2340 Hathor (), provisional designation , 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 ...

, 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 ...

and

potentially hazardous asteroid A potentially hazardous object (PHO) is a near-Earth object – either an asteroid or a comet – with an orbit that can make close approaches to the Earth and which is large enough to cause significant regional damage in the event of impact. Th ...

. It belongs to the

Aten Aten, also Aton, Atonu, or Itn (, reconstructed ) was the focus of Atenism, the religious system formally established in ancient Egypt by the late Eighteenth Dynasty pharaoh Akhenaten. Exact dating for the Eighteenth Dynasty is contested, thou ...

group of asteroids and measures approximately 210 meters in diameter. Discovered by Charles Kowal in 1976, it was later named after the ancient Egyptian goddess

Hathor Hathor (, , , Meroitic language, Meroitic: ') was a major ancient Egyptian deities, goddess in ancient Egyptian religion who played a wide variety of roles. As a sky deity, she was the mother or consort of the sky god Horus and the sun god R ...

Discovery

Hathor was discovered on 22 October 1976, by American astronomer Charles Kowal 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 ...

, California, United States. It was independently discovered by

Eleanor Helin Eleanor Francis "Glo" Helin (née Francis, 19 November 1932 – 25 January 2009) was an American astronomer. She was principal investigator of the Near-Earth Asteroid Tracking (NEAT) program of NASA's Jet Propulsion Laboratory. (Some sources gi ...

and is named for the ancient Egyptian deity

Independent discoveries

On 25 October 1976, Hathor was independently discovered by Eleanor Helin during the

Palomar Planet-Crossing Asteroid Survey The Palomar Planet-Crossing Asteroid Survey (PCAS) was an astronomical survey, initiated by American astronomers Eleanor Helin and Eugene Shoemaker at the U.S Palomar Observatory, California, in 1973. The program is responsible for the discovery ...

(PCAS), and by William Lawrence Sebok, who photographed the same field almost simultaneously using Palomar's 1.22-meter Schmidt telescope. On the same day, the official discoverer Charles Kowal found that ''Hathor'' had already been imaged three days earlier by Palomar's 0.46-meter telescope (the same instrument used by PCAS). A fourth independent discovery was made several days later by

Nikolai Chernykh Nikolai Stepanovich Chernykh ( rus, Никола́й Степа́нович Черны́х, , nʲɪkɐˈlaj sʲtʲɪˈpanəvʲɪtɕ tɕɪrˈnɨx, links=yes; 6 October 1931 – 25 May 2004Казакова, Р.К. Памяти Николая Сте ...

at CrAO on the Crimean peninsula. The multiple discoveries were probably due to its very close approach distance to Earth. After

2062 Aten 2062 Aten , provisional designation , is a stony sub-kilometer asteroid and namesake of the Aten asteroids, a subgroup of near-Earth objects. The asteroid was named after Aten from Egyptian mythology. It was discovered on 7 January 1976, at th ...

, Hathor was the second discovery of an Aten asteroid. In 1978, the third Aten,

2100 Ra-Shalom 2100 Ra-Shalom (Minor planet provisional designation, ''prov. designation'': ) is an asteroid and near-Earth object of the Aten asteroid, Aten group on an eccentric orbit in the inner Solar System. It was discovered on 10 September 1978, by Amer ...

was discovered. The Aten was already identified at Palomar in 1954, but its discovery date was later assigned to a 2003 observation at Lincoln Laboratory ETS, and is now known as .

Orbit and classification

Being a member of the

Aten asteroid The Aten asteroids are a dynamical group of asteroids whose orbits bring them into proximity with Earth. By definition, Atens are Earth-crossing asteroids . The group is named after 2062 Aten, the first of its kind, discovered on 7 Janua ...

s, Hathor orbits the Sun at a distance of 0.5–1.2 AU once every 0 years and 9 months (283 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 0.45 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 6 ° 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 ...

. Its

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 3 days after its official discovery at Palomar, with no

precoveries 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 ...

taken and no prior identifications made. Its orbital solution includes non-gravitational force (A2).

Close approaches

Hathor has an Earth

Minimum orbit 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 o ...

of , which corresponds to 2.7 lunar distances (LD). When it was discovered in 1976, Hathor had one of its closest approaches to Earth at . On 21 October 2014, when it passed Earth at 0.048 AU, or 18.8 LD, it was observed 22 times by the Goldstone Deep Space Network using

radar astronomy Radar astronomy is a technique of observing nearby astronomical objects by reflecting radio waves or microwaves off target objects and analyzing their reflections. Radar astronomy differs from ''radio astronomy'' in that the latter is a passive ob ...

over a period of 21 days from 10 to 31 October. It will pass Earth again at on 21 October 2069.

Physical characteristics

In 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 taxonomy, Hathor has a CSU and Sq

spectral type In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

, respectively.

Diameter and albedo

In the 1990s, Dutch–American astronomer

Tom Gehrels Anton M.J. "Tom" Gehrels (February 21, 1925 – July 11, 2011) was a Dutch–American astronomer, Professor of Planetary Sciences, and Astronomer at the University of Arizona, Tucson. Biography Youth and education Gehrels was born at Ha ...

estimated Hathor's diameter to measure approximately 300 meters, assuming 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 0.15. During its close approach to Earth in October 2014, a team of astronomer published a revised estimate of meters for its diameter. The ''Collaborative Asteroid Lightcurve Link'' adopts this diameter and derives an albedo of 0.3331 with an absolute magnitude of 20.2.

Rotation period

In November 2014, American astronomer Brian Warner obtained 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 Hathor from photometric observations taken at the Palmer Divide Station in Colorado ''(also see )''. Light-curve analysis gave a well-defined

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 3.350 hours with a brightness variation of 0.11

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 ...

().

Naming

In accordance with the custom to name all members of the Aten group after

Ancient Egyptian deities Ancient Egyptian deities are the gods and goddesses worshipped in ancient Egypt. The beliefs and rituals surrounding these gods formed the core of ancient Egyptian religion, which emerged sometime in prehistory. Deities represented natural f ...

, 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 ...

is named for

, sky-goddess and daughter of Ra, who personified the principles of joy, feminine love, and motherhood. The Ancient Greeks sometimes identified Hathor with the goddess

Aphrodite Aphrodite (, ) is an Greek mythology, ancient Greek goddess associated with love, lust, beauty, pleasure, passion, procreation, and as her syncretism, syncretised Roman counterpart , desire, Sexual intercourse, sex, fertility, prosperity, and ...

. Naming was proposed by Eleanor Helin who also participated in the 1981 recovery. The minor planet 161 Athor is also named for Hathor. The official naming citation was published 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 1 June 1981 ().