Recent observations have confirmed that 3I/ATLAS is an alien comet, providing astronomers with a clearer understanding of its size and characteristics. The Hubble Space Telescope has captured the sharpest images to date of this remarkable interstellar object, revealing intriguing details about its icy composition and behavior as it travels through our solar system.
The discovery of 3I/ATLAS marks the third interstellar object to pass through our solar system, generating significant excitement within the astronomy community. Given the limited window of opportunity to study this comet before it exits our solar system forever, astronomers are eager to gather as much data as possible. As a result, an array of increasingly powerful telescopes are being directed towards 3I/ATLAS to enhance our understanding of this alien visitor.
On July 21, astronomers utilized the Hubble Space Telescope to observe 3I/ATLAS for the first time. The resulting images, which showcase the comet against a backdrop of distant stars, confirm its unique characteristics. NASA reports that a blue filter was employed during these observations, helping to highlight the comet's features.
Currently, 3I/ATLAS is enveloped in a cloud of dust, ice, and gas, known as its 'coma', making it challenging to observe the solid nucleus directly, even with Hubble's advanced capabilities. However, by comparing these observations to the behavior of known comets, astronomers have refined their estimates regarding the size of this interstellar object. Initially, estimates suggested that the nucleus could be anywhere from 10 to 20 kilometers in diameter, but new data from Hubble has narrowed this estimate down to an upper limit of 5.6 kilometers wide. This size is still notably larger than previous interstellar visitors, such as 2I/Borisov and 1I/'Oumuamua, which measured approximately 500 meters and 100 meters wide, respectively.
The images captured by Hubble provide additional insights, confirming the cometary nature of 3I/ATLAS. The solid nucleus is observed within the bright region on the left side of the fuzzy structure, while the diffuse area on the right appears to be a plume of dust being ejected as sunlight warms the nucleus's surface. Interestingly, comets often produce tails of dust and ionized gas that typically point away from the Sun. However, it is not uncommon for dust plumes to form in the direction of the Sun when comets are further out in space and begin to experience the Sun's heat.
As 3I/ATLAS continues its journey, astronomers have approximately one month before most telescopes will lose sight of the comet as it moves around the far side of the Sun. During this time, orbiters around Mars may provide a closer look. Starting in early December, astronomers will resume observations, with opportunities to study the comet expected to last until early 2026, when it becomes too distant to observe effectively.
Future observations from other NASA missions, including the James Webb Space Telescope, TESS (Transiting Exoplanet Survey Satellite), and the Neil Gehrels Swift Observatory, along with NASA's collaboration with the W.M. Keck Observatory, will further enhance our understanding of 3I/ATLAS and its chemical composition. The ongoing research aims to unravel the mysteries surrounding this fascinating interstellar traveler.
For more information on celestial events, check out our August Sky Guide, where we highlight a six-planet parade that you won't want to miss!
