Astronomers Study Unique Interstellar Comet 3I/ATLAS
CHILE — On July 1, 2025, astronomers discovered a unique interstellar comet named 3I/ATLAS. This comet, spotted by the Deep Random Survey telescope, is notable because it is not gravitationally bound to the Sun, indicating it originated outside our solar system.
3I/ATLAS is the largest and brightest of three known interstellar comets to pass through our solar system, attracting global research efforts. NASA‘s SPHEREx telescope has detected high levels of carbon dioxide gas and water ice in the comet’s nucleus, marking a significant step in understanding such objects.
“The presence of large amounts of vaporized carbon dioxide suggests that 3I/ATLAS functions similarly to a conventional solar system comet,” said Carey Lisse, an astronomer at Johns Hopkins University and SPHEREx team member. He noted that the composition of comets varies based on their formation location and conditions.
Lisse explained that comets formed near the edges of the solar system are likely to have abundant icy components, while those that are formed closer to the Sun lose some of these elements. The analysis of 3I/ATLAS shows that it likely came from a distant stellar system and exhibits characteristics of well-processed solar system comets.
SPHEREx is specially designed to capture a wide range of wavelengths in light, allowing unprecedented access to comet chemical compositions. “By mapping the entire sky, we can observe various celestial objects, including comets like 3I/ATLAS,” Lisse stated.
As 3I/ATLAS approaches perihelion — its closest point to the Sun — scientists expect it to shed significant amounts of water ice. This will create a large water coma and possibly extend its tail. “3I/ATLAS poses no threat to Earth,” Lisse confirmed.
In October 2025, 3I/ATLAS is anticipated to pass close to the Sun, presenting a unique opportunity for further study. SPHEREx and other spacecraft will monitor the comet to unlock more secrets about its origin and composition.
A recent study revealed that 3I/ATLAS could be significantly older than previously thought — possibly around 7 billion years, indicating a much older formation than our solar system. Researchers emphasized the mission’s importance in drawing connections to early cosmic history.
As the scientific community eagerly awaits more data, the findings from SPHEREx promise to shed light on the nature of interstellar comets and their role in the solar system.
