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Interstellar comet and galaxy
Comet 2I/Borisov appears as a bright dot within a haze of dust, with a distant spiral galaxy in the background of the Hubble Space Telescope image, taken on Nov. 16. The comet was about 203 million miles from Earth when the picture was taken. (NASA / ESA / UCLA / D. Jewitt)

The Hubble Space Telescope has snapped the best images to date showing the interstellar comet known as 2I/Borisov, and one of the pictures shows a faraway spiral galaxy just off to the side.

  • Comet Borisov, whose trajectory has been traced far beyond our solar system, swung around the sun on Dec. 8 and is now heading outward again. Hubble’s image shows the comet as a bright dot, surrounded by a haze of dust trailing off to the upper right. The galaxy that can be seen in a Nov. 16 image — known as 2MASX J10500165-0152029 — looks fuzzy because Hubble was tracking the comet instead.
  • Based on the pictures released today — including another shot that was captured on Dec. 9, just after the closest approach to the sun — astronomers estimate the width of Borisov’s nucleus to be less than half a kilometer (a quarter-mile). That’s 15 times smaller than earlier estimates. “Knowing the size is potentially useful for beginning to estimate how common such objects may be in the solar system and our galaxy,” UCLA’s David Jewitt said in a news release.
  • The studies so far suggest that Borisov’s composition is similar to the chemical makeup of comets born in our own solar system. Such evidence supports the view that comets form around other stars the way they do around our sun. Stay tuned: Borisov makes its closest approach to Earth on Dec. 28, and astronomers are likely to keep tracking the comet as it heads back toward the interstellar abyss.
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