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- By Pallab Ghosh
- scientific correspondent
Image source, NASA/Josefin Larsson
The purple neutron star has been discovered to lie at the center of a bright “string of pearls”-shaped ring of superheated gas.
Scientists say they have solved the mystery of what lies at the heart of a famous cosmic explosion.
In February 1987, a star was seen exploding in a nearby galaxy. It was visible from Earth for months, shining with the power of 100 million suns.
There was so much debris that not even the most powerful telescopes could confirm what remained in its heart.
New results confirm that it is a neutron star, so dense that a teaspoon would weigh 10 million tons.
BBC Sky at Night presenter Dr Maggie Aderin-Pocock said the investigation team had “solved a murder mystery”.
“It’s about the death of a star and the mystery has been what’s in the veils of dust surrounding what’s left,” he said.
The explosion was that of a huge star, 20 times the mass of our Sun, the so-called blue supergiant. Its life ended spectacularly in a process called a supernova, prosaically called SN 1987A, by astronomers. It was the first supernova visible to the naked eye in 400 years, and it came from a star whose details had been captured and recorded by astronomers before it exploded.
Dr. Aderin-Pocock once worked on a project to solve the puzzle of SN 1987A, which she believed was figuratively and literally a big star.
“The fact that it was visible gave it celebrity status outside the world of science. And SN 1987A is also very close to astronomers’ hearts because it was relatively close and they were able to capture many details of the star’s life cycle.” .
Image source, BBC News/Stelios Toukidides
Artwork: Neutron stars collapsed under the weight of their own gravity, crushing the atoms that once made them shine.
The observations made SN 1987A the ideal laboratory in the sky to test the details of theories about how stars die. But a fundamental piece of the puzzle is missing: what was left in his heart after such a catastrophic event.
According to theory, stars collapse when they run out of fuel to carry out the nuclear reactions that make them shine. The mass of the star is so great that its gravitational force crushes its own atoms to produce the densest material in the Universe, which is called a neutron star, or if it is a larger star, it can become a black hole.
But which one was it? This is important for astronomers to know, because supernovae spread the heavy elements that help form and sustain life throughout the Universe.
Researchers writing in the journal Science say they have strong, if not overwhelming, evidence that this is a neutron star.
Professor Claes Fransson, from Stockholm University in Sweden, who led the study, said this was the first time anyone had been able to probe the center of the supernova and what was created there.
“We now know that there is a compact source of ionizing radiation, probably coming from a neutron star. We were looking for it from the moment of the explosion, but we had to wait to verify the predictions.”
The new data indicates that the surface of the neutron star would be at about a million degrees, having cooled from about 100 billion degrees.
baby star
The team will continue to monitor the supernova area to learn more about the precise details of the explosion. And the data gives the team the opportunity to monitor a very early “baby” neutron star and compare it to older ones to see how these cosmic heavyweights evolve over time.
“If we’re lucky, in the next few years we might even be able to properly see the neutron star at the center, taking a relatively close look at one of these intriguing objects at a very early stage in its life.”
The observations were made possible by NASA’s James Webb Space Telescope (JWST). In addition to being the most powerful space observatory ever built, it has instruments that take measurements at infrared frequencies and, therefore, can see beyond the space dust that has blocked our vision for so long.
Professor Mike Barlow, of UCL, says that although there have been several indirect hints, JWST has obtained “the first direct evidence” that it is a neutron star.
“The mystery of whether a neutron star is hiding in dust has raged for more than 30 years and it’s exciting that we’ve solved it.”
The JWST data was analyzed by 34 scientists from 12 countries. They found light from atoms of the elements argon and sulfur that could only have been produced by powerful radiation from a neutron star at the center of the supernova. There is no direct image of the neutron star itself, but it would be difficult for anything else to explain the readings, according to Dr Robert Massey of the Royal Astronomical Society.
“If we’re lucky, in the next few years we might even be able to properly see the neutron star at the center, taking a relatively close look at one of these intriguing objects at a very early stage in its life.”
So while astronomer detectives still don’t have smoking gun proof of the murder mystery, they do have gun smoke.