Arrival of interstellar comet Borisov
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Interstellar comet C/2019 Q4, dubbed 2I/Borisov after its discoverer, will have its closest approach to the sun and Earth in December
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COMET 2I/BORISOV
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Discovered: Aug 30, 2019
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Discoverer: Amateur astronomer Gennady Borisov, from MARGO observatory in Crimea – using 0.65m telescope he built himself
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Maximum velocity: More than 155,000km/h (43km per second)
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Dimensions: Nucleus estimated to be 2-16km in diameter
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Closest approach: 300 million km (twice Earth’s distance from sun)
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PATH OF COMET THROUGH SOLAR SYSTEM
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Oct 26: Crosses ecliptic plane – plane in which planets orbit Sun – at about 40° angle from above
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Dec 7: Closest approach to sun. Comet too dim to see without telescope. Maximum brightness predicted to be only magnitude 15 – about as faint as Pluto
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Oct 2020: Comet no longer observable as it heads out through solar system, never to return
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Oct 12 image of comet

Broad, short tail of dust and gas stretches away from sun

Condensed coma (gas cloud) around small icy nucleus
      
First known interstellar comet ever identified

2I / Borisov

Uranus
Neptune
Earth 
Sun
Mars
Saturn 
Jupiter

Some planets omitted for clarity
                        
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Sources: NASA, ESA, IAU Picture: NASA, ESA and D. Jewitt (UCLA) © GRAPHIC NEWS