ALMA detects signs of a neutron star in supernova 1987A

Hyperaxion Aug 7, 2020

The aftermath of the explosion that happened 33 years ago is still a puzzle – but scientists are getting closer and closer to solving it.

In 1987, the 1987A supernova explosion was detected from Earth thanks to the neutrinos emitted by it. Until recently, however, astronomers did not know what had happened in that region of space after the explosion. The main hypothesis was that a star would have been born, but no evidence had been found to confirm this.

ALMA detects signs of a neutron star in supernova 1987A
Artist’s impression of Supernova 1987A shows the inner region with remnants of the explosion (red), where a neutron star may be hidden. In the outer layer (blue), the energy of the supernova is colliding (green) with the gas ejected by the star before its end. (Credit: NRAO / AUI / NSF, B. Saxton).

The investigations continued over the past three decades until, between 2019 and 2020, two decisive scientific articles were published in The Astrophysical Journal. To conduct the studies, astronomers from different research institutions in several countries used data from the Atacama Large Millimeter/submillimeter Array (ALMA), in Chile.

The telescope array identified a bright spot in the supernova. Investigating it further, scientists realized that the “blob” – as they called it – could be an indication of a neutron star.

The "blob" detected by astronomers.
The “blob” detected by astronomers. (Credit: ALMA (ESO / NAOJ / NRAO), P. Cigan and R. Indebetouw; NRAO / AUI / NSF, B. Saxton; NASA / ESA).

“We were very surprised to see this warm blob made by a thick cloud of dust in the supernova remnant,” said Mikako Matsuura from Cardiff University in the United Kingdom, and co-author of one of the researches. “There has to be something in the cloud that has heated up the dust and which makes it shine. That’s why we suggested that there is a neutron star hiding inside the dust cloud.”

The 2020 study, published on July 30, agrees with the theoretical analysis made by another team of astronomers in a study published in November 2019. “In spite of the supreme complexity of a supernova explosion and the extreme conditions reigning in the interior of a neutron star, the detection of a warm blob of dust is a confirmation of several predictions,” explained Dany Page, co-author of the research published last year.

The blob. Each color represents its detection by a different device.
The blob. Each color represents its detection by a different device. (Credit: ALMA (ESO / NAOJ / NRAO), P. Cigan and R. Indebetouw; NRAO / AUI / NSF, B. Saxton; NASA / ESA).

The predictions in question are the location and temperature of the neutron star. According to supernova computer models, the explosion “kicked” the neutron star from its original location at a speed of hundreds of kilometers per second.

According to the scientists, the observed blob is exactly where astronomers think the neutron star would be today. Its temperature, predicted at about 5 million degrees Celsius, provides enough energy to explain the detected brightness.

“The neutron star behaves exactly like we expected,” said James Lattimer, co-author of one of the studies. “Those neutrinos suggested that a black hole never formed, and moreover it seems difficult for a black hole to explain the observed brightness of the blob. We compared all possibilities and concluded that a hot neutron star is the most likely explanation.”

Related topics:

Neutron star Supernova

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