is an eccentric, 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 ...

and

binary system A binary system is a system of two astronomical bodies of the same kind that are comparable in size. Definitions vary, but typically require the center of mass to be located outside of either object. (See animated examples.) The most common ki ...

, classified as

near-Earth object A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun ( perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit a ...

of the Amor group of asteroids, approximately 900 meters in diameter. It

minor-planet moon A minor-planet moon is an astronomical object that orbits a minor planet as its natural satellite. , there are 457 minor planets known or suspected to have moons. Discoveries of minor-planet moons (and binary objects, in general) are important ...

has an estimated diameter of 270 meters. This asteroid was discovered on 3 August 1998, by the

Lowell Observatory Near-Earth-Object Search Lowell Observatory Near-Earth-Object Search (LONEOS) was a project designed to discover asteroids and comets that orbit near the Earth. The project, funded by NASA, was directed by astronomer Ted Bowell of Lowell Observatory in Flagstaff, Arizo ...

(LONEOS) at

Anderson Mesa Station Anderson Mesa Station is an astronomical observatory established in 1959 as a dark-sky observing site for Lowell Observatory. It is located at Anderson Mesa in Coconino County, Arizona, about southeast of Lowell's main campus on Mars Hill in F ...

, near Flagstaff, Arizona, United States.

Orbit

orbits the Sun at a distance of 1.2–2.8 AU once every 2 years and 10 months (1,046 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 0.39 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 7 ° 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 ...

. A first

precovery In astronomy, precovery (short for pre-discovery recovery) is the process of finding the image of a celestial object in images or photographic plates predating its discovery, typically for the purpose of calculating a more accurate orbit. This ha ...

was taken at

Palomar Observatory The Palomar Observatory is an astronomical research observatory in the Palomar Mountains of San Diego County, California, United States. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...

in 1978, extending 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 ...

by 20 years prior to its official discovery observation at Anderson Mesa.

Close approaches

The asteroid has an ''Earth

minimum orbital intersection distance Minimum orbit intersection distance (MOID) is a measure used in astronomy to assess potential close approaches and collision risks between astronomical objects. It is defined as the distance between the closest points of the osculating orbits of ...

'' of , which translates into approximately 92 lunar distances. It has made multiple close approaches to

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

, with the closest being 35,648,680 kilometers on 15 October 1978. With an aphelion of more than 2.8 AU, is also a

Mars-crosser A Mars-crossing asteroid (MCA, also Mars-crosser, MC) is an asteroid whose orbit crosses that of Mars. Some Mars-crossers numbered below 100000 are listed here. They include the two numbered Mars trojans 5261 Eureka and . Many databases, for i ...

Physical characteristics

Spectral type

In the SMASS taxonomy, is classified as a transitional Sq-type, which is an intermediary between the common stony S-type and the less frequent Q-type asteroids.

Diameter and albedo

According to the 2006-published ''Photometric survey of binary near-Earth asteroids'' by

Petr Pravec Petr Pravec (born September 17, 1967) is a Czech astronomer and a discoverer of minor planets, born in Třinec, Czech Republic. Pravec is a prolific discoverer of binary asteroids, expert in photometric observations and rotational lightcurves ...

and derived data from the ''Collaborative Asteroid Lightcurve Link'' and the "Johnston's archive", measures between 880 and 940 meters 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 ...

of 0.18 and 0.20, respectively.

Rotation

In the late 1990s, a rotational

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 ...

of was obtained from photometric observations by Hungarian astronomers László Kiss,

Gyula Szabó Gyula Szabó (15 July 1930 – 4 April 2014) was a Hungarians, Hungarian actor. He won two Mari Jászai Prizes. He appeared in forty movies between 1953 and 2002. He is best known for appearing in movies such as ''Ifjú szívvel'' (1953), ...

and

Krisztián Sárneczky Krisztián Sárneczky (born 6 November 1974 in Budapest) is a Hungarian people, Hungarian teacher of geography and prolific discoverer of minor planets and supernovae, researching at Konkoly Observatory in Budapest, Hungary. He is a board member ...

. Lightcurve analysis gave a

rotation period In astronomy, the rotation period or spin period of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the '' sidereal rotation period'' (or ''sidereal day''), i.e., the time that the objec ...

of 2.5 hours with a brightness variation of 0.1

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

(). A second lightcurve obtained and published in 2000, by an international collaboration of astronomers gave a rotation period of hours with a brightness amplitude of 0.11 magnitude ().

Moon

During the second photometric observation, it was discovered that is a probable/possible asynchronous

with a

orbiting it every 7.0035 hours, or twice this period solution. The moon remains undesignated. The system has an estimated secondary-to-primary mean-diameter ratio of more than 0.3, which translates into a diameter of 270 meter for the satellite. The "Johnston's archive" also estimates that the moon's orbit has a

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 longe ...

of 1.4 kilometers. From the surface of , the moon would have an angular diameter of about 16.3°. For comparison, the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

appears to be 0.5° from Earth.

Numbering and naming

This

minor planet According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''minor ...

was numbered by the

Minor Planet Center The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory. Funct ...

on 30 November 2001. As of 2018, it has not been named.

Gallery

File:Orbit of 31345.gif, Orbit of File:Asteroids and their Moons Comparison.png, The system compared to other binary asteroids

Notes

References

External links

MPEC 1998-P13 : 1998 PG
''

Minor Planet Electronic Circular The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory. Function ...

'' 6 August 1998
(31345) 1998 PG
at E.A.R.N. – European Asteroid Research Node

Robert Johnston, johnstonsarchive.net

Lance Benner, JPL
Asteroid Lightcurve Database (LCDB)
query form

)
Dictionary of Minor Planet Names
Google books

– Observatoire de Genève, Raoul Behrend * * * {{DEFAULTSORT:1998 PG 031345 031345 031345 031345 19980803