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Distance Modulus
The distance modulus is a way of expressing distances that is often used in astronomy. It describes distances on a logarithmic scale based on the astronomical magnitude system. Definition The distance modulus \mu=m-M is the difference between the apparent magnitude m (ideally, corrected from the effects of interstellar absorption) and the absolute magnitude M of an astronomical object. It is related to the distance d in parsecs by: :\log_(d) = 1 + \frac :\mu=5\log_(d)-5 This definition is convenient because the observed brightness of a light source is related to its distance by the inverse square law (a source twice as far away appears one quarter as bright) and because brightnesses are usually expressed not directly, but in magnitudes. Absolute magnitude M is defined as the apparent magnitude of an object when seen at a distance of 10 parsecs. Suppose a light source has luminosity L(d) when observed from a distance of d parsecs, and luminosity L(10) when observed from a dis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Distance
Distance is a numerical or occasionally qualitative measurement of how far apart objects or points are. In physics or everyday usage, distance may refer to a physical length or an estimation based on other criteria (e.g. "two counties over"). Since spatial cognition is a rich source of conceptual metaphors in human thought, the term is also frequently used metaphorically to mean a measurement of the amount of difference between two similar objects (such as statistical distance between probability distributions or edit distance between strings of text) or a degree of separation (as exemplified by distance between people in a social network). Most such notions of distance, both physical and metaphorical, are formalized in mathematics using the notion of a metric space. In the social sciences, distance can refer to a qualitative measurement of separation, such as social distance or psychological distance. Distances in physics and geometry The distance between physi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Galaxy
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100 million stars, range in size from dwarfs with less than a hundred million stars, to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy's center of mass. Most of the mass in a typical galaxy is in the form of dark matter, with only a few percent of that mass visible in the form of stars and nebulae. Supermassive black holes are a common feature at the centres of galaxies. Galaxies are categorized according to their visual morphology as elliptical, spiral, or irregular. Many are thought to have supermassive black holes at their centers. The Milky Way's central black hole, known as Sagittarius A*, has a mass four million times greater than ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Elske Smith
Elske van Panhuys Smith (born 1929) is a Dutch-American astronomer, academic administrator, and author of books on astronomy. She has also been outspoken about discrimination against women in academia. Education and career Smith was born in 1929 in Monaco as the daughter of a Dutch diplomat. She spent the early years of her life in Austria before moving to the Netherlands, Venezuela, Costa Rica, and finally in 1943 to Boston in the US. She remained in Boston to complete her high school and college education, as her father moved on to more posts. She majored in astronomy at Radcliffe College, after becoming interested in it through a freshman-year friend, and was mentored there by Dutch-American astronomer Bart Bok and by Harlow Shapley. She remained at Harvard University with her husband, Harry Smith, for graduate study on interstellar polarization with Bok. She completed her Ph.D. in 1956. After difficulties finding a satisfactory solution to their two-body problem, Smith and he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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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] |
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SN 1987A
SN 1987A was a type II supernova in the Large Magellanic Cloud, a dwarf satellite galaxy of the Milky Way. It occurred approximately from Earth and was the closest observed supernova since Kepler's Supernova. 1987A's light reached Earth on February 23, 1987, and as the earliest supernova discovered that year, was labeled "1987A". Its brightness peaked in May, with an apparent magnitude of about 3. It was the first supernova that modern astronomers were able to study in great detail, and its observations have provided much insight into core-collapse supernovae. SN 1987A provided the first opportunity to confirm by direct observation the radioactive source of the energy for visible light emissions, by detecting predicted gamma-ray line radiation from two of its abundant radioactive nuclei. This proved the radioactive nature of the long-duration post-explosion glow of supernovae. For over thirty years, the expected collapsed neutron star could not be found, but in 2019, indirect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Virgo Cluster
The Virgo Cluster is a large cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc) away in the constellation Virgo. Comprising approximately 1,300 (and possibly up to 2,000) member galaxies, the cluster forms the heart of the larger Virgo Supercluster, of which the Local Group (containing our Milky Way galaxy) is a member. The Local Group actually experiences the mass of the Virgo Supercluster as the Virgocentric flow. It is estimated that the Virgo Cluster's mass is 1.2 out to 8 degrees of the cluster's center or a radius of about 2.2 Mpc. Many of the brighter galaxies in this cluster, including the giant elliptical galaxy Messier 87, were discovered in the late 1770s and early 1780s and subsequently included in Charles Messier's catalogue of non-cometary fuzzy objects. Described by Messier as nebulae without stars, their true nature was not recognized until the 1920s. The cluster subtends a maximum arc of approximately 8 degrees centered in the constellati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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NGC 4548
Messier 91 (also known as NGC 4548 or M91) is a barred spiral galaxy that is found in the south of Coma Berenices. It is in the local supercluster and is part of the Virgo Cluster of galaxies. It is about 63 million light-years away from our galaxy. It was the last of a group of eight "nebulae" – the term 'galaxy' only coming into use for these objects once it was realized in the 20th century that they were extragalactic – discovered by Charles Messier in 1781. It is the faintest object in the Messier catalog. Because of a bookkeeping error by Messier, M91 was for a long time one of the few missing entries in the Messier catalog, not matching any known object in the sky. It was not until 1969 that amateur astronomer William C. WilliamsWilliam C. WilliamsLetter Sky and Telescope, December 1969, p. 376. Accessed 13 April 2011 realized that M91 was NGC 4548,Students for the Exploration and Development of Spac Accessed online 14 April 2011 which was catalogued by William ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Andromeda Galaxy
The Andromeda Galaxy (IPA: ), also known as Messier 31, M31, or NGC 224 and originally the Andromeda Nebula, is a barred spiral galaxy with the diameter of about approximately from Earth and the nearest large galaxy to the Milky Way. The galaxy's name stems from the area of Earth's sky in which it appears, the constellation of Andromeda, which itself is named after the princess who was the wife of Perseus in Greek mythology. The virial mass of the Andromeda Galaxy is of the same order of magnitude as that of the Milky Way, at . The mass of either galaxy is difficult to estimate with any accuracy, but it was long thought that the Andromeda Galaxy is more massive than the Milky Way by a margin of some 25% to 50%. This has been called into question by a 2018 study that cited a lower estimate on the mass of the Andromeda Galaxy, combined with preliminary reports on a 2019 study estimating a higher mass of the Milky Way. The Andromeda Galaxy has a diameter of about , making it t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Large Magellanic Cloud
The Large Magellanic Cloud (LMC), or Nubecula Major, is a satellite galaxy of the Milky Way. At a distance of around 50 kiloparsecs (≈160,000 light-years), the LMC is the second- or third-closest galaxy to the Milky Way, after the Sagittarius Dwarf Spheroidal (16 kpc) and the possible dwarf irregular galaxy known as the Canis Major Overdensity. Based on the D25 isophote at the B-band (445 nm wavelength of light), the Large Magellanic Cloud is approximately across. It is roughly a hundredth as massive as the Milky WayMagellanic Cloud . ''''. 2009. Encyclopædia Britannica Online. 30 Aug. 2009. and is the fourth-largest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Universe
The universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development of the universe. According to this theory, space and time emerged together ago, and the universe has been expanding ever since the Big Bang. While the spatial size of the entire universe is unknown, it is possible to measure the size of the observable universe, which is approximately 93 billion light-years in diameter at the present day. Some of the earliest cosmological models of the universe were developed by ancient Greek and Indian philosophers and were geocentric, placing Earth at the center. Over the centuries, more precise astronomical observations led Nicolaus Copernicus to develop the heliocentric model with the Sun at the center of the Solar System. In developing the law of universal gravitation, Isaac Newton built upon Copernicus's work as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Interstellar Absorption Coefficient
Interstellar or Interstella may refer to: Space * Interstellar space ** Interstellar medium * Interstellar travel * Interstellar communication * Interstellar probe ** Interstellar Probe (spacecraft) (ISP), a NASA probe proposed in 2018 for launch in the 2030s. ** Interstellar Express (IHP), Chinese probes proposed in 2019 for launch in 2024. Art, entertainment, and media Films and soundtracks * '' Interstella 5555: The 5tory of the 5ecret 5tar 5ystem'', an animated film set to Daft Punk's album ''Discovery'' * ''Interstellar'' (film), a 2014 science fiction film directed by Christopher Nolan ** ''Interstellar'' (soundtrack), the soundtrack to the 2014 film ''Interstellar'' Music Groups * Intastella, a band in the second wave of the Manchester music scene * Interstellar (band), a Canadian rock band Albums *'' Interstellar Space,'' John Coltrane album * ''Interstellar: The String Quartet Tribute to Interpol'', an album by Vitamin String Quartet Songs * "Interstellar", a track f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Astronomy
Astronomy () is a natural science that studies astronomical object, celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and chronology of the Universe, evolution. Objects of interest include planets, natural satellite, moons, stars, nebulae, galaxy, galaxies, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates beyond atmosphere of Earth, Earth's atmosphere. Cosmology is a branch of astronomy that studies the universe as a whole. Astronomy is one of the oldest natural sciences. The early civilizations in recorded history made methodical observations of the night sky. These include the Babylonian astronomy, Babylonians, Greek astronomy, Greeks, Indian astronomy, Indians, Egyptian astronomy, Egyptians, Chinese astronomy, Chinese, Maya civilization, Maya, and many anc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |