4769 Castalia
Encyclopedia
| Orbit Orbit In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System... al characteristics |
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| Orbit type | Near-Earth, Venus-crosser asteroid Venus-crosser asteroid A Venus-crosser is an asteroid whose orbit crosses that of Venus. The known numbered Venus-crossers and outer-grazers are listed below .Venus also has a quasi-satellite, 2002 VE68... , Mars-crosser asteroid Mars-crosser asteroid A Mars-crosser is an asteroid whose orbit crosses that of Mars. The known numbered Mars-crossers are listed here. They include the two numbered Mars trojans 5261 Eureka and .... |
| Semimajor axis | 1.063 AU Astronomical unit An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance.... |
| Eccentricity | 0.4831 |
| Orbital period Orbital period The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of... |
1.10 year |
| Inclination Inclination Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit... |
8.89° |
| Physical characteristics | |
| Diameter Diameter In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle... |
1.8×0.8 km |
| Mass Mass Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:... |
5.0×1011 kg |
| Density Density The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight... |
2.1 g/cm³ |
| Rotation period | 4 h |
| Spectral class Asteroid spectral types Asteroids are assigned a type based on spectral shape, color, and sometimes albedo. These types are thought to correspond to an asteroid's surface composition... |
S S-type asteroid S-type asteroids are of a stony composition, hence the name. Approximately 17% of asteroids are of this type, making it the second most common after the C-type.-Characteristics:... |
| Albedo Albedo Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it... |
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| History | |
| Discoverer | E. F. Helin Eleanor F. Helin Eleanor Francis "Glo" Helin was an American astronomer. She was principal investigator of the Near Earth Asteroid Tracking program of NASA's Jet Propulsion Laboratory. Some sources give her name as Eleanor Kay Helin... , August 9, 1989 |
The asteroid 4769 Castalia (icon ; previously known by the provisional designation 1989 PB) was the first asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
to be modeled by radar imaging. It is an Apollo
Apollo asteroid
The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo, the first asteroid of this group to be discovered by Karl Wilhelm Reinmuth...
, Mars-
Mars-crosser asteroid
A Mars-crosser is an asteroid whose orbit crosses that of Mars. The known numbered Mars-crossers are listed here. They include the two numbered Mars trojans 5261 Eureka and ....
and Venus-crosser asteroid
Venus-crosser asteroid
A Venus-crosser is an asteroid whose orbit crosses that of Venus. The known numbered Venus-crossers and outer-grazers are listed below .Venus also has a quasi-satellite, 2002 VE68...
. It was discovered on August 9, 1989, by Eleanor F. Helin
Eleanor F. Helin
Eleanor Francis "Glo" Helin was an American astronomer. She was principal investigator of the Near Earth Asteroid Tracking program of NASA's Jet Propulsion Laboratory. Some sources give her name as Eleanor Kay Helin...
(Caltech) on photographic plates taken at Palomar Observatory
Palomar Observatory
Palomar Observatory is a privately owned observatory located in San Diego County, California, southeast of Pasadena's Mount Wilson Observatory, in the Palomar Mountain Range. At approximately elevation, it is owned and operated by the California Institute of Technology...
. It is named after Castalia
Castalia
Castalia , in Greek mythology, was a nymph whom Apollo transformed into a fountain at Delphi, at the base of Mount Parnassos, or at Mount Helicon. Castalia could inspire the genius of poetry to those who drank her waters or listened to their quiet sound; the sacred water was also used to clean the...
, a nymph
Nymph
A nymph in Greek mythology is a female minor nature deity typically associated with a particular location or landform. Different from gods, nymphs are generally regarded as divine spirits who animate nature, and are usually depicted as beautiful, young nubile maidens who love to dance and sing;...
in Greek mythology
Greek mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...
.
General information
Castalia's orbitOrbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
took it within eleven lunar distance
Lunar distance (astronomy)
In astronomy, a lunar distance is a measurement of the distance from the Earth to the Moon. The average distance from Earth to the Moon is 384,400 kilometers...
s of Earth, allowing it to be observed with radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
from the Arecibo Observatory
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
by Scott Hudson
Scott Hudson
Raymond Scott Hudson is a professor of electrical engineering and computer science at Washington State University. Hudson was educated at Caltech, where he received his bachelor's degree in engineering and applied science in 1985, his master's degree in electrical engineering in 1986, and his PhD...
(Washington State University
Washington State University
Washington State University is a public research university based in Pullman, Washington, in the Palouse region of the Pacific Northwest. Founded in 1890, WSU is the state's original and largest land-grant university...
) and Steven J. Ostro
Steven J. Ostro
Steven J. Ostro was an American scientist specializing in Radar Astronomy. He worked at NASA's Jet Propulsion Laboratory. Ostro led radar observations of numerous asteroids, as well as the moons of Jupiter and Saturn, Saturn's rings, and Mars and its satellites...
(JPL
Jet Propulsion Laboratory
Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...
). The data allowed Hudson et al. to produce a three-dimensional model
Mathematical model
A mathematical model is a description of a system using mathematical concepts and language. The process of developing a mathematical model is termed mathematical modeling. Mathematical models are used not only in the natural sciences and engineering disciplines A mathematical model is a...
of the object.
Castalia has a peanut shape, suggesting two ~800 m diameter pieces held together by their weak mutual gravity. Since then radar observations of other asteroids have found other contact binaries
Contact binary (asteroid)
In the study of asteroids, a contact binary is caused when two asteroids gravitate toward each other until they touch, forming an oddly-shaped single body. Asteroids suspected of being contact binaries include the unusually elongated 624 Hektor and the bilobated 216 Kleopatra and 4769 Castalia...
.