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June 17, 1997


The Apollo-type asteroid 3671 Dionysus, an Earth-crosser in a 3.25 year orbit, is having a close approach of about 17 million km of Earth in July, when it will brighten to 15th magnitude. When Stefano Motola and Gerhard Hahn of DLR - Institute of Planetary Exploration, Berlin observed its rotational light curve earlier this month, they noticed a brightness change of 0.08 evrey 1.15 days. So probably Dionysus has a companion, and we are now looking right along its orbital plane.

Dionysus would not be the only asteroid with a small moonlet. Four years ago the Galileo spacecraft discovered thay asteroid 243 Ida is orbited by a small moonlet, which was later named Dactyl.

A good photometric coverage is needed to determine the dynamical properties of the probable Dionysus asteroid/satellite system. Mottola and Hahn inivite interested observers that have access to suitable instrumentation to follow Dionysus and perform accurate, time-resolved photometry of this object. Predictions fot expected occultation events can be found on their home page.

June 10, 1997


According the IAU Circular 6680, astronomers S. Mottola, G. Hahn, P. Pravec and L. Sarounova using the European Southern Observatory in Chile may have discovered a satellite orbiting the asteroid 3671 Dionysus. Based on observations made from May 30 to June 8, attenutations in the asteroid's brightness were noted, and a period of 1.155 days was derived from these observations. They interpreted these features as occultations/eclipses of a satellite orbiting the asteroid. Observers are encouraged to participate in a monitoring campaign available at:

Asteroid 3671 Dionysus was discovered by Eugene and Carolyn Shoemaker on May 27, 1984 at the Palomar Observatory. The asteroid was named after the Greek God of vegetation, wine and pleasure. It is an Apollo asteroid and its orbit overlaps the Earth's orbit. Asteroid 3671 Dionysus will make make a close flyby of Earth on July 6 of this year at a distance of 0.1144 AU (10.6 million miles or 17.2 million km) with a expected magnitude of 14.9.

Oribital elements and ephemeris of Asteroid 3671 Dionysus are available at the Minor Planet Center operated by the Smithosian Astrophysical Observatory.

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