An interstellar comet known as 3I/ATLAS has recently completed its closest approach to the sun, embarking on a path that will eventually take it out of our solar system. However, it will not leave our cosmic vicinity just yet. According to EarthSky, the comet came within approximately 126 million miles (203 million kilometers) of the sun.
Currently situated behind the sun from the perspective of Earth-based telescopes, astronomers expect to regain visibility of the comet in the coming weeks. Darryl Seligman, an assistant professor in the department of physics and astronomy at Michigan State University, indicated that stargazers with telescopes should be able to observe the comet starting November 11.
There will be several months remaining for astronomers to study the comet before it continues its journey beyond our solar system. Notably, 3I/ATLAS will make its closest approach to Earth on December 19, coming within about 168 million miles (270 million kilometers). Fortunately, the European Space Agency has confirmed that the comet does not pose any threat to our planet.
This comet is particularly significant as it is only the third known interstellar object to traverse our solar system, having been discovered on July 1. Each observation contributes valuable insights into the nature of this interstellar body and how it may differ from comets that formed within our solar system.
Comets are often described as dirty snowballs from the early solar system, comprising a solid core made of ice, dust, and rock. As they near stars like the sun, they release gas and dust due to heat, resulting in their characteristic tails. Astronomers are eager to gather observations as 3I/ATLAS approaches the sun, as the materials released could offer clues about its composition and the star system from which it originated.
Seligman remarked, “When it gets closest to the sun, you get the most holistic view of the nucleus possible.” One of the primary interests for comet scientists is determining the composition of the volatiles, which can reveal the original primordial material from which the comet formed.
To study the comet, scientists have employed powerful instruments, including the Hubble Space Telescope and the James Webb Space Telescope, as well as various space missions such as SPHEREx. Observations from SPHEREx and Webb have detected gases such as carbon dioxide, water, carbon monoxide, and carbonyl sulfide being released by the comet as it approaches the sun, according to the ESA.
Preliminary estimates suggest that 3I/ATLAS could be between 3 billion and 11 billion years old, as noted in a study coauthored by Seligman and Aster Taylor, a doctoral student at the University of Michigan, in August. For context, our solar system is estimated to be around 4.6 billion years old. Seligman added that carbon dioxide transitions from solid to gas more readily than many other elements, indicating that the comet likely has never been near another star before encountering the sun.
Although 3I/ATLAS faded from the view of ground-based telescopes in October, it remained observable by missions like PUNCH (Polarimeter to Unify the Corona and Heliosphere) and SOHO (Solar and Heliospheric Observatory). The comet also approached Mars closely on October 3, coming within about 18.6 million miles (30 million kilometers) of the planet.
Despite the government shutdown hindering data sharing from NASA missions that have observed the comet since October 1, the ESA”s Mars Express and ExoMars Trace Gas Orbiter managed to capture images of 3I/ATLAS in October. While designed to study Mars”s surface, the ExoMars Trace Gas Orbiter successfully detected the comet as a faint white dot, with principal investigator Nick Thomas commenting on the challenges of such an observation.
The ESA”s Jupiter Icy Moons Explorer (Juice) is also scheduled to attempt observations of 3I/ATLAS in November, using multiple instruments despite the greater distance from the comet compared to earlier observations by Mars orbiters. However, due to the spacecraft”s data transmission rate, results from these observations may not be available until February.
Seligman concluded, “We”ve got several more months to observe it. And there”s going to be amazing science that comes out.”
