My question is whether the flash of starlight at 5:19:46 UTC on July 1, 2025, from the image of comet 3I ATLAS, is an exoplanet or a nova event. The top right of the image I made a blue square appear in the video.
Credit: ATLAS/University of Hawaii/NASA
One would want to first check for a number of instrumental artifacts before making any sort of claim. That would involve looking at the individual raw images, various bias and flat-field calibration frames, etc.
\Brian
Hello Alan,
Brian’s advice is good—it’s important to rule out instrumental artifacts as a potential cause, especially because of the frequencies involved. Something new and undiscovered happens only rarely, but instrumental artifacts happen to every telescope, every night.
Looking at this specific image, I don’t think that this flash was really in deep space. For one, it looks like it has a crisper point spread function—its edges are sharper—than everything else in the field. That’s a strong indication of an artifact; likely a cosmic ray impacting the detector (which is neat in its own right).
Extrasolar events are never observed to be this short, because there is no physical mechanism which could produce a change that large, that fast. Think about it: once something is hot enough to glow, it takes time to cool down, right? Gravitational microlensing and gamma-ray burst optical counterparts are two of the fastest possible “flaring” transients in the extrasolar sky at optical wavelengths, but even the fastest of those events remain observable for hours (lensing) or days (GRB).
For reference, the light curves of novae and exoplanets look like this:
Because of their duration (novae) and amplitude (exoplanet transits), neither phenomena can explain this transient. A cosmic ray appears most likely.
Most likely it is a cosmic ray hit on the detector. Perhaps a piece of space junk providing a glint, flare.
Since ATLAS was designed to find near-Earth asteroids I suspect the “flash” has been characterized and rejected as an artifact by the ATLAS (human/AI) team! Just my opinion based on minimal information.
Jim (DEY)
Is it possible to determine if the flash is a pulsed laser (technology) for Morse code signals?
Yes; that can be ruled out because a source which is outside of Earth’s atmosphere would not appear crisper than the stars around it. There are several sources of blur in this image:
These blurs are all unavoidably imprinted on any light which travels through Earth’s atmosphere and interacts with the telescope’s optics, no matter whether that light comes from a star, a comet, or a laser.
Meanwhile, stray high-energy radiation from cosmic rays (or local sources—all it takes is a single radioactive atom!) is able to effectively “skip past” the atmosphere and the telescope optics, and crash directly into the CCD sensor. That’s why cosmics appear so crisp on a photograph. You can read more about cosmic rays here:
Speaking of lasers…
There is a group out there watching the sky for laser pulses: LaserSETI. They use diffraction gratings to distinguish between transients, artifacts, and true laser pulses (although as far as I know, they haven’t found any yet). You may be interested in reading about the project:
https://www.seti.org/projects/laserseti/
(A few years ago, Jill Tarter presented on SETI & LaserSETI during the AAVSO Superstar Astronomers series; the recording is available to AAVSO members.)
Here is useful reference on cosmic rays hits, kindly presented by JAAVSO Editor.
suppdoc.pdf (945.6 KB)
