In the fall of 1967, Princeton great quantum physicist John Archibald Wheeler was lecturing on pulsars at a conference where he was arguing that we should consider the possibility that the center of a pulsar was an object completely collapsed by gravity. He noted that man could not continue to say “completely ruined object” over and over again. That we needed a shorter descriptive phrase. “What about the black hole?” asked someone in the audience, giving birth to the name of one of the most paradoxical objects in the universe.
Fast forward to 2020, two teams of astronomers searching for a lost compact object that should have formed in the remainder of the 1987A Supernova’s two-year massive explosion, making them wonder if instead of a neutron star he had collapsed into a black hole. A compelling case in the 33-year-old mystery has been made based on the observations of the Array Millacer / Great Atacama submillimeter (ALMA) and a subsequent theoretical study. Scientists provide new insight into the argument that a neutron star is hiding deep inside the remnants of the exploding star – the newest neutron star known to date.
Because particles known as neutrinos were discovered on Earth on February 23, 1987, astronomers expected a neutron star to have formed at the star’s collapsing center. But when scientists could not find any evidence for that star, they began to wonder if it could be Wheeler’s “object completely destroyed by gravity.” For decades, the scientific community has eagerly awaited a signal from this object hiding behind a very thick cloud of dust.
“Blob” in Core of SN 1987A
Recently, observations from the ALMA radio telescope provided the first indication of the missing neutron star after the explosion. Extremely high-resolution images revealed a hot “rocket” in the dusty core of SN 1987A, which is brighter than its surroundings and matches the suspected location of the neutron star.
“We were very surprised to see this warm grief made by a thick cloud of dust in the supernova remnant,” said Mikako Matsuura of Cardiff University and a member of the team that found the ball with ALMA. “There must be something in the cloud that has ignited the dust and made it shine. This is why we suggested that there be a neutron star hiding inside clouds of dust. “
The extremely high-resolution ALMA images above revealed the hotspot in the dusty core of Supernova 1987A (inset), which may be the location of the missing neutron star. The red color indicates the dust and cold gas in the center of the supernova remnant, taken on the radio wavelength with ALMA. The colors green and blue reveal where the shock wave of shock from the exploding star is colliding with a ring of material around the supernova. Green represents the brightness of visible light captured by NASA’s Space Telescope. The blue color detects the hottest gas and is based on data from NASA’s Chandra X-ray Observatory. The ring was originally made to glow from the light bulb from the original blast. Over the following years, the ring material is significantly illuminated as the blast shock wave collides with it.
Although Matsuura and her team were enthusiastic about the result, they thought about the brilliance of the point. “We thought the neutron star might be too bright to exist, but then Dany Page [an astrophysicist at the National Autonomous University of Mexico] and his team published a study that showed that the neutron star can be really bright because it is so very young, “Matsuura said.
“I was in the middle of my doctorate when the supernova happened,” Page said, “it was one of the biggest events in my life that made me change the course of my career to try to solve this mystery. It was like a modern sacred pile. “
“Despite the supreme complexity of a supernova explosion and the extreme conditions that reign inside a neutron star, the discovery of a warm dust cloud is a confirmation of some predictions,” Page explained in the theoretical study by Page and his team, published today in Astrophysical Journal, which strongly supports the suggestion made by the ALMA team that a neutron star is amplifying the point of dust.
Forecasts – Location and Temperature
These predictions were the location and temperature of the neutron star. According to computer models of the supernova, the explosion “hit” the neutron star from its birthplace at a speed of hundreds of kilometers per second (tens of times faster than the fastest rocket). The block is exactly where astronomers think the neutron star would be today. And the temperature of the neutron star, which was predicted to be around 5 million degrees Celsius, provides enough energy to explain the brightness of the point.
“Apparently not Pulsar”
“The power of a pulsar depends on how fast it rotates and its strength in the magnetic field, both of which would have to have very well adjusted values to match the observations, while the thermal energy emitted by the hot surface of the the new neutron star naturally fits the data, Page said, suggesting that contrary to popular expectations, the neutron star – a 25 km wide, extremely hot ball with ultra-dense matter – is unlikely to pulsar life.The teaspoon of its material would weigh more than all the buildings within New York City combined.Because it could only be 33 years old, it would be the youngest neutron star ever found. The second youngest neutron star we know of is located in the remnant of the supernova Cassiopeia A and is 330 years old.
“The neutron star behaves the way we expected it to,” added James Lattimer of Stony Brook University in New York, and a member of Page’s research team. Lattimer also closely followed SN 1987A, having published before SN 1987A predictions of a neutrino signal of a supernova that subsequently matched observations. “These neutrinos suggested that a black hole never formed, and moreover it seems difficult for a black hole to explain the observed brightness of the point. We compared all the possibilities and concluded that a hot neutron star is the most likely explanation. “
Waiting for the dust to settle
Just a direct view of the neutron star would provide clear evidence that it exists, but for that astronomers may have to wait several more decades until the dust and gas in the supernova remnant become more transparent.
Although many telescopes have made images of the SN 1987A, none of them have been able to observe its core with such precision as ALMA. Early (3-D) observations with ALMA already showed the types of molecules found in the supernova residue and confirmed that it produced massive amounts of dust.
“This discovery builds on years of ALMA observations, showing the core of the supernova in more and more detail thanks to continuous improvements in 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.
Sources: ALMA observation of “point”: “ALMA High-resolution images of dust and molecules in SN 1987A Ejecta”, by P. Cigan et al., Astrophysical Journal. https://doi.org/10.3847/1538-4357/ab4b46
Theoretical study favoring a neutron star: “NS 1987A to SN 1987A”, by D. Page et al., Astrophysical Journal. https://doi.org/10.3847/1538-4357/ab93c2
The Daily Galaxy, Max Goldberg, through NRAO
Credit for the image: Chandra X-Ray Observatory at the top of the page and insert ALMA (ESO / NAOJ / NRAO), P. Cigan and R. Indebetouw; NRAO / AUI / NSF, B. Saxton; NASA / ESA