First, what does “Interstellar” mean? Interstellar means outside of our solar system. So, what is “visiting” us from outside of our solar system? It appears to be a comet (it appears to have a coma and maybe, a short tail). It was discovered by amateur astronomer Gennady Borisov of the Ukraine on Aug. 30th, using an 11″ telescope. It is approaching our area of the solar system from beyond Mars. The comet is named C/2019 Q4 (Borisov).
According to NASA’s Jet Propulsion Lab, Comet Borisov will make its closest approach to the sun, at 2 AU, around Dec. 7th. It is expected to make its closest approach to Earth, also 2 AU, near the end of December, three weeks later. At present, the comet is around magnitude +18. How bright it may become by December is anyone’s guess.
Because of its distance from the Sun at its closest approach and its speed (68,700 mph), the Sun will not be able to “capture” it by its gravity. Therefore, it will simply continue on its way, back out of our solar system.
For more detail, including orbital elements and a diagram of the orbit, visit spaceweather.com. Thank you spaceweather.com.