125P/Spacewatch

{{Short description|Periodic comet with 5 year orbit}}

{{For|other comets of the same name|Comet Spacewatch}}

{{Infobox comet

| name=125P/Spacewatch

| image= 125P 2024-06-03 image ZTF-sso-442-zr-size-8.5arcmin.png

| discoverer=Tom Gehrels (Spacewatch)

| discovery_date=September 8, 1991

| designations= P/1991 R2, 1990 XXIX, 1991x, P/1996 F1

| epoch=March 13, 2013 (2456364.5)

| semimajor=3.12812162 AU

| perihelion=1.52546421 AU

| aphelion=4.730779 AU

| eccentricity=0.5123385

| period=5.53 a
2020.8 d

| inclination= 9.98579°

| last_p = 7 March 2024
27 August 2018
16 February 2013

| next_p =

}}

125P/Spacewatch is a periodic Jupiter-family comet. It was discovered on September 8, 1991, by Tom Gehrels using the 0.91 m Spacewatch telescope at the Kitt Peak National Observatory. It was the first comet discovered with the use of a CCD{{cite web |title=SPACEWATCH® News and History |url=https://spacewatch.lpl.arizona.edu/news-history |website=spacewatch.lpl.arizona.edu |access-date=11 August 2024 |language=en}} and also the faintest comet upon discovery up to that point. It has a diameter of 1.6 km.

The comet was discovered in images taken by the 0.91 m Spacewatch telescope at the Kitt Peak National Observatory by Tom Gehrels on September 8, 1991 as an essentially stellar object with an apparent magnitude of 21, with a tail more than 5 arcminutes long.{{cite web |title=IAUC 5341: 1991x; 1991o; SATURN |url=http://www.cbat.eps.harvard.edu/iauc/05300/05341.html |date= 10 September 1991 |website=www.cbat.eps.harvard.edu |access-date=11 August 2024}} Brian G. Marsden calculated a parabolic and an elliptical orbit, with the elliptical orbit suggesting an orbital period of 5.58 years and a perihelion date on 18 December 1990.{{cite web |title=IAUC 5343: 1991x; N Her 1991 |url=http://www.cbat.eps.harvard.edu/iauc/05300/05343.html |website=www.cbat.eps.harvard.edu |date= 12 September 1991 |access-date=11 August 2024}}

The comet was recovered on 21 March 1996 by the Spacewatch telescope from James V. Scotti and J. Montani, with an apparent magnitude of 17.6, a tail measuring 0.66 arcminutes long and a coma measuring 15 arcseconds across. The orbit calculated after the recovery indicates an orbital period of 5.56 years.{{cite journal |last1=Scotti |first1=J. V. |last2=Montani |first2=J. |last3=Nakano |first3=S. |last4=Marsden |first4=B. G. |title=Comet P/1996 F1 (Spacewatch) |journal=International Astronomical Union Circular |date=1 March 1996 |volume=6349 |pages=1 |url=http://www.cbat.eps.harvard.edu/iauc/06300/06349.html#Item1 |issn=0081-0304}} During that apparition the comet experienced an outburst in late July 1996 and brightened to a magnitude of 14.5. During the 2002 apparition the comet brightened to a magnitude of 18.