3671 Dionysus

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3671 Dionysus
Orbit of 3671 Dionysus.gif
Orbit of 3671 Dionysus
Discovered by Carolyn and Gene Shoemaker
Discovery site Palomar Observatory
Discovery date May 27, 1984
MPC designation 3671
Named after
1984 KD[1]
Orbital characteristics[1]
Epoch August 27, 2011 (JD 2455800.5
Aphelion 3.389130075 AU
Perihelion 1.00645923 AU
2.197794652 AU
Eccentricity 0.54205947
3.258283510 yr (1190.088052 d)
Inclination 13.547627°
Known satellites 1
Physical characteristics
Dimensions 1.5 km[1]
Mean density
1.6 g/cm3[2]
2.7053 h[1]

3671 Dionysus is a small binary Amor asteroid, orbiting between Earth and the asteroid belt. It was discovered by Carolyn and Gene Shoemaker at Palomar Observatory on 27 May 1984. It is named after Dionysus, the Greek god of wine. Its provisional designation was 1984 KD. It is an outer Earth grazer because its perihelion is just within Earth's orbit.

Near-Earth object[edit]

Dionysus makes many close approaches to Earth. Its closest approach so far occurred in 1984, when Dionysus passed just 0.03047 astronomical units (4,558,000 km) from Earth.[1] Dionysus is expected to continue to make close approaches.


In 1997, a team of astronomers at the European Southern Observatory announced that lightcurve observations indicate the presence of a small moon orbiting Dionysus. Its provisional designation is S/1997 (3671) 1. This moon measures 300 meters in diameter, and orbits 3.6 km from Dionysus with an eccentricity of 0.07 and an orbital period of 27.72 hours.[3] From the surface of Dionysus, S/1997 (3671) 1 would have an apparent diameter of roughly 3.02 degrees.[a] For comparison, the Sun appears to be 0.5° from Earth.


  1. ^ Calculated by solving the equation  \scriptstyle{\mathrm{tan}\left(\frac{\theta}{2}\right) = \frac{\mathrm{radius~of~moon}}{\mathrm{distance~from~surface~of~asteroid~to~center~of~moon}}}.