Imagine someone slipped us a postcard from another star system—and the postman turned out to be a comet. That’s the vibe 3I/ATLAS brings: a mysterious visitor from across the galaxy, showing up unannounced and giving astronomers front-row seats to cosmic secrets.
A Rare Visitor
- Discovery & Identity
On 1 July 2025, the ATLAS telescope in Chile spotted an object—initially faint—traveling toward the inner solar system. After follow-up observations including by ZTF, scientists realized it wasn’t bound to our Sun. It earned the interstellar label 3I/ATLAS, the third such object known, after 1I/ʻOumuamua (2017) and 2I/Borisov (2019). - Path and Passing
This comet follows a hyperbolic trajectory, meaning it’s just passing through—escaping the solar system after its visit. Its closest approach to the Sun (perihelion) will occur around 29–30 October 2025, at about 1.36 AU—between Earth and Mars. It won’t come closer than 1.8 AU to Earth, so no danger—just a jaw-dropping celestial show.
Cosmic Time Capsule: Age & Origin
- Old and Interstellar
Kicking through the Milky Way’s “thick disk”—a region full of ancient, metal-poor stars—3I/ATLAS may be 7 to 14 billion years old, predating our own 4.6-billion-year-old solar system.
What’s It Made Of?
- Carbon Dioxide Reigns Supreme
The James Webb Space Telescope (JWST) and SPHEREx have confirmed that 3I/ATLAS is rich in carbon dioxide (CO₂), with a CO₂-to-water ratio of about 8:1—one of the highest seen. This suggests the comet may have formed in a cold, radiation-rich environment—far from its parent star’s CO₂ frost line—or perhaps sports an insulating crust that limits water sublimation. - A Little Water and Other Gases
The comet also outgasses small amounts of water ice, water vapor, carbon monoxide (CO), carbonyl sulfide (OCS), cyanide (CN), and even nickel vapor—revealing a diverse chemical signature. - Coma Details
Observations show a fuzzy coma—a cloud of gas and dust—extending perhaps twice the diameter of Earth, glowing reddish in color from organic-rich dust. Notably, TESS images captured cometary activity as early as May 2025, when the comet was still about 6.4 AU from the Sun.
Size & Observability
- How Big Is It?
Initial guesses put the nucleus as wide as 11 km (~7 miles), but Hubble observations refined that to an upper limit of 3.5 miles (5.6 km)—and it could even be as small as 320 meters. - Looking Up
From Earth, 3I/ATLAS will never reach naked-eye brightness—it might only reach around magnitude 11–12, visible through moderate telescopes. As it closes in on the Sun, alignment issues make it difficult to observe from Earth during perihelion—but Mars-based orbiters may get a better view that autumn.
Theories & Speculation
- Just a Comet (Most Scientists Agree)
The scientific consensus is that 3I/ATLAS is a comet—one with classical signs of activity and outgassing. - Alien Spacecraft? (Fringe Talk)
Harvard astrophysicist Avi Loeb sparked debate by suggesting the comet’s trajectory, size, and high CO₂ emissions could hint at non-natural origins—even an alien probe. But most astronomers criticize this as speculative—and all evidence so far supports a natural comet interpretation.
Why 3I/ATLAS Matters to Us at Morphie
Like a blinking cursor in a late-night chatroom, 3I/ATLAS reminds us how fleeting, surprising, and full of wonder our universe can be. For Morphie, this comet symbolizes those scattered, stellar conversations that light up the darkness—just like our chatrooms.
So pop into #3i/Atlas on Morphie, drop a star emoji, share your cosmic theories, or just admire the weird beauty of our universe’s surprises.