Interstellar object mystery: It changes color and shape as it approaches Earth

The latest images of the mysterious interstellar object 3I/ATLAS passing through our Solar System have revealed that it is changing both shape and color. The images captured by Austrian astronomers show that the object, which previously had a reddish glow, has now turned green. Scientists say these changes are unusual and cannot be fully explained by current comet models. CAPTURED DURING A LUNAR ECLIPSE “We captured a detailed image of 3I/ATLAS from the dark sky over Namibia during a total lunar eclipse. By combining multiple exposures taken in blue, green, and red light, we were able to clearly see the comet’s gas-rich coma,” said astronomer Michael Jager. Data released by the team this week revealed that the cloud of light (coma) around the object grows faster as it moves away from the Sun and slows down as it approaches. Researchers suggested that this change was caused by the emission of bright ice particles on the object’s surface. 3I/ATLAS will reach its closest approach to Earth on December 19, 2025. This distance will be approximately 270 million kilometers, or about the distance between Earth and Mars. SPACECRAFT CLAIMS Harvard physicist Avi Loeb argues that 3I/ATLAS could be an “artificial probe,” given the object’s enormous size, extreme brightness, and lack of a distinct tail. However, Austrian astronomers rejected this claim, emphasizing that a coma was clearly visible in their images. Jager said, “The tail documented by Hubble didn’t grow much, it just got a little brighter. The threshold at which gas-rich comets become active was exceeded in early September. We saw the tail brighten on August 28, and a few days later, in images taken with a blue filter, a gas coma began to form.” According to the scientist, this can be explained by the thick crust that has formed on the object’s surface after billions of years of exposure to space radiation. CHARACTERISTICS DIFFERENT FROM EARLIER DISCOVERIES 3I/ATLAS exhibits characteristics distinct from the first interstellar object, 'Oumuamua (which showed no traces of gas or dust), and the second, Borisov (which behaved like a typical comet). These include an anti-tail, extreme color variations, and a giant coma. However, Loeb paints a different picture based on the available data. Citing a study published by Chilean astrophysicists at the end of August, Loeb states that the object's emission of only nickel and no iron is "unnatural." While natural comets emit nickel and iron together, 3I/ATLAS's emission of only nickel, Loeb suggests, could be a "signature of industrial nickel alloy production." The researchers determined that the object was emitting about 5 grams of nickel and 20 grams of cyanide per second, with these amounts increasing sharply as it approached the Sun. However, he also noted that this process could not be explained by known natural cometary mechanisms.