Phocaea (

minor planet designation A formal minor-planet designation is, in its final form, a number–name combination given to a minor planet (asteroid, centaur, trans-Neptunian object and dwarf planet but not comet). Such designation always features a leading number (catalog or ...

: 25 Phocaea) is a stony

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

from the inner regions of the

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 ...

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

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

Phocaea Phocaea or Phokaia (Ancient Greek: Φώκαια, ''Phókaia''; modern-day Foça in Turkey) was an ancient Ionia Ionia () was an ancient region on the western coast of Anatolia, to the south of present-day Izmir. It consisted of the northern ...

Discovery and naming

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

Marseille Observatory Marseille Observatory (french: Observatoire de Marseille) 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 gal ...

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 town and district in Turkey's İzmir Province, on the Aegean Sea, Aegean coast. The town of Foça is situated at about northwest of İzmir's city center. The district also has a township with its own municipality named Yenifoça (lite ...

in Turkey, where the founders of

Marseille Marseille ( , , ; also spelled in English as Marseilles; oc, Marselha ) is the prefecture of the French department of Bouches-du-Rhône and capital of the Provence-Alpes-Côte d'Azur region. Situated in the camargue region of southern Franc ...

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 In meteoritics, a parent body is the celestial body from which originates a meteorite or a class of meteorites. Identification The easiest way to correlate a meteorite with a parent body is when the parent body still exists. This is the case fo ...

and namesake of the Phocaea family (), 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 a ...

of stony asteroids in the

inner Interior may refer to: Arts and media * ''Interior'' (Degas) (also known as ''The Rape''), painting by Edgar Degas * ''Interior'' (play), 1895 play by Belgian playwright Maurice Maeterlinck * ''The Interior'' (novel), by Lisa See * Interior de ...

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 Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

of 22 ° with respect to the

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 again ...

. 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 (german: Universitätssternwarte Wien) 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 ...

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

Physical characteristics

Spectral type

''Phocaea'' is a stony

S-type asteroid S-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 of this type, making it the second ...

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 emission spectrum, color, and sometimes albedo. These types are thought to correspond to an asteroid's surface composition. For small bodies that are not internally differentiat ...

, and has also been characterized as such by others.

Lightcurves

Photometric observations of this asteroid at the Organ Mesa Observatory in

Las Cruces, New Mexico Las Cruces (; "the crosses") is the second-largest city in the U.S. state of New Mexico and the seat of Doña Ana County. As of the 2020 census the population was 111,385. Las Cruces is the largest city in both Doña Ana County and southern New ...

during 2010 gave a

lightcurve In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular frequ ...

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 detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

Diameter and albedo

According to the surveys carried out by the Infrared Astronomical Satellite

IRAS The Infrared Astronomical Satellite (Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a survey of the entire night sky at infrared wavelengths. Launched on 25 January 1983, its mission lasted ten mo ...

, the Japanese Akari satellite and the

NEOWISE Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and SMEX-6) is a NASA infrared astronomy space telescope in the Explorers Program. It was launched in December 2009, and placed in hibernation mode in February 2011, ...

mission of NASA's

Wide-field Infrared Survey Explorer Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and SMEX-6) is a NASA infrared astronomy space telescope in the Explorers Program. It was launched in December 2009, and placed in hibernation mode in February 2011, ...

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

albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...

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 Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse Logarithmic scale, logarithmic Magnitude (astronomy), astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent mag ...

of 7.83.

Mass and density

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.