A rare visitor from another star system, a comet named 3I/ATLAS, is currently passing through our solar system, giving scientists an unprecedented opportunity to study material from deep space. This object is only the third interstellar visitor ever detected, and a global effort is underway to learn its secrets before it disappears back into the cosmos.
The comet, which poses no threat to Earth, has already traveled past Mars and is now making its closest approach to the sun. Its journey provides valuable clues about the composition of distant planetary systems.
Key Takeaways
- 3I/ATLAS is the third interstellar object ever confirmed to have entered our solar system.
- It was discovered in July by the ATLAS telescope team in Chile, a project funded by NASA.
- The comet is traveling at approximately 310,000 km/h (193,000 mph).
- Observations are being conducted by multiple space agencies, including NASA and the European Space Agency (ESA).
- Its closest approach to Earth will occur in December, at a safe distance of 270 million kilometers.
A Visitor From the Stars
Astronomers have confirmed the presence of an ancient comet that originated from a star system far beyond our own. The object, officially designated 3I/ATLAS, was first identified in July by Larry Dennau, a scientist with the Asteroid Terrestrial-impact Last Alert System (ATLAS) located in Chile. The ATLAS project is a NASA-funded initiative operated by the University of Hawaii's Institute for Astronomy.
This discovery marks a significant event in astronomy, as 3I/ATLAS is only the third such interstellar object ever recorded. These visitors provide a direct sample of material from other parts of our galaxy, offering insights that are impossible to obtain through telescopes alone.
Comets are celestial bodies composed of ice, dust, and gas, often described as remnants from the formation of a solar system. Studying an interstellar comet like 3I/ATLAS can help scientists understand if other star systems formed in a similar way to our own.
A Growing List of Interstellar Visitors
Before 3I/ATLAS, only two other interstellar objects were confirmed:
- 1I/’Oumuamua: Discovered in October 2017, this rocky, cigar-shaped object puzzled scientists with its unusual shape and trajectory.
- 2I/Borisov: Detected in August 2019, this was the first object confirmed to be an interstellar comet, exhibiting a familiar fuzzy halo, or coma.
The "I" in their designations officially classifies them as interstellar in origin.
Tracking a High-Speed Journey
The comet is moving at an incredible speed. It was clocked at 310,000 kilometers per hour (about 193,000 miles per hour) as it traveled through the inner solar system. This high velocity is a key indicator that it is not gravitationally bound to our sun and is merely passing through.
Earlier in October, 3I/ATLAS made a relatively close pass of Mars, coming within 29 million kilometers (18 million miles) of the Red Planet. It reached its perihelion, or closest point to the sun, at the end of October.
Its trajectory will bring it closest to Earth in December. However, there is no cause for concern, as it will remain at a vast distance of approximately 270 million kilometers (170 million miles). For perspective, the sun is about 150 million kilometers from Earth.
Did you know? The comet's path is described as hyperbolic, meaning it follows an open curve rather than a closed elliptical orbit. This confirms it will enter and then permanently exit our solar system without being captured by the sun's gravity.
An International Observation Campaign
Because the comet's current position is behind the sun from our viewpoint on Earth, ground-based observations are temporarily impossible. However, a fleet of space-based telescopes and probes has been tasked with tracking the object.
The NASA Hubble Space Telescope captured some of the first clear images in July. These images revealed a teardrop-shaped coma of dust and gas surrounding a solid, icy nucleus. According to NASA, early observations from Hubble suggest the nucleus is no more than 5.6 kilometers (3.5 miles) across and could be as small as 440 meters.
A Coordinated Effort
Multiple space assets are contributing to the study of 3I/ATLAS:
- NASA's Hubble Space Telescope: Providing high-resolution images to determine size and composition.
- European Space Agency's Juice spacecraft: The Jupiter-bound probe is observing the comet throughout November.
- Other NASA assets are also involved, collecting data on its physical properties and chemical makeup.
These combined efforts are crucial for building a complete profile of this interstellar traveler. Scientists are particularly interested in its composition. Darryl Seligman, a planetary scientist at Michigan State University, noted that the comet's coma is rich in carbon dioxide. This suggests it formed in a very cold region far from its parent star.
"By studying these objects, we can learn about the building blocks of planets around other stars, and whether they are similar to or different from the materials that formed our own solar system."
What's Next for 3I/ATLAS
After its closest approach to Earth in December, 3I/ATLAS will continue its journey out of our solar system, eventually returning to interstellar space. It is not expected to be visible from Earth again until it emerges from behind the sun in early December 2025, but by then it will be much farther away.
The data collected over the coming weeks and months will be analyzed by scientists for years. Each new interstellar object provides another piece of the puzzle in understanding our place in the galaxy. The discovery of three such objects in just a few years suggests they may be more common than previously thought, heralding a new era of interstellar astronomy.