April 25, 2024

Comet Borisov: An interstellar guest with special properties

Comet Borisov: An interstellar guest with special properties

Updated March 31, 2021 at 9:54 pm.

  • Only two interstellar objects have been recorded in our solar system in human history.
  • One of them is Comet Borisov, which was discovered in 2019.
  • Researchers have now discovered more about the interstellar visitor and how it happened.

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On August 30, 2019, the amateur astronomer Gennady Borisov discovered a new comet in the Crimea, which soon turned out to be unusual: it is a visitor from interstellar space – a comet that appeared millions of years ago. His solar system He was fired.

But to astronomers ’surprise, they do not seem to differ from the comets known in our solar system. However, new observations made by an international team using the Very Large Telescope of the European Southern Observatory (ESO) now show that Borisov is in a much more primitive state than all known comets in our solar system.

Borisov did not change with difficulty

Stefano Panolo of the Armarge Observatory in Great Britain and colleagues wrote in the journal Nature Communications about measurements of the polarization of light reflected from the comet’s gas and dust envelope – coma.

Scientists say: “The polarization is stronger than usual for comets in our solar system.” From this, astronomers can draw conclusions about the nature of the dust particles in the comet’s coma.

According to Bagnulo and colleagues, the strong polarization shows that the dust particles are small and thin, that is, not well-regulated. The researchers concluded from this that Borisov is unusually “modern” and has not changed due to external influences since its inception.

The only culprit known to have a similarly strong polarization is Hale-Bopp. It’s also a very original comet, which probably only passed through the inner solar system for a second time in 1997 and was exposed there to the influence of solar radiation.

But while the polarization was uneven in Hale-Bopp, in Borisov it was congruent with the entire coma. “This indicates that Borisov is more original than Hale-Bopp,” said Bagnulo and colleagues.

The interstellar visitor may not have approached the central star in its original system. The only known interstellar body in the Solar System is the asteroid Oumuamua, which was discovered in 2017.

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Researchers put forth the theory of how a comet was formed

Observations made by a second international team using the ALMA (Atacama Large Millimeter / Subsillimeter Array) radio telescope system in the northern Chilean Andes allow to draw further conclusions about the history of Borisov’s origins.

As Ben Yang of the ESO Institute in Santiago, Chile, and colleagues write in Nature Astronomy, ALMA measurements refer to a large number of solid rock particles with sizes of more than one millimeter in the coma.

What initially seemed to contradict the observations made by Bagnolo and his team can easily be interpreted, says Yang: “Optical observations are sensitive to small particles in the micrometer range or less, and our observations, on the other hand, are sensitive to millimeters. Particles of size.” The two teams observed various components of the comet coma.

Yang and colleagues concluded from their observations that Borisov’s comet must have formed in an area of ​​its original system where many large rocky bodies already exist.

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According to the researchers, the small rock particles identified by ALMA could only occur through the many collisions of such rocks. (dpa / thp)

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