259P/Garradd

{{short description|Periodic comet with 4.5 year orbit}}

{{Infobox comet

| name = 259P/Garradd

| image = Comet 259P Garradd - Psjabe59df2 hr.jpg

| caption = Comet 259/P Garradd in two different dates, one that was active (left) and one in which it appears inactive (right)

| discovery_ref =

| discoverer = Gordon J. Garradd

| discovery_date = September 2, 2008

| designations = P/2008 R1

| epoch = 26 February 2011

| obs_arc =

| obs =

| aphelion = 3.659 AU

| perihelion = 1.796 AU

| semimajor = 2.727 AU

| eccentricity = 0.3415

| period = 4.50 years

| inclination = 15.899°

| tjup = 3.217

| Earth_moid = 0.858 AU

| dimensions =

| albedo =

| sidereal_day =

| M1 = 13.7

| M2 =

| last_p = 8 February 2022

| next_p = 11 August 2026

| orbit_ref = {{cite web |title=Small-Body Database Lookup: 259P/Garradd |url=https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?des=259P&view=OPC |website=ssd.jpl.nasa.gov |access-date=20 July 2023}}

}}

259P/Garradd is a Jupiter-family comet and active asteroid with an orbital period of 4.5 years. It was discovered in images obtained on 2 September 2008 as part of the Siding Spring Survey by Gordon J. Garradd.{{cite journal |last1=Garradd |first1=G. J. |last2=Sostero |first2=G. |last3=Camilleri |first3=P. |last4=Guido |first4=E. |last5=Jacques |first5=C. |last6=Pimentel |first6=E. |title=Comet C/2008 R1 (Garradd) |journal=International Astronomical Union Circular |date=1 September 2008 |issue=8969 |pages=1 |url=http://www.cbat.eps.harvard.edu/iauc/08900/08969.html#Item1 |issn=0081-0304}}{{cite web |title=MPEC 2008-R22 : COMET C/2008 R1 (GARRADD) |website=www.minorplanetcenter.net |url=https://www.minorplanetcenter.net/mpec/K08/K08R22.html|date= 4 September 2008 |accessdate= 6 September 2024}}

The comet upon discovery had an apparent magnitude of 18.5 and a coma about 15 arcseconds across. The comet dimmed by 1.5 magnitudes until mid November 2008. The spectrum of the comet during that period indicated a lack of gaseous emission lines and the mass loss rate was estimated to be less than 1.5 kg/s. The comet was observed in 2011-12, when it was inactive, with the observations indicating an effective radius of about 0.3 kilometers assuming a geometric albedo of 0.05.{{cite journal |last1=MacLennan |first1=Eric M. |last2=Hsieh |first2=Henry H. |title=The Nucleus of Main-Belt Comet 259P/Garradd |journal=The Astrophysical Journal |date=10 October 2012 |volume=758 |issue=1 |pages=L3 |doi=10.1088/2041-8205/758/1/L3|arxiv=1209.3065 }}{{cite journal |last1=Kleyna |first1=J. |last2=Meech |first2=K. J. |last3=Hainaut |first3=O. R. |title=Faint moving object detection, and the Low Signal-to-Noise recovery of Main Belt comet P/2008 R1 Garradd |journal=Publications of the Astronomical Society of the Pacific |date=October 2012 |volume=124 |issue=920 |pages=1083–1089 |doi=10.1086/668253|arxiv=1209.3833 }}

The comet was observed to be active again during the 2017 perihelion, indicating that the source of activity is sublimation. The activity started to be detected when the comet was about 2 AU from the Sun, indicating that volatile ices are located deeper under the surface, as they have been probably more depleted due to the fact that it approaches closer to the Sun during perihelion than other active asteroids.{{cite journal |last1=Hsieh |first1=Henry H. |last2=Ishiguro |first2=Masateru |last3=Knight |first3=Matthew M. |last4=Moskovitz |first4=Nicholas A. |last5=Sheppard |first5=Scott S. |last6=Trujillo |first6=Chadwick A. |title=The Reactivation of Main-belt Comet 259P/Garradd (P/2008 R1) |journal=The Planetary Science Journal |date=1 April 2021 |volume=2 |issue=2 |pages=62 |doi=10.3847/PSJ/abe59d|doi-access=free |arxiv=2102.06290 }}

The orbit of the comet is unstable within a timescale of tens of millions years. It lies near the 3:8 orbital resonanse with Jupiter. It has a Jupiter Tisserand parameter of over three, indicating that it originates from the main asteroid belt instead of the Kuiper belt.{{cite journal |last1=Jewitt |first1=David |last2=Yang |first2=Bin |last3=Haghighipour |first3=Nader |title=Main-Belt Comet P/2008 R1 (Garradd) |journal=The Astronomical Journal |date=1 May 2009 |volume=137 |issue=5 |pages=4313–4321 |doi=10.1088/0004-6256/137/5/4313}} It does not belong to a known asteroid family.{{cite journal |last1=Hsieh |first1=Henry H. |last2=Novaković |first2=Bojan |last3=Kim |first3=Yoonyoung |last4=Brasser |first4=Ramon |title=Asteroid Family Associations of Active Asteroids |journal=The Astronomical Journal |date=1 February 2018 |volume=155 |issue=2 |pages=96 |doi=10.3847/1538-3881/aaa5a2|doi-access=free |arxiv=1801.01152 }}