96P/Machholz

The orbit of 96P/Machholz corresponds to the Arietids and the Marsden and Kracht comet groups. Its Tisserand parameter with respect to Jupiter, TJ, is 1.94 and comets are generally classified as Jupiter family if TJ > 2. Orbital integrations indicate that TJ was greater than 2 about 2500 years ago. 96P/Machholz is currently in a 9:4 orbital resonance with Jupiter. It will not make another close approach to the Earth until 2028, when it will pass at a distance of . It may eventually be ejected from the Solar System. Perihelion 96P/Machholz has a perihelion (closest approach to the Sun) of for 2028. At perihelion Comet Machholz passes the Sun at . It comes closer to the Sun than any numbered comet less than 321P/SOHO. Between 1897 and 2102 perihelion gradually drops from to . 2081 will be the first perihelion below 0.1 AU. == Observations ==

Machholz 1 entered the field of view of the orbiting Solar and Heliospheric Observatory (SOHO) in 1996, 2002, 2007, 2012, and 2017, where it was seen by the corona-observing LASCO instrument in its C2 and C3 coronagraphs. Data analysis of this sort has become commonplace based on public availability of SOHO images. Sharma became the third Indian to have discovered a comet in this manner. 2012 perihelion Between July 12–17, 2012, 2023 perihelion The January 31, 2023 perihelion passage was the sixth passage observed by SOHO. On February 4, 2023, the comet was recovered in the morning sky 2 degrees above the horizon at around magnitude 7. Using observations through October 2022, which is three months before the 2023 perihelion passage, the comet will next come to perihelion around 12 May 2028. == Unusual composition ==

Spectrographic analysis of the coma of 96P/Machholz was made during its 2007 apparition, as part of the Lowell Observatory comet composition long-term observing program. When compared with the measured abundances of five molecular species in the comae of the other 150 comets in their database, these measurements showed 96P/Machholz to have far fewer carbon molecules. These other comets had on average 72 times as much cyanogen as 96P/Machholz. The only two comets previously seen with similar depletion both in carbon-chain molecules and cyanogens were C/1988 Y1 (Yanaka) and C/2025 K1 (ATLAS), but they both have substantially different orbits. There are currently three hypotheses to explain the chemical composition of 96P/Machholz. One hypothesis for the difference is that 96P/Machholz was an interstellar comet from outside the Solar System and was captured by the Sun. Other possibilities are that it formed in an extremely cold region of the Solar System (such that most carbon gets trapped in other molecules). Given how close it approaches the Sun at perihelion, repeated baking by the Sun may have stripped most of its cyanogen. The following table represents future orbital elements for 96P keeping in mind that results hundreds of years in the future are highly speculative given the uncertain behavior of nongravitational forces over long time intervals and divergent solutions. By the year 2235, the uncertainty in the comets position is more than . ==Notes==