In February 1987, the sky was illuminated. In the Large Magellanic Cloud, 167,644 light years away, astronomers watched a huge star die in a spectacular supernova, the one closest to Earth in hundreds of years.
But when the fireworks went out, there was nothing left. There is no indication that a neutron star should be left.
Today, 33 years later, astronomers finally caught a glimpse of the dead star, shining from the thick, hazy dust cloud of the hot remnants of the star’s internal organs in the center of the supernova remnant.
The multi-wavelength image of SN1
There are several types of supernovae, depending on the type of star death. Those stars that produce neutron stars (type II supernovae) have a starting mass that is 8 to 30 times the mass of the sun. As the mass is insufficient to support nuclear fusion, the mass becomes increasingly unstable.
Eventually, it exploded, ejecting its outer material, spewing light and neutrinos into the entire space, and the core collapsed into a neutron star.
In the case of the 1987 supernova, everything happened as expected. An ancient blue supergiant star called Sanduleak -69 202, which is about 20 times the mass of the sun, flew up in a spectacular light show-so bright and visible to the naked eye-corresponding to the neutrino rain found on Earth.
The incident left the remains of a glowing supernova named SN 1987A. But at the center, astronomers could not find the trace of the expected newborn neutron star.
Then, in November last year, a team of researchers led by Phil Cigan of Cardiff University in the United Kingdom announced that they had finally used Chile’s Atacama large millimeter/submillimeter arrays in the residual A hot bright spot was found in the core of the object. They said this is consistent with a neutron star shrouded in thick dust clouds.
“We were surprised to see the warm spots formed by the thick dust cloud in the supernova remnant. Something in the cloud must have heated the dust and made it glow. That’s why we suggested that there is a neutron star hidden in the dust cloud,” added Seiko Matsuura, an astrophysicist at Huo University, explained.
But there is still a problem. No matter what is glowing inside the clump, it may seem too bright to be a neutron star.
The team led by Dany Page, an astrophysicist at the National Autonomous University of Mexico, came in there. Page was a doctoral student when Sandudak -69 202 was admitted to Kablooey, and he has been studying SN 1987A ever since.
In a new paper, Page and his team proved theoretically that the luminous spots can indeed be neutron stars. Its brightness is consistent with the heat emitted by very young neutron stars-in other words, supernova explosions are still very, very hot. They named the neutron star NS 1987A.
Page said: “Despite the extreme complexity of the supernova explosion and the extreme conditions inside the neutron star, the detection of a warm dust cluster confirms some predictions.”
One of these heat is about 5 million degrees Celsius (9 million degrees Fahrenheit). The other is the position of the stars. It is not completely located in the center of the supernova, but moves away from it at speeds of up to 700 kilometers per second (435 miles per second).
This is simply unusual-if the supernova explodes unevenly, it will guide the collapsed stellar nucleus out of the entire galaxy at an absolutely crazy speed.
The team also compared the observations with other possible scenarios, such as radioactive decay of isotopes. They also checked the suitability of pulsars (a fast-rotating, pulsed neutron star) or black holes. None of these explanations fit the data like normal neutron stars.
According to the analysis of the research team, the flight distance of NS 1987A is about 25 kilometers, which is about 1.38 times the mass of the sun-which is extremely normal for neutron stars.
But this is also the youngest neutron star we have ever seen-the second youngest is in the supernova left by Cassiopeia A, which is 11,000 light years away from us and exploded in the 17th century-which means it can provide Valuable insights into the evolution of stars in this metamorphic stage.
Astronomer James Latimer of Stony Brook University said: “The behavior of neutron stars is exactly what we expected.”
“Those neutrinos imply that black holes never formed, and it seems difficult for black holes to explain the brightness of the observed spots. We compared all the possibilities and concluded that the most likely explanation is a hot neutron star.”
Since the hypothetical neutron star is still shrouded in dust, it is not yet possible to directly confirm this discovery. Astronomers will have to observe it for decades before they can see what emerges from that gloomy butterfly.
The research has been published in Astrophysical Journal.