An interstellar comet known as 3I/ATLAS is set to make its closest pass by Earth on Friday, December 8, 2023. This celestial visitor, first detected in July, will come within approximately 167 million miles (or 270 million kilometers) of our planet, although it will be positioned on the opposite side of the sun. For context, the sun is about 93 million miles (or 150 million kilometers) away from Earth.
Although 3I/ATLAS will not be visible to the naked eye, those with access to an 8-inch (20-centimeter) telescope or larger may catch a glimpse. The Virtual Telescope Project, led by astronomer Gianluca Masi, will provide a livestream of the comet at 04:00 UTC on Saturday, December 9, or 23:00 ET on Friday. This event comes after cloudy weather disrupted an earlier streaming opportunity.
Scientific Observations and Composition
The comet has been the subject of intense scrutiny since its discovery. Scientists aim to learn about its origins and characteristics as it approaches the sun. Comets are often described as “dirty snowballs,” comprised of ice, dust, and rock. When they near a star, they release gas and dust, forming their distinctive tails.
Observations from numerous missions, including the Hubble and James Webb Space Telescopes, have revealed significant findings. Initial studies suggest that 3I/ATLAS is between 3 billion and 11 billion years old, making it a relic from the early universe. Notably, carbon dioxide, water, and other substances have been detected as the comet nears the sun, indicating its complex makeup.
Astronomer J. D. Seligman emphasized the importance of these observations: “When it gets closest to the sun, you get the most holistic view of the nucleus possible.” The data gathered could provide insights into the primordial materials from which the comet formed.
Future Observations and Findings
While ground-based telescopes lost sight of 3I/ATLAS in October, it remains observable by space missions such as PUNCH (Polarimeter to Unify the Corona and Heliosphere) and SOHO (Solar and Heliospheric Observatory). In October, the comet made its closest approach to Mars, coming within 18.6 million miles (or 30 million kilometers) of the red planet.
Despite challenges presented by a recent government shutdown limiting data sharing from NASA missions, the European Space Agency’s Mars Express and ExoMars Trace Gas Orbiter captured images of 3I/ATLAS. The latter mission managed to observe the comet as a faint dot against the Martian landscape, an impressive feat considering its low brightness.
As 3I/ATLAS continues its journey, the European Space Agency’s Jupiter Icy Moons Explorer will also attempt observations in November, although results may not be available until February.
One particularly exciting aspect of the comet is its potential X-ray emissions. Previous attempts to detect X-rays from interstellar comets had been unsuccessful, but 3I/ATLAS may change that. Japan’s XRISM mission observed the comet for 17 hours, detecting X-ray emissions extending up to 248,000 miles (or 400,000 kilometers) from its nucleus.
The findings from this comet could enhance our understanding of both interstellar and solar system comets. The ongoing research efforts highlight the significance of 3I/ATLAS as it continues its journey beyond our solar system, providing scientists with a unique opportunity to study an object from outside our cosmic neighborhood.
