15666

15666 is a numbered minor planet located in the main asteroid belt between Mars and Jupiter. The object was discovered on 4 January 1996 by the Belgian astronomer Eric W. Elst at ESA’s La Silla Observatory in Chile. Its provisional designation was 1996 FA, and it was subsequently assigned the permanent number 15666 once its orbit had been well established.

The asteroid has an orbital period of approximately 4.1 Earth years. Its semimajor axis is about 2.60 astronomical units from the Sun, and it follows a nearly circular path with an eccentricity of 0.10. The orbital inclination relative to the ecliptic is modest, around 6°. Observations indicate that 15666 is a stony S‑type asteroid, which is common among bodies in the inner portion of the main belt.

Cumulative photometric observations have yielded a light curve that suggests a rotation period of about 7.8 hours, though the amplitude of brightness variation remains low, implying a relatively spheroidal shape. No significant satellites or rings have been detected around the body to date.

Since its discovery, 15666 has been observed regularly by both amateur and professional observatories, contributing to refinements in its orbital parameters. Its size, derived from its absolute magnitude of 14.3 and assuming a typical albedo for S‑type asteroids, is estimated to be roughly 6 kilometers in diameter. The asteroid has not been named beyond its numeric designation, remaining simply as minor planet 15666.