Comet Borisov has high levels of carbon monoxide
The presence of the chemical suggests the comet hails from a much colder climate
Interstellar comet 2I/Borisov has been found to have high levels of carbon monoxide, giving a hint to what kind of planetary system it originated from.
The recent discovery came after astronomers analysed images from the Hubble Space Telescope, taken when the comet flew through the Solar System in late 2019. Borisov attracted the attention of astronomers after its trajectory suggested it started life around another star. As comets are thought to be the icy remnants of when the planets first formed, it gave planetary scientists a unique chance to look at some of the chemical building blocks of another planetary system.
“We’ve been studying the composition of comets here for decades and using this information to understand how planets in our Solar System formed and evolved,” says Kathleen Mandt from the Johns Hopkins University, who took part in the study.
While astronomers believe they have found a few comets in orbit around other stars, they are too far away to learn anything detailed about their composition. Borisov, however, was close enough for telescopes to measure. Using Hubble’s ultraviolet instruments, astronomers were able to gauge how much water, oxygen, carbon dioxide and carbon monoxide the comet possesses.
After months of analysis, the team have now studied some of these observations, revealing that Borisov has 50 per cent more carbon monoxide than water. As carbon monoxide is a volatile compound, which boils away when exposed to heat or sunlight, the chemical’s abundance gives a clue about where the comet originated. “The high amount of carbon monoxide is an indication that it comes from a very cold place, either extremely far away from its host star or from a relatively cold star,” says Jian-Yang Li from the Planetary Science Institute who helped lead the observations. “We think it’s more likely to be the latter case and it comes from a cold red dwarf, because there are far more red dwarfs in our Milky Way than other hotter stars. However, we are still far from saying exactly what was going on around its host star when planets formed there.”
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