Welcome to the April episode of Comet Watch featuring special guest, Michelle Thaller Ph.D . My thanks, as always to my co-host Neil Norman! Mary McIntyre is unwell and will be joining us again next month.
BAA Comet Section Visual Observations Page
Comet Lexell was discovered by Charles Mesier on June 14th,1770.
At this one and only apparition, it passed by Earth on its way to a August 14th perihelion, at a distance of 0.015 AU’s or 1,400,000 miles.
The comet was a member of the Jupiter family comets and originally had a perihelion distance of beyond 2 AU’s, but a close Jupiter approach by the comet in 1767 lead to its perihelion distance being radically changed . Comet Lexell holds the distinctions of being the first known JFC and also first NEO.
The comet again approached close to Jupiter in 1779 and the perihelion distance was increased greatly to some 3.3 AU’s.
The comet is today considered lost, but many still speculate that the comet was eventually expelled from the Solar System by Jupiter.
The debate continues………..
D/1770 L1 (Lexell) http://cometography.com/pcomets/1770l1.html
Finding long lost Lexell’s comet: the fate of the first discovered near-earth object https://arxiv.org/pdf/1802.08904.pdf
Evolution of orbit of Lexell’s Comet https://vimeo.com/58118316
The Late Heavy Bombardment (abbreviated LHB and also known as the lunar cataclysm) is an event thought to have occurred approximately 4.1 to 3.8 billion years (Ga) ago, at a time corresponding to the Neohadean and Eoarchean eras on Earth.
Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets https://www.nature.com/articles/nature03676
Asteroid Day https://asteroidday.org/
NEOShield Official Youtube channel https://www.youtube.com/channel/UCbWym2jfxVXn9hEd7sUqrfA
Northolt Branch Observatories
BAA Comet Section page
BAA YouTube Channel
The Astronomer Youtube Channel
The German Comet Group
Seiichi Yoshida’s page
Liga Iberoamericana de Astronomia
The Sky Live (Comets)
Minor Planets Center (IAU)