Webb Telescope data confirms longstanding theory about last supernova visible from Earth

(CN) — Astronomers using the James Webb Space Telescope have found evidence that a neutron star formed in the remnants of the most-studied supernova in history, helping to confirm a decades-old theory.

Supernova 1987A made international news when, in February of 1987, the explosion of a star could be seen on Earth. Before that, the last supernova visible to the naked eye was in 1604.

Using infrared wavelength and gas data gathered by the telescope, a team of researchers from around the world concluded that a neutron star formed after the large star exploded, in an event known as a supernova. The scientists, led by Claes Fransson of Stockholm University, published their findings Thursday in the journal Science.

Located in a satellite galaxy called the Large Magellanic Cloud, Supernova 1987A gave modern scientists their first real chance to study a supernova in great detail and led to theories that the explosion may have left behind a black hole or neutron star.

The event was what's known as a “core-collapse supernova,” when a star eight times the mass of the sun explodes at the end of its life and leaves behind a black hole or much smaller neutron star made of the densest material in the universe. 

Neutrinos, the most common particles in the universe, were produced in the star’s explosion and were detected by observatories a few hours before the light of the supernova could be seen on Earth.

This suggested that a neutron star had been formed, but scientists have previously been left to only theorize what happened in the aftermath of the supernova because expanding debris — gas and dust — concealed what was left behind.

While indirect evidence gathered by other telescopes suggested that a neutron star had formed after the supernova, the study offers the most concrete evidence for that theory to date.

Using instruments on the James Webb Space Telescope, the researchers studied the supernova remnant at infrared wavelengths and using spectroscopy examined its gas composition, finding highly ionized argon and sulfur gas where the star exploded.

The lines they observed wouldn't be produced by a black hole, so the gas composition and ionization must be the product of a bright source of ultraviolet and X-ray radiation from a neutron star — either directly or indirectly, according to a press release.

According to researchers' estimates, the progenitor star of Supernova 1987A lost too much mass in the explosion to form a black hole.

The exact nature and condition of that star, researchers say, will require further studies.

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