Metal leaked from interstellar comet Borisov as it passed us in 2020

Gaseous nickel leaked from interstellar comet 2I/Borisov during its brief visit to our solar system two years ago, a new study shows. It sounds like weird behavior for comets, but as related research shows, the ejection of atomic metals may actually be a regular behavior of comets, both locally and across the galaxy.

Two new papers published in the journal Nature are updating our understanding of comets, both their origin and the conditions under which they formed. Combined, the papers allow for an unprecedented comparative analysis, in which astronomers pit local comets against comets that formed far away.

We're talking about the 2I/Borisov interstellar comet, which visited our solar system in January 2020. Astronomers were able to determine its interstellar properties due to its special orbit. Recent research suggests that Borisov is a fragment of a Pluto-like object that has formed in the Kuiper Belt of its parent star system. Borisov is often overshadowed by "Oumuamua," the first known interstellar object to visit our solar system (it did in 2017), but Borisov Rafa is also of concern, mainly because of its similarities to native comets.

In the first of the two papers, a team led by Piotr Guzik of the University of Jagiellonie in Poland discovered traces of nickel vapor in the tail of Comet Boris. Guzik explained in an email that his team "investigated the chemical composition of the object" and "discovered some emission signatures that were not known at the time to our knowledge" and that "our goal was to identify and quantify. they."

Using data collected by the Very Large Telescope in Chile, the research team performed a spectroscopic analysis of the comet. This technique enables scientists to study the chemical composition of celestial objects because the light of the target object can be split by a spectrometer, resulting in a colored spectrum that identifies specific atoms or molecules.

Comets are filled with pristine ice and dust that emerged while the planets were still coalescing. Even when the comet is far from the sun, water ice and other volatiles sublime (convert directly from solid to gas), forming a sphere of gas around the nucleus. As for expelling gaseous nickel or other metals, that's not what comets usually do, at least when comets stay at a distance from the sun.

"Nickel is a metal that only sublimates at high temperatures," Guzik explained. "So, while it's relatively common in and out of the solar system, we didn't expect to find it in the cold gas around cometary cores."

Indeed, the detection of nickel vapor from Borisov was unexpected, as the object is believed to be too cold to trigger metal sublimation, which requires temperatures in excess of 700 Kelvin (800 degrees Fahrenheit). It did happen, for example, when Comet Igia-Kiki passed by the Sun in 1965 "at a distance of about 30 and 13 solar radii," according to the paper. But Borisov didn't come close to the sun (at a distance of no less than 2.322 AU, or 216 million miles), and the temperature on the comet never exceeded the estimated 180 degrees Kelvin (-136 degrees Fahrenheit). Scientists now need to explain the mechanism that triggers the release of these metals on Borisov.

"The detection of gaseous nickel in the cold gas around the comet's core raises a question about its origin," Guzik said. "We found that the spatial distribution of nickel atoms hints at some short-lived parent molecule. If It would be interesting to find it in the spectrum of other bright comets."

In fact, the second detection of an interstellar comet would be a big help, as it would allow astronomers to study its chemical composition and compare it to Comet Borisov and our solar system homegrown comets .

"Each new, unexpected discovery in this field opens new horizons for further research, as comets and asteroids are 'time capsules' that contain information about the formation processes of the planetary systems from which they originated." "Interstellar objects that pass through our neighborhood are a bridge between our solar system and distant planetary systems, and because our galaxy is too far away to study [in situ]," Guzik said, "the study of its chemical composition is Understanding the general principles underlying the formation of galactic planetary systems creates a context."

In a related study, also in the journal Nature, a team of researchers led by Jean Manfroid of the University of Liege in Belgium, report detections detected in the spectra produced by comets native to our solar system. The case of atomic iron and atomic nickel. Using the Very Large Telescope, the team was able to calculate the rate at which these metals seep out of the cold cores of solar system comets. It's not much -- just 1 gram per second -- but it's still a measurable amount.

"Coincidentally, the amount of nickel produced every second is almost exactly the nickel content of a U.S. five-cent coin," Auburn University astronomers Dennis Bodowitz and Steven Bromley said in a related article. Explained in the News & Views article.

Taken together, the two papers point to a common process in the origin of comets. These shared chemistries mean that native and Borisov comets formed under similar conditions, in similar locations in their respective star systems. As Bodowitz and Bromley explain, if astronomers can "unravel the origins of iron and nickel in ordinary comets and this interstellar object," they may "unravel the differences between a shared system of different planets." Organic Chemistry Stories".

Other star systems experience processes similar to those we observe, which is not surprising since the laws of physics are consistent throughout the universe. Still, it would be nice to have actual evidence to back up these suspicions. As these studies show, it is now possible to study the chemical makeup of other star systems without actually going there.