A rare visitor from beyond the solar system is offering astronomers and skywatchers a short but meaningful window of observation.
Interstellar comet 3I/ATLAS, only the third confirmed object of its kind, is scheduled to make its closest approach to Earth in the early hours of Friday morning, passing at a distance of about 168 million miles.
While it won’t be visible without optical aid, its scientific value is drawing global attention.
A Rare Object With an Unusual Origin
Comet 3I/ATLAS was first identified in July 2025 during a routine sky scan by the Asteroid Terrestrial-impact Last Alert System (ATLAS). Once confirmed, it earned its name and historic designation. The “3I” label stands for “third interstellar,” placing it in an exclusive category that includes 1I/‘Oumuamua discovered in 2017 and 2I/Borisov identified in 2019.
Unlike typical comets that orbit the Sun, 3I/ATLAS follows a strongly hyperbolic path. This means it is traveling fast enough to resist the Sun’s gravity and continue onward through space. Even at its closest solar pass on October 30, when it came within 130 million miles of the Sun, the comet maintained enough speed to avoid being pulled in. For comparison, Earth sits roughly 93 million miles from the Sun.
NASA Missions Track the Comet in Detail
Instagram | newscientist | 3I/ATLAS follows a strongly hyperbolic path.
Several NASA missions have gathered valuable data on 3I/ATLAS, adding clarity to its behavior and structure.
NASA’s Psyche mission captured four observations across eight hours on September 8 and 9, 2025, when the comet was about 33 million miles from the spacecraft. Using a multispectral imager, the mission helped refine the comet’s trajectory and revealed details about its faint coma, the cloud of gas surrounding its nucleus.
The Hubble Space Telescope observed the comet on July 21, 2025, while it was 277 million miles from Earth. Hubble images showed a teardrop-shaped dust cocoon trailing from a solid, icy core.
The James Webb Space Telescope joined the effort on August 6, using its Near-Infrared Spectrograph to analyze the comet’s composition.
These combined observations are allowing scientists to build a clearer picture of a traveler that formed far beyond the Sun’s reach.
When and Where to Look From Earth
The comet will reach its closest point to Earth on Friday, December 19, during the pre-dawn hours between 2:30 a.m. and 5 a.m. Observers in the United States should look toward the east-northeast, near Regulus, the brightest star in the constellation Leo.
The distance is still vast, and visibility remains limited. The comet cannot be seen with the naked eye and appears only as a faint, misty smudge through a small telescope or strong binoculars.
For those without equipment, Space.com is hosting a livestream in collaboration with the Virtual Telescope Project. The broadcast begins at 10 p.m. CT on Thursday, December 18, continuing into the early hours of December 19.
Why 3I/ATLAS Matters to Science
Interstellar objects carry material formed around other stars, offering a rare opportunity to compare distant planetary systems with the solar system.
Space.com describes such objects as “cosmic time capsules, delivering samples from distant exoplanetary systems we could never otherwise visit and study directly.” The detection of 3I/ATLAS adds momentum to a growing field focused on understanding how planetary systems form across the galaxy.
This opportunity, however, is brief. When first detected, the comet was racing through the solar system at roughly 130,000 miles per hour, a speed NASA described as the highest ever recorded for a visiting object. Its velocity has likely increased since then, and it is expected to exit the solar system entirely in the near future.
Size, Age, and Composition
Instagram | earth_unreal | 3IATLAS has a miles-wide icy nucleus, though its origin remains a mystery.
Follow-up studies revealed that 3I/ATLAS has a solid, icy nucleus estimated to be between 1,000 feet and 3.5 miles wide. According to David Jewitt of the University of California, who led the Hubble science team, pinpointing the comet’s origin remains nearly impossible.
“No one knows where the comet came from,” Jewitt said. “It’s like glimpsing a rifle bullet for a thousandth of a second. You can’t project that back with any accuracy to figure out where it started on its path.”
Chemical signatures suggest the comet formed in a cold, distant region of its original system, under conditions very different from those near the Sun. The Planetary Society estimates the object may be three to 14 billion years old, making it potentially older than the solar system itself, which formed about 4.6 billion years ago.
Addressing Claims of Alien Technology
Public speculation increased after Avi Loeb, an astrophysicist at Harvard University and head of the Galileo Project, co-authored a paper in July proposing the object could be hostile alien technology. The theory cited its trajectory, alignment with the ecliptic plane, and unusual physical traits.
That claim faced strong criticism from the scientific community. NASA scientists emphasized that the evidence supports a natural explanation.
“It looks like a comet. It does comet things,” said Tom Statler, a lead scientist at NASA. “It very strongly resembles the comets that we know. Some properties differ slightly, but it behaves like a comet. The evidence overwhelmingly points to this object being natural.”
Loeb made a similar claim in 2017 regarding 1I/‘Oumuamua. That theory was later rejected by multiple research institutions, including leading astrophysics programs at the University of Hawaii.
Comet 3I/ATLAS provides a rare opportunity to study material formed around another star. Its speed, age, and composition offer insight into planetary systems beyond the Sun. Although the comet will soon leave the solar system, the data collected during this pass will support long-term research and deepen understanding of interstellar objects.