Gemini North images resolve the 1181 supernova remnant Pa 30 into chains of gas knots

The new detail came from two emission lines: red light from ionized sulfur, S II, and blue-green light from doubly ionized oxygen, O III ^[18]. The factor of 10 in the sulfur data is a count against what earlier images could resolve ^[19], so it measures how much sharper the view has become.

Along each filament the knots form tight chains, and they appear to have remarkably uniform sizes ^[11]. "The planetary region of our solar system could fit in each knot about 10 times with room to spare," said Ilaria Caiazzo of the Institute of Science and Technology Austria, who co-led the team with Tim Cunningham ^[1][12]. "The knots are quite strikingly uniform. We are excited to try to model them." ^[12] The published accounts do not give a measured spread of knot sizes or a knot count.

The thing this doesn't tell you is why the gas clumps at one scale. The paper's title, "Detection of knots in the supernova type Iax remnant Pa 30" ^[15], describes a detection, and Caiazzo's own words put the modelling still ahead ^[12]. In my view the uniformity is the most useful part of the result anyway. A simulation of how an incomplete explosion throws off its debris now has a concrete check. It has to make chains of similar-sized clumps, and smooth streaks fail. That holds only if the size distribution in the paper is as narrow as the description.

Distance is why the check exists at all. Pa 30 is about 7,500 light-years away, and the galaxy's center is about 26,000 ^[5]. That puts the remnant at less than a third of the distance to the center ^[20]. "We can see this much detail because of Pa 30's proximity to Earth," Caiazzo said. "This proximity makes Pa 30 uniquely valuable for study." ^[8]

The star that survived is what makes this a Type Iax supernova, a rare class in which the blast does not fully destroy the star ^[7][17]. Researchers have proposed that Pa 30 formed when two white dwarfs, dense Earth-sized stellar remnants, collided ^[7]. Both reports present that origin as a proposal. The star sits almost exactly at the nebula's center ^[13], a position The Independent calls unusual ^[14].

In the Milky Way, the sample is one. The 1181 event is one of just five supernovae recorded before the telescope era whose remnants had long remained unidentified ^[4]. Cunningham, of the Center for Astrophysics | Harvard & Smithsonian and now an assistant professor at the University of Warwick ^[1][16], expects more. "Reliable historical records of stellar explosions extend back only about a thousand years. For all we know, there might well be similar remnants still lurking in the dark in our own galaxy," he said ^[9]. "We will likely identify more similar objects as new telescopes continue to inspect the depths of our night sky." ^[10]