Milky Way. Because of this location, many clusters and nebulae are found within its borders, but they are dim and galaxies are few. History Aquila was one of the 48 constellations described by the second-century astronomer Ptolemy. It had been earlier mentioned by Eudoxus in the fourth century BC and Aratus in the third century BC. It is now one of the 88 constellations defined by the International Astronomical Union. The constellation was also known as ''Vultur volans'' (the flying vulture) to the Romans, not to be confused with ''Vultur cadens'' which was their name for Lyra. It is often held to represent the eagle which held Zeus's/Jupiter's t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
J2000
In astronomy, an epoch or reference epoch is a instant, moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a Astronomical object, celestial body, as they are subject to Perturbation (astronomy), perturbations and vary with time. These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or Perihelion and aphelion, aphelion of its orbit, or the size of the major axis of its orbit. The main use of astronomical quantities specified in this way is to calculate other relevant parameters of motion, in order to predict future positions and velocities. The applied tools of the disciplines of celestial mechanics or its subfield orbital mechanics (for predicting orbital paths and positions for bodies in motion under the gravitational effects of other bodi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HII Region
An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds of light years, and density from a few to about a million particles per cubic centimetre. The Orion Nebula, now known to be an H II region, was observed in 1610 by Nicolas-Claude Fabri de Peiresc by telescope, the first such object discovered. The regions may be of any shape because the distribution of the stars and gas inside them is irregular. Hertzsprung-Russell diagram, The short-lived blue stars created in these regions emit copious amounts of ultraviolet light that ionize the surrounding gas. H II regions—sometimes several hundred light-years across—are often associated with giant molecular clouds. They often appear clumpy and filamentary, sometimes showing intricate shapes such as the Horsehead Nebula. H II regio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gart Westerhout
Gart Westerhout (15 June 1927 – 14 October 2012) was a Dutch-American astronomer. Well before completing his university studies at Leiden, he had already become well-established internationally as a radio astronomer in the Netherlands, specializing in studies of radio sources and the Milky Way Galaxy based on observations of radio continuum emissions and 21-cm spectral line radiation that originates in interstellar hydrogen. He emigrated to the United States, became a naturalized citizen, and held a number of important scientific and management positions in academic and government institutions. Career Westerhout was born in The Hague, and studied at the University of Leiden ( Sterrewacht te Leiden) with Hendrik van de Hulst and Jan Hendrik Oort. Contemporaries and colleagues in the Netherlands included Hugo van Woerden, C. Lex Muller, Maarten Schmidt, Kwee Kiem King, Lodewijk Woltjer, and Charles L. Seeger, III (son of the ethnomusicologist, brother of Pete Seeger and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galactic Center
The Galactic Center or Galactic Centre is the rotational center, the barycenter, of the Milky Way galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a compact radio source which is almost exactly at the galactic rotational center. The Galactic Center is approximately away from Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius, where the Milky Way appears brightest, visually close to the Butterfly Cluster (M6) or the star Shaula, south to the Pipe Nebula. There are around 10 million stars within one parsec of the Galactic Center, dominated by red giants, with a significant population of massive supergiants and Wolf–Rayet stars from star formation in the region around 1 million years ago. The core stars are a small part within the much wider galactic bulge. Discovery Because of interstellar dust along the line of sight, the Galactic Center cannot be studied at v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NGC 3603
NGC 3603 is a nebula situated in the Carina–Sagittarius Arm of the Milky Way around 20,000 light-years away from the Solar System. It is a massive H II region containing a very compact open cluster (probably a super star cluster) HD 97950. Observations NGC 3603 was observed by John Herschel on 14 March 1834 during his visit to South Africa, who remarked that it was "a very remarkable object...perhaps a globular cluster". Herschel catalogued it as nebula 3334 in his ''Results of Astronomical Observations made at the Cape of Good Hope'', published in 1847. In 1864 the Royal Society published his ''General Catalogue of Nebulae and Clusters'', where he listed it as number 2354. It was subsequently incorporated into the '' New General Catalogue'' as by J. L. E. Dreyer as NGC 3603. The central cluster was catalogued as the star HD 97950, but has long been recognised as nebulous or multiple. It was also noted for having an unusual emission spectrum and the spectral type was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supernova
A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when a white dwarf is triggered into runaway nuclear fusion. The original object, called the ''progenitor'', either collapses to a neutron star or black hole, or is completely destroyed. The peak optical luminosity of a supernova can be comparable to that of an entire galaxy before fading over several weeks or months. Supernovae are more energetic than novae. In Latin language, Latin, ''nova'' means "new", referring astronomically to what appears to be a temporary new bright star. Adding the prefix "super-" distinguishes supernovae from ordinary novae, which are far less luminous. The word ''supernova'' was coined by Walter Baade and Fritz Zwicky in 1929. The last supernova to be directly observed in the Milky Way was Kepler's Supernova in 160 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Masers
A maser (, an acronym for microwave amplification by stimulated emission of radiation) is a device that produces coherent electromagnetic waves through amplification by stimulated emission. The first maser was built by Charles H. Townes, James P. Gordon, and Herbert J. Zeiger at Columbia University in 1953. Townes, Nikolay Basov and Alexander Prokhorov were awarded the 1964 Nobel Prize in Physics for theoretical work leading to the maser. Masers are also used as the timekeeping device in atomic clocks, and as extremely low-noise microwave amplifiers in radio telescopes and deep-space spacecraft communication ground stations. Modern masers can be designed to generate electromagnetic waves at not only microwave frequencies but also radio and infrared frequencies. For this reason, Townes suggested replacing ''microwave'' with the word ''molecular'' as the first word in the acronym ''maser''. The laser works by the same principle as the maser but produces higher frequency coherent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Very Large Telescope
The Very Large Telescope (VLT) is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each with a primary mirror 8.2 m across, which are generally used separately but can be used together to achieve very high angular resolution. The four separate optical telescopes are known as ''Antu'', ''Kueyen'', ''Melipal'', and ''Yepun'', which are all words for astronomical objects in the Mapuche language. The telescopes form an array complemented by four movable Auxiliary Telescopes (ATs) of 1.8 m aperture. The VLT operates at visible light, visible and infrared wavelengths. Each individual telescope can detect objects roughly four billion times fainter than can be detected with the naked eye, and when all the telescopes are combined, the facility can achieve an angular resolution of about 0.002 arcsecond. In single telescope mode of operation angular resolution is ab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Mass
The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass of the Sun. This equates to about two nonillion (short scale), two quintillion (long scale) kilograms or 2000 quettagrams: The solar mass is about times the mass of Earth (), or times the mass of Jupiter (). History of measurement The value of the gravitational constant was first derived from measurements that were made by Henry Cavendish in 1798 with a torsion balance. The value he obtained differs by only 1% from the modern value, but was not as precise. The diurnal parallax of the Sun was accurately measured during the transits of Venus in 1761 and 1769, yielding a value of (9 arcseconds, compared to the present value of ). From the value of the diurnal parallax, one can determine the distance to the Sun from the geometry o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Most Luminous Stars
This is a list of stars arranged by their absolute magnitude – their intrinsic stellar luminosity. This cannot be observed directly, so instead must be calculated from the apparent magnitude (the brightness as seen from Earth), the distance to each star, and a correction for interstellar extinction. The entries in the list below are further corrected to provide the bolometric magnitude, i.e. integrated over all wavelengths; this relies upon measurements in multiple photometric filters and extrapolation of the stellar spectrum based on the stellar spectral type and/or effective temperature. Entries give the bolometric luminosity in multiples of the luminosity of the Sun () and the bolometric absolute magnitude. As with all magnitude systems in astronomy, the latter scale is logarithmic and inverted i.e. more negative numbers are more luminous. Most stars on this list are not bright enough to be visible to the naked eye from Earth, because of their high distances, high ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Most Massive Stars
This is a list of the most massive stars that have been discovered, in solar masses (). Uncertainties and caveats Most of the masses listed below are contested and, being the subject of current research, remain under review and subject to constant revision of their masses and other characteristics. Indeed, many of the masses listed in the table below are inferred from theory, using difficult measurements of the stars' temperatures and absolute brightnesses. All the masses listed below are uncertain: Both the theory and the measurements are pushing the limits of current knowledge and technology. Both theories and measurements could be incorrect. For example, VV Cephei could be between , or , depending on which property of the star is examined. Complications with distance and obscuring clouds Since massive stars are rare, astronomers must look very far from Earth to find them. All the listed stars are many thousands of light years away, which makes measurements difficult. In addi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.jpg "Click for more on -> Very Large Telescope")
