View source for 87P/Bus

{{short description|Periodic comet}}
{{Use dmy dates|date=June 2025}}
{{Infobox comet
| name            = 87P/Bus
| image           = Comet 87P Bus u65z1f02r.fits.gz sci.jpg
| caption         = Comet 87P/Bus photographed by the [[Hubble Space Telescope]] on 7 June 2001
| discovery_ref   = {{r|IAUC_3578}}
| discoverer      = [[Schelte J. Bus]]
| discovery_site  = [[Siding Spring Observatory]]<br>{{small|([[UK Schmidt Telescope]])}}
| discovery_date  = 2 March 1981
| mpc_name        = P/1981 E1, P/1987 B4
| designations    = {{unbulleted|1981 XI, 1987 XXXIV|1994 XVI|1981b, 1987f, 1993b}}
| orbit_ref       = {{r|jpldata|MPC}}
| epoch           = 31 May 2025 ([[Julian day|JD]] 2459000.5)
| observation_arc = 39.57 years
| earliest_precovery_date = 9 February 1981
| obs             = 801
| perihelion      = 2.099 AU
| aphelion        = 4.776 AU
| semimajor       = 3.438 AU
| eccentricity    = 0.38918
| period          = 6.374 years
| inclination     = 2.603°
| asc_node        = 181.87°
| arg_peri        = 24.932°
| mean            = 3.356°
| tjup            = 3.009
| Earth_moid      = 1.098 AU
| Jupiter_moid    = 0.181 AU
| physical_ref    = {{r|Lamy_2009}}
| mean_radius     = {{val|0.27|0.01}} km
| spectral_type   = (V–R) {{=}} {{val|0.545|0.02}}{{r|Meech_2004}}
| rotation        = {{val|32.0|9.0}} hours
| M1              = 12.7
| M2              = 16.1
| magnitude       = 
| last_p          = 9 May 2020
| next_p          = 7 June 2029{{r|Horizons2029}}
}}

'''87P/Bus''' is an [[List of numbered comets|Encke-type comet]] with a current orbital period of 6.37 years around the [[Sun]]. It is the only comet discovered by Australian astronomer, [[Schelte J. Bus]].

== Observational history ==
It was discovered by [[Schelte J. Bus]] on the night of 2 March 1981 from a photographic plate taken with the 1.2m UK Schmidt telescope at the [[Siding Spring Observatory]].{{r|IAUC_3578}} Additional observations by [[Kenneth S. Russell]] noticed a faint [[comet tail|tail]] about 20 arcseconds in length to the northwest, estimated to be 17.5 in apparent magnitude.{{r|IAUC_3579}} Preliminary orbital calculations in 9 March 1981 had [[Brian G. Marsden]] to conclude that the comet may be a short-periodic one,{{r|IAUC_3581}} which was later confirmed after Bus was able to find precovery images as early as 9–13 February 1981.{{r|IAUC_3582}}

It has been observed on each of its subsequent apparitions, most recently in 2020.{{r|Yoshida}}

== Physical characteristics ==
Preliminary [[charged couple device|CCD]] photometry from the [[La Palma Observatory]] in December 1998 obtained an upper limit value of around {{cvt|0.6|–|0.8|km|mi}} for the comet's nuclear radius.{{r|Lowry_1999}} Later observations from the [[Hubble Space Telescope]] in 2009 revised the size of its nucleus, which is now estimated to be {{val|0.27|0.01}} km in radius.{{r|Lamy_2009}} Hubble data also showed the comet to be elongated in shape, with an a/b ratio greater than 2.2.{{r|Lamy_2009}} Its rotational period is estimated to be around {{val|32.0|9.0}} hours in length.{{r|Lamy_2009}}

== Orbit ==
{| class=wikitable style="text-align:center; font-size:11px; float:right; margin:2px"
|- bgcolor= style="font-size: smaller;"
| colspan="8" style="text-align:center;"|'''Perihelion distance<br/>at different epochs'''{{r|Kinoshita}}
|-
! [[Epoch (astronomy)|Epoch]] !! [[Perihelion]]<br/>([[Astronomical unit|AU]])
|-
| 1942 || 4.43
|-
| 1955 || 2.13
|-
| 2029 || 3.69
|}

A close approach to [[Jupiter]] on 13 May 1952, at a distance of {{convert|0.0668|AU|e6km|abbr=unit}}, lowered the orbital period from 12.46 years and the perihelion distance from 4.43 AU to 6.43 years and 2.13 AU respectively. Another close approach to Jupiter on 24 February 2023, at a distance of {{convert|0.182|AU|e6km|abbr=unit}}, raised the perihelion to 3.62 AU and the orbital period to 9.58 years.{{r|Kinoshita}}

== References ==
{{Reflist|refs=

<ref name="Horizons2029">{{cite web
| title= Horizons Batch for 87P/Bus (90000883) on 2029-Jun-07
| publisher= [[JPL Horizons On-Line Ephemeris System|JPL Horizons]]
| type= Perihelion occurs when rdot flips from negative to positive
| url= https://ssd.jpl.nasa.gov/api/horizons.api?format=text&COMMAND=%27DES%3D87P%3BCAP%27&START_TIME=%272029-Jun-05%27&STOP_TIME=%272029-Jun-10%27&STEP_SIZE=%273%20hours%27&QUANTITIES=%2719%27
| access-date= 2022-06-27 }} (JPL#K203/18 Soln.date: 2020-Sep-28)
</ref>

<ref name="IAUC_3578">{{cite journal
| author1= S. J. Bus
| author2= K. S. Russell
| editor1= D. W. Green
| title= Comet Bus (1981b)
| url= http://www.cbat.eps.harvard.edu/iauc/03500/03578.html
| journal= IAU Circular
| date= 1981-03-04
| volume= 3578
| issue= 1
| bibcode= 1981IAUC.3578....1B
| issn= 0081-0304 }}
</ref>

<ref name="IAUC_3579">{{cite journal
| author1= S. J. Bus
| author2= K. S. Russell
| editor1= B. G. Marsden
| title= Comet Bus (1981b)
| url= http://www.cbat.eps.harvard.edu/iauc/03500/03579.html
| journal= IAU Circular
| date= 1981-03-05
| volume= 3579
| issue= 1
| bibcode= 1981IAUC.3579....1B
| issn= 0081-0304 }}
</ref>

<ref name="IAUC_3581">{{cite journal
| author1= C. Y. Shao
| author2= G. Schwartz
| author3= T. Seki
| editor1= B. G. Marsden
| title= Comet Bus (1981b)
| url= http://www.cbat.eps.harvard.edu/iauc/03500/03581.html
| journal= IAU Circular
| date= 1981-03-09
| volume= 3581
| issue= 2
| bibcode= 1981IAUC.3581....2S
| issn= 0081-0304 }}
</ref>

<ref name="IAUC_3582">{{cite journal
| author1= S. J. Bus
| author2= K. S. Russell
| author3= M. Hartley
| editor1= B. G. Marsden
| title= Periodic Comet Bus (1981b)
| url= http://www.cbat.eps.harvard.edu/iauc/03500/03582.html
| journal= IAU Circular
| date= 1981-03-10
| volume= 3582
| issue= 1
| bibcode= 1981IAUC.3582....1B
| issn= 0081-0304 }}
</ref>

<ref name="jpldata">{{cite web
| title= 87P/Bus – JPL Small-Body Database Lookup
| url= https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=87P
| website= ssd.jpl.nasa.gov
| publisher= [[Jet Propulsion Laboratory]]
| access-date= 2016-03-20 }}
</ref>

<ref name="Kinoshita">{{cite web
| author1= K. Kinoshita
| title= 87P/Bus: Past, Present and Future orbital elements
| url= https://jcometobs.web.fc2.com/pcmtn/0087p.htm
| work= Comet Orbit
| date= 2014-02-13
| access-date= 2024-11-13 }}
</ref>

<ref name="Lamy_2009">{{cite journal
| author1= P. L. Lamy
| author2= I. Toth
| author3= H. A. Weaver
| author4= M. F. A'Hearn
| author5= L. Jorda
| title= Properties of the nuclei and comae of 10 ecliptic comets from Hubble Space Telescope multi-orbit observations
| url= https://academic.oup.com/mnras/article-pdf/412/3/1573/3580898/mnras0412-1573.pdf
| journal= Monthly Notices of the Royal Astronomical Society
| year= 2011
| volume= 412
| issue= 3
| pages= 1573–1590
| doi= 10.1111/j.1365-2966.2010.17934.x
| doi-access= free }}
</ref>

<ref name="Lowry_1999">{{cite journal
| author1= S. C. Lowry
| author2= A. Fitzsimmons
| title= CCD photometry of distant comets II
| url= https://www.aanda.org/articles/aa/pdf/2001/02/aa9718.pdf
| journal= Astronomy & Astrophysics
| year= 1999
| volume= 365
| pages= 204–213
| bibcode= 1999A&A...349..649L
| doi= 10.1051/0004-6361:20000180
| doi-access= free }}
</ref>

<ref name="Meech_2004">{{cite journal
| author1= K. J. Meech
| author2= O. R. Hainaut
| author3= B. G. Marsden
| title= Comet nucleus size distributions from HST and Keck telescopes
| journal= Icarus
| year= 2004
| volume= 170
| issue= 2
| pages= 463–491
| bibcode= 2004Icar..170..463M
| doi= 10.1016/j.icarus.2004.03.014 }}
</ref>

<ref name="MPC">{{cite web
| title= 87P/Bus Orbit
| url= https://www.minorplanetcenter.net/db_search/show_object?object_id=87P
| publisher= [[Minor Planet Center]]
| access-date= 2014-06-16 }}
</ref>

<ref name="Yoshida">{{cite web
| author1= S. Yoshida
| title= 87P/Bus
| url= http://www.aerith.net/comet/catalog/0087P/index.html
| website= www.aerith.net
| access-date= 2015-05-15 }}
</ref>

}}

== Bibliography ==
* {{Cite book
| last1=Kronk    | first1=Gary W.
| last2=Meyer    | first2= Maik
| last3=Seargent | first3= David A. J.
| date= 2009
| title=Cometography: A Catalog of Comets
| volume= 6: 1983–1993
| publisher= Cambridge University Press
| isbn= 978-0-521-87216-4
}}

== External links ==
* {{JPL Small Body|id=1000010}}
* [https://cometography.com/pcomets/087p.html 87P/Bus] at Gary W. Kronk's ''Cometography''
* [http://www.aerith.net/comet/catalog/0087P/index.html 87P/Bus] at Seiichi Yoshida's website

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{{DEFAULTSORT:Bus, 087P}}
[[Category:Periodic comets]]
[[Category:Numbered comets|0087]]
[[Category:Encke-type comets|087P]]
[[Category:Comets in 2007|087P]]
[[Category:Comets in 2013|087P]]
[[Category:Comets in 2020|087P]]
[[Category:Discoveries by Schelte J. Bus]]
[[Category:Astronomical objects discovered in 1981]]