“A near-perfect circle in a messy universe is a special find.” With those sentiments, astrophysicist Miroslav Filipović of Western Sydney University encapsulated the amazement of astronomers across the globe upon finding Teleios, a supernova remnant whose symmetry is so exact it challenges the normal disorder of cosmic explosions. Caught in the farthest reaches of the Milky Way by the Australian Square Kilometre Array Pathfinder (ASKAP), Teleios its name derives from the Greek for “perfect” has become one of the most geometrically perfect remnants ever observed in a very short time.
ASKAP, a state-of-the-art radio telescope array surveying the southern sky as part of the Evolutionary Map of the Universe (EMU) survey, played a key role in this discovery. Its sensitivity to weak radio emissions allowed scientists to uncover Teleios’s ghostly remnant, which shines in radio waves alone, avoiding detection at optical, infrared, and X-ray wavelengths. Filipović told Space.com, “I was looking at these images as they became available, searching for anything interesting, or not seen before, and came across Teleios.” Its perfectly circular shape was unusual, and so I investigated further. Its unusually circular shape was unexpected, and so I researched further. The remnant’s circularity rating of 95.4% makes it one of the most symmetrical supernova remnants ever recorded in the Milky Way.
Teleios is not merely a novelty for shape, however. The remnant’s distance from Earth stubbornly refuses to be pinned down, with guesses divided between 7,175 and 25,114 light-years. This is translated into a huge range for its physical dimensions either 46 or 157 light-years in diameter and an age that might be under 1,000 years or over 10,000. The problem, as described by Filipović and others in their arXiv preprint, is that “working out distances to things in space is surprisingly quite difficult.” The radio-faintness of Teleios makes it difficult to utilize conventional distance measurement methods, like the parallax or known stellar cluster associations applied to other supernova remnants.
The enigma continues with the absence of X-ray emissions. If it follows the models that currently exist, a Type Ia supernova remnant which is created when a white dwarf in a binary system gains enough mass from its partner to pass the Chandrasekhar limit and explode must emit X-rays as it shocks material in the surrounding area. But Teleios is quiet here on the spectrum. “All possible scenarios have their challenges, especially considering the lack of X-ray emission that is expected to be detectable given our evolutionary modelling,” the researchers stated in their report.
This uncertainty has prompted a suggestion of an alternative: Teleios could be the remains of a less common Type Iax supernova, a subcategory of Type Ia supernovae that produces so-called “zombie star” remnants. In this case, the remnant would be much nearer around 3,262 light-years from Earth and smaller, around 11 light-years in diameter. Interestingly, there is a potential candidate star at this distance that would fit the bill, but none of the independent distance estimates agree with such proximity based on current research.
It is Teleios’s beauty of symmetry that stands out because it defies the typical destiny of supernova remnants. The majority are scattered by the turbulence of their surroundings engaging with interstellar clouds, buffeted by stellar winds, or torn apart by the inconsistency of the explosion itself. But Teleios seems to have developed in a very sparsely populated area of space, 2.2 degrees below the Galactic Plane, where interstellar dust and gas are thin. “What makes Teleios’ shape so remarkable is that it displays none of these asymmetries; it effectively looks like an explosion that has happened with almost perfect initial parameters and with almost no disruption while expanding,” Filipović told Space.com.
The consequences of Teleios’s discovery resonate far beyond its beauty. Type Ia supernovae have been the cosmic distance-measuring gold standard for a long time, acting as “standard candles” because their maximum brightness is always the same. This accuracy supports the so-called cosmic distance ladder, a system that has allowed astronomers to map the size of the universe and even discover the accelerating expansion fueled by dark energy as founded by supernova surveys. As the NASA/LAMBDA Archive Team describes, the peak brightness of the light curve of Type Ia supernovae was found to provide a reliable standard candle for exploring the behavior of the expansion in the low-redshift regime. The validity of this technique relies on the homogeneity of Type Ia explosions a homogeneity now questioned by mysterious objects such as Teleios.
ASKAP’s involvement in this finding underlines the revolutionizing potential of future-generation radio astronomy. Its capability to pick up very faint, large-scale radio structures has already uncovered a treasure trove of strange objects, such as the so-called Odd Radio Circles (ORCs) and now Teleios. Filipović said, as quoted, “These are the ‘golden days’ for radio astronomy as the new instruments, such as ASKAP and MeerKAT, are opening windows for new discoveries” in his interview.
Teleios is at once wonder and provocation a well-formed survivor whose existence compels astronomers to reconsider the suppositions about stellar demise, interstellar distances, and the development of the Milky Way’s interstellar medium. While scientists demand more sensitive, high-resolution observations to tease out its true nature, Teleios grows, an impassive and symmetrical testament to the universe’s most violent processes.
