An Interstellar Comet
On Sunday, a comet from beyond our solar system will make its closest approach to the sun.
NASA, ESA, D. Jewitt (UCLA)
The comet’s icy core is only a mile or so wide, but its surrounding cloud of gas and dust is many times larger than Earth.
Relative size
of Earth
Relative size
of Earth
Relative size
of Earth
Pieter van Dokkum, Cheng-Han Hsieh, Shany Danieli, Gregory Laughlin (Yale)
Just Passing Through
The comet, known as 2I/Borisov, is moving about 20 miles a second, fast enough to slip through the solar system and escape back into interstellar space.
NASA, ESA, J. DePasquale (STScI)
Discovery
The comet was first spotted on Aug. 30 by Gennady Borisov, a comet hunter in Crimea who has discovered nine comets since 2013.
The comet moving across background stars Gennady Borisov
Comet 2I/Borisov is the second interstellar object ever observed inside our solar system, earning it the prefix “2I.”
The alien comet resembles other comets in our solar system, but likely formed around another star before being kicked out into interstellar space.
Gemini Observatory/N.S.F./AURA
The sun’s gravity will bend the comet’s path, but not capture it. The comet will continue to brighten and will make its closest approach to Earth on Dec. 28.
National Optical-Infrared Astronomy Research Laboratory/Gemini Observatory/N.S.F./AURA
Oumuamua
The first interstellar object found passing through our solar system was 1I/Oumuamua, which was spotted in 2017 already moving away from the sun.
Oumuamua is circled in blue ESO/K. Meech et al.
Oumuamua was thought to be a reddish, cigar-shaped asteroid because it lacked a halo and reflected light in different ways as it turned.
A glimpse of Oumuamua Gemini Observatory/AURA/National Science Foundation
But recent observations suggest Oumuamua might actually be a comet with no tail, accelerating away from the sun with the slight kick of escaping gas.
Astronomers should have many future chances to observe alien comets. Dozens of interstellar objects are thought to pass through the solar system every year, unseen until now.
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Sources: NASA, Gennady Borisov and the Jet Propulsion Laboratory’s Small-Body Database Browser
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2019-12-07 10:00:00Z
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