(Photo: Wikimedia Commons/NASA, ESA & the Hubble Heritage Team (STScI/AURA))
Planetary Nebula Sulfur Mystery Finally Solved

Scientists wondered where sulfur went as they couldn't trace it in the remains of dead stars. The planetary sulfur mystery had left researchers scratching their heads, but a discovery may have been the reason for what used to be an unexplainable phenomenon.

Planetary Nebula Sulfur Mystery Solved?

In principle, star wreckage locations all over the universe should contain a significant amount of sulfur. Nevertheless, scientists could not explain why they couldn't detect any sulfur in planetary nebulas.

Professional and amateur astronomers alike find planetary nebulas fascinating due to their astounding variety of shapes and hues. These nebulas offer brief "snapshots" of stars' deaths. They serve as a crucial window into the last stages of a star's hydrogen-burning "main sequence" existence and inspire in-depth analyses of its chemical makeup.

Scientists at The University of Hong Kong (HKU)'s Laboratory for Space Research (LSR) have finally figured out why sulfur levels in these gaseous and dusty remnant parts of space, known as "planetary nebulas," don't appear to be as high as they should be. Planetary nebulas can be found around stars that have run out of nuclear fuel and become dense, star-like corpses known as white dwarfs.

The researchers examined 130 planetary nebulas in the center of the Milky Way, an unparalleled dataset free of undesired or background noise, to solve the sulfur enigma of planetary nebulas.

The dataset from the Very Large Telescope, one of the most sophisticated optical telescopes in the world, situated at the Paranal Observatory in Chile's Atacama Desert, seemingly provided the much-needed answer.

Chemical elements have distinct wavelengths at which they absorb and emit light. As a result, when light travels through a cloud of gas and dust, the elements within leave their marks on the light, or "spectra," which makes spectroscopy an investigative technique possible. The study revealed that the absence of sulfur is the product of faulty information about the light radiated by the planetary nebula.

The researchers observed a strong "lockstep" relationship between sulfur and other elements for the first time, with the previous anomaly practically disappearing, using their big sample of the planetary nebula with its high signal-to-noise ratio.

The group hypothesizes that these findings demonstrate the critical role that high-quality data plays in solving scientific enigmas.

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What Is Planetary Nebula

A planetary nebula is an area of cosmic gas and dust created when a dying star's outer layers are thrown out. Planetary nebulae are unrelated to planets despite their name.

Red giants are formed when stars with an intermediate mass-more than 80% of the Sun's mass but less than eight times its mass expand after dying. The dying star will keep releasing gas while its surviving core constricts and momentarily starts to emit energy once more. The gas is removed due to this energy, which causes the gas's atoms and molecules to ionize, become charged, and start to release light. Planetary nebulas are made of incandescent gas that is thrown off.

Planetary nebulae are, therefore, categorized as emission nebulae and have nothing to do with planets. The historical misclassification gave rise to the misnomer. When astronomers saw the colorful display of planetary nebulae through their smaller telescopes 250 years ago, they believed they were viewing gas planets. Planetary nebulae are an extremely short-lived component of the star life cycle, with a lifespan of only 20,000 years or less.

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