Comet 3I/Atlas continues be full of surprises. Fresh analysis shows that it is only the third interstellar object ever detected, but it produces hydroxyl (OH) emissions, and these compounds indicate the presence of water on its surface. The discovery was made by a team of scientists from Auburn University in Alabama using NASA’s Neil Gehrels Swift Observatory and described in a study published in the journal Letters from an astrophysics journal.
Hydroxyl compounds can be detected by the ultraviolet signature they produce. However, on Earth, many UV wavelengths are blocked by the atmosphere, so researchers had to utilize the Neil Gehrels Swift Observatory, a space telescope free from the interference experienced by observatories on Earth.
Water is present in virtually every comet seen in the solar system, so much so that the chemical and physical reactions of water are used to measure, catalog and track these celestial bodies and their response to solar heat. Finding it on 3I/ATLAS means we can study its characteristics using the same scale as for regular comets, and this information could in the future become useful data for studying processes in comets from other star systems as well.
“When we detect water – or even its faint ultraviolet echo, OH – from an interstellar comet, we are reading a note from another planetary system,” Dennis Bodewits, a physicist at Auburn University who collaborated on the research, said in his paper press statement. “It tells us that the components of the chemistry of life are not unique to us.”
There are comets frozen pieces of rock, gases and dust that usually orbit stars (the exception are the three interstellar objects found so far). When they are far from the star, they are completely frozen, but as they approach, solar radiation causes their frozen elements to heat up and sublimate – turning from a solid to a gas – and some of this material is emitted from the comet’s nucleus thanks to the star’s energy. creating a “tail”.
However, the data collected with 3I/ATLAS revealed an unexpected detail: the comet’s OH production was already occurring far from the Sun – when the comet was more than three times farther from the Sun than Earth – in a region of the Solar System where temperatures are not usually sufficient to easily trigger ice sublimation. However, even at this distance, water was leaking from 3I/ATLAS at a rate of approximately 40 kilograms per second, which is a flow comparable – as the study authors explain – to a “maximum power hydrant”.
This detail appears to indicate a more elaborate structure than what is typically observed in solar system comets. This could, for example, be explained by the presence of diminutive fragments of ice detaching from the comet’s nucleus, which then evaporate under the influence of solar heat and feed the gas cloud surrounding the celestial body. This is a phenomenon that has only been observed in a diminutive number of extremely distant comets so far, but could provide valuable information about the processes that created 3I/ATLAS.
“Every interstellar comet so far has been a surprise,” said Zexi Xing, a researcher at Auburn University and co-author of the discovery, in his paper. press statement. “‘Oumuamua was dry, Borisov was rich in carbon monoxide, and now ATLAS is releasing water at distances we didn’t expect. Each of them is rewriting what we thought we knew about how planets and comets form around stars.”
This story originally appeared on WIRE Italy and was translated from Italian.