Editing 4769 Castalia

{{Short description|Asteroid}}
{{Use dmy dates|date=October 2019}}
{{Infobox planet
| minorplanet = yes
| background = #FFC2E0
| name = 4769 Castalia
| image = 4769Castalia-P36165BC-crop.gif
| image_scale =
| caption = [[Arecibo Observatory|Arecibo]] [[radar astronomy|radar]] image showing Castalia as a [[contact binary (asteroid)|contact binary]]
| discovery_ref = <ref name=jpldata/>
| discoverer = [[Eleanor F. Helin|E. F. Helin]]<br />[[Palomar Observatory]] ([[List of observatory codes#600-699|675]])
| discovered = 9 August 1989
| mpc_name = (4769) Castalia
| alt_names = 1989 PB
| named_after = [[Castalia]]
| pronounced = {{IPAc-en|k|æ|ˈ|s|t|eɪ|l|i|ə}}<ref>{{OED|Castalia}}</ref>
| mp_category = {{Ubl
 | [[List of Apollo asteroids|Apollo]]
 | [[Near-Earth object|NEO]]
 | [[Potentially hazardous object|PHA]]<ref name="jpldata"/>
 | [[Venus-crosser asteroid]]
 | [[Mars-crosser asteroid]]
 }}
| orbit_ref = <ref name="jpldata"/>
| epoch = 13 January 2016 ([[Julian day|JD]]&nbsp;2457400.5)
| observation_arc = 9467 days (25.92&nbsp;yr)
| uncertainty = 0
| aphelion = {{Convert|1.5770|AU|Gm|abbr=on|lk=on}}
| perihelion = {{Convert|0.54957|AU|Gm|abbr=on}}
| semimajor = {{Convert|1.0633|AU|Gm|abbr=on}}
| eccentricity = 0.48313 (e)
| period = 1.10&nbsp;[[Julian year (astronomy)|yr]] (400.46&nbsp;[[Julian year (astronomy)|d]])
| inclination = 8.8863°
| asc_node = 325.59°
| mean_motion = {{Deg2DMS|0.89896|sup=ms}} / day
| mean_anomaly = 327.23[[Degree (angle)|°]]
| arg_peri = 121.35°
| satellites = 1 [[contact binary (asteroid)|contact binary]]
| moid = {{Convert|0.0199|AU|LD|abbr=on}}<ref name=jpldata />
| mean_diameter = {{Ubl
 | 1.4&nbsp;km<ref name=jpldata/>
 | 1.8×0.8&nbsp;km
 }}
| rotation = {{Convert|4.095|h|d|abbr=on|lk=on}}<ref name=jpldata />
| albedo = 
| spectral_type = 
| magnitude = 
| abs_magnitude = 16.9<ref name="jpldata"/>
}}

'''4769 Castalia''' ({{IPAc-en|k|ə|ˈ|s|t|eɪ|l|i|ə}}; ''[[Minor planet provisional designation|prov. designation]]:'' {{mp|1989 PB}}) is a [[near-Earth object]] and [[potentially hazardous asteroid]] of the [[Apollo asteroid|Apollo group]], approximately {{convert|1.4|km|mi|abbr=off|sp=us}} 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-crosser asteroid|Mars-]] and [[Venus-crosser asteroid]].<ref name=jpldata />

==General information==

On 25 August 1989 Castalia passed {{convert|0.0269378|AU|km mi|abbr=on|lk=on}}<ref name=jpl-close/> (within eleven [[Lunar distance (astronomy)|lunar distance]]s) of Earth, allowing it to be observed with [[Radar astronomy|radar]] from the [[Arecibo Observatory]] by [[Scott Hudson (electrical engineer)|Scott Hudson]] ([[Washington State University]]) and [[Steven J. Ostro]] ([[Jet Propulsion Laboratory|JPL]]). The data allowed Hudson et al. to produce a three-dimensional [[Mathematical model|model]] of the object. During the 1989 passage Castalia peaked at an [[apparent magnitude]] of 12.<ref name="NEODyS1989"/>

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 binary (asteroid)|contact binaries]].<ref name="Binary"/>

Castalia is a [[potentially hazardous asteroid]] (PHA) because its [[minimum orbit intersection distance]] (MOID) is less than 0.05&nbsp;AU and its diameter is greater than 150 meters. The Earth-MOID is {{convert|0.0204|AU|km mi|abbr=on|lk=on}}.<ref name=jpldata/> Its orbit is well-determined for the next several hundred years.

{| class="wikitable" style="font-size: 0.9em;"
|+Earth Approach on 22 August 2023<ref name=jpldata/>
! Date
! [[JPL Horizons]]<br />[[Curve fitting|nominal]] geocentric<br />distance ([[astronomical unit|AU]])
! uncertainty<br />region<br />([[3-sigma]])
|-
|2023-Aug-22 09:21 ||{{Convert|0.11003|AU|e6km|abbr=unit|lk=on}}<ref name="jpldata"/> || ±{{val|6|u=km}}<ref name="CA2023"/>
|}

==See also==
* [[List of notable asteroids]]

== References ==
{{reflist|refs=

<ref name=jpldata>{{cite web
  |title=JPL Small-Body Database Browser: 4769 Castalia (1989 PB)
  |url=https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Castalia
  |publisher=Jet Propulsion Laboratory
  |access-date=14 April 2016}}</ref>

<ref name=jpl-close>{{cite web
  |title=JPL Close-Approach Data: 4769 Castalia (1989 PB)
  |url=https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Castalia;cad=1#cad
  |access-date=2012-06-17}}</ref>

<ref name="NEODyS1989">{{cite web
  |title=(4769) Castalia Ephemerides for August 1989
  |publisher=NEODyS (Near Earth Objects{{Snd}} Dynamic Site)
  |url=https://newton.spacedys.com/neodys/index.php?pc=1.1.3.1&n=4769&oc=500&y0=1989&m0=8&d0=1&h0=0&mi0=0&y1=1989&m1=9&d1=3&h1=0&mi1=0&ti=1.0&tiu=days
  |access-date=2012-06-20}}</ref>

<ref name="Binary">{{cite web
  |date=2013-11-18
  |title=Binary and Ternary near-Earth Asteroids detected by radar
  |publisher=NASA/JPL Asteroid Radar Research
  |author=Lance A. M. Benner
  |url=http://echo.jpl.nasa.gov/~lance/binary.neas.html
  |archive-url=https://web.archive.org/web/20040608071121/http://echo.jpl.nasa.gov/~lance/binary.neas.html
  |archive-date=2004-06-08
  |access-date=2014-03-01}}</ref>

<ref name="CA2023">{{cite web
  |title=Horizons Batch for 2023-08-22 Close Approach
  |publisher=[[JPL Horizons On-Line Ephemeris System|JPL Horizons]]
  |url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Castalia%27&START_TIME=%272023-08-22%2009:21%27&STOP_TIME=%272023-08-23%27&STEP_SIZE=%271%20day%27&QUANTITIES=%2720,39%27
  |archive-url=https://web.archive.org/web/20221026114836/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Castalia%27&START_TIME=%272023-08-22%2009:21%27&STOP_TIME=%272023-08-23%27&STEP_SIZE=%271%20day%27&QUANTITIES=%2720,39%27
  |archive-date=2022-10-26
  |url-status=live
  |accessdate=2022-10-26}} RNG_3sigma = uncertainty range in km. (JPL#95/Soln.date: 2022-Jul-11 generates RNG_3sigma = {{val|5.8|u=km}})</ref>

}} <!-- end of reflist -->

==External links==
* {{cite web
  |date=1996-05-15
  |title=Radar image of 4769 Castalia
  |publisher=Arecibo Observatory
  |author=Mike Nolan
  |url=http://www.naic.edu/~nolan/radar/Castalia.html
  |access-date=2012-06-19}}
* [http://echo.jpl.nasa.gov/asteroids/4769_Castalia/cast01.html NASA Asteroid Radar Search – The 228 Radar-Detected Asteroids: Asteroid 4769 Castalia]
* {{NeoDys|4769}}
* {{ESA-SSA|4769|Castalia}}
* {{JPL small body}}

{{Minor planets navigator |4768 Hartley |number=4769 |4770 Lane}}
{{Authority control}}

{{DEFAULTSORT:Castalia}}
[[Category:Apollo asteroids|004769]]
[[Category:Discoveries by Eleanor F. Helin]]
[[Category:Named minor planets]]
[[Category:Potentially hazardous asteroids|004769]]
[[Category:Contact binary (small Solar System body)|004769]]
[[Category:Radar-imaged asteroids|004769]]
[[Category:Astronomical objects discovered in 1989|19890809]]
[[Category:Near-Earth objects in 2023|20230822]]