Astronomers Finally Find Neutron Star in Famous Supernova Remnant | Astronomy

Supernova 1987A (SN 1987A) was first observed on February 23, 1987 in a nearby dwarf galaxy, the Large Magellanic Cloud, some 164,000 light-years away. For decades, astronomers have searched for a neutron star that should have been left behind by the explosion. A new analysis of X-ray data from NASA’s Chandra and NuSTAR space observatories shows that a pulsar wind nebula created by such a neutron star may be present in the remnant of SN 1987A.

SN 1987A: the panel on the left contains a 3D computer simulation, based on Chandra data, of the supernova debris from SN 1987A crashing into a surrounding ring of material; the artist’s illustration (right panel) depicts a so-called pulsar wind nebula, a web of particles and energy blown away from a pulsar, which is a rotating, highly magnetized neutron star. Image credit: NASA / Chandra / CXC / University di Palermo / E. Greco / INAF-Osservatorio Astronomico di Palermo / Salvatore Orlando.

“For 34 years, astronomers have been sifting through the stellar debris of SN 1987A to find the neutron star we expect to be there,” said Dr. Emanuele Greco, an astronomer at the University of Palermo.

“There have been lots of hints that have turned out to be dead ends, but we think our latest results could be different.”

With the new data from Chandra and NuSTAR, Dr. Greco and colleagues found relatively low-energy X-rays from SN 1987A’s debris crashing into surrounding material.

They also found evidence of high-energy particles using NuSTAR’s ability to detect more energetic X-rays.

There are two likely explanations for this energetic X-ray emission: either a pulsar wind nebula, or particles being accelerated to high energies by the blast wave of the explosion. The latter effect doesn’t require the presence of a pulsar and occurs over much larger distances from the center of the explosion.

The new X-ray data support the case for the pulsar wind nebula by arguing on a couple of fronts against the scenario of blast wave acceleration.

First, the brightness of the higher energy X-rays 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 astronomers estimate it would take almost 400 years to accelerate the electrons up to the highest energies seen in the NuSTAR data, which is over 10 times older than the age of the remnant.

“Astronomers have wondered if not enough time has passed for a pulsar to form, or even if SN 1987A created a black hole,” said Dr. Marco Miceli, also from the University of Palermo.

“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 new data also support a recent result from the ground-based Atacama Large Millimeter Array (ALMA) that provided possible evidence for the structure of a pulsar wind nebula in the millimeter wavelength band.

While this blob has other potential explanations, its identification as a pulsar wind nebula could be substantiated with the new X-ray data. This is more evidence supporting the idea that there is a neutron star left behind.

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

“Being able to watch a pulsar essentially since its birth would be unprecedented,” said Dr. Salvatore Orland, an astronomer at the Palermo Astronomical Observatory.

“It might be an once-in-a-lifetime opportunity to study the development of a baby pulsar.”

The team’s results will be published in the Astrophysical Journal Letters.

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Emanuele Greco et al. 2021. Indication of a Pulsar Wind Nebula in the hard X-ray emission from SN 1987A. ApJL, in press; arXiv: 2101.09029