Artist’s illustration of Supernova 1987A shows the dusty interior regions of the remnants of the exploded star (red), in which a neutron star could be hidden. This inner region contrasts with the outer shell (blue), where the supernova energy is colliding (green) with the gas envelope ejected from the star before its powerful detonation. Credit: NRAO / AUI / NSF, B. Saxton
Two teams of astronomers have presented a compelling case in the 33-year-old mystery surrounding Supernova 1987A. Based on observations from the Atacama Large Millimeter / submillimeter Array (ALMA) matrix and a theoretical follow-up study, the scientists provide a new insight into the argument that a neutron star hides inside the remnants of the exploded star . This would be the youngest known neutron star to date.
Ever since astronomers witnessed one of the brightest bursts of a star in the night sky, creating Supernova 1987A (SN 1987A), they have been searching for a compact object that should have formed in the remnants of the explosion.
Because the particles known as neutrinos were detected on Earth on the day of the explosion (February 23, 1987), astronomers expected a neutron star to have formed at the collapsed center of the star. But when scientists couldn’t find any evidence for that star, they began to wonder if it subsequently collapsed into a black hole. For decades, the scientific community has been anxiously waiting for a signal from this object that has hidden behind a very thick dust cloud.
The drop’
Recently, observations from the ALMA radio telescope provided the first indication of the missing neutron star after the explosion. Very high resolution images revealed a hot “drop” in SN 1987A’s dusty core, which is brighter than its surroundings and matches the suspicious location of the neutron star.
The extremely high-resolution ALMA images revealed a hot “drop” in the dusty core of Supernova 1987A (inset), which could be the location of the missing neutron star. The red color shows dust and cold gas in the center of the supernova remnant, taken in radio waves with ALMA. The shades of green and blue reveal where the blasting blast wave from the exploded star collides with a ring of material around the supernova. Green represents the glare of visible light, captured by NASA’s Hubble Space Telescope. The blue color reveals the hottest gas and is based on data from NASA’s Chandra X-ray Observatory. The ring was initially made to glow by the flash of light from the original explosion. In the following years, the ring material has lit up considerably as the shock wave from the explosion crashes into it. 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 bubble made by a thick dust cloud in the supernova remnant,” said Mikako Matsuura of Cardiff University and a team member who found the bubble with ALMA. “There has to be something in the cloud that has heated the dust and made it glow. That is why we suggest that there is a neutron star hidden within the dust cloud.”
Although Matsuura and his team were excited about this result, they wondered about the brightness of the bubble. “We thought that the neutron star might be too bright to exist, but then Dany Page and his team published a study indicating that the neutron star can be so bright because it is so young,” said Matsuura.
Dany Page is an astrophysicist from the National Autonomous University of Mexico and has been studying SN 1987A from the beginning. “I was halfway through my doctorate when the supernova occurred,” he said, “it was one of the most important events in my life that made me change the course of my career to try to solve this mystery. It was like a modern Holy Grail.” .
The theoretical study of Page and his team, published today in The Astrophysical Journal, strongly supports the suggestion made by the ALMA team that a neutron star is feeding the mass of dust. “Despite the supreme complexity of a supernova explosion and the extreme conditions that reign inside a neutron star, the detection of a drop of hot dust is confirmation of several predictions,” Page explained.
These predictions were the location and temperature of the neutron star. According to supernova computer models, the explosion has “ejected” the neutron star from its birthplace at a speed of hundreds of kilometers per second (tens of times faster than the fastest rocket). The drop is exactly where astronomers think the neutron star would be today. And the neutron star’s temperature, which is forecast to be around 5 million degrees Celsius, provides enough energy to explain the brightness of the bubble.
This multi-wavelength colorful image of the intricate remains of Supernova 1987A is produced with data from three different observatories. The red color shows dust and cold gas in the center of the supernova remnant, taken in radio waves with ALMA. The shades of green and blue reveal where the blast wave from the exploded star is colliding with a ring of material around the supernova. Green represents the glare of visible light, captured by NASA’s Hubble Space Telescope. The blue color reveals the hottest gas and is based on data from NASA’s Chandra X-ray Observatory. The ring was initially made to glow by the flash of light from the original explosion. In the following years, the ring material has lit up considerably as the shock wave from the explosion crashes into it. Credit: ALMA (ESO / NAOJ / NRAO), P. Cigan and R. Indebetouw; NRAO / AUI / NSF, B. Saxton; NASA / ESA
It is not a pulsar or a black hole
Contrary to common expectations, the neutron star is probably not a pulsar. “The power of a pulsar depends on how fast it rotates and the intensity of its magnetic field, which would need to have very well adjusted values to match the observations,” Page said, “while the thermal energy emitted by the surface the youngster’s hot neutron star naturally fits the data. “
“The neutron star behaves exactly as we expected,” added James Lattimer of Stony Brook University in New York, and a member of the Page research team. Lattimer has also closely followed SN 1987A, having published pre-SN 1987A predictions of the neutrino signal from a supernova that subsequently matched the observations. “Those neutrinos suggested that a black hole never formed, and it also seems difficult for a black hole to explain the observed brightness of the bubble. We compared all the possibilities and concluded that a hot neutron star is the most likely explanation.”
This neutron star is an extremely hot ball of ultra-dense matter 25 km wide. A teaspoon of their material would weigh more than all the buildings in New York City combined. Because it can only be 33 years old, it would be the youngest neutron star ever found. The second youngest neutron star we know of is found in the supernova remnant Cassiopeia A and is 330 years old.
Only a direct image of the neutron star would give definitive proof that it exists, but astronomers may need to wait a few more decades for the dust and gas in the supernova remnant to become more transparent.
ALMA Detailed Images
Although many telescopes have imaged SN 1987A, none have been able to observe its nucleus as accurately as ALMA. Previous (3-D) observations with ALMA have already shown the types of molecules found in the supernova remnant and confirmed that it produced massive amounts of dust.
“This discovery is based on years of ALMA observations, showing the supernova nucleus in more and more detail thanks to continuous improvements in the telescope and data processing,” said Remy Indebetouw of the National Radio Astronomy Observatory and the University of Virginia, who has been part of the ALMA imaging team.
Scientists find evidence of missing neutron star
Dany Page et al., NS 1987A in SN 1987A, The Astrophysical Journal (2020). DOI: 10.3847 / 1538-4357 / ab93c2
Provided by the National Radio Astronomy Observatory
Citation: ALMA finds possible neutron star sign in supernova 1987A (2020, July 30) retrieved on July 30, 2020 from https://phys.org/news/2020-07-alma-neutron-star-supernova- 1987a.html
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