E. F. Helin
(5496) 1973 NA
Minor planet category
Apollo · NEO
4 July 1973
Eleanor F. Helin
4 July 1973
1973 NA · 1992 OA
41.30 yr (15,086 days)
(5496) 1973 NA, is a very eccentric and heavily tilted asteroid, classified as near-Earth object of the Apollo group, approximately 2 kilometers in diameter. It was discovered on 4 July 1973, by American astronomer Eleanor Helin at the U.S. Palomar Observatory in California. At the time of its discovery, it was the most highly inclined minor planet known to exist.
The asteroid orbits the Sun at a distance of 0.9–4.0 AU once every 3 years and 10 months (1,388 days). Its orbit has an eccentricity of 0.64 and an inclination of 68° with respect to the ecliptic. No precoveries were taken. The asteroid's observation arc even begins 2 days after its discovery.
The body was also one of the first known near-Earth asteroids. Its discovery happened just two days after it had passed 0.07984 AU (11,900,000 km) from Earth on one of its closest approaches ever computed. It was then tracked for more than a month, but was not seen again until its next close approach in 1992, when it was recovered by the Siding Spring Observatory in Australia. Its minimum orbit intersection distance with Earth is now 0.0902 AU (13,500,000 km).
The stony S-type asteroid is also classified as a transitional C/X-type according to observations by the NASA IRTF telescope. A rotational light-curve for this asteroid was obtained by American astronomer Brian Skiff from photometric observations made in June 2011. The light-curve gave a rotation period of 7000285500000000000♠2.855±0.001 hours with a brightness variation of 0.15 in magnitude (U=3). The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 1.88 kilometers, based on an absolute magnitude of 16.0.
The asteroid is expected to be related to the Quadrantids January meteor shower.