October 15, 2019
from SpaceWeather Website






When interstellar visitor 'Oumuamua flew through our solar system in 2017, researchers could not figure out what the cigar-shaped object was.


Ideas ranged from an alien light sail to a fossilized comet...


Now another interstellar visitor has arrived:


And it's definitely a comet.


This Oct. 11th video recorded by amateur astronomer Michael Jäger of Weißenkirchen, Austria, clearly shows Borisov's tadpole-like tail:



Capturing an interstellar comet tail with a backyard telescope is an impressive accomplishment.

"2I/Borisov is very faint - about 17th magnitude," notes Jäger.


"The seemingly-bright stars in the animation are actually quite dim, ~8th to 9th magnitude. They don't even have proper names."




What's the tail made of?


To answer that question, in September an international team of astronomers led by Alan Fitzsimmons took a closer look using the 4.2 m William Herschel Telescope (WHT) on La Palma.


They've just reported the results.


The near-UV spectrum of 2I/Borisov

obtained at the William Herschel Telescope.



Borisov's tail is rich in CN, a.k.a. cyanide.


The comet's nucleus is pumping out approximately 4x1024 CN molecules every second.


That may sound extraordinary, but it is not. Here in the Solar System, cyanide is commonly found in comet tails, and the production rate in Borisov is similar to that of local comets.


Combining the production rate of CN with other factors, such as the comet's brightness and apparent dustiness, the researchers calculate that 2I/Borisov's core is between 0.7 km to 3.3 km wide - again, typical of ordinary comets.

"Overall," the authors note, "we find the gas, dust and nuclear properties for this first active Interstellar Object are similar to normal Solar System comets."

In other words, wherever Comet Borisov came from, it must be a lot like here.