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1345 Potomac
1345 Potomac (), provisional designation , is a dark Hildian asteroid from the outermost regions of the asteroid belt, approximately in diameter. It was discovered on 4 February 1908, by American astronomer Joel Metcalf at the Taunton Observatory in Massachusetts, United States. The X-type asteroid has a rotation period of 11.4 hours. It was named for the Potomac River on which Washington, D.C. is located. Orbit and classification ''Potomac'' is member of the dynamical Hilda group, which stays in 3:2 orbital resonance with Jupiter. It is, however, not a member of the Hilda family but a non-family asteroid of the main belt's background population when applying the Hierarchical Clustering Method to its proper orbital elements. It orbits the Sun in the outermost asteroid belt at a distance of 3.3–4.7 AU once every 7 years and 12 months (2,910 days; semi-major axis of 3.99 AU). Its orbit has an eccentricity of 0.18 and an inclination of 11 ° with respect to t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Joel Hastings Metcalf
Joel Hastings Metcalf (January 4, 1866 – February 23, 1925) was an American astronomer, humanitarian and Minister (Christianity), minister. Reverend Metcalf graduated from Harvard Divinity School in 1892. He served as a Unitarianism, Unitarian minister in Burlington, Vermont and in Taunton, Massachusetts, Winchester, Massachusetts and Portland, Maine. He discovered or co-discovered several comets, including 23P/Brorsen-Metcalf and 97P/Metcalf-Brewington, and also 41 asteroids during 1905–1914, as credited by the Minor Planet Center. Two of his discoveries, the main-belt asteroids 726 Joëlla and 792 Metcalfia, were named in his honor. Bibliography See also References External links Joel Hastings Metcalf – Minister, Humanitarian, AstronomerMetcalf, Joel Hastings (1866-1925) {{DEFAULTSORT:Metcalf, Joel Hastings 1866 births 1925 deaths American astronomers Discoverers of asteroids Discoverers of comets Harvard Divinity School alumni People from Bu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asteroid Belt
The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, called asteroids or minor planets. This asteroid belt is also called the main asteroid belt or main belt to distinguish it from other asteroid populations in the Solar System such as near-Earth asteroids and trojan asteroids. The asteroid belt is the smallest and innermost known circumstellar disc in the Solar System. About 60% of its mass is contained in the four largest asteroids: Ceres, Vesta, Pallas, and Hygiea. The total mass of the asteroid belt is calculated to be 3% that of the Moon. Ceres, the only object in the asteroid belt large enough to be a dwarf planet, is about 950 km in diameter, whereas Vesta, Pallas, and Hygiea have mean diameters less than 600 km. The remaining bodies range down to the size of a dust particle. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United States Naval Observatory
United States Naval Observatory (USNO) is a scientific and military facility that produces geopositioning, navigation and timekeeping data for the United States Navy and the United States Department of Defense. Established in 1830 as the Depot of Charts and Instruments, it is one of the oldest scientific agencies in the United States, and remains the country's leading authority for astronomical and timing data for all purposes. The observatory is located in Northwest Washington, D.C. at the northwestern end of Embassy Row. It is among the few pre-20th century astronomical observatories located in an urban area; initially located in Foggy Bottom near the city's center, it was relocated to its current location in 1893 to escape light pollution. The USNO has conducted significant scientific studies throughout its history, including measuring the speed of light, observing solar eclipses, and discovering the moons of Mars. Its achievements including providing data for the first ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Observation Arc
In observational astronomy, the observation arc (or arc length) of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly used in the discovery and tracking of asteroids and comets. Arc length has the greatest influence on the accuracy of an orbit. The number and spacing of intermediate observations has a lesser effect. Short arcs A very short arc leaves a high uncertainty parameter. The object might be in one of many different orbits, at many distances from Earth. In some cases, the initial arc was too short to determine if the object was in orbit around the Earth, or orbiting out in the asteroid belt. With a 1-day observation arc, was thought to be a trans-Neptunian dwarf planet, but is now known to be a 1 km main-belt asteroid. With an observation arc of 3 days, was thought to be a Mars-crossing asteroid that could be a threat to Earth, but was later ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ecliptic
The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic against the background of stars. The ecliptic is an important reference plane and is the basis of the ecliptic coordinate system. Sun's apparent motion The ecliptic is the apparent path of the Sun throughout the course of a year. Because Earth takes one year to orbit the Sun, the apparent position of the Sun takes one year to make a complete circuit of the ecliptic. With slightly more than 365 days in one year, the Sun moves a little less than 1° eastward every day. This small difference in the Sun's position against the stars causes any particular spot on Earth's surface to catch up with (and stand directly north or south of) the Sun about four minutes later each day than it would if Earth did not orbit; a day on Earth is therefore 24 hours ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Inclination
Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Earth directly above the Equator, the plane of the satellite's orbit is the same as the Earth's equatorial plane, and the satellite's orbital inclination is 0°. The general case for a circular orbit is that it is tilted, spending half an orbit over the northern hemisphere and half over the southern. If the orbit swung between 20° north latitude and 20° south latitude, then its orbital inclination would be 20°. Orbits The inclination is one of the six orbital elements describing the shape and orientation of a celestial orbit. It is the angle between the orbital plane and the plane of reference, normally stated in degrees. For a satellite orbiting a planet, the plane of reference is usually the plane containing the planet's equator. For pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Eccentricity
In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values between 0 and 1 form an elliptic orbit, 1 is a parabolic escape orbit (or capture orbit), and greater than 1 is a hyperbola. The term derives its name from the parameters of conic sections, as every Kepler orbit is a conic section. It is normally used for the isolated two-body problem, but extensions exist for objects following a rosette orbit through the Galaxy. Definition In a two-body problem with inverse-square-law force, every orbit is a Kepler orbit. The eccentricity of this Kepler orbit is a non-negative number that defines its shape. The eccentricity may take the following values: * circular orbit: ''e'' = 0 * elliptic orbit: 0 < ''e'' < 1 * [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semi-major Axis
In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the longest semidiameter or one half of the major axis, and thus runs from the centre, through a focus, and to the perimeter. The semi-minor axis (minor semiaxis) of an ellipse or hyperbola is a line segment that is at right angles with the semi-major axis and has one end at the center of the conic section. For the special case of a circle, the lengths of the semi-axes are both equal to the radius of the circle. The length of the semi-major axis of an ellipse is related to the semi-minor axis's length through the eccentricity and the semi-latus rectum \ell, as follows: The semi-major axis of a hyperbola is, depending on the convention, plus or minus one half of the distance between the two branches. Thus it is the distance from the center ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proper Orbital Elements
__NOTOC__ The proper orbital elements or proper elements of an orbit are constants of motion of an object in space that remain practically unchanged over an astronomically long timescale. The term is usually used to describe the three quantities: *''proper semimajor axis'' (''ap''), *''proper eccentricity'' (''ep''), and *''proper inclination'' (''ip''). The proper elements can be contrasted with the osculating Keplerian orbital elements observed at a particular time or epoch, such as the semi-major axis, eccentricity, and inclination. Those osculating elements change in a quasi-periodic and (in principle) predictable manner due to such effects as perturbations from planets or other bodies, and precession (e.g. perihelion precession). In the Solar System, such changes usually occur on timescales of thousands of years, while proper elements are meant to be practically constant over at least tens of millions of years. For most bodies, the osculating elements are relatively close ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hierarchical Clustering Method (asteroids)
An asteroid family is a population of asteroids that share similar proper orbital elements, such as semimajor axis, eccentricity, and orbital inclination. The members of the families are thought to be fragments of past asteroid collisions. An asteroid family is a more specific term than asteroid group whose members, while sharing some broad orbital characteristics, may be otherwise unrelated to each other. General properties Large prominent families contain several hundred recognized asteroids (and many more smaller objects which may be either not-yet-analyzed, or not-yet-discovered). Small, compact families may have only about ten identified members. About 33% to 35% of asteroids in the main belt are family members. There are about 20 to 30 reliably recognized families, with several tens of less certain groupings. Most asteroid families are found in the main asteroid belt, although several family-like groups such as the Pallas family, Hungaria family, and the Phocaea family ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asteroid Family
An asteroid family is a population of asteroids that share similar proper orbital elements, such as semimajor axis, eccentricity, and orbital inclination. The members of the families are thought to be fragments of past asteroid collisions. An asteroid family is a more specific term than asteroid group whose members, while sharing some broad orbital characteristics, may be otherwise unrelated to each other. General properties Large prominent families contain several hundred recognized asteroids (and many more smaller objects which may be either not-yet-analyzed, or not-yet-discovered). Small, compact families may have only about ten identified members. About 33% to 35% of asteroids in the main belt are family members. There are about 20 to 30 reliably recognized families, with several tens of less certain groupings. Most asteroid families are found in the main asteroid belt, although several family-like groups such as the Pallas family, Hungaria family, and the Phocaea family ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hilda Family
The Hilda asteroids (adj. ''Hildian'') are a dynamical group of more than 5,000 asteroids located beyond the asteroid belt but within Jupiter's orbit, in a 3:2 orbital resonance with Jupiter. The namesake is the asteroid 153 Hilda. Hildas move in their elliptical orbits in such a fashion that they arrive closest to Jupiter's orbit (i.e. at their aphelion) just when either one of Jupiter's , or Lagrange points arrives there. On their next orbit their aphelion will synchronize with the next Lagrange point in the –– sequence. Since , and are 120° apart, by the time a Hilda completes an orbit, Jupiter will have completed 360° − 120° or two-thirds of its own orbit. A Hilda's orbit has a semi-major axis between 3.7 and 4.2 AU (the average over a long time span is 3.97), an eccentricity less than 0.3, and an inclination less than 20°. Two collisional families exist within the Hilda group: the Hilda family and the Schubart family. The namesake for the latter fa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
