On July 1, 2025, astronomers detected 3I/ATLAS, an interstellar comet entering our solar system. Discovered by the ATLAS survey telescope in Chile, this marks only the third known interstellar object observed passing through our solar system, following 1I/ʻOumuamua in 2017 and 2I/Borisov in 2019.
3I/ATLAS is traveling at a high velocity, approximately 61 kilometers per second, and is currently about 670 million kilometers from the Sun. Its trajectory indicates it originated from outside our solar system, as it follows a hyperbolic path that will not return. The comet is expected to make its closest approach to the Sun around October 30, 2025, passing just inside the orbit of Mars.
Observations suggest that 3I/ATLAS is an active comet, exhibiting a coma—a cloud of gas and dust—surrounding its nucleus. This activity is typical of comets as they approach the Sun, causing the release of gases and dust from their icy cores. The exact size of the comet's nucleus remains uncertain, but it is estimated to be several kilometers in diameter.
Scientists are closely monitoring 3I/ATLAS to study its composition and behavior, providing valuable insights into the characteristics of interstellar objects and the processes occurring in other star systems. The comet's passage through our solar system offers a unique opportunity to observe and analyze material from beyond our own cosmic neighborhood.