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Scientists to look at the role of supernovae as element-makers

RCW 86, the oldest documented supernova. (Reference image by NASA.)

A researcher at Virginia Tech College of Science’s Department of Physics began using NASA’s James Webb Space Telescope to collect data on the presence of heavy elements in exploding dying stars, or supernovae. 

As James Webb’s Baltimore-based mission operations center relays commands to the distant telescope to gather observations on the supernovae targeted by Chris Ashall, his team at Virginia Tech will study the collected data alongside more than 30 other scientists from around the world as part of the Mid-Infrared Supernova Collaboration.

“Pretty much everything around us comes from dying stars,” Ashall said in a media statement. “We’re made of stardust. Being able to study that fact—what we’re made out of—in detail, and to understand where the elements around us come from, is truly amazing.”

Stars produce heavy elements through the process of stellar nucleosynthesis. As stars burn, die, and explode, thermonuclear reactions take place inside them.

Supernovae are one of the highest-temperature and highest-density places in the universe. The material in stars burns and burns to form heavier and heavier elements, from hydrogen to helium, helium to carbon, carbon to oxygen, and so forth, all the way through the Periodic Table to iron.

When the stars finally explode, they throw all of this material back out into the universe at speeds up to 30% of the speed of light to make the next generation of stars and planets. “That’s how the planet and everything around us can have all of these heavy elements,” Ashall said. “They were made in dying stars.”

It’s widely accepted that most of the heavy elements in the universe are made by way of stellar nucleosynthesis, but Ashall wants to know more—to trace particular elements to the varieties of supernovae out there and to measure at what levels those elements are made by the stars.

Looking for manganese, chromium, cobalt and nickel

In his first project, the scientist will look for elements commonly found on earth, such as manganese, chromium, cobalt, and nickel, by focusing the James Webb Telescope on one supernova in particular: a third-generation white dwarf titled SN2021aefx, which exploded a year ago in the spiral galaxy NGC1566, also known as the Spanish Dancer.

Ashall will use the telescope to collect imaging and spectroscopy data on elements inside SN2021aefx. Spectroscopy involves looking at spectra produced by a material when it interacts with or emits light by breaking the light into its component colours, per NASA. 

“Spectroscopy tells us about different elemental lines,” the researcher said. “If there’s a line, we know the element is there.”

Ashall’s second project will focus on detecting carbon monoxide and silicon monoxide, also building blocks for life in the universe, in core-collapse supernovae. 

Core-collapse supernovae are massive dying stars more than eight times the mass of our sun. When these stars die, they collapse in on themselves and make an explosion more than 100 billion times brighter than the sun.

Using the observations made by the James Webb Space Telescope, Ashall will work to not only source heavy elements but to investigate when they were ejected by the exploding supernova. 

“When we measure these lines, we can figure out velocities of the explosion,” Ashall said. “So then we’ll understand how fast these elements are thrown out into the universe.”

Starting with the single type Ia supernova, Ashall hopes to build a sample of different varieties of supernovae to produce meaningful statistics on their role as element-makers. 

“If we don’t find those elements coming from supernovae, then we have to reassess what we know about how stars die and how these elements are released into the universe,” the scientist said.