James Webb Space Telescope begins new exploration into iconic supernova

(CN) — NASA announced Thursday morning that the James Webb Space Telescope had turned its infrared cameras on Supernova 1987a, continuing a history of observation going back almost 40 years. The new images show features in and around the supernova’s central structure, including gaseous “crescents” which were not detected with earlier generations of devices, providing insight both into the power of this massive stellar explosion and the limits of our own technology.

“These crescents are thought to be a part of the outer layers of gas shot out from the supernova explosion. Their brightness may be an indication of limb brightening, an optical phenomenon that results from viewing the expanding material in three dimensions,” NASA said in a statement accompanying the new images. “In other words, our viewing angle makes it appear that there is more material in these two crescents than there actually may be.”

Supernovas occur after massive stars many times larger than the sun burn through all their hydrogen fuel for sustaining atomic fusion in their cores. All stars exist in a constant tug-of-war between the force of fusion reactions pushing material outward from the core, and gravity trying to pull all that material back in. So long as these forces are in equilibrium, the star is stable. But once its core runs out of hydrogen to fuse into helium, gravity wins.

The force of gravity condensing the star makes its core burn even hotter, reigniting fusion first with helium as fuel and continuing on through progressively heavier elements as the lighter ones are expended. This in turn causes the star’s outer layers to expand due to the condensed core’s higher temperatures.

Smaller stars like our sun don’t have enough energy to fuse anything heavier than helium into carbon and oxygen. Once they run out fuel completely, their expanded but less-dense outer layers dissipate into a nebula, leaving behind only the shrunken core to slowly cool for eons as a white dwarf.

But larger stars have the energy and matter to go through repeated cycles of fusion stalling and restarting with progressively heavier elements, all the way to iron. Since iron fusion reactions produce almost no additional energy, when the star reaches that point its core has nothing left to fight the force of gravity pulling its massive outer layers inward. In a flash these outer layers collapse and rebound off the dense core, creating a supernova explosion that can spread for light-years and shine brighter than a galaxy.

Supernova 1987a is one such explosion. It’s located roughly 168,000 light-years away in the Large Magellanic Cloud, a satellite galaxy orbiting the Milky Way. Astronomers working at the Las Campanas Observatory in Chile were the first to discover it in February 1987, within just a few hours of its light arriving at Earth. Since then scientists around the globe have studied 1987a extensively with multiple instruments, including NASA’s Hubble Space Telescope and Chandra X-Ray Observatory, Chile’s Atacama Large Millimeter Array and the retired Soviet telescope Astron.

Scientists have been able to chart the evolution of the supernova over the last 36 years; a real-time study of the aftereffects of massive stars’ deaths. But Webb’s infrared cameras can capture features obscured in the visible spectrum of light, including a dense “keyhole” region in the very center of the expanding gas and dust cloud. What this region is composed of and what may lie inside it is still a mystery for future observation; the material is packed so densely that even infrared light has trouble penetrating it.

Surrounding the “keyhole” is a ring of material studded with bright spots. The former star expelled the ring of gas and dust itself thousands of years before it exploded, and the luminous spots show where the supernova shockwave collided with it most violently. Though the Hubble Telescope has observed the evolution of this ring for decades, the new Webb images show bright spots and scattered debris clouds beyond the ring’s main body, implying the supernova shockwave is still expanding.

“These [outer bright spots] are the locations of supernova shocks hitting more exterior material,” NASA said.

What the new images do not show is definitive, visual confirmation of a neutron star, the super-dense core of a collapsed massive star that’s typically left behind after a supernova. Scientists have searched for decades for the missing neutron star within 1987a, and while some studies have produced compelling evidence for its presence, it has never been observed directly. Other researchers have theorized that the supernova may have instead produced a black hole, where matter is condensed so tightly into a single point in spacetime that not even light can escape its gravity.

Either way, NASA said Thursday that Webb will work in conjunction with other telescopes to continue study of 1987a, in hopes of discovering the object’s deeper mysteries.

“Webb will continue to collaborate with Hubble, Chandra, and other observatories to provide new insights into the past and future of this legendary supernova,” NASA said.

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