259P/Garradd
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 Comet 259P/Garradd in two different dates, one that was active (left) and one in which it appears inactive (right) | |
| Discovery[1] | |
|---|---|
| Discovered by | Gordon J. Garradd |
| Discovery site | Siding Spring Observatory |
| Discovery date | 2 September 2008 |
| Designations | |
| P/2008 R1 | |
| Garradd 4 | |
| Orbital characteristics[2][3] | |
| Epoch | 26 July 2017 (JD 2457960.5) |
| Observation arc | 9.05 years |
| Number of observations | 68 |
| Aphelion | 3.654 AU |
| Perihelion | 1.809 AU |
| Semi-major axis | 2.731 AU |
| Eccentricity | 0.33771 |
| Orbital period | 4.514 years |
| Inclination | 15.889° |
| 51.484° | |
| Argument of periapsis | 257.50° |
| Mean anomaly | 358.03° |
| Last perihelion | 8 February 2022 |
| Next perihelion | 11 August 2026 |
| TJupiter | 3.217 |
| Earth MOID | 0.858 AU |
| Jupiter MOID | 1.925 AU |
| Physical characteristics[4] | |
Mean radius | 0.30±0.02 km |
| 0.05 (assumed) | |
| Comet total magnitude (M1) | 13.7 |
| Comet nuclear magnitude (M2) | 18.9 |
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.[1][5]
The comet upon discovery had an apparent magnitude of 18.5 and a coma about 15 arcseconds across.[1] 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.[6] 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.[4][7]
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.[8]
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