Comet 2I/Borisov likely formed in extremely cold environment, high amounts of carbon monoxide show
ALMA observed hydrogen cyanide gas (HCN, left) and carbon monoxide gas (CO, right)
coming out of interstellar comet 2I/Borisov. The ALMA images show that the comet
contains an unusually large amount of CO gas. ALMA is the first telescope to measure
the gases originating directly from the nucleus of an object that travelled to us from
another planetary system. Credit: ALMA (ESO/NAOJ/NRAO), M. Cordiner & S. Milam;
NRAO/AUI/NSF, S. Dagnello
A galactic visitor entered our solar system last year – interstellar comet 2I/Borisov. When astronomers pointed the Atacama Large Millimeter/submillimeter Array (ALMA) toward the comet on 15 and 16 December 2019, for the first time they directly observed the chemicals stored inside an object from a planetary system other than our own. ...
The ALMA observations from a team of international scientists led by Martin Cordiner and Stefanie Milam at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, revealed that the gas coming out of the comet contained unusually high amounts of carbon monoxide (CO). The concentration of CO is higher than anyone has detected in any comet within 2 au from the Sun (within less than 186 million miles, or 300 million kilometers). 2I/Borisov’s CO concentration was estimated to be between nine and 26 times higher than that of the average solar system comet. ...
ALMA detected two molecules in the gas ejected by the comet: hydrogen cyanide (HCN) and carbon monoxide (CO). While the team expected to see HCN, which is present in 2I/Borisov at similar amounts to that found in solar system comets, they were surprised to see large amounts of CO. “The comet must have formed from material very rich in CO ice, which is only present at the lowest temperatures found in space, below -420 degrees Fahrenheit (-250 degrees Celsius),” said planetary scientist Stefanie Milam. ...
Unusually High CO Abundance of the First Active Interstellar Comet ~ M. A. Cordiner et al
Studies of a comet from beyond our Solar System have yielded insights into how other star systems may have formed.
Interstellar comet 2I/Borisov, observed using the Hubble Space Telescope, displayed a high amount of carbon monoxide, CO, relative to the amount of water it contains, compared to the comets from our Solar System, said Planetary Science Institute Senior Scientist Jian-Yang Li.
“The biggest news is probably the first measurement of the CO composition in a sample from another star. This has never been possible to do due to the enormous distance to another planetary system and the extreme faintness of these small objects around other stars,” Li said. “Given the frequency of recent discoveries of such interstellar objects – two in just two years – and thanks to the advance of telescopes and survey techniques, we can expect more and more such objects discovered and characterized in the near future. This comet may represent the start of a new era in studying extrasolar planet formation.” ...
Observations were made in ultraviolet, which is severely blocked by Earth’s atmosphere. Hubble, above the atmosphere, was needed to make the observations, Li said.
“The high amount of CO 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. We think it’s more likely to be the latter case – it comes from a cold red dwarf because there are far more red dwarfs in our Milky Way galaxy than other hotter stars,” Li said. ...
Watch how NASA’s Neil Gehrels Swift Observatory tracked water production by
interstellar comet 2I/Borisov as it sped through the solar system. On average,
Borisov produced enough water to fill a standard bathtub in 10 seconds. It shares
many traits with solar system comets, which may mean that comets form similarly
in different planetary systems. Credit: NASA/GSFC/SVS
Music: "Mesmeric Thoughts" from Universal Production Music
For the first time, NASA’s Neil Gehrels Swift Observatory tracked water loss from an interstellar comet as it approached and rounded the Sun. The object, 2I/Borisov, traveled through the solar system in late 2019.
At peak activity, Borisov shed eight gallons (30 liters) of water per second, enough to fill a bathtub in about 10 seconds. During its trip through the solar system, the comet lost nearly 61 million gallons (230 million liters) of water — enough to fill over 92 Olympic-size swimming pools. As it moved away from the Sun, Borisov’s water loss dropped off — and did so more rapidly than any previously observed comet. Xing said this could have been caused by a variety of factors, including surface erosion, rotational change and even fragmentation. In fact, data from Hubble and other observatories show that chunks of the comet broke off in late March. ...
Swift’s water production measurements also helped the team calculate that Borisov’s minimum size is just under half a mile (0.74 kilometer) across. The team estimates at least 55% of Borisov’s surface — an area roughly equivalent to half of Central Park — was actively shedding material when it was closest to the Sun. That’s at least 10 times the active area on most observed solar system comets. Borisov also differs from solar system comets in other aspects. For example, astronomers working with Hubble and the Atacama Large Millimeter/submillimeter Array, a radio telescope in Chile, discovered Borisov produced the highest levels of carbon monoxide ever seen from a comet at that distance from the Sun. ...
Water Production Rates and Activity of Interstellar Comet 2I/Borisov ~ Zexi Xing et al