 Comet Machholz photographed by Ralf Weber fromAndalusia, Spain in February 2005 | |
| Discovery | |
|---|---|
| Discovered by | Donald Machholz |
| Discovery date | 27 August 2004 |
| Orbital characteristics[1][2] | |
| Epoch | 30 March 2005 (JD 2453459.52005) |
| Observation arc | 2.03 years |
| Number of observations | 3,612 |
| Aphelion | ~5,100 AU (inbound) ~1,100 AU (outbound) |
| Perihelion | 1.205 AU |
| Semi-major axis | ~2,400 AU |
| Eccentricity | 0.99950 |
| Orbital period | ~130,000 years (inbound) ~12,400 years (outbound) |
| Inclination | 38.589° |
| 93.622° | |
| Argument of periapsis | 19.505° |
| Mean anomaly | 0.001° |
| Last perihelion | 24 January 2005 |
| TJupiter | 1.066 |
| EarthMOID | 0.249 AU |
| JupiterMOID | 1.973 AU |
| Physical characteristics[3][4][5] | |
| Dimensions | 4.2–7.8 km (2.6–4.8 mi) |
Mean diameter | 6.0 km (3.7 mi) |
| Mass | 1.0×1013 kg |
| 9.1±0.2 hours | |
| Comet total magnitude (M1) | 11.2 |
Comet Machholz,formally designatedC/2004 Q2, is anon-periodic comet discovered byDonald Machholz on 27 August 2004. It reachednaked eye brightness in January 2005. Unusual for such a relatively bright comet, itsperihelion was farther from theSun than theEarth's orbit.
During its closest approach to Earth in January 2005, ground observations fromLa Palma, Spain revealed that the comet may have a rotation period of9.1±0.2 hours,[3] although a 2012 study regarding the morphological structures in its coma suggested it may have an orbital period of 0.74 days instead.[6]
Between December 2004 and January 2005, observations fromLulin andLa Silla observatories spotted two jets of carbon andcyanogen (CN) compounds that form a spiral-like structure within the coma, which were caused by two active surface regions in itsnucleus.[7] In March 2005, theGALEX spacecraft observed the comet in far-ultraviolet (FUV) light, where it determined that ionizedmethane (CH
4) molecules dominated itscoma, which explained the shorter than expected lifetime of carbon molecules detected.[8]
Near-infrared measurements of the comet has indicated that its surface material generate an outflow in the form of fragments that separated into gas and dust under sublimation on time scales of the order of days.[9]
Its nucleus has a mean diameter of 6.0 km (3.7 mi).[5]
Given theorbital eccentricity of this object, differentepochs can generate quite different heliocentric unperturbedtwo-bodybest-fit solutions to the aphelion distance (maximum distance) of this object. For objects at such high eccentricity, the Sunsbarycentric coordinates are more stable than heliocentric coordinates. UsingJPL Horizons the barycentric orbital elements for epoch 2050 generate asemi-major axis of 537 AU (80.3 billion km) and a period of approximately 12,400 years.[1]
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