1995 Hajek

1995 Hajek, provisional designation 1971 UP₁, is a metallic asteroid from the middle region of the asteroid belt, approximately 13 kilometers in diameter.

1995 Hajek

Discovery[1]
Discovered by	L. Kohoutek
Discovery site	Bergedorf Obs.
Discovery date	26 October 1971
Designations
MPC designation	(1995) Hajek
Named after	Tadeáš Hájek (astronomer)[2]
Alternative designations	1971 UP1 · 1941 EA
Minor planet category	main-belt · (middle)[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	76.21 yr (27,836 days)
Aphelion	2.6677 AU
Perihelion	2.3911 AU
Semi-major axis	2.5294 AU
Eccentricity	0.0547
Orbital period (sidereal)	4.02 yr (1,469 days)
Mean anomaly	6.1573°
Mean motion	0° 14m 42s / day
Inclination	10.825°
Longitude of ascending node	47.232°
Argument of perihelion	134.65°
Physical characteristics
Dimensions	6.50 km (calculated)[3] 12.683±0.288 km[4][5] 14.45±2.58 km[6] 15.29±1.04 km[7]
Synodic rotation period	10 h[8]
Geometric albedo	0.040±0.025[6][5] 0.063±0.010[7] 0.0833±0.0249[4] 0.20 (assumed)[3]
Spectral type	P[4] · X[3][9][10]
Absolute magnitude (H)	12.80[4][7] · 13.06±0.33[9] · 13.3[1][3][6]

It was discovered on 26 October 1971, by Czech astronomer Luboš Kohoutek at the Bergedorf Observatory in Hamburg, Germany.^[11] It was named after Renaissance astronomer Tadeáš Hájek.^[2]

Orbit and classification

Hajek orbits the Sun in the middle main-belt at a distance of 2.4–2.7 AU once every 4.02 years (1,469 days). Its orbit has an eccentricity of 0.05 and an inclination of 11° with respect to the ecliptic.^[1] It was first identified as 1941 EA at Heidelberg in 1941. The body's used observation was a precovery taken at Palomar Observatory in 1951, extending its observation arc by 20 years prior to the official discovery observation at Heidelberg.

Physical characteristics

A first rotational lightcurve of Hajek was obtained by French amateur astronomers Alain Klotz, Marc Rieugné, and Pierre Thierry in October 2013. It gave a provisional rotation period of 10 hours with a brightness variation of 0.10 magnitude (U=1+).^[8]

Hajek has the spectral properties of a metallic X-type asteroid.^[3][9][10] It is also classified as a dark P-type asteroid by NASA's Wide-field Infrared Survey Explorer (WISE).^[4]

According to the surveys carried out by the Japanese Akari satellite and WISE space-telescope with its subsequent NEOWISE mission, Hajek measures between 12.7 and 15.3 kilometers in diameter and its surface has an albedo of 0.040 and 0.083.^[4][6][7] The Collaborative Asteroid Lightcurve Link strongly disagrees with the space-based observations and assumes a standard albedo for stony asteroids of 0.200 and calculates a much smaller diameter of 6.5 kilometers.^[3] These contrasting albedo and diameter figures closely correspond to a generic magnitude-to-diameter conversion, where, for an absolute magnitude of 13.3, the body's diameter is in the range of 6 to 14 kilometers, based on an albedo between 0.05 and 0.25.^[12]

Naming

This minor planet was named after the Bohemian astronomer Tadeáš Hájek (1525–1600), better known by his Latinized name, Thaddaeus Hagecius. He was one of the founders of modern stellar and cometary astronomy, who studied the Great Comet of 1577 and the supernova SN 1572, also known as Tycho's Nova. The lunar crater Hagecius is also named in his honour.^[2] The official naming citation was published by the Minor Planet Center on 1 April 1978 (M.P.C. 4358).^[13]