NASA’s SPHEREx mission has observed the interstellar comet 3I/ATLAS, revealing crucial details about its size, physical properties, and chemical composition.
Why it matters: As 3I/ATLAS originates from outside our solar system, studying it provides valuable insights into interstellar objects and improves our understanding of the universe beyond our cosmic neighborhood.
The details:
- SPHEREx images show 3I/ATLAS as a point source with no visible dust coma or tail, but a bright cloud of carbon dioxide (CO2) extending up to 348,000 kilometers from the object was detected.
- The CO2 mass loss rate is estimated at 70 kilograms per second, while no water was detected, setting an upper limit on the water mass loss rate at 4.5 kilograms per second.
- The flux detected at a wavelength of 1 micrometer suggests a large nucleus with a diameter of 46 kilometers, making 3I/ATLAS significantly more massive than previous interstellar comets.
- The surface of 3I/ATLAS shows a mix of water and carbon dioxide ices combined with organics, similar to Kuiper belt objects in our solar system.
The modest CO2 mass loss implies that a thin outer layer of the object is sufficient to maintain the observed CO2 cloud. The object’s large size relative to previously discovered interstellar objects presents a puzzle, leading to the hypothesis that 3I/ATLAS may have been targeted to align with the plane of the solar system’s planets.
What they’re saying:
- “The lack of a bright water gas coma is puzzling since 3I/ATLAS was not too far outside the Solar System’s ‘water ice line’ at 2.5 AU during the observations.” – Avi Loeb, astrophysicist
- “Another intriguing possibility is that 3I/ATLAS might have targeted the inner solar system through technological design, consistent with the alignment of its trajectory with the orbital plane of the planets around the Sun—a coincidence of one in 500 for a random orientation.” – Avi Loeb, astrophysicist
What’s next: As the Sun heats 3I/ATLAS in the coming months, further observations using Earth and space-based telescopes could reveal more about its true nature and origin. Scientists eagerly await the release of additional data to unravel the mysteries surrounding this fascinating interstellar visitor.
Recent from X
Whoa! Also dropping just a few hours ago: JWST 🔭 observations of 3I/ATLAS. Brilliant spectroscopy in addition to images of the CO2 coma – see link to paper. (P.S. still no evidence of alien engineering.) https://t.co/11muFDfL4L
— Dr Heidi B. Hammel (@hbhammel) August 25, 2025
1-in-500 cosmic coincidence? Avi Loeb cites NASA data to suggest 3I/ATLAS could be millions of times bigger than 2I/Borisov
READ: https://t.co/dHpfMsiEw7https://t.co/dHpfMsiEw7
— WION (@WIONews) August 26, 2025
Humanity will be altered forever if interstellar object 3I/ATLAS turns out to be an alien spaceship, and may be even in a good way
Read: https://t.co/MLZ9u6iLCZhttps://t.co/MLZ9u6iLCZ
— WION (@WIONews) August 25, 2025
