For now, the comet has slipped out of sight, hidden by the sun’s glare as it completes its orbit this week. But researchers and amateur astronomers haven’t lost track. Using data from multiple spacecraft, they’ve been following its journey toward perihelion — the point where it swings closest to the sun.
The brightening of comet 3I/ATLAS
Observations show that 3I/ATLAS has been glowing more intensely as it arcs behind our star. The comet reached its perihelion on Thursday, October 29, disappearing briefly from Earth’s view.
While most of the world waits for it to reappear, a handful of dedicated sky-watchers continue tracking it from spacecraft. On October 18, Thai amateur astronomer and veteran comet hunter Worachate Boonplod spotted 3I/ATLAS in images from the GOES-19 satellite, part of NOAA’s weather-monitoring fleet. The satellite’s CCOR-1 instrument, normally used to observe the sun, caught the comet moving across its field.
Tracking the comet from space
Boonplod noted that the comet’s brightness was similar to nearby stars, around magnitude 11, and that it would remain visible until October 24. “It’s moving from left to right across the field,” he wrote in the Comets Mailing List, “and should leave the CCOR-1 view soon.”
Other spacecraft were watching as well. NASA’s PUNCH mission — a set of four small satellites dedicated to studying the sun — and the joint NASA–ESA SOHO observatory also followed the comet’s progress. SOHO, orbiting nearly a million miles from Earth, used its LASCO C3 coronagraph to monitor 3I/ATLAS until October 26. These instruments block the sun’s light to reveal the outer solar atmosphere, or corona.
What caused the brightening
Then, on October 28, two researchers posted a paper on arXiv describing how 3I/ATLAS had brightened sharply before reaching perihelion, peaking at around magnitude 9. That’s still too faint to see without a telescope, but bright enough for home observers under the right conditions.
Their analysis showed that the comet appeared distinctly blue — a telltale sign of gas emissions. As comets near the sun, their frozen surfaces sublimate into gas, creating a glowing envelope and long tail. Sunlight ionizes these gases, adding even more brilliance.
The age and journey of 3I/ATLAS
Since its discovery in July, astronomers have been eager to study 3I/ATLAS, only the third interstellar comet ever recorded. Current data show it’s racing through the solar system at over 130,000 miles per hour.
Despite rumors suggesting it might be an alien probe, scientists agree this visitor is simply a natural object — a rocky remnant from a distant galaxy. Its incredible velocity, the fastest ever measured for a solar system object, hints that it’s been traveling for billions of years, slingshotting past stars and nebulae along the way.
Some studies even suggest 3I/ATLAS could be roughly 3 billion years older than our 4.6-billion-year-old solar system, making it perhaps the oldest comet ever observed. Hubble data also indicate it’s massive — about 3.5 miles (5.6 km) across.
What’s next for comet watchers
The comet should reappear by early December, once again visible to ground-based telescopes. And if predictions hold true, spacecraft orbiting Jupiter might catch a glimpse as it passes the giant planet in March 2026.
