Radar imaging of binary near-earth asteroid (66391) 1999 KW4

Steven J. Ostro, Jean Luc Margot, Lance A.M. Benner, Jon D. Giorgini, Daniel J. Scheeres, Eugene G. Fahnestock, Stephen B. Broschart, Julie Bellerose, Michael C. Nolan, Christopher Magri, Petr Pravec, Petr Scheirich, Randy Rose, Raymond F. Jurgens, Eric M. De Jong, Shigeru Suzuki

Research output: Contribution to journalArticlepeer-review

234 Scopus citations


High-resolution radar images reveal near-Earth asteroid (66391) 1999 KW4 to be a binary system. The ∼1.5-kilometer-diameter primary (Alpha) is an unconsolidated gravitational aggregate with a spin period ∼2.8 hours, bulk density ∼2 grams per cubic centimeter, porosity ∼50%, and an oblate shape dominated by an equatorial ridge at the object's potential-energy minimum. The ∼0.5-kilometer secondary (Beta) is elongated and probably is denser than Alpha. Its average orbit about Alpha is circular with a radius ∼2.5 kilometers and period ∼17.4 hours, and its average rotation is synchronous with the long axis pointed toward Alpha, but librational departures from that orientation are evident. Exotic physical and dynamical properties may be common among near-Earth binaries.

Original languageEnglish (US)
Pages (from-to)1276-1280
Number of pages5
Issue number5803
StatePublished - Nov 24 2006
Externally publishedYes

ASJC Scopus subject areas

  • General


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