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NASA’s STEREO (Solar Terrestrial Relations Observatory), the NASA/ESA SOHO (Solar and Heliospheric Observatory), and NASA’s PUNCH (Polarimeter to Unify the Corona and Heliosphere) objectives have the distinct capability to observe locations of the sky near the Sun, which permitted them to track 3I/ATLAS as it passed behind our Sun as seen from Earth.
Taking a trip through our Solar System at an incredible 209,000 km (130,000 miles )per hour, 3I/ATLAS was made noticeable by utilizing a series of colorized stacked images from September 11-25, 2025, utilizing the Heliocentric Imager-1 instrument, a visible-light imager on NASA’s STEREO-A spacecraft. Image credit: NASA/ Lowell Observatory/ Qicheng Zhang.
STEREO observed the interstellar comet 3I/ATLAS from September 11 to October 2, 2025.
Developed to study the Sun’s activity and its impact throughout the Solar System, the objective belongs to a fleet of NASA spacecraft observing the comet, together offering more info about its size, physical residential or commercial properties, and chemical makeup.
Initially, comet 3I/ATLAS was anticipated to be too faint for STEREO’s instruments to see, however comprehensive image processing and overlaying (or ‘stacking’) telescope images utilizing the Heliospheric Imager-1 instrument, a visible-light telescope, brought 3I/ATLAS into view.
Stacking and lining up numerous direct exposures eventually produced numerous images where the comet appears as a minor lightening up in the.
This picture of 3I/ATLAS integrates observations from the NASA/ESA SOHO objective in between October 15 and 26, 2025. Image credit: NASA/ ESA/ Lowell Observatory/ Qicheng Zhang.
The SOHO spacecraft caught a glance of 3I/ATLAS on October 15-26, 2025.
Throughout this time duration, SOHO’s Large Angle and Spectrometric Coronagraph( LASCO )instrument suite found the comet crossing its field of vision from around 358 million km(222 million miles )away, or more than two times Earth’s range from the Sun.
SOHO orbits the Sun-Earth Lagrange point 1, an area of gravitational balance around 1/6 million km (one million miles) closer to the Sun along the Sun-Earth line.
Members of the SOHO group likewise utilized the stacking approach to produce the image of 3I/ATLAS.
3I/ATLAS looks like an intense things near the center of this image, made from integrating observations from NASA’s PUNCH objective drawn from September 20 to October 3, 2025. Image credit: NASA/ Southwest Research Institute.
PUNCH objective observed 3I/ATLAS from September 20 to October 3, 2025.
The observations exposed the comet’s tail, noticeable as a small elongation to the lower.
The comet was extremely faint throughout these observations, so the PUNCH group was unsure whether the spacecraft would have the ability to see it plainly, as the spacecraft is developed to study the Sun’s environment and solar wind– not comets.
Stacking numerous observations from PUNCH brought out 3I/ATLAS and its tail.
“We’re actually pressing the limitations of the system,” stated Dr. Kevin Walsh, a planetary researcher at the Southwest Research Institute who led PUNCH’s observations of the comet.
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