1.
Stellar classification
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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 absorption lines, each line indicates an ion of a certain chemical element, with the line strength indicating the abundance of that ion. The relative abundance of the different ions varies with the temperature of the photosphere, the spectral class of a star is a short code summarizing the ionization state, giving an objective measure of the photospheres temperature and density. Most stars are classified under the Morgan–Keenan system using the letters O, B, A, F, G, K, and M. Each letter class is subdivided using a numeric digit with 0 being hottest and 9 being coolest. The sequence has been expanded with classes for other stars and star-like objects that do not fit in the system, such as class D for white dwarfs. In the MK system, a luminosity class is added to the class using Roman numerals. This is based on the width of absorption lines in the stars spectrum. The full spectral class for the Sun is then G2V, indicating a main-sequence star with a temperature around 5,800 K, the conventional color description takes into account only the peak of the stellar spectrum. This means that the assignment of colors of the spectrum can be misleading. There are no green, indigo, or violet stars, likewise, the brown dwarfs do not literally appear brown. The modern classification system is known as the Morgan–Keenan classification, each star is assigned a spectral class from the older Harvard spectral classification and a luminosity class using Roman numerals as explained below, forming the stars spectral type. The spectral classes O through M, as well as more specialized classes discussed later, are subdivided by Arabic numerals. For example, A0 denotes the hottest stars in the A class, fractional numbers are allowed, for example, the star Mu Normae is classified as O9.7. The Sun is classified as G2, the conventional color descriptions are traditional in astronomy, and represent colors relative to the mean color of an A-class star, which is considered to be white. The apparent color descriptions are what the observer would see if trying to describe the stars under a dark sky without aid to the eye, or with binoculars. However, most stars in the sky, except the brightest ones, red supergiants are cooler and redder than dwarfs of the same spectral type, and stars with particular spectral features such as carbon stars may be far redder than any black body. O-, B-, and A-type stars are called early type
2.
Leuschner Observatory
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Leuschner Observatory, originally called the Students Observatory, is an observatory jointly operated by the University of California, Berkeley and San Francisco State University. The observatory was built in 1886 on the Berkeley campus, for many years, it was directed by Armin Otto Leuschner, for whom the observatory was renamed in 1951. In 1965, it was relocated to its present home in Lafayette, California, in 2012, the physics and astronomy department of San Francisco State University became a partner. Presently, Leuschner Observatory has two operating telescopes, one is a 30-inch optical telescope, equipped with a CCD for observations in visible light and an infrared detector used for infrared astronomy. The other is a 12-foot radio dish used for a radio astronomy course. The observatory has used to perform professional astronomy research, such as orbit determination of small solar system bodies in the early 1900s. It has also served as a tool in the education of graduate and undergraduate students at UC Berkeley. Very quickly, the Students Observatory became seen as a ground for students studying astronomy. This contributed to the separation of the departments of engineering and astronomy in the mid-1890s. In 1898, Armin Otto Leuschner was appointed the director of the Students Observatory, during this time, the observatory became a center for the computation of the orbits of comets, minor planets, and satellites. Astronomer Simon Newcomb said that Leuschner organized the department and observatory into a school of astronomy. After he stepped down, the observatory was directed by a series of well regarded astronomers, including Otto Struve from 1950–59, the Students Observatory was renamed Leuschner Observatory by the Regents of the University of California in 1951 in honor of A. O. Leuschner. The Space Sciences Lab, which operates SETI, began operations in 1960 at Leuschner Observatory until a permanent home in the Berkeley hills was completed in 1966. In 1965, the observatory was relocated a short distance east of the Berkeley campus in the hills of Lafayette, California, in 1968, the observatory was equipped with a new 30-inch Ritchey-Chretien telescope built by Tinsley Laboratories. Since, the observatory has used as a testing ground for a variety of experiments and instruments. Leuschner Observatorys 30-inch telescope continues to be used in undergraduate astronomical instruction. In 2012, the physics and astronomy department of San Francisco State University bought into the 30-inch telescope, Leuschner Observatory houses two optical telescopes, one with a 30-inch diameter and the other with a 20-inch diameter. As of 2010, the 20-inch telescope is not usable, both optical telescopes are also outfitted with control systems which allow them be automated, meaning observations are made with minimal human intervention
3.
Constellation
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A constellation is formally defined as a region of the celestial sphere, with boundaries laid down by the International Astronomical Union. The constellation areas mostly had their origins in Western-traditional patterns of stars from which the constellations take their names, in 1922, the International Astronomical Union officially recognized the 88 modern constellations, which cover the entire sky. They began as the 48 classical Greek constellations laid down by Ptolemy in the Almagest, Constellations in the far southern sky are late 16th- and mid 18th-century constructions. 12 of the 88 constellations compose the zodiac signs, though the positions of the constellations only loosely match the dates assigned to them in astrology. The term constellation can refer to the stars within the boundaries of that constellation. Notable groupings of stars that do not form a constellation are called asterisms, when astronomers say something is “in” a given constellation they mean it is within those official boundaries. Any given point in a coordinate system can unambiguously be assigned to a single constellation. Many astronomical naming systems give the constellation in which an object is found along with a designation in order to convey a rough idea in which part of the sky it is located. For example, the Flamsteed designation for bright stars consists of a number, the word constellation seems to come from the Late Latin term cōnstellātiō, which can be translated as set of stars, and came into use in English during the 14th century. It also denotes 88 named groups of stars in the shape of stellar-patterns, the Ancient Greek word for constellation was ἄστρον. Colloquial usage does not draw a distinction between constellation in the sense of an asterism and constellation in the sense of an area surrounding an asterism. The modern system of constellations used in astronomy employs the latter concept, the term circumpolar constellation is used for any constellation that, from a particular latitude on Earth, never sets below the horizon. From the North Pole or South Pole, all constellations south or north of the equator are circumpolar constellations. In the equatorial or temperate latitudes, the term equatorial constellation has sometimes been used for constellations that lie to the opposite the circumpolar constellations. They generally include all constellations that intersect the celestial equator or part of the zodiac, usually the only thing the stars in a constellation have in common is that they appear near each other in the sky when viewed from the Earth. In galactic space, the stars of a constellation usually lie at a variety of distances, since stars also travel on their own orbits through the Milky Way, the star patterns of the constellations change slowly over time. After tens to hundreds of thousands of years, their familiar outlines will become unrecognisable, the terms chosen for the constellation themselves, together with the appearance of a constellation, may reveal where and when its constellation makers lived. The earliest direct evidence for the constellations comes from inscribed stones and it seems that the bulk of the Mesopotamian constellations were created within a relatively short interval from around 1300 to 1000 BC
4.
Virgo (constellation)
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Virgo is one of the constellations of the zodiac. Its name is Latin for virgin, and its symbol is ♍, lying between Leo to the west and Libra to the east, it is the second largest constellation in the sky. It can be found through its brightest star, Spica. The bright Spica makes it easy to locate Virgo, as it can be found by following the curve of the Big Dipper/Plough to Arcturus in Boötes and continuing from there in the same curve. Due to the effects of precession, the First Point of Libra and this is one of the two points in the sky where the celestial equator crosses the ecliptic This point will pass into the neighbouring constellation of Leo around the year 2440. Besides Spica, other stars in Virgo include β Virginis, γ Vir, δ Virginis. Other fainter stars that were given names are ζ Virginis, η Virginis, ι Virginis. The star 70 Virginis has one of the first known extrasolar planetary systems with one confirmed planet 7.5 times the mass of Jupiter, the star Chi Virginis has one of the most massive planets ever detected, at a mass of 11.1 times that of Jupiter. The sun-like star 61 Virginis has three planets, one is a super-Earth and two are Neptune-mass planets, SS Virginis is a variable star with a noticeable red color. It varies in magnitude from a minimum of 9.6 to a maximum of 6.0 over a period of one year. There are 35 verified exoplanets orbiting 29 stars in Virgo, including PSR B1257+12,70 Virginis, Chi Virginis,61 Virginis, NY Virginis, and 59 Virginis. Because of the presence of a cluster within its borders 5° to 12° west of ε Vir. Some examples are Messier 49, Messier 58, Messier 59, Messier 60, Messier 61, Messier 84, Messier 86, Messier 87, Messier 89, a noted galaxy that is not part of the cluster is the Sombrero Galaxy, an unusual spiral galaxy. It is located about 10° due west of Spica, NGC4639 is a face-on barred spiral galaxy located 78 Mly from Earth. Its outer arms have a number of Cepheid variables, which are used as standard candles to determine astronomical distances. Because of this, astronomers used several Cepheid variables in NGC4639 to calibrate type 1a supernovae as standard candles for more distant galaxies, Virgo possesses several galaxy clusters, one of which is HCG62. A Hickson Compact Group, HCG62 is at a distance of 200 Mly from Earth and it has a heterogeneous halo of extremely hot gas, posited to be due to the active galactic nucleus at the core of the central elliptical galaxy. M87 is the largest galaxy in the Virgo cluster, and is at a distance of 60 Mly from Earth and it is a major radio source, partially due to its jet of electrons being flung out of the galaxy by its central supermassive black hole
5.
Right ascension
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Right ascension is the angular distance measured eastward along the celestial equator from the vernal equinox to the hour circle of the point in question. When combined with declination, these astronomical coordinates specify the direction of a point on the sphere in the equatorial coordinate system. Right ascension is the equivalent of terrestrial longitude. Both right ascension and longitude measure an angle from a direction on an equator. Right ascension is measured continuously in a circle from that equinox towards the east. Any units of measure could have been chosen for right ascension, but it is customarily measured in hours, minutes. Astronomers have chosen this unit to measure right ascension because they measure a stars location by timing its passage through the highest point in the sky as the Earth rotates. The highest point in the sky, called meridian, is the projection of a line onto the celestial sphere. A full circle, measured in units, contains 24 × 60 × 60 = 86 400s, or 24 × 60 = 1 440m. Because right ascensions are measured in hours, they can be used to time the positions of objects in the sky. For example, if a star with RA = 01h 30m 00s is on the meridian, sidereal hour angle, used in celestial navigation, is similar to right ascension, but increases westward rather than eastward. Usually measured in degrees, it is the complement of right ascension with respect to 24h and it is important not to confuse sidereal hour angle with the astronomical concept of hour angle, which measures angular distance of an object westward from the local meridian. The Earths axis rotates slowly westward about the poles of the ecliptic and this effect, known as precession, causes the coordinates of stationary celestial objects to change continuously, if rather slowly. Therefore, equatorial coordinates are inherently relative to the year of their observation, coordinates from different epochs must be mathematically rotated to match each other, or to match a standard epoch. The right ascension of Polaris is increasing quickly, the North Ecliptic Pole in Draco and the South Ecliptic Pole in Dorado are always at right ascension 18h and 6h respectively. The currently used standard epoch is J2000.0, which is January 1,2000 at 12,00 TT, the prefix J indicates that it is a Julian epoch. Prior to J2000.0, astronomers used the successive Besselian Epochs B1875.0, B1900.0, the concept of right ascension has been known at least as far back as Hipparchus who measured stars in equatorial coordinates in the 2nd century BC. But Hipparchus and his successors made their star catalogs in ecliptic coordinates, the easiest way to do that is to use an equatorial mount, which allows the telescope to be aligned with one of its two pivots parallel to the Earths axis
6.
Declination
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In astronomy, declination is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declinations angle is measured north or south of the celestial equator, the root of the word declination means a bending away or a bending down. It comes from the root as the words incline and recline. Declination in astronomy is comparable to geographic latitude, projected onto the celestial sphere, points north of the celestial equator have positive declinations, while those south have negative declinations. Any units of measure can be used for declination, but it is customarily measured in the degrees, minutes. Declinations with magnitudes greater than 90° do not occur, because the poles are the northernmost and southernmost points of the celestial sphere, the Earths axis rotates slowly westward about the poles of the ecliptic, completing one circuit in about 26,000 years. This effect, known as precession, causes the coordinates of stationary celestial objects to change continuously, therefore, equatorial coordinates are inherently relative to the year of their observation, and astronomers specify them with reference to a particular year, known as an epoch. Coordinates from different epochs must be rotated to match each other. The currently used standard epoch is J2000.0, which is January 1,2000 at 12,00 TT, the prefix J indicates that it is a Julian epoch. Prior to J2000.0, astronomers used the successive Besselian Epochs B1875.0, B1900.0, the declinations of Solar System objects change very rapidly compared to those of stars, due to orbital motion and close proximity. This similarly occurs in the Southern Hemisphere for objects with less than −90° − φ. An extreme example is the star which has a declination near to +90°. Circumpolar stars never dip below the horizon, conversely, there are other stars that never rise above the horizon, as seen from any given point on the Earths surface. Generally, if a star whose declination is δ is circumpolar for some observer, then a star whose declination is −δ never rises above the horizon, as seen by the same observer. Likewise, if a star is circumpolar for an observer at latitude φ, neglecting atmospheric refraction, declination is always 0° at east and west points of the horizon. At the north point, it is 90° − |φ|, and at the south point, from the poles, declination is uniform around the entire horizon, approximately 0°. Non-circumpolar stars are visible only during certain days or seasons of the year, the Suns declination varies with the seasons. As seen from arctic or antarctic latitudes, the Sun is circumpolar near the summer solstice, leading to the phenomenon of it being above the horizon at midnight
7.
NGC 4526
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NGC4526 is a lenticular galaxy in the Virgo constellation that is seen nearly edge-on. The morphological classification is SAB0°, which indicates a structure with a weak bar across the center. It belongs to the Virgo cluster and is one of the brightest known lenticular galaxies, the inner nucleus of this galaxy displays a rise in stellar orbital motion that indicates the presence of a central dark mass. The best fit model for the motion of gas in the core region suggests there is a supermassive black hole with about 4. 5+4.2 −3. 0×108 times the mass of the Sun. This is the first object to have its mass estimated by measuring the rotation of gas molecules around its centre with an Astronomical interferometer. Supernova SN 1969E was discovered in this galaxy in 1969, reaching a magnitude of 16. In 1994, a Type 1a supernova was discovered two weeks before reaching peak brightness. Designated SN 1994D, it was caused by the explosion of a dwarf star composed of carbon. Black Eye Galaxy Lost Galaxy in Virgo
