Leonard David's INSIDE OUTER SPACE

The Green Bank Telescope is the largest moving structure on land, and the largest fully-steerable telescope in the world. It was completed in 2000 and remains the most accurate and versatile large single-dish telescope in use today.
Image credit: NRAO/AUI/NSF

Mum’s the word from 3I/ATLAS!

That interstellar object oddity made its closest approach to Earth on December 19.

On December 18, a Breakthrough Listen-funded program carried out a “technosignature” search of the celestial intruder for evidence of it being a probe dispatched by extraterrestrial intelligence.

Tasked for the “listen up” was the 100 meter Robert C. Byrd Green Bank Telescope at 1–12 Gigahertz (GHz) frequency.

Results

The results are detailed in a preprint – “Breakthrough Listen Observations of 3I/ATLAS with the Green Bank Telescope at 1–12 GHz” – posted on the arXiv server.

Lead author, Ben Jacobson-Bell of the Department of Astronomy at the University of California, Berkeley, reports “we find no credible detections of narrowband radio technosignatures originating from 3I/ATLAS.”

The paper notes that there is currently no evidence to suggest that interstellar objects (ISOs) are anything other than natural astrophysical objects.

NASA’s Hubble Space Telescope reobserved interstellar comet 3I/ATLAS Nov. 30, with its Wide Field Camera 3 instrument.
Image credit: NASA, ESA, STScI, D. Jewitt (UCLA), M.-T. Hui (Shanghai Astronomical Observatory). Image Processing: J. DePasquale (STScI)

However, given the small number of ISOs known (only three observed to date), and the plausibility of interstellar probes as a technosignature, a thorough study was warranted.

Narrowband

“Putative nonanthropogenic interstellar probes are likely to communicate via narrowband radio signals for transmission efficiency and for the low extinction of such signals across interstellar space,” Jacobson-Bell and colleagues explain.

The Breakthrough Listen (BL) funding was provided by the Breakthrough Prize Foundation.

For details, go to the research paper findings at:

https://arxiv.org/pdf/2512.19763