4769 Castalia (/kəˈsteɪliə/; prov. designation: 1989 PB) is a near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 1.4 kilometers (0.87 miles) in diameter and was the first asteroid to be modeled by radar imaging. It was discovered on 9 August 1989, by American astronomer Eleanor Helin (Caltech) on photographic plates taken at Palomar Observatory in California. It is named after Castalia, a nymph in Greek mythology. It is also a Mars- and Venus-crosser asteroid.[1]

4769 Castalia

Arecibo radar image showing Castalia as a contact binary
Discovery[1]
Discovered by	E. F. Helin Palomar Observatory (675)
Discovery date	9 August 1989
Designations
MPC designation	(4769) Castalia
Pronunciation	/kæˈsteɪliə/[2]
Named after	Castalia
Alternative designations	1989 PB
Minor planet category	Apollo NEO PHA[1] Venus-crosser asteroid Mars-crosser asteroid
Orbital characteristics[1]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 0
Observation arc	9467 days (25.92 yr)
Aphelion	1.5770 AU (235.92 Gm)
Perihelion	0.54957 AU (82.215 Gm)
Semi-major axis	1.0633 AU (159.07 Gm)
Eccentricity	0.48313 (e)
Orbital period (sidereal)	1.10 yr (400.46 d)
Mean anomaly	327.23°
Mean motion	0° 53m 56.256s / day
Inclination	8.8863°
Longitude of ascending node	325.59°
Argument of perihelion	121.35°
Known satellites	1 contact binary
Earth MOID	0.0199 AU (7.7 LD)[1]
Physical characteristics
Mean diameter	1.4 km[1] 1.8×0.8 km
Synodic rotation period	4.095 h (0.1706 d)[1]
Absolute magnitude (H)	16.9[1]

General information

On 25 August 1989 Castalia passed 0.0269378 AU (4,029,840 km; 2,504,020 mi)[3] (within eleven lunar distances) of Earth, allowing it to be observed with radar from the Arecibo Observatory by Scott Hudson (Washington State University) and Steven J. Ostro (JPL). The data allowed Hudson et al. to produce a three-dimensional model of the object. During the 1989 passage Castalia peaked at an apparent magnitude of 12.[4]

Castalia has a peanut shape, suggesting two approximately 800-meter-diameter pieces held together by their weak mutual gravity. Since then radar observations of other asteroids have found other contact binaries.[5]

Castalia is a potentially hazardous asteroid (PHA) because its minimum orbit intersection distance (MOID) is less than 0.05 AU and its diameter is greater than 150 meters. The Earth-MOID is 0.0204 AU (3,050,000 km; 1,900,000 mi).[1] Its orbit is well-determined for the next several hundred years.

See also

• List of notable asteroids

References

External links

• Mike Nolan (15 May 1996). "Radar image of 4769 Castalia". Arecibo Observatory. Retrieved 19 June 2012.
• NASA Asteroid Radar Search – The 228 Radar-Detected Asteroids: Asteroid 4769 Castalia
• 4769 Castalia at NeoDyS-2, Near Earth Objects—Dynamic Site
  • Ephemerides · Observation prediction · Orbital info · MOID · Proper elements · Observational info · Close approaches · Physical info · Orbit animation
• 4769 Castalia at ESA–space situational awareness
  • Ephemerides · Observations · Orbit · Physical properties · Summary
• 4769 Castalia at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters

На других языках

[de] (4769) Castalia

[ru] (4769) Касталия