Dwarf planet
A dwarf planet is a planetary-mass object, neither a true planet nor a natural satellite. That is, it is in direct orbit of a star, is massive enough for its gravity to compress it into a hydrostatically equilibrious shape, but has not cleared the neighborhood of other material around its orbit; the term dwarf planet was adopted in 2006 as part of a three-way categorization of bodies orbiting the Sun, brought about by an increase in discoveries of objects farther away from the Sun than Neptune that rivaled Pluto in size, precipitated by the discovery of an more massive object, Eris. The exclusion of dwarf planets from the roster of planets by the IAU has been both praised and criticized; as of July 2008 the International Astronomical Union recognizes five dwarf planets: Ceres in the asteroid belt, Pluto, Haumea and Eris in the outer Solar System. Only two of these bodies and Pluto, have been observed in enough detail to demonstrate that they fit the IAU's definition; the IAU accepted Eris as a dwarf planet.
They subsequently decided that unnamed trans-Neptunian objects with an absolute magnitude brighter than +1 are to be named under the assumption that they are dwarf planets. At the time, the only additional bodies to meet this secondary criterion were Makemake. Starting in 1801, astronomers discovered Ceres and other bodies between Mars and Jupiter which were for decades considered to be planets. Between and around 1851, when the number of planets had reached 23, astronomers started using the word asteroid for the smaller bodies and stopped naming or classifying them as planets. With the discovery of Pluto in 1930, most astronomers considered the Solar System to have nine planets, along with thousands of smaller bodies. For 50 years Pluto was thought to be larger than Mercury, but with the discovery in 1978 of Pluto's moon Charon, it became possible to measure Pluto's mass and to determine that it was much smaller than initial estimates, it was one-twentieth the mass of Mercury, which made Pluto by far the smallest planet.
Although it was still more than ten times as massive as the largest object in the asteroid belt, Ceres, it had one-fifth the mass of Earth's Moon. Furthermore, having some unusual characteristics, such as large orbital eccentricity and a high orbital inclination, it became evident that it was a different kind of body from any of the other planets. In the 1990s, astronomers began to find objects in the same region of space as Pluto, some farther away. Many of these shared several of Pluto's key orbital characteristics, Pluto started being seen as the largest member of a new class of objects, plutinos; this led. Several terms, including subplanet and planetoid, started to be used for the bodies now known as dwarf planets. By 2005, three trans-Neptunian objects comparable in size to Pluto had been reported, it became clear that either they would have to be classified as planets, or Pluto would have to be reclassified. Astronomers were confident that more objects as large as Pluto would be discovered, the number of planets would start growing if Pluto were to remain a planet.
Eris was discovered in January 2005. As a consequence, the issue became a matter of intense debate during the IAU General Assembly in August 2006; the IAU's initial draft proposal included Charon and Ceres in the list of planets. After many astronomers objected to this proposal, an alternative was drawn up by the Uruguayan astronomers Julio Ángel Fernández and Gonzalo Tancredi: they proposed an intermediate category for objects large enough to be round but which had not cleared their orbits of planetesimals. Dropping Charon from the list, the new proposal removed Pluto and Eris, because they have not cleared their orbits; the IAU's final Resolution 5A preserved this three-category system for the celestial bodies orbiting the Sun. It reads: Although concerns were raised about the classification of planets orbiting other stars, the issue was not resolved; the term dwarf planet has itself been somewhat controversial, as it could imply that these bodies are planets, much as dwarf stars are stars.
This is the conception of the Solar System. The older word planetoid has no such connotation, is used by astronomers for bodies that fit the IAU definition. Brown states that planetoid is "a good word", used for these bodies for years, that the use of the term dwarf planet for a non-planet is "dumb", but that it was motivated by an attempt by the IAU division III plenary session to reinstate Pluto as a planet in a second resolution. Indeed, the draft of Resolution 5A had called these median bodies planetoids, but the plenary session voted unanimously to change the name to dwarf planet; the second resolution, 5B, defined dwarf planets as a subtype of planet, as Stern had intended, distinguished from the other eight that were to be called "classical planets". Under this arrangement, the twelve planets of the rejected proposal were to be preserved in a distinction between eight classical planets and four dwarf planets. Resolution 5B was defeated in the same session; because of the semantic inconsistenc
President's Award for Distinguished Federal Civilian Service
Established by President Dwight D. Eisenhower on 27 June 1957 by Executive Order 10717, the President's Award for Distinguished Federal Civilian Service was created to allow the President to recognize civilian officers or employees of the federal government who have made contributions "so outstanding that the officer or employee is deserving of greater public recognition than that which can be accorded by the head of the department or agency in which he is employed." President John F. Kennedy in Executive Order 10979 directed that potential recipients of the award are recommended to the President by the Distinguished Civilian Service Awards Board, who had responsibility for recommending people to be awarded the Presidential Medal of Freedom. Executive Order 12014, by Jimmy Carter abolished the Distinguished Civilian Service Awards Board and turned over the responsibility for recommending recipients to the Chairman of the United States Civil Service Commission; this executive order was subsequently modified again by Jimmy Carter in Executive Order 12107 which named the Director of the Office of Personnel Management as the person responsible for making recommendations to the President.
The President's Award for Distinguished Federal Civilian Service is the highest honorary award that the Federal Government can grant a career civilian employee. President Kennedy limited the award to only five people per year. Awards and decorations of the United States government
Comet nucleus
The nucleus is the solid, central part of a comet, popularly termed a dirty snowball or an icy dirtball. A cometary nucleus is composed of rock and frozen gases; when heated by the Sun, the gases sublimate and produce an atmosphere surrounding the nucleus known as the coma. The force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous tail to form, which points away from the Sun. A typical comet nucleus has an albedo of 0.04. This is blacker than coal, may be caused by a covering of dust. Results from the Rosetta and Philae spacecraft show that the nucleus of 67P/Churyumov–Gerasimenko has no magnetic field, which suggests that magnetism may not have played a role in the early formation of planetesimals. Further, the ALICE spectrograph on Rosetta determined that electrons produced from photoionization of water molecules by solar radiation, not photons from the Sun as thought earlier, are responsible for the degradation of water and carbon dioxide molecules released from the comet nucleus into its coma.
On 30 July 2015, scientists reported that the Philae spacecraft, that landed on comet 67P/Churyumov-Gerasimenko in November 2014, detected at least 16 organic compounds, of which four were detected for the first time on a comet. Comets, or their precursors, formed in the outer Solar System millions of years before planet formation. How and when comets formed is debated, with distinct implications for Solar System formation and geology. Three-dimensional computer simulations indicate the major structural features observed on cometary nuclei can be explained by pairwise low velocity accretion of weak cometesimals; the favored creation mechanism is that of the nebular hypothesis, which states that comets are a remnant of the original planetesimal "building blocks" from which the planets grew. Astronomers think that comets originate in both the scattered disk. Most cometary nuclei are thought to be no more than about 16 kilometers across; the largest comets that have come inside the orbit of Saturn are C/2002 VQ94, Hale–Bopp, 29P, 109P/Swift–Tuttle, 28P/Neujmin.
The potato-shaped nucleus of Halley's comet contains equal amounts of dust. During a flyby in September 2001, the Deep Space 1 spacecraft observed the nucleus of Comet Borrelly and found it to be about half the size of the nucleus of Halley's Comet. Borrelly's nucleus was potato-shaped and had a dark black surface. Like Halley's Comet, Comet Borrelly only released gas from small areas where holes in the crust exposed the ice to sunlight; the nucleus of comet Hale–Bopp was estimated to be 60 ± 20 km in diameter. Hale-Bopp appeared bright to the unaided eye because its unusually large nucleus gave off a great deal of dust and gas; the nucleus of P/2007 R5 is only 100–200 meters in diameter. The largest centaurs are estimated to be 250 km to 300 km in diameter. Three of the largest would include 10199 Chariklo, 2060 Chiron, the lost 1995 SN55. Known comets have been estimated to have an average density of 0.6 g/cm3. Below is a list of comets that have had estimated sizes and masses. About 80% of the Halley's Comet nucleus is water ice, frozen carbon monoxide makes up another 15%.
Much of the remainder is frozen carbon dioxide and ammonia. Scientists think; the nucleus of Halley's Comet is an dark black. Scientists think that the surface of the comet, most other comets, is covered with a black crust of dust and rock that covers most of the ice; these comets release gas only when holes in this crust rotate toward the Sun, exposing the interior ice to the warming sunlight. The composition of water vapor from Churyumov–Gerasimenko comet, as determined by the Rosetta mission, is different from that found on Earth; the ratio of deuterium to hydrogen in the water from the comet was determined to be three times that found for terrestrial water. This makes it unlikely. On 67P/Churyumov–Gerasimenko comet, some of the resulting water vapour may escape from the nucleus, but 80% of it recondenses in layers beneath the surface; this observation implies that the thin ice-rich layers exposed close to the surface may be a consequence of cometary activity and evolution, that global layering does not occur early in the comet's formation history.
Measurements carried out by the Philae lander on 67P/Churyumov–Gerasimenko comet, indicate that the dust layer could be as much as 20 cm thick. Beneath, hard ice, or a mixture of ice and dust. Porosity appears to increase toward the center of the comet. While most scientists thought that all the evidence indicated that the structure of nuclei of comets is processed rubble piles of smaller ice planetesimals of a previous generation, the Rosetta mission dispelled the idea that comets are "rubble piles" of disparate material; the nucleus of some comets may be fragile, a conclusion supported by the observation of comets splitting apart. Splitting comets include 3D/Biela in 1846, Shoemaker–Levy 9 in 1992, 73P/Schwassmann–Wachmann from 1995 to 2006. Greek historian Ephorus reported that a comet split apart as far back as the winter of 372–373 BC. Comets are suspected of splitting due to internal gas pressure, or impact. Comets 42P/Neujmin and 53P/Van Biesbroeck appear to be fragments of a parent comet.
Numerical integrations have shown that both comets h
Sputnik 1
Sputnik 1 was the first artificial Earth satellite. The Soviet Union launched it into an elliptical low Earth orbit on 4 October 1957, orbiting for three weeks before its batteries died silently for two more months before falling back into the atmosphere, it was a 58 cm diameter polished metal sphere, with four external radio antennas to broadcast radio pulses. Its radio signal was detectable by radio amateurs, the 65° inclination and duration of its orbit made its flight path cover the entire inhabited Earth; this surprise success precipitated the American Sputnik crisis and triggered the Space Race, a part of the Cold War. The launch was the beginning of a new era of political, military and scientific developments. Tracking and studying Sputnik 1 from Earth provided scientists with valuable information; the density of the upper atmosphere could be deduced from its drag on the orbit, the propagation of its radio signals gave data about the ionosphere. Sputnik 1 was launched during the International Geophysical Year from Site No.1/5, at the 5th Tyuratam range, in Kazakh SSR.
The satellite travelled at about 29,000 kilometres per hour, taking 96.2 minutes to complete each orbit. It transmitted on 20.005 and 40.002 MHz, which were monitored by radio operators throughout the world. The signals continued for 21 days until the transmitter batteries ran out on 26 October 1957. Sputnik burned up on 4 January 1958 while reentering Earth's atmosphere, after three months, 1440 completed orbits of the Earth, a distance travelled of about 70 million km. On 17 December 1954, chief Soviet rocket scientist Sergei Korolev proposed a developmental plan for an artificial satellite to the Minister of the Defence Industry, Dimitri Ustinov. Korolev forwarded a report with an overview of similar projects abroad. Tikhonravov had emphasized that the launch of an orbital satellite was an inevitable stage in the development of rocket technology. On 29 July 1955, U. S. President Dwight D. Eisenhower announced through his press secretary that, during the International Geophysical Year, the United States would launch an artificial satellite.
A week on 8 August, the Politburo of the Communist Party of the Soviet Union approved the proposal to create an artificial satellite. On 30 August Vasily Ryabikov – the head of the State Commission on the R-7 rocket test launches – held a meeting where Korolev presented calculation data for a spaceflight trajectory to the Moon, they decided to develop a three-stage version of the R-7 rocket for satellite launches. On 30 January 1956 the Council of Ministers approved practical work on an artificial Earth-orbiting satellite; this satellite, named Object D, was planned to be completed in 1957–58. The first test launch of "Object D" was scheduled for 1957. Work on the satellite was to be divided among institutions as follows: the USSR Academy of Sciences was responsible for the general scientific leadership and the supply of research instruments the Ministry of the Defence Industry and its primary design bureau, OKB-1, were assigned the task of building the satellite the Ministry of the Radiotechnical Industry would develop the control system, radio/technical instruments, the telemetry system the Ministry of the Ship Building Industry would develop gyroscope devices the Ministry of the Machine Building would develop ground launching and transportation means the Ministry of the Defense was responsible for conducting launchesPreliminary design work was completed in July 1956 and the scientific tasks to be carried out by the satellite were defined.
These included measuring the density of the atmosphere and its ion composition, the solar wind, magnetic fields, cosmic rays. These data would be valuable in the creation of future artificial satellites. A system of ground stations was to be developed to collect data transmitted by the satellite, observe the satellite's orbit, transmit commands to the satellite; because of the limited time frame, observations were planned for only 7 to 10 days and orbit calculations were not expected to be accurate. By the end of 1956 it became clear that the complexity of the ambitious design meant that'Object D' could not be launched in time because of difficulties creating scientific instruments and the low specific impulse produced by the completed R-7 engines; the government rescheduled the launch for April 1958. Object D would fly as Sputnik 3. Fearing the U. S. would launch a satellite before the USSR, OKB-1 suggested the creation and launch of a satellite in April–May 1957, before the IGY began in July 1957.
The new satellite would be simple and easy to construct, forgoing the complex, heavy scientific equipment in favour of a simple radio transmitter. On 15 February 1957 the Council of Ministers of the USSR approved this simple satellite, designated'Object PS'; this version allowed the satellite to be tracked visually by Earth-based observers, it could transmit tracking signals to ground-based receiving stations. The launch of two satellites, PS-1 and PS-2, with two R-7 rockets was approved, provided that the R-7 completed at least two successful test flights; the R-7 Semyorka was designed as an intercontinental ballistic missile by OKB-1. The decision to build it was made by the Central Committee of the Communist Party of the Soviet Union and the Council of Ministers of the USSR on 20 M
Harvard College Observatory
The Harvard College Observatory is an institution managing a complex of buildings and multiple instruments used for astronomical research by the Harvard University Department of Astronomy. It is located in Cambridge, Massachusetts, USA, was founded in 1839. With the Smithsonian Astrophysical Observatory, it forms part of the Harvard–Smithsonian Center for Astrophysics. HCO houses a collection of 500,000 astronomical plates taken between the mid-1880s and 1989; this 100-year coverage is a unique resource for studying temporal variations in the universe. The Digital Access to a Sky Century @ Harvard project is digitally scanning and archiving these photographic plates. In 1839, the Harvard Corporation voted to appoint William Cranch Bond, a prominent Boston clockmaker, as "Astronomical Observer to the University"; this marked the founding of the Harvard College Observatory. HCO's first telescope, the 15-inch Great Refractor, was installed in 1847; that telescope was the largest in the United States from installation until 1867.
Between 1847 and 1852 Bond and pioneer photographer John Adams Whipple used the Great Refractor telescope to produce images of the moon that are remarkable in their clarity of detail and aesthetic power. This was the largest telescope in North America at that time, their images of the moon took the prize for technical excellence in photography at the 1851 Great Exhibition at The Crystal Palace in London. On the night of July 16–17, 1850, Whipple and Bond made the first daguerreotype of a star. Harvard College Observatory is important to astronomy, as many women including Annie Jump Cannon, Henrietta Swan Leavitt, Cecilia Payne-Gaposchkin, Williamina Fleming performed pivotal stellar classification research. Cannon and Leavitt were hired as "computers" to perform calculations and examine stellar photographs, but made insightful connections in their research. From 1898 to 1926, a series of Bulletins were issued containing many of the major discoveries of the period; these were replaced by Announcement Cards which continued to be issued until 1952.
In 1908, the observatory published the Harvard Revised Photometry Catalogue, which gave rise to the HR star catalogue, now maintained by the Yale University Observatory as the Bright Star Catalogue. William Cranch Bond 1839–1859 George Phillips Bond 1859–1865 Joseph Winlock 1866–1875 Edward Charles Pickering 1877–1919 Solon Irving Bailey 1919–1921 Harlow Shapley 1921–1952 Donald H. Menzel 1952–1953. Field 1971–1972 Harvard Computers Sears Tower – Harvard Observatory The Minor Planet Center credits many asteroid discoveries to "Harvard Observatory." See List of largest optical refracting telescopes, for other'great refractors' Dava Sobel. The Glass Universe:. Viking. ISBN 978-0670016952. HCO home page Harvard-Smithsonian Center for Astrophysics Harvard College Observatory Bulletins Harvard College Announcement Cards
Astronomer
An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, moons and galaxies – in either observational or theoretical astronomy. Examples of topics or fields astronomers study include planetary science, solar astronomy, the origin or evolution of stars, or the formation of galaxies. Related but distinct subjects like physical cosmology. Astronomers fall under either of two main types: observational and theoretical. Observational astronomers analyze the data. In contrast, theoretical astronomers create and investigate models of things that cannot be observed; because it takes millions to billions of years for a system of stars or a galaxy to complete a life cycle, astronomers must observe snapshots of different systems at unique points in their evolution to determine how they form and die. They use these data to create models or simulations to theorize how different celestial objects work.
Further subcategories under these two main branches of astronomy include planetary astronomy, galactic astronomy, or physical cosmology. Astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using physical laws. Today, that distinction has disappeared and the terms "astronomer" and "astrophysicist" are interchangeable. Professional astronomers are educated individuals who have a Ph. D. in physics or astronomy and are employed by research institutions or universities. They spend the majority of their time working on research, although they quite have other duties such as teaching, building instruments, or aiding in the operation of an observatory; the number of professional astronomers in the United States is quite small. The American Astronomical Society, the major organization of professional astronomers in North America, has 7,000 members; this number includes scientists from other fields such as physics and engineering, whose research interests are related to astronomy.
The International Astronomical Union comprises 10,145 members from 70 different countries who are involved in astronomical research at the Ph. D. beyond. Contrary to the classical image of an old astronomer peering through a telescope through the dark hours of the night, it is far more common to use a charge-coupled device camera to record a long, deep exposure, allowing a more sensitive image to be created because the light is added over time. Before CCDs, photographic plates were a common method of observation. Modern astronomers spend little time at telescopes just a few weeks per year. Analysis of observed phenomena, along with making predictions as to the causes of what they observe, takes the majority of observational astronomers' time. Astronomers who serve as faculty spend much of their time teaching undergraduate and graduate classes. Most universities have outreach programs including public telescope time and sometimes planetariums as a public service to encourage interest in the field.
Those who become astronomers have a broad background in maths and computing in high school. Taking courses that teach how to research and present papers are invaluable. In college/university most astronomers get a Ph. D. in astronomy or physics. While there is a low number of professional astronomers, the field is popular among amateurs. Most cities have amateur astronomy clubs that meet on a regular basis and host star parties; the Astronomical Society of the Pacific is the largest general astronomical society in the world, comprising both professional and amateur astronomers as well as educators from 70 different nations. Like any hobby, most people who think of themselves as amateur astronomers may devote a few hours a month to stargazing and reading the latest developments in research. However, amateurs span the range from so-called "armchair astronomers" to the ambitious, who own science-grade telescopes and instruments with which they are able to make their own discoveries and assist professional astronomers in research.
List of astronomers List of women astronomers List of Muslim astronomers List of French astronomers List of Hungarian astronomers List of Russian astronomers and astrophysicists List of Slovenian astronomers Dallal, Ahmad. "Science and Technology". In Esposito, John; the Oxford History of Islam. Oxford University Press, New York. ISBN 0-300-15911-0. Kennedy, E. S.. "A Survey of Islamic Astronomical Tables. 46. Philadelphia: American Philosophical Society. Toomer, Gerald. "Al-Khwārizmī, Abu Jaʿfar Muḥammad ibn Mūsā". In Gillispie, Charles Coulston. Dictionary of Scientific Biography. 7. New York: Charles Scribner's Sons. ISBN 0-684-16962-2. American Astronomical Society European Astronomical Society International Astronomical Union Astronomical Society of the Pacific Space's astronomy news
Cambridge, Massachusetts
Cambridge is a city in Middlesex County and part of the Boston metropolitan area. Situated directly north of Boston, across the Charles River, it was named in honor of the University of Cambridge in England, an important center of the Puritan theology embraced by the town's founders. Harvard University and the Massachusetts Institute of Technology are in Cambridge, as was Radcliffe College, a college for women until it merged with Harvard on October 1, 1999. According to the 2010 Census, the city's population was 105,162; as of July 2014, it was the fifth most populous city in the state, behind Boston, Worcester and Lowell. Cambridge was one of two seats of Middlesex County until the county government was abolished in Massachusetts in 1997. In December 1630, the site of what would become Cambridge was chosen because it was safely upriver from Boston Harbor, making it defensible from attacks by enemy ships. Thomas Dudley, his daughter Anne Bradstreet, her husband Simon were among the town's first settlers.
The first houses were built in the spring of 1631. The settlement was referred to as "the newe towne". Official Massachusetts records show the name rendered as Newe Towne by 1632, as Newtowne by 1638. Located at the first convenient Charles River crossing west of Boston, Newe Towne was one of a number of towns founded by the 700 original Puritan colonists of the Massachusetts Bay Colony under Governor John Winthrop, its first preacher was Thomas Hooker, who led many of its original inhabitants west in 1636 to found Hartford and the Connecticut Colony. The original village site is now within Harvard Square; the marketplace where farmers sold crops from surrounding towns at the edge of a salt marsh remains within a small park at the corner of John F. Kennedy and Winthrop Streets; the town comprised a much larger area than the present city, with various outlying parts becoming independent towns over the years: Cambridge Village in 1688, Cambridge Farms in 1712 or 1713, Little or South Cambridge and Menotomy or West Cambridge in 1807.
In the late 19th century, various schemes for annexing Cambridge to Boston were pursued and rejected. In 1636, the Newe College was founded by the colony to train ministers. According to Cotton Mather, Newe Towne was chosen for the site of the college by the Great and General Court for its proximity to the popular and respected Puritan preacher Thomas Shepard. In May 1638, The settlement's name was changed to Cambridge in honor of the university in Cambridge, England. Newtowne's ministers and Shepard, the college's first president, major benefactor, the first schoolmaster Nathaniel Eaton were Cambridge alumni, as was the colony's governor John Winthrop. In 1629, Winthrop had led the signing of the founding document of the city of Boston, known as the Cambridge Agreement, after the university. In 1650, Governor Thomas Dudley signed the charter creating the corporation that still governs Harvard College. Cambridge grew as an agricultural village eight miles by road from Boston, the colony's capital.
By the American Revolution, most residents lived near the Common and Harvard College, with most of the town comprising farms and estates. Most inhabitants were descendants of the original Puritan colonists, but there was a small elite of Anglican "worthies" who were not involved in village life, made their livings from estates and trade, lived in mansions along "the Road to Watertown". Coming north from Virginia, George Washington took command of the volunteer American soldiers camped on Cambridge Common on July 3, 1775, now reckoned the birthplace of the U. S. Army. Most of the Tory estates were confiscated after the Revolution. On January 24, 1776, Henry Knox arrived with artillery captured from Fort Ticonderoga, which enabled Washington to drive the British army out of Boston. Between 1790 and 1840, Cambridge grew with the construction of the West Boston Bridge in 1792 connecting Cambridge directly to Boston, so that it was no longer necessary to travel eight miles through the Boston Neck and Brookline to cross the Charles River.
A second bridge, the Canal Bridge, opened in 1809 alongside the new Middlesex Canal. The new bridges and roads made what were estates and marshland into prime industrial and residential districts. In the mid-19th century, Cambridge was the center of a literary revolution, it was home to some of the famous Fireside Poets—so called because their poems would be read aloud by families in front of their evening fires. The Fireside Poets—Henry Wadsworth Longfellow, James Russell Lowell, Oliver Wendell Holmes—were popular and influential in their day. Soon after, turnpikes were built: the Cambridge and Concord Turnpike, the Middlesex Turnpike, what are today's Cambridge and Harvard Streets connected various areas of Cambridge to the bridges. In addition, the town was connected to the Boston & Maine Railroad, leading to the development of Porter Square as well as the creation of neighboring Somerville from the rural parts of Charlestown. Cambridge was incorporated as a city in 1846 despite persistent tensions between East Cambridge and Old Cambridge stemming from differences in culture, sources of income, the national origins of the resident
