4769 Castalia


F. Helin - 1989.

Diameter (km)

1.8 x 0.8

Mass (kg)


Rotation period (hrs)


Orbital period (yrs)


Semimajor axis (AU)


Orbital eccentricity


Orbital Inclination (deg)






Asteroid 4769 Castalia is a near-Earth asteroid that was discovered by Eleanor F. Helin on August 9, 1989. Named for Castalia, a nymph pursued by Apollo (asteroid 1862) . Fleeing his attention, she dived into the earth, whence a spring burst forth and was given her name. The mythical spring, on Mount Parnassus at Delphi, was the site of the most important oracle to ancient Greece. Castalia was sacred to the muses and was considered a divine source of poetic inspiration. The name also refers to a genus of aquatic plants of the water-lily family, distinguished by rounded, floating leaves and large, fragrant flowers of various colors. Name suggested by S. Ostro, who captured the stunning radar images of 1989 PB, soon after its discovery.

Scientists used radar and computer modeling to generate images of Castalia. They obtained the data for the computer model in 1989 using the Arecibo radio telescope when the asteroid passed within 5.6 million kilometers of the Earth. Castalia has a peanut shape and is about 1.8 kilometers across at its widest. Its two distinct lobes are about 750 meters across. It is possible that two lobes were separate objects that came together after a relatively gentle collision. The surfaces of both lobes have similar composition and roughness.

Images of Castalia

The most useful observations, on Aug. 22, yielded a 64-frame sequence of images that resolve the asteroid in time delay (range) and Doppler frequency (line-of-sight velocity). Here the images are shown smoothed and color-coded for intensity. These images are covering 60% of the asteroid's 4.07 hour rotation period.

The 64 images may also be viewed at their raw resolution. The equivalent linear dimensions of the radar resolution cells in these images are 150 x 170 meters.

This view of Castalia shows one of 16 different views of a 3D computer model. All 16 views can be obtained by selecting this image.

(Credit NASA-JPL)

Another 3D computer model.

(Credit Scott Hudson)

What would happen if you left a hose running on Castalia? The resulting "gravitational isopotentials" (i.e., "sea-levels") are illustrated in this image.

(Credit Scott Hudson)


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Last updated: March 15, 2002.