C/2017 T2 (PanSTARRS) is an Oort cloud comet discovered on 2 October 2017 when it was from the Sun. The closest approach to Earth was on 28 December 2019 at a distance of . It came to perihelion (closest approach to the Sun) on 4 May 2020 when it was safe from disintegration at 1.6 AU from the Sun. (Mars is also roughly 1.6 AU from the Sun.)
Observational history Comet C/2017 T2 (PanSTARRS) brightened to apparent magnitude 8 and was visible with 50mm binoculars. On 22-24 May 2020, the comet passed near the galaxy pair of Messier 81 and Messier 82, passing less than one degree from the latter. In early June 2020 the comet was near the magnitude 1.8 star Dubhe in Ursa Major.
Based on the light curve of the comet nucleus, it has been estimated that the nucleus has a rotational period of 5.6759 ± 0.0046 h. The comet at perihelion had a water production of 6×1028 molecules/s. Also when observed in CN featured two side jets in June 2020, but they weren't observed one month later. Concentric structures were observed in the inner coma in May 2020, probably created by a jet with rotation axis towards the Earth.
JPL Horizons using an epoch 1950 orbit solution models that C/2017 T2 took millions of years to come from the Oort cloud at a distance of roughly .
References "C/2017 T2 (PANSTARRS) plot"
Solution using the Solar System Barycenter. Ephemeris Type:Elements and Center:@0 (To be outside planetary region, inbound epoch 1950 and outbound epoch 2050. For epoch 1950-Jan-01 orbit period is "PR= 2.6E+09 / 365.25 days" = ~7.1 million years)
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