Finding unusual things in the sky should no longer astound us. It’s pretty much par for the course these days in astronomy, what with new instrumentation like JWST and the soon to be arriving Extremely Large Telescope family coming online. Recently we’ve had planet-forming disks in the inner reaches of the galaxy and the discovery of a large molecular cloud (Eos by name) surprisingly close to our Sun at the edge of the Local Bubble, about 300 light years out.

So I’m intrigued to learn now of Teleios, which appears to be a remnant of a supernova. The name, I’m told, is classical Greek for ‘perfection,’ an apt description for this evidently perfect bubble. An international team led by Miroslav Filipović of Western Sydney University in Australia is behind this work and has begun to analyze what could have produced the lovely object in a paper submitted to Publications of the Astronomical Society of Australia (citation below). Fortunately for us, Teleios glows at radio wavelengths in ways that illuminate its origins.

Image: Australian Square Kilometre Array Pathfinder radio images of Teleios as Stokes (the Stokes parameters are a set of numbers used to describe the polarization state of electromagnetic radiation). Credit: Filipović et al.

I’m not going to spend much time on Teleios, although its wonderful symmetry sets it apart from most supernova remnants without implying anything other than a chance occurrence in an unusually empty part of space. Its lack of X-ray emissions is a curiosity, to be sure, as the authors point out:

We have made an exhaustive exploration of the possible evolutionary state of the SN based on its surface brightness apparent size and possible distances. All possible scenarios have their challenges, especially considering the lack of X-ray emission that is expected to be detectable given our evolutionary modelling. While we deem the Type Ia scenario the most likely, we note that no direct evidence is available to definitively confirm any scenario and new sensitive and high-resolution observations of this object are needed.

Odd Optical Pulses

So there you are, a celestial mystery. Another one comes from Richard Stanton, now retired but for years a fixture at JPL, where he worked on Voyager, among other missions. These days he runs Shay Meadow Observatory near Big Bear, CA where he deploys a 30-inch telescope coupled with a photometer designed by himself for the task at hand – the search for optical SETI signals. Thus far the indefatigable retiree has observed more than 1300 stars in this quest.

Several unusual things have turned up in his data. What they mean demands further study. The star HD 9389 produced “two fast identical pulses, separated by 4.4s,” according to the paper on his work. That was interesting, but even more so is the fact that looking back over his earlier data, Stanton realized that a pair of similar pulses had occurred in observations of the star HD 217014 that were taken four years before. In the ‘second’ observation, the twin pulses were separated by 1.3 seconds, 3.5 times less than for the HD 89389 event. But Stanton notes that while the separation is less, the pulse shapes and separation are very similar in both events.

Stanton’s angle into optical SETI differs from the norm, as he describes it in a paper in Acta Astronautica. The work is:

…different from that employed in many other optical SETI searches. Some [3,4] look for nanosecond pulses of sufficient intensity to momentarily outshine the host star’s light, as first suggested by Schwartz and Townes [5]. Others search optical spectra of stars for unusual features [6] or emission close to a star that could have been sent from an orbiting planet [7]. The equipment used here is not capable of making any of these measurements. Instead it relies on detecting unexplained changes in a star’s light as indications of intelligent activity. Starting with time samples of 100μs, the search is capable of detecting optical pulses of this duration and longer, and also of finding optical tones in the frequency range ∼0.01–5000Hz.

HD 89389 is an F-class star about 100 light years away from the Solar System. Using the equipment Stanton has been working with, all kinds of things can present a problem, everything from an airplane blocking out starlight, satellites (a growing problem because of the increasing number of Internet access satellites), meteors and birds. Atmospheric scintillation and noise has to be accounted for as well. I’m simplifying here and send you to the paper, where all these factors are painstakingly considered. Stanton’s analysis is thorough.

Here is a photograph which shows the typical star-field during an observation of HD 89389, with the target star in the center of a field that is roughly 15 × 20 arcmin in size. The unusual pulses from this star occurred during this exposure.

Image: The HD 89389 star-field. “A careful examination was made of each photograph to detect any streaks or transitory point images that might have been objects moving through the field. Nothing was found in any of these frames, suggesting that the source of the pulses was either invisible, such as due to some atmospheric effect, or too far away to be detected.” Credit: Richard Stanton.

A closer look at these unusual observations: They consisted of two identical pulses, with the star rapidly brightening, then decreasing in brightness, then increasing again, all in the fraction of a single second. The second pulse followed 4.2 seconds later in the case of HD 89389, and 1.3 seconds later at HD 217014. According to Stanton, in over 1500 hours of searching he had never seen a pulse like this, in which the star’s light is attenuated by about 25 percent.

Note this: “This is much too fast to attribute to any known phenomenon at the star’s distance. Light from a star a million kilometers across cannot be attenuated so quickly.” In other words, something on the scale of a star cannot partially disappear in a fraction of a second, meaning the cause of this effect is not as distant as the star. If the star’s light is modulated without something moving across the field of view, then what process could cause this?

The author argues that the starlight variation in each pulse itself eliminates all the common signals discussed above, from airplanes to meteors. He also notes that unlike what happens when an asteroid or airplane occultation occurs, the star never disappears during the event. The second event, in the light of the star HD 217014, was discovered later, although the data were taken four years earlier. Stanton runs through all the possibilities, including shock waves in the atmosphere, partial eclipses by orbiting bodies, and passing gravity waves.

One way of producing this kind of modulation, Stanton points out, is through diffraction of starlight by a distant body between us and the star. Keep in mind that we are dealing with two stars that have shown the same pattern, with similar pulses. Edge diffraction results when light is diffracted by a straight edge, producing ‘intensity ripples’ that correspond to the pulses. The author gives this phenomenon considerable attention, explaining how the pulses would change with distance but coming up short on a distance to the sources here.

From his conclusion:

The fact that these pulses have been detected only in pairs must surely be a clue to their origin. How can the two detected events separated by years, and from seemingly random directions in the sky, be so similar to each other? Even if the diffraction theory is correct, these data alone cannot determine the object’s distance or velocity.

He goes on to produce a model that could explain the pulses, using the figure below.

This thin opaque ring, located somewhere in the solar system, would sequentially occult the star as it moved across the field. If anything like this were found, it would immediately raise the questions of where it came from and how it could survive millions of years of collisions with other objects. Alternatively, if the measured transverse velocity proved greater than that required to escape our solar system, a different set of questions would arise. Whatever is found, those speculating that our best chance of finding evidence of extraterrestrial intelligence lies within our own solar system [15], might have much to ponder!

If there is indeed some sort of occulting object, observations with widely spaced telescopes could potentially determine its size and distance. Meanwhile, a third double pulse event has turned up in Stanton’s data from January 18, 2025, where light from the star HD 12051 is found to pulse, with the pulses separated by 1.52 seconds. This last observation doesn’t make it into the paper other than as a footnote, but it’s an indication that Stanton may be on to something that is going to continue creating ripples. As in the case of Teleios, we have an unusual phenomenon that demands continued observation.

The paper on the unusual circular object is Filipović et al., “Teleios (G305.4-2.2) — the mystery of a perfectly shaped new Galactic supernova remnant,” accepted at Publications of the Astronomical Society of Australia and available as a preprint. The paper on the pulse phenomenon is Stanton, “Unexplained starlight pulses found in optical SETI searches,” Acta Astronautica Vol. 233 (August 2025), pp. 302-314. Full text. Thanks to Centauri Dreams readers Frank Henriquez and Antonio Tavani for the pointer to this work.