Astronomers found the squashed stellar core that was left behind by a famous supernova

A reclusive neutron star may have been found in a famous supernova.

In 1987, astronomers captured the first supernova named Supernova 1987A (or SN 1987A for short). Since then, astronomers are searching for the squashed stellar core that should have been left behind.

Supernova 1987A sparked great excitement among scientists and soon became one of the most studied objects in the sky. The supernova is located in the Large Magellanic Cloud, a small companion galaxy to our own Milky Way, only about 170,000 light-years from Earth.

While looking for debris to explode outward from the detonation site, they also looked for what should have remained of the star’s core: a neutron star.

In a new study, astronomers gathered the data from NASA’s Chandra X-ray Observatory, NASA‘s Nuclear Spectroscopic Telescope Array (NuSTAR), and ground-based Atacama Large Millimeter Array (ALMA). They found an intriguing collection of evidence for the neutron star’s presence at the center of SN 1987A.

The study leader, Emanuele Greco, of the University of Palermo in Italy, said, “For 34 years, astronomers have been sifting through the stellar debris of SN 1987A to find the neutron star we expect to be there. There have been lots of hints that have turned out to be dead ends, but we think our latest results could be different.”

With Chandra and NuSTAR, the team found relatively low-energy X-rays from SN 1987A’s debris crashing into the surrounding material. The team also found evidence of high-energy particles using NuSTAR’s ability to detect more energetic X-rays.

There are two possible explanations for this emission: 1. A pulsar wind nebula, and 2. Particles being accelerated to high energies by the blast wave of the explosion.

This new study supports the idea of a pulsar wind nebula that implies a neutron star’s presence- by arguing on a couple of fronts against the scenario of blast wave acceleration. First, the higher energy X-rays’ brightness remained about the same between 2012 and 2014, while the radio emission detected with the Australia Telescope Compact Array increased. This goes against expectations for the blast wave scenario. Next, the authors estimate it would take almost 400 years to accelerate the electrons up to the highest energies seen in the NuSTAR data, which is over ten times older than the remnant’s age.

Co-author Marco Miceli, also from the University of Palermo, said, “Astronomers have wondered if not enough time has passed for a pulsar to form, or even if SN 1987A created a black hole. This has been an ongoing mystery for a few decades and we are very excited to bring new information to the table with this result.”

The data from Chandra and NuSTAR also supports the result from ALMA that offers possible evidence for the structure of a pulsar wind nebula in the millimeter wavelength band. Despite other explanations, its identification as a pulsar wind nebula could be substantiated with the latest X-ray data supporting the idea of a neutron star’s presence.

Astronomers noted, “If this is indeed a pulsar at the center of SN 1987A, it would be the youngest one ever found.”

Co-author Salvatore Orlando of the Palermo Astronomical Observatory, a National Institute for Astrophysics (INAF) research facility in Italy, said“Being able to watch a pulsar essentially since its birth would be unprecedented. It might be a once-in-a-lifetime opportunity to study the development of a baby pulsar.”

The core of the supernova is surrounded by gas and dust. Using advanced simulations, scientists were able to understand how this material would absorb X-rays at different energies. This approach also allowed them to measure the amount of X-rays at different energies accurately.

Although, more data is required to strengthen the case for the pulsar wind nebula.

The other authors of the paper are Barbara Olmi and Fabrizio Bocchino, also from INAF-Palermo; Shigehiro Nagataki and Masaomi Ono from the Astrophysical Big Bang Laboratory, RIKEN in Japan; Akira Dohi from Kyushu University in Japan, and Giovanni Peres from the University of Palermo.

Journal Reference:
  1. Emanuele Greco et al. Indication of a Pulsar Wind Nebula in the hard X-ray emission from SN 1987A. arXiv:2101.09029

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