 Comet Lulin as seen on January 31st (top) and February 4th of 2009. | |
| Discovery[1][2][3] | |
|---|---|
| Discovered by | Ye Quanzhi Lin Chi-Sheng |
| Discovery site | Lulin Observatory (D35) 0.41-mRitchey–Chrétien |
| Discovery date | 11 July 2007 |
| Designations | |
| Comet Lulin CK07N030 | |
| Orbital characteristics[4][5][6] | |
| Epoch | 6 December 2008 (JD 2454806.5) |
| Aphelion | ~64,000 AU (inbound) ~2,400 AU (outbound) |
| Perihelion | 1.212 AU |
| Semi-major axis | 1200 AU |
| Eccentricity | 0.99998 |
| Orbital period | 42,000 years (outbound) |
| Inclination | 178.37° |
| 338.54° | |
| Argument of periapsis | 136.86° |
| Last perihelion | 10 January 2009[4] |
| TJupiter | –1.365 |
| EarthMOID | 0.211 AU |
| JupiterMOID | 0.101 AU |
| Physical characteristics[7] | |
Mean radius | 6.10±0.25 km |
| 41.45±0.05 hours | |
| Comet total magnitude (M1) | 10.2 |
| 4.5–5.0 (2009 apparition) | |
Comet Lulin, formal designationC/2007 N3, (Traditional Chinese:鹿林彗星) is anon-periodic comet. It was discovered by Ye Quanzhi and Lin Chi-Sheng fromLulin Observatory.[2][3][8] It peaked in brightness atmagnitude between +4.5 and +5,[3][9][10][11] becoming visible to the naked eye,[12] and arrived atperigee for observers onEarth on February 24, 2009,[5] and at 0.411 AU (61.5 million km; 38.2 million mi) from Earth.[5]
The comet was first photographed byastronomer Lin Chi-Sheng (林啟生) with a 0.41-metre (16 in) telescope at the Lulin Observatory inNantou,Taiwan on July 11, 2007. However, it was the 19-year-old Ye Quanzhi (葉泉志) fromSun Yat-sen University in China, who identified the new object from three of the photographs taken by Lin.[13]
Initially, the object was thought to be a magnitude 18.9asteroid, but images taken a week after the discovery with a larger 0.61-metre (24 in) telescope revealed the presence of a faintcoma.[2][1][13]
The discovery occurred as part of theLulin Sky Survey project to identify small objects in theSolar System, particularlyNear-Earth Objects. The comet was named "Comet Lulin" after the observatory, and its official designation is Comet C/2007 N3.[14]
The comet became visible to the naked eye from dark-sky sites around February 7.[15] It figured near thedouble starZubenelgenubi on February 6, nearSpica on February 15 and 16, nearGamma Virginis on February 19 and near thestar clusterM44 on March 5 and 6. It also figured near theplanetary nebulaNGC 2392 on March 14, and near thedouble starWasat around March 17.[16][17] The comet was nearconjunction withSaturn on February 23, and outward-first headed towards its aphelion, against the present position of background stars, in the direction ofRegulus in theconstellation ofLeo, as noted on February 26 and 27, 2009.[3][8] It passed nearComet Cardinal on May 12, 2009.[18]
According toNASA, Comet Lulin'sgreen color comes from a combination of gases that make up its local atmosphere, primarilydiatomic carbon, which appears as a green glow when illuminated bysunlight in thevacuum of space. WhenSWIFT observed comet Lulin on 28 January 2009; the comet was shedding nearly 3,000 litres (800 US gal) of water each second.[19] Comet Lulin wasmethanol-rich.
AstronomerBrian Marsden of theSmithsonian Astrophysical Observatory calculated that Comet Lulin reached itsperihelion on January 10, 2009, at a distance of 182 million km (113 million mi) from theSun.
The orbit of Comet Lulin is very nearly aparabola (parabolic trajectory), according to Marsden.[14] The comet had anepoch 2009 eccentricity of 0.999986,[4] and has an epoch 2010 eccentricity of 0.999998.[4] It is moving in aretrograde orbit at a very low inclination of just 1.6° from theecliptic.[14]
Given the extremeorbital 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 sun'sbarycentric coordinates are more stable than heliocentric coordinates. UsingJPL Horizons, the barycentric orbital elements for epoch 2014-Jan-01 generate a semi-major axis of about 1200 AU and a period of about 42,000 years.[6]
On February 4, 2009, a team ofItalian astronomers witnessed "an intriguing phenomenon in Comet Lulin's tail". Team leader Ernesto Guido explains:
"We photographed the comet using a remotely controlled telescope in New Mexico, and our images clearly showed a disconnection event. While we were looking, part of the comet's plasma tail was torn away."[20]
Guido and colleagues believe the event was caused by a magnetic disturbance in thesolar wind hitting the comet. Magnetic mini-storms in comet tails have been observed before—most famously in 2007, when NASA'sSTEREO spacecraft watched acoronal mass ejection crash intoComet Encke. Encke lost its tail in dramatic fashion, much as Comet Lulin did on February 4.[20]
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