209P/LINEAR is a periodic comet with an orbital period of 5.1 years. The comet has extremely low activity for its size and is probably in the process of evolving into an extinct comet.[6]
Observational history
The comet discovered on 3 February 2004 by Lincoln Near-Earth Asteroid Research (LINEAR) using a 1.0-metre (39 in) reflector.[1] Initially it was observed without a coma and named 2004 CB as a minor planet or asteroid, but in March 2004 Robert H. McNaught observed a comet tail which confirmed it as a comet.[8] It was given the permanent number 209P on 12 December 2008 as it was the second observed appearance of the comet.[9] Prediscovery images of the comet, dating back to December 2003, were found during 2009.[8]
209P/LINEAR came to perihelion (closest approach to the Sun) on 6 May 2014.[3] On 29 May 2014 the comet passed 0.0554 AU (8,290,000 km; 5,150,000 mi) from Earth,[5] but only brightened to about apparent magnitude 12.[10] The 2014 Earth approach was the 9th closest known comet approach to Earth.[11] The close approach allowed the comet nucleus to be imaged by Arecibo, producing the most detailed radar image of a comet nucleus to that date.[12] The radar imaging showed the comet nucleus is elongated and about 2.4 km by 3 km in size,[12] later refined to 3.9 × 2.7 × 2.6 km.[6] No evidence of large dust particles were detected in the coma.[7] The comet also had very low water production, (2.5±0.2)×1025 mol/s, from an active area measuring just 0.007 km².[6]
209P/LINEAR was recovered on 31 December 2018 at magnitude 19.2 by Hidetaka Sato.[13]
Associated meteor showers
Preliminary results by Esko Lyytinen and Peter Jenniskens, later confirmed by other researchers, predicted[14][15][16] 209P/LINEAR might a big meteor shower which would come from the constellation Camelopardalis on the night of 23/24 May 2014. It was possible that there could be 100 to 400 meteors per hour.[14] All the trails from the comet from 1803 through 1924 were expected to intersect Earth's orbit during May 2014.[14] The peak activity was expected to occur around 24 May 2014 7h UT when dust trails produced from past returns of the comet could pass 0.0002 AU (30,000 km; 19,000 mi) from Earth.[16] The 2014 Camelopardalids only generated 10–15 visual meteors per hour.[17][18] But the expected radiant and date of visual maximum were correctly predicted.[18] The shower peaked around 6h UT on 24 May 2014.[18] The Canadian Meteor Orbit Radar (CMOR) detected the shower using HF/VHF radar echos but the particles were too small for visual detection. Earth encountered the 1939 stream around 24 May 2019 8h UT with a ZHR of ~5. The Eta Aquariids also occur at this time of year.[19]
209P/LINEAR may also be the source of the weak 6–14 June meteor shower "sigma Ursae Majorids" (SIM #677).[11]
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