Newly Discovered Interstellar Comet Appears Indistinguishable from the Native Solar System Comets

Image credit:NASA, ESA, D. Jewitt (UCLA)

A second interstellar object, designated C/2019 Q4 (2I/Borisov), was discovered on August 30, 2019, by Gennady Borisov at the MARGO observatory in Nauchnij, Crimea. A new paper published in Nature Astronomy reports on the initial characterization of this object using images taken with the William Herschel Telescope and the Gemini North Telescope, which showed an extended coma and a faint, broad tail. 2I/Borisov’s high orbital velocity indicates that it originated outside the solar system and is not gravitationally bound to the Sun. This makes it the first certain case of an interstellar comet and the second known interstellar minor body identified in the solar system (after ‘Oumuamua). Moreover, its estimated nucleus size, approximately 1 kilometer, and measured slightly reddish color make it look much more like an ordinary comet than ‘Oumuamua did. Astronomers will continue to study 2I/Borisov as it will make its closest approach to Earth on December 28, 2019 at 1.9 au. READ MORE