Since its discovery in early July, scientists have been captivated by the interstellar object known as 3I/ATLAS, marking the third such object identified passing through our solar system from interstellar space. This celestial visitor, which is generally believed to be a comet, is traveling at an extraordinary speed and is set to reach its closest point to the Sun on October 29.
During this close approach, astronomers were taken aback by the rapid increase in brightness of 3I/ATLAS, which occurred much sooner than they had expected. Typically, as comets near the Sun, they form a tail of gas and dust due to the sublimation of ice into gas, which enhances their luminosity. However, the speed of brightening observed in 3I/ATLAS has left scientists puzzled.
Researchers utilized data from multiple solar observatories, including NASA”s Solar Terrestrial Relations Observatory (STEREO) and the European Space Agency”s Solar and Heliospheric Observatory (SOHO), as well as the National Oceanic and Atmospheric Administration”s GOES-19 weather satellite. Earth-based observatories cannot track the object until it reappears from behind the Sun in early December.
In a preliminary paper, Karl Battams, an astrophysicist at the Naval Research Laboratory, and Qicheng Zhang, a postdoctoral fellow at Lowell Observatory, expressed uncertainty regarding the cause of the rapid brightening, which is significantly greater than that of most comets from the Oort cloud at similar distances. They proposed several possibilities, including the object”s high velocity, which is approximately 137,000 miles per hour, making it faster than the two previously identified interstellar objects.
Another theory suggests that the composition of 3I/ATLAS could be a factor. The researchers noted peculiar characteristics in the nucleus”s properties, such as its composition, shape, or structure, which may have been influenced by its origin or its journey through interstellar space.
Additionally, the astronomers observed that 3I/ATLAS exhibits a distinctly bluer hue than the Sun, indicating that gas emissions might significantly contribute to its visible brightness as it approaches perihelion.
Despite these insights, many questions remain unanswered, necessitating further observations to clarify the reasons behind the object”s behavior. The researchers noted, “Without an established physical explanation, the outlook for 3I”s postperihelion behavior remains uncertain, and a plateau in brightness — or even a brief continuation of its preperihelion brightening — appears as plausible as rapid fading past perihelion.”
As 3I/ATLAS remains obscured from Earth”s view behind the Sun, astronomers are urged to exercise patience. Following its perihelion on October 29, 2025, the object will gradually return to visibility, allowing for more detailed observations in November and December.
