Interstellar Object 2I/ Borisov

1. Interstellar Object 2I/Borisov arXiv:1909.05851 arXiv:1909.12144 communicated by Maxim Trushin

2. Interstellar comets/asteroids known so far • 1I/2017 ‘Oumuamua • originally classified as comet C/2017 U1, reclassified as asteroid A/2017 U1 • theinterstellar asteroid first ever detected • 2I/2019Borisov • discovered by the end of August 2019 before perihelion • already 5 preprints in arXiv within last 3 weeks

3. Trajectory of 2I/2019 Borisov

4. ArXiv:1909.05851 Interstellar comet C/2019 Q4 (Borisov) • Solution fitting 129 positions over 12 days interval suggests • Eccentricity: 3.16 • Perihelion distance: 1.96 a.u • Cannot be explained by internal perturbations inside the Solar System

5. ArXiv:1909.05851 Interstellar comet C/2019 Q4 (Borisov) • Image: Gemini North Telescope (Maunakea). • Photometric magnitude suggest the nucleus size of about 0.5 km. • Not reliable as the comet is already active.

6. ArXiv:1909.12144 Detection of CN gas in Interstellar Object 2I/Borisov • Submitted to ApJ Letters: • Received September 26, 2019 • Revised September 30, 2019 • Accepted October 1, 2019

7. What is it made of?

8. CN (Cyanide) • Known to exist in Solar System (e.g on Titan, a Saturn’s moon) and in the interstellar medium. • Created from HNC by photodissociation • + ν = + H • No other emission features were apparent. HCN (photon) CN (hydrogen)

9. Other numbers • Yield: Q(dust) from 1 kg/s to 30 kg/s depending on the grain size and velocity. • Yield: Q(gas) 4x1024 molecule/s • All parameters are similar to other comets found in the Solar System

10. Interesting facts about 2I/2109 • Earlier estimations of orbital parameters ignited an alarm indicating a potentially dangerous near-Earth trajectory. • Super fast: 32 km/s hyperbolic excess velocity. • The most interesting observations will be performed in December (closest approach to the Earth). • Discovered by an amateur astronomer using a home-built telescope!