Comet 3I/ATLAS is making headlines again. This interstellar object, known to be one of the fastest we’ve ever spotted, is doing something curious: it’s ejecting a lot of dust as it approaches the Sun. While comets generally emit gas and dust in a tail behind them, this comet is sending out particles in the Sun’s direction.
Comets are often called “dirty snowballs” because they contain ice, gas, rock, and dust. When they near the Sun, their solid surface turns to gas, forming a fuzzy cloud called a coma. Interestingly, while the nucleus can be tiny—like the size of a neighborhood—the coma can grow larger than Earth. As solar wind interacts with the comet, it shapes its tails: the main tail of gas and dust curves for a dramatic effect, while a straighter ion tail forms from ionized gas.
But with Comet 3I/ATLAS, we’re seeing something unusual. According to emerging research using the Hubble Space Telescope, the comet seems to lose dust only on the sunlit side. On its dark side, there’s little to no sublimation.
Astronomers suggest two main reasons for this odd behavior. One possibility is that the comet spins so that its pole faces the Sun, making its night side always in darkness. The second theory is that the comet has been around for billions of years, exposed to intense cosmic radiation, which has damaged its surface. This long exposure could make it harder for the comet to create a spectacular tail like others in our Solar System.
Discovered on July 1 by NASA’s Asteroid Terrestrial-impact Last Alert System (ATLAS), Comet 3I/ATLAS is the third interstellar object identified, following ’Oumuamua in 2017 and Comet 2I/Borisov in 2019. It’s notable for traveling at an impressive speed of about 58 kilometers (35 miles) per second. Some researchers believe it could even be larger than its predecessors.
Mark your calendars: on October 30, 2025, it will come within 210 million kilometers (130 million miles) of the Sun, well beyond Earth’s orbit. You’ll have a chance to see it from Earth until September, when it will briefly disappear behind the Sun’s glare, only to reappear in December.
For those interested in the science behind it, you can check out the full study on the arXiv.
This latest discovery not only adds to our understanding of comets but also sparks curiosity about what else is out there in our universe. Keep an eye on the skies. You never know what might be coming next!
