2340 Hathor (), provisional designation , is an eccentric 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. ...

, classified as near-Earth object 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 is large enough to cause significant regional damage in the event of impact. They are ...

. It belongs to the Aten group of asteroids and measures approximately 210 meters in diameter. Discovered by

Charles Kowal Charles Thomas Kowal (November 8, 1940 – November 28, 2011) was an American astronomer known for his observations and discoveries in the Solar System. As a staff astronomer at Caltech's Mount Wilson and Palomar Mountain observatories between ...

in 1976, it was later named after the ancient Egyptian goddess Hathor.

Discovery

''Hathor'' was discovered on 22 October 1976, by American astronomer

Palomar Observatory Palomar Observatory is an astronomical research observatory in San Diego County, California, United States, in the Palomar Mountain Range. 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 and is named for the ancient Egyptian deity Hathor.

Independent discoveries

On 25 October 1976, ''Hathor'' was independently discovered by Eleanor Helin during the Palomar Planet-Crossing Asteroid Survey (PCAS), and by William Lawrence Sebok, who photographed the same field almost simultaneously using Palomars 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 Palomars 0.46-meter telescope (the same instrument used by PCAS). A fourth independent discovery was made several days later by Nikolai Chernykh 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 the ...

, ''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 Ameri ...

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 The MIT Lincoln Laboratory, located in Lexington, Massachusetts, is a United States Department of Defense federally funded research and development center chartered to apply advanced technology to problems of national security. Research and dev ...

, and is now known as .

Orbit and classification

Being a member of the Aten asteroids, ''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 of 0.45 and an inclination of 6 ° with respect to the ecliptic. Its observation arc begins 3 days after its official discovery at Palomar, with no precoveries taken and no prior identifications made. Its orbital solution includes non-gravitational forces.

Close approaches

''Hathor'' has an ''Earth Minimum orbit intersection distance'' , 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 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, 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 Haa ...

estimated ''Hathor''s diameter to measure approximately 300 meters, assuming an albedo 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 of ''Hathor'' from photometric observations taken at the Palmer Divide Station in Colorado ''(also see )''. Light-curve analysis gave a well-defined

rotation period The rotation period of a celestial object (e.g., star, gas giant, planet, moon, asteroid) may refer to its sidereal rotation period, i.e. the time that the object takes to complete a single revolution around its axis of rotation relative to the ...

of 3.350 hours with a brightness variation of 0.11 magnitude ().

Naming

In accordance with the custom to name all members of the Aten group after Ancient Egyptian deities, this minor planet is named for Hathor, 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. Naming was proposed by Eleanor Helin who also participated in the 1981-recovery. The minor planet

161 Athor 161 Athor is an M-type Main belt asteroid that was discovered by James Craig Watson on April 19, 1876, at the Detroit Observatory and named after Hathor, an Egyptian fertility goddess. It is the namesake of a proposed Athor asteroid family, ...

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. Function ...

on 1 June 1981 ().