48 Scientific American, October 2020 Illustration by Matthew Twombly
SOURCE: SMALL-BODY DATABASE BROWSER, JET PROPULSION LABORATORY/NASA (trajectory)HeliopausePlane of
solar systemCurrent location
(October 2020)March 2037SunEarthVenus MercuryMars
November 30December 30
Planets positioned
according to date
of discoveryJanuary 30, 2020
February 29SunOctober 30SaturnUranusNeptuneJupiter orbitIncoming velocity
32.2 kilometers per
second (6.8 AU/year)800–1,000 meters‘Oumuamua
shown for
reference2I/Borisov
Discovered:
August 30, 2019September 30Snow line2I/Borisov
The second known interstellar interloper contrasts in many ways with the first.
It resembles an ordinary comet with a typical roundish shape and no unexpected
movement. Borisov matches astronomers’ predictions for a visitor from beyond
the solar system and most likely represents a leftover planetary building block ejected
from the outer, icy region of a nascent planetary system.DISCOVERY
Found by amateur astronomer
Gennadiy Borisov in Ukraine
using his 0.65-meter
homemade telescope.APPEARANCE
Its true shape is unknown,
but it is believed to resemble
a typical comet with a radius of
400 to 500 meters. It displays
a classic comet tail.OUTGASSING
Like most comets, Borisov
releases gas as ice sublimates
off its surface, providing
an extra push.ORIGIN
Because of its ice content,
Borisov is thought to have been
ejected from the cold outer edge
of a distant planetary system.TRAJECTORY
Borisov was detected earlier
in its foray into our solar
system, coming from above
the plane of our system.
It has now crossed the plane
out beyond the orbit
of Mars and is still visible
to our telescopes.© 2020 Scientific American