162P/Siding Spring

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

{{For|other comets discovered by the Siding Spring Observatory|Comet Siding Spring (disambiguation)}}

{{Infobox comet

| name = 162P/Siding Spring

| image = P2004TU12 20041112 J87.jpg

| caption = The comet on 12 November 2004, displaying a narrow tail

| discovery_ref =

| discoverer = Siding Spring Observatory

| discovery_date = October 10, 2004

| designations = {{mp|P/2004 TU|12}}

| epoch = 27 October 2010

| obs_arc =

| obs =

| aphelion = 4.873 AU

| perihelion = 1.233 AU

| semimajor = 3.053 AU

| eccentricity = 0.5961

| period = 5.33 years

| inclination = 27.817°

| tjup = 2.792

| Earth_moid = 0.239 AU

| dimensions = 14.06 ± 0.96 km

| albedo = 0.022 ± 0.003

| sidereal_day = 32.86 hours

| M1 = 15.2

| M2 =

| last_p = 7 December 2020

| next_p = 17 May 2026

| orbit_ref = {{cite web |title=Small-Body Database Lookup: 162P/Siding Spring |url=https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?des=162P&view=OPC |website=ssd.jpl.nasa.gov |access-date=20 July 2023}}

}}

162P/Siding Spring is a Jupiter-family comet with an orbital period of 5.3 years. It was discovered in images obtained on 10 October 2004 as part of the Siding Spring Survey.{{cite journal |last1=Mallia |first1=F. |last2=Masi |first2=G. |last3=Wilcox |first3=R. |last4=Lacruz |first4=J. |title=Comet P/2004 TU_12 (Siding Spring) |journal=International Astronomical Union Circular |date=1 November 2004 |issue=8436 |pages=1 |url=http://www.cbat.eps.harvard.edu/iauc/08400/08436.html |issn=0081-0304}}

The comet was discovered during the Siding Spring Survey as an asteroidal object shining with an apparent magnitude of 14.1 but a tail extending for about 4 arcminutes was observed on 12 November 2004, indicating that it is a comet. The tail grew longer the next days, reaching a length of over 10 arcminutes on 15 November. Two days later the tail was fainter, and barely visible within one arcminute from the nucleus.{{cite journal |last1=Masi |first1=G. |title=Comet P/2004 TU_12 (Siding Spring) |journal=International Astronomical Union Circular |date=1 November 2004 |issue=8439 |pages=1 |url=http://www.cbat.eps.harvard.edu/iauc/08400/08439.html#Item1 |issn=0081-0304}} On 21 October 2031 the comet will approach Earth at a distance of {{convert|0.2456|AU|e6km|abbr=unit}}.

The comet was observed by NASA Infrared Telescope Facility in 2004, finding that the nucleus has an effective radius of 6.0 ± 0.8 km, which corresponds to a visual albedo of 0.034 ± 0.014,{{cite journal |last1=Fernández |first1=Y. R. |last2=Campins |first2=H. |last3=Kassis |first3=M. |last4=Hergenrother |first4=C. W. |last5=Binzel |first5=R. P. |last6=Licandro |first6=J. |last7=Hora |first7=J. L. |last8=Adams |first8=J. D. |title=Comet 162P/Siding Spring: A Surprisingly Large Nucleus |journal=The Astronomical Journal |date=September 2006 |volume=132 |issue=3 |pages=1354–1360 |doi=10.1086/506252|arxiv=astro-ph/0608387 |bibcode=2006AJ....132.1354F }} and a reflectance spectrum typical of a D-type asteroid.{{cite journal |last1=Campins |first1=Humberto |last2=Ziffer |first2=Julie |last3=Licandro |first3=Javier |last4=Pinilla-Alonso |first4=Noemí |last5=Fernández |first5=Yanga |last6=León |first6=Julia de |last7=Mothé-Diniz |first7=Thais |last8=Binzel |first8=Richard P. |title=Nuclear Spectra of Comet 162P/Siding Spring (2004 TU12) |journal=The Astronomical Journal |date=September 2006 |volume=132 |issue=3 |pages=1346–1353 |doi=10.1086/506253|bibcode=2006AJ....132.1346C }} Further observations by the Spitzer Space Telescope indicate an effective radius of 7.03 ± 0.48 km.{{cite journal |last1=Fernández |first1=Y.R. |last2=Kelley |first2=M.S. |last3=Lamy |first3=P.L. |last4=Toth |first4=I. |last5=Groussin |first5=O. |last6=Lisse |first6=C.M. |last7=A’Hearn |first7=M.F. |last8=Bauer |first8=J.M. |last9=Campins |first9=H. |last10=Fitzsimmons |first10=A. |last11=Licandro |first11=J. |last12=Lowry |first12=S.C. |last13=Meech |first13=K.J. |last14=Pittichová |first14=J. |last15=Reach |first15=W.T. |last16=Snodgrass |first16=C. |last17=Weaver |first17=H.A. |title=Thermal properties, sizes, and size distribution of Jupiter-family cometary nuclei |journal=Icarus |date=September 2013 |volume=226 |issue=1 |pages=1138–1170 |doi=10.1016/j.icarus.2013.07.021|arxiv=1307.6191 |bibcode=2013Icar..226.1138F }} This is one of the largest nuclei of Jupiter family comets with known radius. More detailed observations indicate that the nucleus has axis ratios a/b = 1.56 and b/c = 2.33, and could possibly have two lobes.{{cite journal |last1=Donaldson |first1=A |last2=Kokotanekova |first2=R |last3=Rożek |first3=A |last4=Snodgrass |first4=C |last5=Gardener |first5=D |last6=Green |first6=S F |last7=Masoumzadeh |first7=N |last8=Robinson |first8=J |title=Characterizing the nucleus of comet 162P/Siding Spring using ground-based photometry |journal=Monthly Notices of the Royal Astronomical Society |date=2 March 2023 |volume=521 |issue=1 |pages=1518–1531 |doi=10.1093/mnras/stad616|doi-access=free |arxiv=2302.12141 }} The sidereal period of the comet is 32.864 ± 0.001 hours.