858 El Djezaïr

For the Algerian city, see Algiers.

858 El Djezaïr /ɛlˌdʒɛzɑːˈɪər/ is a stony asteroid from the asteroid belt, about 24 kilometers in diameter. It was discovered on 26 May 1916, by French astronomer Frédéric Sy at the Algiers Observatory in Algeria, North Africa, and given the provisional designation 1916 a.^[1]

858 El Djezaïr

Discovery[1]
Discovered by	F. Sy
Discovery site	Algiers Observatory
Discovery date	26 May 1916
Designations
MPC designation	(858) El Djezaïr
Pronunciation	/ɛlˌdʒɛzɑːˈɪər/
Named after	Algiers (Arabic name)[2]
Alternative designations	1916 a · A908 UC A911 HE
Minor planet category	main-belt
Orbital characteristics[1]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc	106.80 yr (39010 days)
Aphelion	3.0983 AU (463.50 Gm)
Perihelion	2.5252 AU (377.76 Gm)
Semi-major axis	2.8118 AU (420.64 Gm)
Eccentricity	0.10192
Orbital period (sidereal)	4.71 yr (1722.1 d)
Mean anomaly	102.29°
Mean motion	0° 12m 32.544s / day
Inclination	8.8726°
Longitude of ascending node	67.197°
Argument of perihelion	179.05°
Earth MOID	1.51148 AU (226.114 Gm)
Jupiter MOID	1.9171 AU (286.79 Gm)
TJupiter	3.296
Physical characteristics
Mean radius	11.755±1.3 km
Synodic rotation period	22.31 h (0.930 d)
Geometric albedo	0.3197±0.085
Spectral type	Tholen = S
Absolute magnitude (H)	10.2

The asteroid orbits the Sun at a distance of 2.5–3.1 AU once every 4.71 years (1,722 days). The bright S-type asteroid has a very high geometric albedo of 0.32. Its rotation period has been measured to take 22 hours and 20 minutes.^[3] Along with the asteroids 68 Leto and 236 Honoria, it is a member of the Leto family, a small, well-defined group of asteroids, all with a semi-major axis of close to 2.8 AU.

El Djezaïr is the French spelling of the Arabic name for Algiers, the capital of Algeria. It means "the islands". The asteroid was the first minor planet to receive a name that consists of more than one word.^[2] Its designation, 1916 a, is a superseded version of the modern two-letter code system of provisional designation, implemented just a few years later in 1925.