Mysterious interstellar object defies expectations as it nears Earth

"New scans of the interstellar visitor known as 3I/ATLAS have found that it is likely an unusual comet that's much smaller than it previously appeared and is unexpectedly releasing loads of carbon dioxide gas (CO2). The large amount of CO2 pouring out, about 940 trillion molecules per second, is a major finding, suggesting 3I/ATLAS formed in a star system that doesn't look anything like ours, where comets are much different than the ones we see orbiting our sun."

"Based on all the light coming from 3I/ATLAS, scientists originally suspected the object was more than 12 miles in diameter. Now, NASA's most powerful telescopes have cut that estimate down to 1.7 miles. The comet seemed larger because over 99 percent of the light observed came from a large, bright cloud of dust and gas surrounding it, called a coma."

3I/ATLAS is an interstellar object identified in July 2025 that now appears to be a small comet about 1.7 miles across. Telescopic observations show that over 99 percent of its brightness originates from a large dust-and-gas coma rather than its solid nucleus, causing earlier size overestimates near 12 miles. NASA's SPHEREx telescope detected strong CO2 emission—about 940 trillion molecules per second—and widespread water ice on the surface, while water vapor and carbon monoxide emissions remain weak. The composition and outgassing pattern suggest formation in a star system with cometary chemistry unlike the solar system. The object lies roughly 298 million miles from Earth.

Read at Mail Online