The Antennae Galaxies known as NGC 4038/NGC 4039, are a pair of interacting galaxies in the constellation Corvus. They are going through a starburst phase, in which the collision of clouds of gas and dust, with entangled magnetic fields, causes rapid star formation, they were discovered by William Herschel in 1785. The Antennae Galaxies are undergoing a galactic collision. Located in the NGC 4038 group with five other galaxies, these two galaxies are known as the Antennae Galaxies because the two long tails of stars and dust ejected from the galaxies as a result of the collision resemble an insect's antennae; the nuclei of the two galaxies are joining to become one giant galaxy. Most galaxies undergo at least one significant collision in their lifetimes; this is the future of our Milky Way when it collides with the Andromeda Galaxy. Five supernovae have been discovered in NGC 4038: SN 1921A, SN 1974E, SN 2004GT, SN 2007sr and SN 2013dk. A recent study finds that these interacting galaxies are less remote from the Milky Way than thought—at 45 million light-years instead of 65 million light-years.
They are located 0.25 ° north of 3.25 ° southwest of Gamma Corvi. The Antennae galaxies contain a young collection of massive globular clusters that were formed as a result of the collision between the two galaxies; the young age of these clusters is in contrast to the average age of most known globular clusters, around 12 billion years old, with the formation of the globulars originating from shockwaves, generated by the collision of the galaxies, compressing large, massive molecular clouds. The densest regions of the collapsing and compressing clouds are believed to be the birthplace of the clusters. About 1.2 billion years ago, the Antennae were two separate galaxies. NGC 4038 was a barred spiral galaxy and NGC 4039 was a spiral galaxy. Before the galaxies collided, NGC 4039 was larger than NGC 4038. 900 million years ago, the Antennae began to approach one another, looking similar to NGC 2207 and IC 2163. 600 million years ago, the Antennae passed through each other. 300 million years ago, the Antennae's stars began to be released from both galaxies.
Today the two streamers of ejected stars extend far beyond the original galaxies, resulting in the antennae shape. Within 400 million years, the Antennae's nuclei will collide and become a single core with stars and dust around it. Observations and simulations of colliding galaxies suggest that the Antennae Galaxies will form an elliptical galaxy. Areas containing large amounts of neon and silicon were found when the Chandra X-ray Observatory analyzed the Antennae Galaxies; these elements are necessary in order for planets. The clouds imaged contain 24 times as much silicon as the Sun. Whirlpool Galaxy List of largest galaxies Astronomy Picture of the Day: The Antennae Galaxies Astronomy Picture of the Day: The Antennae Astronomy Picture of the Day: The Antennae Astronomy Picture of the Day: The Antennae The Register: Galactic prang fingered in star formation mystery ESA/Hubble News Release ESA/Hubble images of Antennae Galaxies Animations of galactic collision producing antennae structures Antennae Galaxies on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Sky Map and images Antennae Galaxies at Constellation Guide
Galaxy morphological classification
Galaxy morphological classification is a system used by astronomers to divide galaxies into groups based on their visual appearance. There are several schemes in use by which galaxies can be classified according to their morphologies, the most famous being the Hubble sequence, devised by Edwin Hubble and expanded by Gérard de Vaucouleurs and Allan Sandage; the Hubble sequence is a morphological classification scheme for galaxies invented by Edwin Hubble in 1926. It is known colloquially as the “Hubble tuning-fork” because of the shape in which it is traditionally represented. Hubble's scheme divides galaxies into three broad classes based on their visual appearance: Elliptical galaxies have smooth, featureless light distributions and appear as ellipses in images, they are denoted by the letter "E", followed by an integer n representing their degree of ellipticity on the sky. Spiral galaxies consist of a flattened disk, with stars forming a spiral structure, a central concentration of stars known as the bulge, similar in appearance to an elliptical galaxy.
They are given the symbol "S". Half of all spirals are observed to have a bar-like structure, extending from the central bulge; these barred spirals are given the symbol "SB". Lenticular galaxies consist of a bright central bulge surrounded by an extended, disk-like structure but, unlike spiral galaxies, the disks of lenticular galaxies have no visible spiral structure and are not forming stars in any significant quantity; these broad classes can be extended to enable finer distinctions of appearance and to encompass other types of galaxies, such as irregular galaxies, which have no obvious regular structure. The Hubble sequence is represented in the form of a two-pronged fork, with the ellipticals on the left and the barred and unbarred spirals forming the two parallel prongs of the fork. Lenticular galaxies are placed between the ellipticals and the spirals, at the point where the two prongs meet the “handle”. To this day, the Hubble sequence is the most used system for classifying galaxies, both in professional astronomical research and in amateur astronomy.
The de Vaucouleurs system for classifying galaxies is a used extension to the Hubble sequence, first described by Gérard de Vaucouleurs in 1959. De Vaucouleurs argued that Hubble's two-dimensional classification of spiral galaxies—based on the tightness of the spiral arms and the presence or absence of a bar—did not adequately describe the full range of observed galaxy morphologies. In particular, he argued that rings and lenses are important structural components of spiral galaxies; the de Vaucouleurs system retains Hubble's basic division of galaxies into ellipticals, lenticulars and irregulars. To complement Hubble's scheme, de Vaucouleurs introduced a more elaborate classification system for spiral galaxies, based on three morphological characteristics: The different elements of the classification scheme are combined — in the order in which they are listed — to give the complete classification of a galaxy. For example, a weakly barred spiral galaxy with loosely wound arms and a ring is denoted SABc.
Visually, the de Vaucouleurs system can be represented as a three-dimensional version of Hubble's tuning fork, with stage on the x-axis, family on the y-axis, variety on the z-axis. De Vaucouleurs assigned numerical values to each class of galaxy in his scheme. Values of the numerical Hubble stage T run from −6 to +10, with negative numbers corresponding to early-type galaxies and positive numbers to late types. Elliptical galaxies are divided into three'stages': compact ellipticals, normal ellipticals and late types. Lenticulars are subdivided into early and late types. Irregular galaxies can be of type magellanic irregulars or'compact'; the use of numerical stages allows for more quantitative studies of galaxy morphology. Created by American astronomer William Wilson Morgan. Together with Philip Keenan, Morgan developed the MK system for the classification of stars through their spectra; the Yerkes scheme uses the spectra of stars in the galaxy. Thus, for example, the Andromeda Galaxy is classified as kS5.
Morphological Catalogue of Galaxies Galaxy color–magnitude diagram Galaxy Zoo William Wilson Morgan Fritz Zwicky Galaxies and the Universe - an introduction to galaxy classification Near-Infrared Galaxy Morphology Atlas, T. H. Jarrett The Spitzer Infrared Nearby Galaxies Survey Hubble Tuning-Fork, SINGS Spitzer Space Telescope Legacy Science Project Go to GalaxyZoo.org to try your hand at classifying galaxies as part of an Oxford University open community project
Halton Christian "Chip" Arp was an American astronomer. He was known for his 1966 Atlas of Peculiar Galaxies, which catalogues many examples of interacting and merging galaxies, though Arp disputed the idea, claiming apparent associations were prime examples of ejections. Arp was known as a critic of the Big Bang theory and for advocating a non-standard cosmology incorporating intrinsic redshift. Arp was born on March 1927, in New York City, he was married three times, has four daughters and five grandchildren. His bachelor's degree was awarded by Harvard, his PhD by Caltech. Afterward he became a Fellow of the Carnegie Institution of Washington in 1953, performing research at the Mount Wilson Observatory and Palomar Observatory. Arp became a Research Assistant at Indiana University in 1955, in 1957 became a staff member at Palomar Observatory, where he worked for 29 years. In 1983 he joined the staff of the Max Planck Institute for Astrophysics in Germany, he died in Munich, Germany on December 28, 2013.
He was an atheist. Arp compiled a catalog of unusual galaxies titled Atlas of Peculiar Galaxies, first published in 1966. Arp realized that astronomers understood little about how galaxies change over time, which led him to work on this project; this atlas was intended to provide images that would give astronomers data from which they could study the evolution of galaxies. Arp used the atlas as evidence in his debate on quasi-stellar objects. Based on its citation by other astronomers, Arp's atlas is recognized now as an excellent compilation of interacting and merging galaxies. Many objects in the atlas are referred to by their Arp number. Many of these objects are used as spectral templates for studying high-redshift galaxies. Arp disputed the idea that the peculiar galaxies were merging, rather, that apparent associations were prime examples of ejections from a host galaxy. During the 1950s bright radio sources, now known as quasars, had been discovered that did not appear to have an optical counterpart.
In 1960 one of these sources, 3C 48, was found to be associated with what appeared to be a small blue star. When the spectrum of the star was measured, it contained unidentifiable spectral lines that defied all attempts at explanation. In 1963 Maarten Schmidt found a visible companion to the quasar 3C 273. Using the Hale telescope, Schmidt found the same odd spectra, but was able to demonstrate that it could be explained as the spectrum of hydrogen, shifted by a large 15.8% If this was due to the physical motion of the "star", it would represent a speed of 47,000 km/s, far beyond the speed of any known star and defying an obvious explanation. Schmidt noted that redshift is associated with the expansion of the universe, as codified in Hubble's law. If the measured redshift was due to expansion the object in question would have to be far away, therefore have an extraordinarily high luminosity beyond any object seen to date; this extreme luminosity would explain the large radio signal. Schmidt concluded quasars are distant luminous objects.
Schmidt's explanation for the high redshift was not universally accepted at the time. Another explanation, offered was that it was gravitational redshift, being measured. Several other mechanisms were proposed as well, each with their own problems. In 1966, Arp published the Atlas of Peculiar Galaxies, which contained photographs of 338 nearby galaxies that did not fall into any of the classic categories of galaxy shapes, his goal was to produce a selection that modellers could use in order to test theories of galactic formation. By testing against the collection, one could see how well a particular theory stood up. One group of these, numbers 1 through 101, were otherwise conventional galaxies that appeared to have small companion objects of unknown origin. In 1967 Arp noted. In some photographs a quasar is in the foreground of known galaxies, in others there appeared to be matter bridging the two objects, implying they are close in space. If they are, the redshifts were due to Hubble expansion both objects should have similar redshifts.
The galaxies had much smaller redshifts than the quasars. Arp noted that quasars were not evenly spread over the sky, but tended to be more found in positions of small angular separation from certain galaxies; this being the case, they might be in some way related to the galaxies. Arp argued that the redshift was not due to Hubble expansion or physical movement of the objects, but must have a non-cosmological or "intrinsic" origin, that quasars were local objects ejected from the core of active galactic nuclei. Nearby galaxies with both strong radio emission and peculiar morphologies M87 and Centaurus A, appeared to support Arp's hypothesis. Since the 1960s, telescopes and astronomical instrumentation have advanced greatly: the Hubble Space Telescope was launched, cosmological theory and observation has advanced considerably. Black holes and supermassive black holes have been directly as well as indirectly detected distant objects are studied and contextualized, multiple 8-10 meter telescopes have become operational, detectors such as CCDs are now more employed.
These developments, have led to quasars being understood to be distant active galaxies with high redshifts. Many imaging surveys, most notably the Hubble Deep Field, have found many high-reds
NGC 4030 is a grand design spiral galaxy located about 64 million light years away in the constellation Virgo. With an apparent visual magnitude of 10.6, it is visible with a small telescope as a 3 arc minute wide feature about 4.75° to the southeast of the star Beta Virginis. It is inclined by an angle of 47.1° to the line of sight from the Earth and is receding at a velocity of 1,465 km/s. The morphological classification of NGC 4030 in the De Vaucouleurs system is SAbc, which indicates a spiral structure with no bar and moderate to loosely wound arms; the inner part of the galaxy shows a complex structure with multiple spiral arms, which becomes a symmetric, double arm pattern beyond 49″ from the core. The central bulge is young with an estimated age of two billion years, while the nucleus is inactive. In 2007, a supernova explosion was discovered in the galaxy from images taken on February 19 from the 1 m Swope telescope at Las Campanas Observatory in Chile. Designated SN 2007aa, it was a type IIP supernova positioned 68″.5 north and 60″.8 east of the galactic nucleus.
The progenitor was a red giant star with 8.5–16.5 times the mass of the Sun
X-ray astronomy is an observational branch of astronomy which deals with the study of X-ray observation and detection from astronomical objects. X-radiation is absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, satellites. X-ray astronomy is the space science related to a type of space telescope that can see farther than standard light-absorption telescopes, such as the Mauna Kea Observatories, via x-ray radiation. X-ray emission is expected from astronomical objects that contain hot gases at temperatures from about a million kelvin to hundreds of millions of kelvin. Moreover, the maintenance of the E-layer of ionized gas high in the Earth's Thermosphere suggested a strong extraterrestrial source of X-rays. Although theory predicted that the Sun and the stars would be prominent X-ray sources, there was no way to verify this because Earth's atmosphere blocks most extraterrestrial X-rays, it was not until ways of sending instrument packages to high altitude were developed that these X-ray sources could be studied.
The existence of solar X-rays was confirmed early in the rocket age by V-2s converted to sounding rocket purpose, the detection of extraterrestrial X-rays has been the primary or secondary mission of multiple satellites since 1958. The first cosmic X-ray source was discovered by a sounding rocket in 1962. Called Scorpius X-1, the X-ray emission of Scorpius X-1 is 10,000 times greater than its visual emission, whereas that of the Sun is about a million times less. In addition, the energy output in X-rays is 100,000 times greater than the total emission of the Sun in all wavelengths. Many thousands of X-ray sources have since been discovered. In addition, the space between galaxies in galaxy clusters is filled with a hot, but dilute gas at a temperature between 10 and 100 megakelvins; the total amount of hot gas is five to ten times the total mass in the visible galaxies. The first sounding rocket flights for X-ray research were accomplished at the White Sands Missile Range in New Mexico with a V-2 rocket on January 28, 1949.
A detector was placed in the nose cone section and the rocket was launched in a suborbital flight to an altitude just above the atmosphere. X-rays from the Sun were detected by the U. S. Naval Research Laboratory Blossom experiment on board. An Aerobee 150 rocket was launched on June 12, 1962 and it detected the first X-rays from other celestial sources, it is now known that such X-ray sources as Sco X-1 are compact stars, such as neutron stars or black holes. Material falling into a black hole may emit X-rays; the energy source for the X-ray emission is gravity. Infalling gas and dust is heated by the strong gravitational fields of these and other celestial objects. Based on discoveries in this new field of X-ray astronomy, starting with Scorpius X-1, Riccardo Giacconi received the Nobel Prize in Physics in 2002; the largest drawback to rocket flights is their short duration and their limited field of view. A rocket launched from the United States will not be able to see sources in the southern sky.
In astronomy, the interstellar medium is the gas and cosmic dust that pervade interstellar space: the matter that exists between the star systems within a galaxy. It fills interstellar space and blends smoothly into the surrounding intergalactic medium; the interstellar medium consists of an dilute mixture of ions, molecules, larger dust grains, cosmic rays, magnetic fields. The energy that occupies the same volume, in the form of electromagnetic radiation, is the interstellar radiation field. Of interest is the hot ionized medium consisting of a coronal cloud ejection from star surfaces at 106-107 K which emits X-rays; the ISM is full of structure on all spatial scales. Stars are born deep inside large complexes of molecular clouds a few parsecs in size. During their lives and deaths, stars interact physically with the ISM. Stellar winds from young clusters of stars and shock waves created by supernovae inject enormous amounts of energy into their surroundings, which leads to hypersonic turbulence.
The resultant structures are stellar wind superbubbles of hot gas. The Sun is traveling through the Local Interstellar Cloud, a denser region in the low-density Local Bubble. To measure the spectrum of the diffuse X-ray emission from the interstellar medium over the energy range 0.07 to 1 keV, NASA launched a Black Brant 9 from White Sands Missile Range, New Mexico on May 1, 2008. The Principal Investigator for the mission is Dr. Dan McCammon of the University of Wisconsin–Madison. Balloon flights can carry instruments to altitudes of up to 40 km above sea level, where they are above as much as 99.997% of the Earth's atmosphere. Unlike a rocket where data are collected during a brief few minutes, balloons are able to stay aloft for much longer; however at such altitudes, much of the X-ray spectrum is still absorbed. X-rays with energies less than 35 keV cannot reach balloons. On July 21, 1964, the Crab Nebula supernova remnant was discovered to be a hard X-ray source by a scintillation counter flown on a balloon launched from Palestine, United States.
This was the first balloon-based detection of X-rays from a discrete cosmic X-ray source. The high-energy focusing telescope is a balloon-borne experiment to
New General Catalogue
The New General Catalogue of Nebulae and Clusters of Stars is a catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. It expands upon the cataloguing work of William and Caroline Herschel, John Herschel's General Catalogue of Nebulae and Clusters of Stars; the NGC contains 7,840 objects, known as the NGC objects. It is one of the largest comprehensive catalogues, as it includes all types of deep space objects, including galaxies, star clusters, emission nebulae and absorption nebulae. Dreyer published two supplements to the NGC in 1895 and 1908, known as the Index Catalogues, describing a further 5,386 astronomical objects. Objects in the sky of the southern hemisphere are catalogued somewhat less but many were observed by John Herschel or James Dunlop; the NGC had many errors, but an attempt to eliminate them was initiated by the NGC/IC Project in 1993, after partial attempts with the Revised New General Catalogue by Jack W. Sulentic and William G. Tifft in 1973, NGC2000.0 by Roger W. Sinnott in 1988.
The Revised New General Catalogue and Index Catalogue was compiled in 2009 by Wolfgang Steinicke. The original New General Catalogue was compiled during the 1880s by John Louis Emil Dreyer using observations from William Herschel and his son John, among others. Dreyer had published a supplement to Herschel's General Catalogue of Nebulae and Clusters, containing about 1,000 new objects. In 1886, he suggested building a second supplement to the General Catalogue, but the Royal Astronomical Society asked Dreyer to compile a new version instead; this led to the publication of the New General Catalogue in the Memoirs of the Royal Astronomical Society in 1888. Assembling the NGC was a challenge, as Dreyer had to deal with many contradicting and unclear reports, made with a variety of telescopes with apertures ranging from 2 to 72 inches. While he did check some himself, the sheer number of objects meant Dreyer had to accept them as published by others for the purpose of his compilation; the catalogue contained several errors relating to position and descriptions, but Dreyer referenced the catalogue, which allowed astronomers to review the original references and publish corrections to the original NGC.
The first major update to the NGC is the Index Catalogue of Nebulae and Clusters of Stars, published in two parts by Dreyer in 1895 and 1908. It serves as a supplement to the NGC, contains an additional 5,386 objects, collectively known as the IC objects, it summarizes the discoveries of galaxies and nebulae between 1888 and 1907, most of them made possible by photography. A list of corrections to the IC was published in 1912; the Revised New Catalogue of Nonstellar Astronomical Objects was compiled by Jack W. Sulentic and William G. Tifft in the early 1970s, was published in 1973, as an update to the NGC; the work did not incorporate several previously-published corrections to the NGC data, introduced some new errors. Nearly 800 objects are listed as "non-existent" in the RNGC; the designation is applied to objects which are duplicate catalogue entries, those which were not detected in subsequent observations, a number of objects catalogued as star clusters which in subsequent studies were regarded as coincidental groupings.
A 1993 monograph considered the 229 star clusters called non-existent in the RNGC. They had been "misidentified or have not been located since their discovery in the 18th and 19th centuries", it found that one of the 229—NGC 1498—was not in the sky. Five others were duplicates of other entries, 99 existed "in some form", the other 124 required additional research to resolve; as another example, reflection nebula NGC 2163 in Orion was classified "non-existent" due to a transcription error by Dreyer. Dreyer corrected his own mistake in the Index Catalogues, but the RNGC preserved the original error, additionally reversed the sign of the declination, resulting in NGC 2163 being classified as non-existent. NGC 2000.0 is a 1988 compilation of the NGC and IC made by Roger W. Sinnott, using the J2000.0 coordinates. It incorporates several errata made by astronomers over the years; the NGC/IC Project is a collaboration formed in 1993. It aims to identify all NGC and IC objects, collect images and basic astronomical data on them.
The Revised New General Catalogue and Index Catalogue is a compilation made by Wolfgang Steinicke in 2009. It is a authoritative treatment of the NGC and IC catalogues. Messier object Catalogue of Nebulae and Clusters of Stars Astronomical catalogue List of astronomical catalogues List of NGC objects The Interactive NGC Catalog Online Adventures in Deep Space: Challenging Observing Projects for Amateur Astronomers. Revised New General Catalogue