The entry of a third known object into our solar system has been confirmed on July 1, 2025 by the astronomers. This object is named 3I/ATLAS, where 3I stands for “Third Interstellar”, having a highly hyperbolic (eccentricity ≈ 6.2) orbit, confirming it is not bound to the Sun but is a true interstellar visitor. Only two such visitors, 1I/ʻOumuamua (2017) and 2I/Borisov (2019), had been seen before. Notably, 3I/ATLAS appears to be the largest and brightest interstellar wanderer yet discovered.

Comparison with previous interstellars

According to NASA, astronomers from the ATLAS survey first spotted the object on July 1, 2025, using a telescope in Chile. It immediately drew attention for its unusual motion. Shortly after discovery, observers saw a faint coma and tail, leading to its classification as comet C/2025 N1 (ATLAS).

This comet-like appearance is shared with 2I/Borisov, the second interstellar visitor. Global observatories now track 3I/ATLAS. It poses no threat but offers a rare opportunity to study alien material. Since 1I/ʻOumuamua was observed only as it was leaving the solar system, it was difficult for astronomers to get enough data on it to confirm its exact nature — hence the crazy theories about it being an alien spaceship — though it’s almost certainly an asteroid or a comet.

Size and Significance

3I/ATLAS is much larger and brighter than earlier interstellar visitors. It is about 15 kilometers (km) [9 miles] in diameter, with huge uncertainty, compared to 100m for 1I/’Oumuamua and less than 1km for 2I/Borisov. This brightness and size makes it a a better target for study. Astronomers are planning to analyze its light for chemical signatures from its home system to get clues about the formation of distant planetary systems.