3700 Geowilliams, provisional designation 1984 UL₂, is a stony background asteroid from the inner regions of the asteroid belt, approximately 8 kilometers (5 miles) in diameter. It was discovered on 23 October 1984, by American astronomer couple Carolyn and Eugene Shoemaker at the Palomar Observatory in California, United States. ^[1] The S k-subtype has a rotation period of 14.38 hours. It was named for Australian geologist George E. Williams. ^[1]

Geowilliams is a non- family asteroid from the main belt's background population. ^[4] It orbits the Sun in the inner main-belt at a distance of 1.9–3.0  AU once every 3 years and 9 months (1,371 days; semi-major axis of 2.41 AU). Its orbit has an eccentricity of 0.23 and an inclination of 12 ° with respect to the ecliptic. ^[2] The body's observation arc begins with its first observation as 1973 YF₂ at Crimea-Nauchnij in December 1973, almost 11 years prior to its official discovery observation at Palomar. ^[1]

In the SMASS classification, Geowilliams is a Sk-subtype that transitions between the common S-type asteroid and the K-type asteroid. The latter spectral type is often found among members of the Eos family. ^[2]

In January 2008, a rotational lightcurve of Geowilliams was obtained from photometric observations by Australian amateur astronomer David Higgins at the Hunters Hill Observatory ( E14). Lightcurve analysis gave a well-defined rotation period of 14.387 hours with a brightness variation of 0.40 magnitude ( U=3). ^[a] In July 2010, a similar period of 14.383 hours and an amplitude of 0.42 was measured at the Palomar Transient Factory in California ( U=2). ^[10]

According to the surveys carried out by the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Geowilliams measures between 7.712 and 8.82 kilometers in diameter and its surface has an albedo between 0.227 and 0.297. ^{[5] [6] [7] [8] [9]}

The Collaborative Asteroid Lightcurve Link assumes a standard albedo for a stony asteroid of 0.20, and calculates a diameter of 8.97 kilometers based on an absolute magnitude of 12.6. ^[3]

This minor planet was named after Australian geologist George E. Williams who discovered the Acraman crater when he worked for BHP in South Australia. The old 90-kilometer impact structure is one of the largest meteorite impact craters known on Earth and the largest one on the Australian continent. ^[1] The official naming citation was published by the Minor Planet Center on 2 February 1988 ( M.P.C. 12810). ^[12]

• "Lightcurves by David Higgins". Archived from the original on 25 October 2010. Retrieved 14 May 2018.
• George E. Williams – University Staff Director, University of Adelaide
• Asteroid Lightcurve Database (LCDB), query form ( info Archived 16 December 2017 at the Wayback Machine)
• Dictionary of Minor Planet Names, Google books
• Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
• 3700 Geowilliams at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 3700 Geowilliams at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters