3I/ATLAS, an interstellar comet, achieved its closest approach to the Sun, known as perihelion, on Wednesday. While this celestial object has not been visible from Earth since September, space-based observatories successfully monitored its trajectory, observing a significant increase in brightness as it neared our star.
The heat from the Sun caused the comet”s icy exterior to rapidly transition from solid to gas, skipping the liquid phase entirely. This process led to the formation of a bright, glowing cloud of gas around the comet”s nucleus, termed a coma, which resulted in a visible tail.
Comets like 3I/ATLAS provide rare opportunities for scientists to study the characteristics of other solar systems and shed light on the far reaches of our galaxy. Astronomers are particularly keen on examining the comet during perihelion, as the gases and dust released from its nucleus can offer insights into its composition.
Recent observations from NASA and the European Space Agency utilizing the STEREO-A and SOHO space observatories, along with data from NASA”s GOES-19 satellite, may reveal new details about this interstellar object, which is only the third of its kind ever identified. A study detailing these observations was authored by scientists Qicheng Zhang of Lowell Observatory and Karl Battams from the U.S. Naval Research Laboratory, and it was published on the preprint server arXiv on Wednesday.
At perihelion, 3I/ATLAS brightened to a magnitude of approximately 9, making it detectable with a backyard telescope if it were visible from Earth. The researchers also noted that the comet appeared “distinctly bluer than the Sun,” a hue consistent with the gaseous emissions that contributed to its brightness as it approached perihelion.
Interestingly, 3I/ATLAS exhibited a rapid increase in brightness that outpaced many comets originating from the Oort cloud—an area believed to be filled with icy objects at the edges of our solar system, though it has yet to be directly observed. In their analysis, Zhang and Battams propose that unique features of the comet”s nucleus, such as its composition, shape, or structure, may explain this unusual brightness. These characteristics could stem from its original star system or the lengthy interstellar journey it undertook to reach our solar system.
As this interstellar wanderer moves away from the inner solar system, astronomers anticipate that 3I/ATLAS may reappear in Earth”s view in late November or early December, with its closest approach occurring around December 19. After this date, the comet will gradually fade from view as it continues its journey away from our solar system. However, future spacecraft missions such as NASA”s Psyche mission to the asteroid of the same name or the Lucy mission targeting Jupiter”s Trojan asteroids may have the opportunity to observe the comet again, potentially providing additional insights into its origins and composition.
Initial findings indicate that 3I/ATLAS is particularly unique, possessing one of the highest ratios of carbon dioxide to water ever recorded in any comet. As researchers delve into the data collected during perihelion, it is likely that this cosmic visitor will continue to yield surprising revelations.
