编辑“︁C/2021 O3”︁

{{Infobox Comet
| name           = C/2021 O3 (PanSTARRS)
| image          =
| caption        = 在2021年8月5日加法夏望遠鏡拍攝的C/2021 O3(泛星彗星)。彗星位於中心，有一條向西南方向的微弱尾巴（右下）。
| discoverer     = [[泛星計畫]]
| discovery_date = 2021年7月26日
| designations   = <!-- please use for old-style designations only -->
| epoch          = 2021年8月21日
| obs_arc        = 53 天
| obs            = 279
| orbit          = [[歐特雲]]<ref name="horizons"/>
| perihelion     = 0.287 AU<ref name="jpldata"/>
| eccentricity   = 1.00005(1950曆元)<ref name="horizons"/><br/>1.002(2021年曆元) <ref name="jpldata"/><br/>1.0001 (epoch 2100)<ref name="horizons"/>
| max_speed      = 
| inclination    = 56.75°
| node           = 189.03°
| peri           = 299.97°
| tjup           = 0.446
| Earth_moid     = 0.062 au<ref name="jpldata"/>
| Jupiter_moid   = 2.16 au
| dimensions     = 
| albedo         = 
| M1             = 10.6
| M2             = 
| next_p         = 2022年4月21日
| b_semimajor    = <!--barycentric semimajor axis, generally used only for long-period or hyperbolic comets -->
| b_period       = 
}}

'''C/2021 O3 (泛星彗星)'''是顆來自[[歐特雲]]的[[彗星]]，它於[[泛星計畫]]在2021年7月21日的巡天調查中發現。它將於2022年4月21日最接近太陽，以{{Convert | 0.287 | AU | e6km | abbr=unit | lk=on}}的距離通過[[近日點]]。到2022年4月底，它的[[視星等]]可能達到5-7等，但離太陽只有15度<ref name="CBET5009"/><ref name="Yoshida"/>。C/2021 O3將於2022年5月8日最接近地球，距離為{{Convert | 0.60 | AU | e6km | abbr=unit}}<ref name="Earth"/>。做為一顆來自歐特雲的新彗星動態，解體的風險很高。

== 軌道 ==
[[File:C2021-O3-orbit.png|left|thumb|320x320px|C/2021 O3穿過太陽系內部的軌道]]
{{clear|left}}

在[[觀測弧]]只有7天的短期間，[[小行星中心]]使用離心率1.0的假設作為軌道解<ref name="MPEC2021-P05"/>。由於統計數字較少，在10天的短觀測弧中，JPL的離心率為{{val | 0.99595 | 0.00444}}，可能高達1.00039或低至0.99151<ref name=jpl-10days/>；觀察弧為53天時，[[噴氣推進實驗室線上曆書系統|JPL Horizons]]顯示出這顆彗星進入和離開內太陽系的離心率均大於1<ref name="horizons"/>。

C/2021 O3可能需要數百萬年才能從外層歐特雲抵達內太陽系，並可能從太陽系逃逸<ref name="horizons"/>。

== 參考資料 ==
{{reflist|refs=

<ref name="jpldata">{{cite web
  |title      = JPL Small-Body Database Browser: C/2021 O3 (PANSTARRS)
  |url      = https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=2021O3
  |publisher      = [[Jet Propulsion Laboratory]]
  |accessdate      = 28 September 2021
  |archive-date      = 2022-11-18
  |archive-url      = https://web.archive.org/web/20221118233034/https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=2021O3
  |dead-url      = no
  }}</ref>

<ref name="horizons">{{cite web
 |title        = JPL Horizons On-Line Ephemeris for 2021 O3 at epoch 1950 and 2100 (barycentric)
 |url          = https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272021+O3%27&TABLE_TYPE=%27ELEMENTS%27&START_TIME=%271950-01-01%27&STOP_TIME=%272100-01-01%27&STEP_SIZE=%27150%20years%27&CENTER=%27@0%27&OUT_UNITS=%27AU-D%27
 |work         = [[JPL Horizons On-Line Ephemeris System]]
 |publisher    = [[Jet Propulsion Laboratory]]
 |access-date  = 29 September 2021
 |archive-date = 2021-09-29
 |archive-url  = https://web.archive.org/web/20210929134237/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272021+O3%27&TABLE_TYPE=%27ELEMENTS%27&START_TIME=%271950-01-01%27&STOP_TIME=%272100-01-01%27&STEP_SIZE=%27150%20years%27&CENTER=%27%400%27&OUT_UNITS=%27AU-D%27
 |dead-url     = no
}} Solution using the Solar System [[Barycenter]]. Ephemeris Type:Elements and Center:@0 (To be outside planetary region, inbound epoch 1950 and outbound epoch 2100. Aphelia/orbital periods defined while in the planetary-region are misleading for knowing the long-term inbound/outbound solutions.)</ref>

<ref name="Earth">{{cite web
  |title=Closest Approach to Earth 2022
  |publisher=[[JPL Horizons On-Line Ephemeris System|JPL Horizons]]
  |type=Closest Earth approach occurs when deldot flips from negative to positive
  |url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272021+O3%27&START_TIME=%272022-05-01%27&STOP_TIME=%272022-05-20%27&STEP_SIZE=%273%20hours%27&QUANTITIES=%2720%27
  |accessdate=2021-09-29
  |archive-date=2021-09-29
  |archive-url=https://web.archive.org/web/20210929195638/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272021+O3%27&START_TIME=%272022-05-01%27&STOP_TIME=%272022-05-20%27&STEP_SIZE=%273%20hours%27&QUANTITIES=%2720%27
  |dead-url=no
  }}</ref>

<ref name="CBET5009">{{cite web
  |title=Electronic Telegram No. 5009
  |url=http://www.cbat.eps.harvard.edu/iau/cbet/005000/CBET005009.txt
  |work=Central Bureau Electronic Telegrams
  |date=1 August 2021
  |access-date=2021-09-24
  |archive-date=2022-04-21
  |archive-url=https://web.archive.org/web/20220421112320/http://www.cbat.eps.harvard.edu/iau/cbet/005000/CBET005009.txt
  |dead-url=no
  }}</ref>

<ref name="Yoshida">{{cite web
  |title=C/2021 O3 ( PanSTARRS )
  |url=http://www.aerith.net/comet/catalog/2021O3/2021O3.html
  |work=Seiichi Yoshida
  |access-date=2021-10-13
  |archive-date=2022-09-25
  |archive-url=https://web.archive.org/web/20220925072726/http://www.aerith.net/comet/catalog/2021O3/2021O3.html
  |dead-url=no
  }}</ref>

<ref name="MPEC2021-P05">{{cite web
  |title=MPEC 2021-P05 : COMET C/2021 O3 (PANSTARRS)] (7-day arc)
  |url=http://mpcweb1.cfa.harvard.edu/mpec/K21/K21P05.html
  |work=Minor Planet Electronic Circulars
  |publisher=Minor Planet Center
  |date=1 August 2021}}</ref>

<ref name=jpl-10days>Archive of [https://web.archive.org/web/20210816174313/https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=C/2021%20O3;orb=0;cov=0;log=0;cad=0 JPL #2] (with a 10 day arc)</ref>

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

== 外部連結 ==
* {{JPL small body|id=1003796}}

{{彗星}}

{{DEFAULTSORT:C/2021 O3 (PanSTARRS)}}

[[Category:非週期彗星]]
[[Category:2021年彗星]]
[[Category:彗星]]
[[Category:歐特雲]]
[[Category:2021年發現的天體|20210726]]
[[Category:泛星計畫發現的天體]]