(12538) 1998 OH

(12538) 1998 OH is a stony asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 1.8 kilometers (1.1 miles) in diameter. It was discovered on 19 July 1998, by astronomers of the Near-Earth Asteroid Tracking program at the Haleakala Observatory in Hawaii, United States. In 2019, the asteroid came within about 73 lunar distances of Earth.

Numbering and naming
This minor planet was numbered by the Minor Planet Center on 23 November 1999. As of 2018, it has not been named.

Orbit and classification
is a member of the Apollo group of asteroids, which are Earth-crossing asteroids. They are the largest group of near-Earth objects with approximately 10 thousand known members.

It orbits the Sun at a distance of 0.9–2.2 AU in 1 year and 11 months (699 days). Its orbit has an eccentricity of 0.41 and an inclination of 25° with respect to the ecliptic. The body's observation arc begins with a precovery taken at Palomar Observatory in October 1991, more than 7 years prior to its official discovery observation at Haleakala.

Close approaches
The asteroid has an Earth minimum orbital intersection distance of 0.0280 AU, which corresponds to 10.9 lunar distances and makes it a potentially hazardous asteroid due to its sufficiently large size. It will pass close to Earth in 2042 and 2132, at a distance of 0.0292 AU and 0.0317 AU, respectively.

Physical characteristics
In the SMASS classification, is a common stony S-type asteroid.

Rotation period
In 2014, several rotational lightcurves of were obtained from photometric observations by American astronomer Brian Warner at the Palmer Divide Station in California, by the Spanish amateur astronomer group OBAS, and by astronomers of the EURONEAR lightcurve NEO survey. Lightcurve analysis gave a rotation period of 5.154 hours with an alternative period solution of 2.58 hours, or half the period. The asteroid's brightness amplitude is rather low with a maximum between 0.11 and 0.20 magnitude, which is indicative for a spherical rather than elongated shape (U=3/3/2-/3/2/2).

Diameter and albedo
According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, measures 1.663 kilometers in diameter and its surface has an albedo of 0.232. The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 2.06 kilometers based on an absolute magnitude of 15.8.