An interstellar comet known as 3I/ATLAS has recently made its closest approach to the sun, positioning it for an outward journey through space. However, it will remain within our solar neighborhood for a while longer. According to EarthSky, the comet passed approximately 126 million miles (203 million kilometers) from the sun.
Currently, the comet is obscured from view by the sun when observed from ground-based telescopes on Earth. However, astronomers expect to observe 3I/ATLAS again in a few weeks. Darryl Seligman, an assistant professor in the Department of Physics and Astronomy at Michigan State University, noted that stargazers with telescopes should be able to see the comet in the predawn sky starting November 11.
Researchers will have the opportunity to study the comet for several months before it begins its exit from our solar system. The comet is projected to make its closest approach to Earth on December 19, coming within about 168 million miles (270 million kilometers). The European Space Agency has confirmed that this approach poses no threat to our planet.
3I/ATLAS is only the third known interstellar object to traverse our solar system, and astronomers have been closely monitoring it since its discovery on July 1. These observations are crucial for understanding how this comet differs from those that originated within our solar system.
The cores of comets, often described as “dirty snowballs,” are composed of ice, dust, and rocky material. As a comet approaches a star, it heats up, releasing gas and dust that form its characteristic tails. Astronomers aim to gather as many observations as possible, particularly as the comet nears the sun, to glean insights into its composition and the star system from which it came. Seligman emphasized, “When it gets closest to the sun, you get the most holistic view of the nucleus possible.” One of the main inquiries among comet scientists involves the composition of the volatiles, which can reveal the primordial material from which the comet was formed.
Advanced instruments, including the Hubble Space Telescope and the James Webb Space Telescope, alongside various space missions such as SPHEREx, have been employed to study the comet. Observations from SPHEREx and Webb have detected the release of carbon dioxide, water, carbon monoxide, carbonyl sulfide, and water ice as the comet approaches the sun, according to the European Space Agency.
Initial studies suggest that 3I/ATLAS could be between 3 billion and 11 billion years old, as indicated by research coauthored by Seligman and doctoral student Aster Taylor from the University of Michigan in August. For comparison, our solar system is estimated to be about 4.6 billion years old. Seligman noted that carbon dioxide transitions directly from solid to gas with temperature changes more readily than most other elements, implying that this comet has likely never come close to another star before its recent encounter with the sun.
Although 3I/ATLAS faded from the view of ground-based telescopes in October, it remained detectable for missions such as PUNCH (Polarimeter to Unify the Corona and Heliosphere) and SOHO (Solar and Heliospheric Observatory). The comet also passed closest to Mars on October 3, coming within about 18.6 million miles (30 million kilometers) of the planet and its orbiting spacecraft.
Since October 1, the U.S. government shutdown has hindered data sharing from NASA missions that observed the comet, but the European Space Agency”s Mars Express and ExoMars Trace Gas Orbiter made efforts to capture images of 3I/ATLAS during October. Although the cameras on these missions are tailored for studying Mars” surface, the ExoMars Trace Gas Orbiter was able to capture the comet as a faint dot. Nick Thomas, the principal investigator for the orbiter”s camera, remarked that this observation was particularly challenging, as the comet is estimated to be around 10,000 to 100,000 times fainter than their usual targets.
In November, the European Space Agency”s Jupiter Icy Moons Explorer (Juice) will also attempt to observe 3I/ATLAS using multiple instruments, despite the comet being farther away than when it was monitored by the Mars orbiters. However, astronomers anticipate receiving these observations only in February due to the data transmission rate of the spacecraft.
Seligman concluded, “We”ve got several more months to observe it. And there”s going to be amazing science that comes out.”
