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]
| 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 | |
| (4769) Castalia | |
| Pronunciation | /kæˈsteɪliə/[2] |
Named after | Castalia |
| 1989 PB | |
| 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) |
| 1.0633 AU (159.07 Gm) | |
| Eccentricity | 0.48313 (e) |
| 1.10 yr (400.46 d) | |
| 327.23° | |
| 0° 53m 56.256s / day | |
| Inclination | 8.8863° |
| 325.59° | |
| 121.35° | |
| Known satellites | 1 contact binary |
| Earth MOID | 0.0199 AU (7.7 LD)[1] |
| Physical characteristics | |
| |
| 4.095 h (0.1706 d)[1] | |
| 16.9[1] | |
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.
| Date | JPL Horizons nominal geocentric distance (AU) | uncertainty region (3-sigma) |
|---|---|---|
| 2023-Aug-22 09:21 | 0.11003 AU (16.460 million km)[1] | ±6 km[6] |
- ^ a b c d e f g h i j k “JPL Small-Body Database Browser: 4769 Castalia (1989 PB)”. Jet Propulsion Laboratory. Retrieved 14 April 2016.
- ^ “Castalia”. Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
- ^ “JPL Close-Approach Data: 4769 Castalia (1989 PB)”. Retrieved 17 June 2012.
- ^ “(4769) Castalia Ephemerides for August 1989”. NEODyS (Near Earth Objects – Dynamic Site). Retrieved 20 June 2012.
- ^ Lance A. M. Benner (18 November 2013). “Binary and Ternary near-Earth Asteroids detected by radar”. NASA/JPL Asteroid Radar Research. Archived from the original on 8 June 2004. Retrieved 1 March 2014.
- ^ “Horizons Batch for 2023-08-22 Close Approach”. JPL Horizons. Archived from the original on 26 October 2022. Retrieved 26 October 2022. RNG_3sigma = uncertainty range in km. (JPL#95/Soln.date: 2022-Jul-11 generates RNG_3sigma = 5.8 km)
- 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
- 4769 Castalia at ESA–space situational awareness
- 4769 Castalia at the JPL Small-Body Database
