Discoverer

E. F. Helin - 1991

Diameter (km)

0.35 x 0.25 x 0.25

Mass (kg)

?

Rotation period (hrs)

6.02640

Orbital period (yrs)

3.98561

Semimajor axis (AU)

2.51535

Orbital eccentricity

0.597909

Orbital Inclination (deg)

2.291

Albedo

0.6

Type

V

Named to honor the success of the multinational radar observations of this minor planet in June 1985. The 70-m Goldstone antenna in California provided the transmitted signal, and echoes from the object were detected by the Russian 70-m antenna near the Crimean city of Evpatoria, and also by the Japanese 34-m antenna at Kashima. This experiment, which produced the first international radar astronomy observations and also initiated planetary radar astronomy in Japan, was done during the closest approach of this minor planet for at least the next several centuries. The discoverer has encouraged radar and remote sensing observations for many years and is pleased with the results. The name is composed by the leading letters of the names of the observing places: GOLdstone - EVpatoria - KAshima. Name proposed by the discoverer following a suggestion by A. L. Zajtsev.

The approach of asteroid 6489 Golevka (1991 JX) to 0.034 AU from Earth on June 9, 1995 (its closest for at least the next two centuries), provided an excellent opportunity for radar investigations. Observations were continued on June 3, 4, and 6-15, using a variety of radar configurations.

On two dates we conducted radar aperture-synthesis observations, with Goldstone transmitting and the VLA receiving.

On June 13-15 was carried out the first intercontinental radar astronomy observations, consisting of Goldstone transmissions and reception of the asteroid's echoes with the Evpatoria (Ukraine) 70-m antenna on each of those dates and reception of echoes with the Kashima (Japan) 34-m antenna on June 15.

All pointing and delay-Doppler prediction ephemerides for this experiment were generated at Goldstone with JPL's On-site Orbit Determination program. By June 8, inclusion of radar astrometry had produced a solution that was extremely accurate -- its prediction for the asteroid's delay-Doppler trajectory during June 9-15 was found to be accurate to within 30 m.

Golevka is no more than 0.6 km in maximum overall dimension. Its pole-on elongation is 1.4 and its three-dimensional shape is strikingly irregular and angular.

The spectrum of 6489 Golevka was originally interpreted as a V-type, comparable to the class of what is thought to be achondritic asteroids associated with 4 Vesta. Though it is becoming quite obvious that a significant fraction of small Earth-approaching asteroids exhibit colors and spectra across visible wavelengths consistent with ordinary chondritic meteorites, more work is needed at longer wavelengths to help resolve ambiguities in the interpretation of their spectra.

6489 Golevka was observed with NSFCAM on the NASA IRTF telescope on the nights of June 15 and 16 1999, obtaining several spectra. Preliminary reduction of the NSFCAM spectra reveals an object with deep 1 and 2-micron absorptions, consistent with a pyroxene rich surface.

Images of Golevka

Asteroid 6489 Golevka is strikingly irregular and angular. It is one of the smallest objects imaged so far. Smaller asteroids are 1998 KY26 and 1996 JG.

Delay-Doppler radar images were obtained by Ostro at Goldstone during June 1995. If you click on the image you'll see the imaging data set with "low-resolution" images (38 meter) on the left and "high-resolution" images (19 meters) on the right.

Dan Scheeres of University of Michigan calculated the gravitational slopes on the surface of Golevka and Eric de Jong and Shigeru Suzuki of JPL's DIAL laboratory rendered them in the image at left. Golevka's very angular shape results in some very steep slopes on its surface, some larger than 45 degrees. It is likely that no loose material could stay put on such a sloped surface, so these areas, at least, are probably exposed rock. The shape and the large slopes also argue against Golevka being a loosely bound "rubble pile" of much smaller, gravel-like fragments.

Golevka has a bizarre, very angular shape. Click on the left image to see several views of the shape model with lines of longitude and latitude draw every 10 degrees.

Credit Scott Hudson