# 3800 Karayusuf

3800 Karayusuf, provisional designation 1984 AB, is a Mars-crossing asteroid and suspected binary system from inside the asteroid belt, approximately 2.5 kilometers (1.6 miles) in diameter. It was discovered on 4 January 1984, by American astronomer Eleanor Helin at the Palomar Observatory in California. The S/L-type asteroid has a short rotation period of 2.2 hours. It was named after Syrian physician Alford Karayusuf, a friend of the discoverer.

## Orbit and classification

Karayusuf is a Mars-crossing asteroid, a dynamically unstable group between the main-belt and the near-Earth populations, crossing the orbit of Mars at 1.66 AU. It orbits the Sun at a distance of 1.46–1.70 AU once every 2 years (724 days; semi-major axis of 1.58 AU). Its orbit has an eccentricity of 0.08 and an inclination of 15° with respect to the ecliptic. On 11 June 1938, Karayusuf passed 0.0151 AU (2,260,000 km; 1,400,000 mi) from Mars.
The body's observation arc begins with its first observations as 1975 XL$_4$ at Crimea–Nauchnij in December 1975, almost 12 years prior to its official discovery observation at Palomar.

## Naming

This minor planet was named after Syrian physician Alford Karayusuf, a supporter of the Near-earth asteroid research projects at JPL and a leader of the World Space Foundation's program of Solar System exploration. The official naming citation was published by the Minor Planet Center on 2 November 1990 (M.P.C. 17221). The main-belt asteroid 5255 Johnsophie, also discovered by Helin, was named after Alford Karayusuf's children, John and Sophie (also see the asteroid's citation).

## Physical characteristics

In the SMASS classification, Karayusuf is a common, stony S-type asteroid. The asteroid has also been characterized as an L-type asteroid by the Sloan Digital Sky Survey and Pan-STARRS' photometric survey.

### Rotation period

In March 2008, a rotational lightcurve of Karayusuf was obtained from photometric observations by Brian Warner at his Palmer Divide Observatory in Colorado. Lightcurve analysis gave a well-defined rotation period of 2.2319±0.0001 hours with a rather small brightness amplitude of 0.15 magnitude (U=3). The body's rotation is close to the threshold-period of that of a fast rotator, which would fly apart if they were not composed of a solid, monolithic structure.
Follow-up observations by Warner in 2010, 2014 and 2018 gave similar results. The asteroid was also observed by Brian Skiff (2.225 h) and William Ryan (2.23 h) in 2018.

### Binary candidate

During Brian Warner's photometric observations, two possible mutual eclipsing/occultation events were observed, indicating that Karayusuf is a binary asteroid with a satellite in its orbit. The data, however, was insufficient to calculate a rotation period. In 2010 and in 2014, when observing conditions had a nearly identical phase angle, no evidence of an orbiting minor-planet moon was found. The results of the 2018-observation have not yet been published.

### Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Karayusuf measures 2.51 kilometers in diameter and its surface has an albedo between 0.281, while other NEOWISE observations gave a diameter of 1.624 kilometers with a not very plausible albedo of 0.657. The Collaborative Asteroid Lightcurve Link assumes a standard albedo for a stony asteroid of 0.20 and calculates a diameter of 2.97 kilometers based on an absolute magnitude of 15.0.