2340 Hathor

2340 Hathor (/ˈhæθɔːr, -ər/), provisional designation 1976 UA, is an eccentric stony asteroid, classified as near-Earth object and potentially hazardous asteroid. It belongs to the Aten 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.

2340 Hathor

Discovery
Discovered by	C. Kowal
Discovery site	Palomar Obs.
Discovery date	22 October 1976
Designations
MPC designation	(2340) Hathor
Pronunciation	/ˈhæθɔːr, -ər/
Named after	Hathor (Egyptian deity)
Alternative designations	1976 UA
Minor planet category	Aten · NEO · PHA
Orbital characteristics
Epoch 11 August 2004 (JD 2453228.5)
Uncertainty parameter 0
Observation arc	38.00 yr (13,878 days)
Aphelion	1.2235 AU
Perihelion	0.4642 AU
Semi-major axis	0.8438 AU
Eccentricity	0.4499
Orbital period (sidereal)	0.78 yr (283 days)
Mean anomaly	42.104°
Mean motion	1° 16m 17.4s / day
Inclination	5.8546°
Longitude of ascending node	211.54°
Argument of perihelion	39.926°
Earth MOID	0.0069 AU · 2.7 LD
Physical characteristics
Dimensions	0.210±0.030 km 0.3 km (dated)
Synodic rotation period	3.350±0.002 h
Geometric albedo	0.15 (dated) 0.3331 (derived)
Spectral type	CSU (Tholen) Sq (SMASS) · S  B–V = 0.770 U–B = 0.500
Absolute magnitude (H)	20.2

Discovery

Hathor was discovered on 22 October 1976, by American astronomer Charles Kowal at Palomar Observatory, 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, Hathor was the second discovery of an Aten asteroid. In 1978, the third Aten, 2100 Ra-Shalom was discovered. The Aten 1954 XA 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 (363505) 2003 UC₂₀.

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 force (A2).

Close approaches

Hathor has an Earth Minimum orbit intersection distance of 0.0069 AU (1,030,000 km), which corresponds to 2.7 lunar distances (LD).

When it was discovered in 1976, Hathor had one of its closest approaches to Earth at 0.007752 AU (1,160,000 km). 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 0.00658 AU (984,000 km) on 21 October 2069.

Physical characteristics

In the Tholen and SMASS taxonomy, Hathor has a CSU and Sq spectral type, respectively.

Diameter and albedo

In the 1990s, Dutch–American astronomer Tom Gehrels 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 210±30 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 § External links). Light-curve analysis gave a well-defined rotation period of 3.350 hours with a brightness variation of 0.11 magnitude (U=3).

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 is also named for Hathor. The official naming citation was published by the Minor Planet Center on 1 June 1981 (M.P.C. 6060).

External links

• Lightcurve plot (i) for (2340) Hathor, 21–22 October 2014, Brian Warner, CS3
• Lightcurve plot (ii) for (2340) Hathor, 30 October to 3 November 2014, Brian Warner, CS3
• Goldstone Asteroid Schedule
• Asteroid Lightcurve Database (LCDB), query form (info Archived 16 December 2017 at the Wayback Machine)
• Dictionary of Minor Planet Names, Google books
• Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend
• 2340 Hathor at NeoDyS-2, Near Earth Objects—Dynamic Site
  • Ephemerides · Observation prediction · Orbital info · MOID · Proper elements · Observational info · Close approaches · Physical info · Orbit animation
• 2340 Hathor at ESA–space situational awareness
  • Ephemerides · Observations · Orbit · Physical properties · Summary
• 2340 Hathor at the JPL Small-Body Database