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EI2GYB > ASTRO 14.10.25 13:03z 43 Lines 4881 Bytes #28 (0) @ WW
BID : 46557_EI2GYB
Subj: A Message in a Bottle from Another Star
Path: SR8BBS<OK0NBR<OK2PEN<N3HYM<VE2PKT<PY2BIL<EI2GYB
Sent: 251014/1210Z 46557@EI2GYB.DGL.IRL.EURO LinBPQ6.0.25
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A Message in a Bottle from Another Star
An interstellar comet is as its name suggests, a comet that originated outside our Solar System and travels through interstellar space before entering our neighbourhood. Unlike comets that orbit the Sun and formed within our Solar System, these rare visitors come from other star systems, traveling for millions or even billions of years across interstellar space. When they pass through our Solar System, their trajectories are hyperbolic rather than elliptical, meaning they're just passing through rather than remaining bound by the Sun's gravity. The most famous example is 2I/Borisov, discovered in 2019, which became the first confirmed interstellar comet observed.
Until now, water has never been detected from an interstellar comet but a team from Auburn University did just that. In comets native to our Solar System, water serves as the primary way to measure the comet's activity. Water loss is tracked to understand how sunlight drives the release of other volatile gases locked within a comet's icy nucleus. Finding the same chemical signature in an interstellar visitor means astronomers can finally begin comparing 3I/ATLAS directly with Solar System comets, offering the first opportunity to compare the chemistry of planetary systems across the Galaxy.
What makes this detection particularly intriguing is the distance at which it occurred. Swift's observations captured hydroxyl emissions when 3I/ATLAS was nearly three times farther from the Sun than Earth, well beyond the region where surface ice typically turns straight to a gas easily. At that distance, the comet was losing water at roughly 40 kilograms per second, that's the kind of output from a fire hose! Most Solar System comets remain dormant at such distances, suggesting something unusual is happening with ATLAS.
The strong ultraviolet signal that the team detected hints at a complex process where sunlight heats small icy grains released from the nucleus, allowing them to vaporise and contribute to the surrounding gas cloud. These extended water sources have been observed in only a handful of distant comets and point toward layered ices that preserve clues about how these objects originally formed in their parent star system.
Each interstellar comet discovered so far has revealed dramatically different chemistry. 'Oumuamua, the first interstellar visitor identified in 2017, appeared remarkably dry, lacking any appreciable water content. The second, 2I/Borisov, proved rich in carbon monoxide. Now 3I/ATLAS is releasing water at unexpected distances. These differences demonstrate how varied the building blocks of planetary systems can be, driven by factors like temperature, radiation exposure, and local composition during formation.
To make their discovery, the team used NASA's Swift Observatory which carries a modest 30 centimetre telescope, but its location above Earth's atmosphere allows it to detect ultraviolet wavelengths that are almost completely absorbed before reaching ground based observatories. Free from atmospheric interference, Swift achieves sensitivity comparable to a four metre ground telescope at these wavelengths. Thankfully the team captured the data before 3I/ATLAS disappeared from view but it will become observable again after mid November, offering another opportunity to track how its activity evolves as it moves closer to the Sun.
Source : Physicists uncork a message in a bottle from another star
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