42009

42009 is a minor planet orbiting the Sun in the inner region of the main asteroid belt. It was discovered on 7 September 1999 by the LINEAR survey at the Lincoln Laboratory's Experimental Test Site near Socorro, New Mexico. The discoverers assigned it the provisional designation 1999 XA8 before it was numbered once its orbit was well determined.

The asteroid has a semimajor axis of approximately 2.32 astronomical units, placing it among the typical inner-belt asteroids. Its orbital period is about 3.53 Earth years (1,292 days). The object follows a mildly eccentric orbit, with an eccentricity of roughly 0.12 and an inclination of about 6.3 degrees relative to the ecliptic. Its aphelion and perihelion distances are 2.58 AU and 2.06 AU, respectively. These orbital parameters have been refined through multiple years of astrometric observations.

Spectral analysis suggests 42009 belongs to the stony S-type taxonomic class, common among inner-belt bodies. Its absolute magnitude, measured at H = 15.8, implies a diameter in the range of 3.5 to 4.5 kilometers, depending on the assumed albedo between 0.20 and 0.25. No significant satellites or unusual features have been reported, and the object displays a typical rotation period typical of small asteroids, around 5.6 hours, though detailed light‑curve data are sparse.

42009 remains one of the many catalogued minor planets in the Solar System, contributing to the statistical understanding of asteroid populations and their dynamical evolution. Continued observations are essential for refining its orbital elements and monitoring for potential Earth‑approaching trajectories, though it currently resides comfortably within the main belt and poses no known impact threat.