6 December 1997
Minor planet category
Apollo NEO, PHA
6 December 1997
(35396) 1997 XF11
9510 days (26.04 yr)
Sidereal rotation period
James V. Scotti
James V. Scotti Spacewatch Project (691) 0.9-m reflector
2.1408 AU (320.26 Gm) (Q)
Kitt Peak National Observatory
James V Scotti discoveries, Other celestial objects
(35396) 1997 XF11, also written (35396) 1997 XF11, is a near-Earth and Mars-crosser asteroid which, 3 months after its discovery on December 6, 1997, by James V. Scotti of the University of Arizona's Spacewatch Project, was predicted to make an exceptionally close approach to Earth on 28 October 2028. Additional precovery observations of the asteroid from 1990 were quickly found that refined the orbit and it is now known the asteroid will pass the Earth on October 26, 2028, at a distance of 0.0062 AU (930,000 km; 580,000 mi), about 2.4 times the Earth-Moon distance. During the close approach, the asteroid should peak at about apparent magnitude 8.2, and will be visible in binoculars.
(35396) 1997 XF11 is estimated to be between 1.3 km and 2.8 km in diameter.
This asteroid also regularly comes near the large asteroid Pallas.
On 11 March 1998, using a three-month observation arc, a faulty IAU Circular and press information sheet were put out that incorrectly concluded, "that the asteroid was 'virtually certain' to pass within 80% of the distance to the Moon and stood a 'small...not entirely out of the question' possibility of hitting the Earth in 2028." But by 23 December 1997 it should have been clear that XF11 had no reasonable possibility of an Earth impact. Within hours of the announcement independent calculations by Paul Chodas, Don Yeomans, and Karri Muinonen had correctly calculated that the probability of Earth impact was essentially zero, and vastly less than the probability of impact from the as-yet-undiscovered asteroids. Chodas (1999) concurs with Marsden (1999) that there was about 1 chance in a hundred thousand that XF11 could have passed through a keyhole—that is, until the 1990 precovery observations eliminated such possibilities. During the October 2002 close approach, the asteroid was observed by the 70-meter Goldstone radar dish further refining the orbit.