25 Phocaea () is a stony

asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

from the inner regions of the

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids ...

, approximately 75 kilometers in diameter. It is the parent body of the

Phocaea family The Phocaea family ( ; adj. ''Phocaean''; ) is a collisional family of asteroids located between 2.25 and 2.5 AU in the inner region of the asteroid belt. Phocaea asteroids are of stony S-type composition and have orbits with eccentricities ...

. Discovered by

Jean Chacornac Jean Chacornac (21 June 1823 – 23 September 1873) was a French astronomer and discoverer of a comet and several asteroids. He was born in Lyon and died in Saint-Jean-en-Royans, southeastern France. Working in Marseille and Paris, he discove ...

in 1853, it was named after the ancient Greek city of

Phocaea Phocaea or Phokaia (Ancient Greek language, Ancient Greek: Φώκαια, ''Phókaia''; modern-day Foça in Turkey) was an ancient Ionian Ancient Greece, Greek city on the western coast of Anatolia. Colonies in antiquity, Greek colonists from Phoc ...

Discovery and naming

''Phocaea'' was discovered on 6 April 1853, by French astronomer

Marseille Observatory Marseille Observatory () is an astronomical observatory located in Marseille, France, with a history that goes back to the early 18th century. In its 1877 incarnation, it was the discovery site of a group of galaxies known as Stephan's Quintet, ...

in southern France. It was his first

discovery out of a total of six. The asteroid was named after the ancient Ionian Greek city of

, modern-day

Foça Foça is a municipality and Districts of Turkey, district of İzmir Province, Turkey. Its area is 251 km2, and its population is 34,946 (2022). The town of Foça is situated at about northwest of İzmir's city center on the Aegean Sea, Aege ...

in Turkey, where the founders of

Marseille Marseille (; ; see #Name, below) is a city in southern France, the Prefectures in France, prefecture of the Departments of France, department of Bouches-du-Rhône and of the Provence-Alpes-Côte d'Azur Regions of France, region. Situated in the ...

came from. The naming was proposed by French astronomer

Benjamin Valz Jean Elias Benjamin Valz (May 27, 1787 – April 22, 1867) was a French astronomer. He was born in Nîmes and trained as an engineer. He was the son of politician Jean Valz and the grandson of the doctor, meteorologist and naturalist Pierre ...

Classification and orbit

''Phocaea'' is the

parent body A parent body in meteoritics is the celestial body from which originates a meteorite or a class of meteorites. Identification It is easiest to correlate a meteorite with a parent body when the parent body still exists. This is the case for Lun ...

and namesake of the

(), a large

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 ...

of stony asteroids in the inner main belt. It orbits the Sun at a distance of 1.8–3.0 AU once every 3 years and 9 months (1,358 days). Its orbit has an

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

of 0.25 and an

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 Eart ...

of 22 ° with respect to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

. The body's

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 use ...

begins at

Vienna Observatory The Vienna Observatory () is an astronomical observatory in Vienna, Austria. It is part of the University of Vienna. The first observatory was built in 1753–1754 on the roof of one of the university buildings. A new observatory was built betwe ...

in March 1860, almost 7 years after its official discovery observation at Marseille.

Physical characteristics

''Phocaea'' is a stony

S-type asteroid S-type (stony-type or silicaceous-type) asteroids are asteroids with a spectral type that is indicative of a siliceous (i.e. stony) mineralogical composition, hence the name. They have relatively high density. Approximately 17% of asteroids are ...

in both the

Tholen Tholen () is a 25,000 people municipality in the southwest of the Netherlands. The municipality of Tholen takes its name from the town of Tholen, which is the largest population center in the municipality. The municipality consists of two peninsu ...

and

SMASS classification An asteroid spectral type is assigned to asteroids based on their reflectance spectrum, color, and sometimes albedo. These types are thought to correspond to an asteroid's surface composition. For small bodies that are not internally different ...

, and has also been characterized as such by others. Photometric observations of this asteroid at the Organ Mesa Observatory in

Las Cruces, New Mexico Las Cruces (; ; lit. 'the crosses') is the List of municipalities in New Mexico, second-most populous city in the U.S. state of New Mexico and the county seat, seat of Doña Ana County, New Mexico, Doña Ana County. As of the 2020 United States ce ...

during 2010 gave a

lightcurve In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis ...

with a period of 9.9341 ± 0.0002 hours. The brightness near the deepest minimum of the light curve showed changes with phase angle, which is the result of shadows extending across surface irregularities. Several other lightcurves have also been obtained. ''Phocaea'' has also been studied by

radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...

. According to the surveys carried out by the Infrared Astronomical Satellite

IRAS The Infrared Astronomical Satellite (Dutch language, Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a astronomical survey, survey of the entire night sky at infrared wavelengths. Launched on 25 Janu ...

, the Japanese Akari satellite and the

NEOWISE Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and MIDEX-6) was a NASA infrared astronomy space telescope in the Explorers Program launched in December 2009.. . WISE discovered thousands of minor planets and nu ...

mission of NASA's

Wide-field Infrared Survey Explorer Wide-field Infrared Survey Explorer (WISE, List of observatory codes, observatory code C51, Explorer 92 and MIDEX-6) was a NASA infrared astronomy Space observatory, space telescope in the Explorers Program launched in December 2009.. . WISE L ...

, ''Phocaea'' measures between 61.05 and 83.21 kilometers in diameter and its surface has an

albedo Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...

between 0.189 and 0.350. The ''Collaborative Asteroid Lightcurve Link'' adopts the results obtained by IRAS, that is, an albedo of 0.2310 and a diameter of 75.13 kilometers based on an absolute magnitude of 7.83. The asteroid has a mass of (5.99 ± 0.60) × 10¹⁷ kilograms and a mean density of grams per cubic centimeters, which lies approximately in between the density of limestone and concrete/gravel.

Discovery and naming

Classification and orbit

Physical characteristics

References

External links