3I/ATLAS originated from place much colder than our solar system - CNN

Astronomers using radio telescope observations to get an inside look at an interstellar comet have gleaned new insights into when and where the celestial object formed.

The comet, named 3I/ATLAS, gained global attention when researchers first discovered it zipping through our solar system in July. It’s only the third interstellar object, or celestial body that originated outside our solar system, to be spotted passing through our corner of the universe. The comet began its exit of our solar system in December.

Initial research about the comet’s composition, published April 23 in the journal Nature Astronomy, shows that it originated somewhere very different from our own solar system, according to the study authors.

The observations were made using the Atacama Large Millimeter/submillimeter Array, or ALMA, in Chile in early November, just days after the comet passed closest to our sun.

The ALMA radio telescope enabled researchers to measure deuterium within the comet, marking the first time this isotope of hydrogen has been detected in an interstellar object.

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“Deuterium is generally found in the water of Solar System comets and in Earth’s oceans in the form of deuterated water, HDO, also called semi-heavy water,” lead study author Luis Eduardo Salazar Manzano, a doctoral candidate in the department of astronomy at the University of Michigan, wrote in an email.

“Our observations with ALMA indicate that the abundance of deuterium in the water of 3I/ATLAS is more than 40 times the value in Earth’s oceans and more than 30 times the value in Solar System comets.”

The findings may allow researchers to better understand the extreme conditions of the comet’s planetary system — and even discern what the Milky Way galaxy was like long before our solar system appeared.

“Interstellar objects are time capsules that bring material from the environments where other planetary systems formed, and our measurements are finally allowing us to open those time capsules and peek at the physical conditions where these objects originated,” Salazar Manzano said.

An ancient and unusual object

Water, or H2O, typically contains two hydrogen atoms and one oxygen atom. The hydrogen atoms include a single proton, or a positively charged subatomic particle. Deuterated water differs slightly in that the hydrogen atoms each also contain a single neutron, or a subatomic particle with no charge. The addition of the neutron means that deuterated water is heavier than H20.

Studying the abundance of deuterated water within 3I/ATLAS can reveal signatures of where the comet formed, the researchers said.

“The enrichment in deuterium generally happens when water forms in cold molecular clouds in interstellar space, which is generally around the same time that solar systems around other stars form,” Salazar Manzano said.

Researchers believe that the planetary system where the interstellar comet originated was incredibly cold, much colder than our own solar system during its formation, he said.

“The temperature in the formation environment of 3I/ATLAS was less than 30 Kelvin, which corresponds to -243.14 Celsius, or -405.67 Fahrenheit,” he said.

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Earlier research has indicated that the interstellar comet could be up to 11 billion years old, much older than our solar system or sun, which formed 4.5 billion years ago.

The water still trapped within the comet likely formed long before its host star, but 3I/ATLAS was born afterward from a protoplanetary disk of gas and dust that swirled around the star — the same disk where planets form, Salazar Manzano said.

Given that hotter temperatures can reduce the amount of deuterium due to chemical reactions, the researchers believe that 3I/ATLAS formed and spent most of its time on the outer reaches of the protoplanetary disk, preserving its deuterated water abundance.

The new findings agree with previous observations that found a high abundance of carbon dioxide within the interstellar comet, also consistent with an object that formed in the outer part of a protoplanetary disk.

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