Interstellar Comet Borisov makes its closest approach to the sun

An intriguing interstellar comet from beyond our solar system made its closest approach to the sun on Sunday, and may be visible in some small telescopes, according to SkyandTelescope.com.

Comet 2I/Borisov was discovered in late August by amateur astronomer Gennady Borisov. The comet has an extremely extended orbit, which indicates it came from outside our solar system, beyond the sun's influence. 

NASA's Hubble Space Telescope captured this view of the interstellar object Comet 2I/Borisov on Oct. 12, 2019. (Image credit: NASA/ESA/D. Jewitt (UCLA))

The interstellar comet reached perihelion (closest approach to the sun) on Sunday, at which point it was about 2 astronomical units (AUs) from the sun. One AU is the average distance between Earth and the sun, about 93 million miles (150 million kilometers). The comet will then pass closest to Earth a few weeks later on Dec. 28. 

A depiction of the path of interstellar Comet Borisov, which makes its closest approach to the sun on Dec. 8, 2019. It may be visible in small telescopes.
(Image: © ESA)

Observations show that Borisov has a small, bright head with a faint, extended tail, and its surface is reddish in color. The comet is expected to reach a visual magnitude peak of 15 during perihelion, suggesting it may be visible using an 8 or 10-inch telescope under clear skies, according to SkyandTelescope.com. 

"Right now, Comet Borisov is small and compact with a short tail pointing northwest. If the comet remains compact or nearly stellar and reaches magnitude 15.0, experienced observers might spot it in a 10-inch [telescope]," according to SkyandTelescope.com. "Chances improve for telescopes 12 inches (30.5-cm) or larger under dark, moonless skies. Equally important is to use high magnification to 'expand' the small object and further darken the sky background."

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