Discovered by C. O. Lampland Discovery date 24 March 1931 Minor planet category main-belt · Eos Orbits Sun Discoverer Carl Otto Lampland Asteroid family Eos family | Discovery site Lowell Obs. MPC designation 1604 Tombaugh Discovered 24 March 1931 Spectral type X-type asteroid Named after Clyde Tombaugh | |
Alternative names 1931 FH · 1930 DX
1933 SA1 · 1936 FA
1937 JH · 1941 CF
1943 OE · 1948 ME
1949 ST1 · A920 EC Similar 2839 Annette, Solar System, Sun, Asteroid belt, Pluto | ||
1604 Tombaugh, provisional designation 1931 FH, is a rare-type Eoan asteroid from the outer region of the asteroid belt, approximately 32 kilometers in diameter. It was discovered on 24 March 1931, by American astronomer Carl Otto Lampland at Lowell Observatory in Flagstaff, Arizona, in the United States.
Tombaugh is a member of the Eos family. It is classified as a X-type asteroid, as well as a rare XSCU and intermediate Xc type in the Tholen and SMASS taxonomy, respectively. It orbits the Sun at a distance of 2.7–3.3 AU once every 5 years and 3 months (1,920 days). Its orbit has an eccentricity of 0.10 and an inclination of 9° with respect to the ecliptic. Previously identified as A920 EC and 1930 DX at Heidelberg in 1920 and 1930, Tombaugh's observation arc begins one year prior to its official 1931-discovery at Flagstaff.
In April 2010 and November 2012, two rotational light-curves of Tombaugh were obtained from photometric observations at Oakley Southern Sky Observatory, Australia, and at Bassano Bresciano Observatory, Italy, respectively. The light-curve analysis gave a rotation period of 7.047 and 7.056 hours with a brightness variation of 0.16 and 0.35 magnitude, respectively (U=2+/2+), These periods supersede previous results obtained by astronomers Claes-Ingvar Lagerkvist (1975), Richard P. Binzel (1984) and Krisztián Sárneczky (U=1/2/2).
According to the surveys carried out by the Infrared Astronomical Satellite IRAS and the Japanese Akari satellite, Tombaugh measures 28.78 and 32.33 kilometers in diameter, and its surface has an albedo of 0.138 and 0.104, respectively. The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0933 and a diameter of 32.25 kilometers using an absolute magnitude of 10.65.
This minor planet was named for American astronomer Clyde Tombaugh (1906–1997), famous for his discovery of Pluto in 1930. The Lowell Observatory named the body on the occasion of a symposium on Pluto, held in 1980. When Tombaugh examined the photographic plates during the trans-Saturnian search program at the Lowell Observatory, he also marked over 4,000 minor planets on these plates. Naming citation was published on 1 April 1980 (M.P.C. 5280).