Astrophysicists crack the case of ‘disappearing’ sulfur in planetary nebulae

Two astrophysicists from the Laboratory for Area Analysis (LSR) on the College of Hong Kong (HKU) have lastly solved a 20-year-old astrophysical puzzle in regards to the lower-than-expected quantities of the factor sulfur present in planetary nebulae (PNe) compared to expectations and measurements of different parts and different forms of astrophysical objects.

The anticipated ranges of sulfur have lengthy seemed to be “lacking in motion.” Nonetheless, they’ve now lastly reported for obligation after hiding in plain sight, on account of leveraging extremely correct and dependable information. The crew has not too long ago reported their findings in The Astrophysical Journal Letters.

PNe are the short-lived glowing, ejected, gaseous shrouds of dying stars which have lengthy fascinated and enthused skilled and beginner astronomers alike with their colourful and different shapes. PNe stay for just a few tens of hundreds of years in comparison with their host stars, which may take billions of years earlier than they go via the PN phase on the best way to changing into white dwarfs.

Consequently, PNe present an virtually instantaneous snapshot of stellar demise throes. They’re an important, scientific window into late-stage stellar evolution as their wealthy emission line spectra allow detailed research of their chemical compositions.

The enigmatic sulfur anomaly

Previous research confirmed that PNe optical spectra appeared to have a various deficit of the factor sulfur. This deficit was tough to clarify as a result of sulfur, referred to as an α factor, ought to be produced in lockstep with different parts like oxygen, neon, argon and chlorine in additional huge stars. Because of this, its cosmic abundance also needs to be instantly proportional.

Surprisingly, whereas sturdy correlations between sulfur and oxygen abundances have been noticed in H II areas (Hydrogen ionized area) and blue compact galaxies, PNe originating from low- to intermediate-mass stars persistently exhibit decrease sulfur ranges, giving rise to the mysterious “sulfur anomaly” that has perplexed and aggravated astronomers for many years.

Fixing the thriller

Shuyu Tan, a graduate of HKU MPhil in Physics and Analysis Assistant at HKU LSR, alongside together with her supervisor Professor Quentin Parker, the Director of LSR, used an unprecedented pattern of remarkable excessive sign to noise (S/N) optical spectra for about 130 PNe situated within the middle of our galaxy. This distinctive dataset had minimal background noise, permitting for a transparent and detailed examination of the spectral options, serving to the crew successfully sort out and clear up the thriller.

These PNe have been noticed utilizing the world-leading European Southern Observatory (ESO) 8m Very Giant Telescope in Chile. It seems the anomaly was basically a results of poor information high quality for sulfur emission strains in PNe spectra. It was discovered that utilizing oxygen as the bottom metallicity comparator to different parts was not correct, and as a substitute, argon demonstrated a stronger correlation with oxygen for sulfur and has been prompt as a extra dependable indicator of metallicity and an acceptable comparability factor.

So, when a big, rigorously chosen pattern of PNe are spectroscopically noticed at excessive S/N on a large telescope, not solely did the information reveal a powerful lockstep habits of sulfur in PNe for the primary time, as seen and anticipated for different forms of astrophysical objects, however the anomaly itself successfully went away.

The authors have successfully disproven earlier claims suggesting that the sulfur anomaly in planetary nebulae was a results of underestimated larger sulfur ionization levels or weak sulfur line fluxes. This discovering underscores the important significance of high-quality information in unraveling scientific mysteries.