Giant Comet Bernardinelli-Bernstein Releases Gas from 2 Billion Miles Away

Scientists have recently observed the giant comet C/2014 UN271, known as Bernardinelli-Bernstein, actively emitting gas from a distance of approximately 2 billion miles from the sun. This comet, which is notably one of the largest and most distant ever detected, has displayed unexpected activity as it traverses the cold outskirts of the solar system. Using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile, researchers were able to detect significant outgassing of carbon monoxide from the comet, a phenomenon not typically seen at such vast distances.

The observations were conducted in March 2024, and according to Nathan Roth, a researcher at NASA and the lead author of a study published in The Astrophysical Journal Letters, the comet has been exhibiting explosive outgassing patterns, raising questions about its evolution as it continues its journey toward the inner solar system. Roth stated, "These measurements give us a look at how this enormous, icy world works."

Bernardinelli-Bernstein, which has an estimated nucleus width of 85 miles and weighs around 500 trillion tons, is believed to originate from the Oort Cloud, a theoretical region filled with ancient, icy objects surrounding our solar system. The comet follows an orbit estimated to last around 3 million years, with its closest approach to the sun expected in early 2031. This unique trajectory places it about half a light-year away from the sun, and it has remained active for at least the past year, as highlighted by the findings from the ALMA telescope.

The detection of carbon monoxide jets, which are typically absent in astronomical observations at such distances, prompted significant interest among scientists. The gas is believed to evaporate at low temperatures, suggesting that the comet's surface may be undergoing complex changes, with different jets of gas emerging from varying locations over time. Prior to the observations, the comet experienced an outburst, further indicating its dynamic surface.

The historical context of comets, often regarded as time capsules of the early solar system, adds a layer of intrigue to this discovery. Comets are remnants from the formative years of the solar system, roughly 4.6 billion years ago, and are thought to contain vital information regarding the origins of water and other essential chemicals on Earth. As Roth mentioned, "As UN271 continues to approach the Sun, additional volatiles should be expected to activate, revealing the primitive chemistry preserved within."

Scientists have cataloged over 4,000 known comets, and observations of Bernardinelli-Bernstein are crucial for understanding the characteristics of Kuiper Belt Objects—icy bodies that have remained relatively unchanged over billions of years. The potential emergence of other gases, such as methane, ethane, and possibly ammonia, as the comet nears the sun will further enhance our understanding of its composition and the processes at play.

The implications of this discovery extend beyond the comet itself. Understanding the behavior and composition of such celestial bodies can provide insights into the early solar system's formation and the chemical processes that may have facilitated the emergence of life on Earth. With continued observations as the comet approaches the sun, scientists hope to uncover more about the complex dynamics of icy bodies and their roles in our cosmic neighborhood. As Roth concluded, the comet offers a rare "window" into the evolution of primordial materials in our solar system, potentially reshaping our understanding of its history and future.