In the fall of 1967, Princeton’s great quantum physicist John Archibald Wheeler gave a lecture on pulsars at a conference where he focused on the possibility that the center of a pulsar was a whole gravitationally that collapsed thing. He said one could not keep saying “gravitationally completely collapsed thing” over and over. We need a shorter phrase description. “How about the black hole?” asked a man in the audience, who gave birth to the name of one of the most paradoxical things in the universe.
Fast forward to 2020, two teams of astronomers looking for a missing compact object that must have formed in the remnants of the two-light-up explosion of the Supernova 1987A, leading them to wonder if instead a neutron star dropped it into a Black hole. A compelling case in the 33-year-old mystery was made based on the observations of the Atacama Large Millimeter / submillimeter Array (ALMA) and a theoretical follow-up study. Scientists provide a new perspective for the argument that a neutron star hides deep inside the remains of an exploding star – the youngest neutron star known to date.
Since particles known as neutrinos were found on Earth on February 23, 1987, astronomers expected a neutron star to form in the collapsed center of the star. But when scientists could not find any evidence for that star, they began to wonder if it could “gravitationally completely collapse the Wheeler thing.” For decades, the scientific community has been eagerly awaiting a signal from this object hiding behind a very thick cloud of dust.
The “Blob” in the Core of SN 1987A
Recently, observations from ALMA radio provided the first indication of the missing neutron star after the explosion. Extremely high resolution image revealed a hot “blob” on the dusty core of SN 1987A, which is brighter than its surroundings and corresponds to the suspected location of the neutron star.
“We were shocked to see this hot blob made by a thick cloud of dust on the remnants of the supernova,” said Mikako Matsuura from Cardiff University and a team member who found the blast at ALMA. “There must be something in the cloud that heats up the dust and dazzles it. That’s why we suggested that there was a neutron star hiding inside the dust.
Extremely high resolution ALMA images above revealed a hot “blob” on the dusty core of Supernova 1987A (inset), which could be the location of the missing neutron star. The red color indicates dust and cold gas in the center of the supernova debris, taken at radio wavelengths along with ALMA. Green and blue hues revealed where the expanding shock wave from the exploding star collided with a ring of material around the supernova. Green represents the glow 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 first made to glow by a flash of light from the original explosion. In the following years the ring material became very clear as a bursting wave erupted inside it.
Although Matsuura and his team were pleased with this result, they wondered about the brightness of the field. “We thought the neutron star could be clearly existing, but then Dany Page [an astrophysicist at the National Autonomous University of Mexico] and his team published a study indicating that the neutron star is really bright because it is so young, “Matsuura said.
“I was halfway through my PhD when the supernova happened,” Page said, “it was one of the biggest events in my life that changed the course of my career to try to solve this mystery. It was like a modern holy grail. “
“Despite the supreme complexity of the supernova explosion and the extreme conditions prevailing within a neutron star, the discovery of a hot dust blob is a confirmation of many predictions,” Page explains theoretically study by Page and his team, published today in The Astrophysical Journal, strongly supports the ALMA team’s suggestion that a neutron star prove to be a dust blob.
Prediction – Location and Temperature
These predictions are the location and temperature of the neutron star. According to supernova computer models, the explosion “kicked away” the neutron star from its birthplace at speeds of hundreds of kilometers per second (tens of times faster than the fastest rocket). The blob is exactly the place where astronomers think it will be the neutron star today. And the neutron star temperature, predicted to be around 5 million degrees Celsius, provides enough energy to illuminate the globe.
“Probably Not a Pulsar”
“The strength of a pulsar depends on how fast it rotates and the strength of the magnetic field, both of which must have very well tuned values to match the observations, while the thermal energy released by the heat surface of the young neutron star naturally fits the data, Page said, suggesting that contrary to expectations, the neutron star –a 25 km wide, extremely hot ball of ultra-dense matter.-unlikely a pulsar.A teaspoon of its material weighs more than all the buildings inside New York City combined.Because it can only be 33 years old, it will be the youngest neutron star found.The second youngest neutron star we know is found in the supernova remnants Cassiopeia A and 330 years old.
“The neutron star is acting exactly as we expected,” added James Lattimer of Stony Brook University in New York, and a member of the research team. Lattimer also followed SN 1987A, which was published before SN 1987A predictions of a neutrino signal supernova following observations. “Neutrinos suggest that a black hole is not formed, and moreover, it is difficult for a black hole to explain the perceived brightness of the blob. We compared all the possibilities and decided that a hot star the neutron is the most likely explanation. “
Waiting for Dust to Fix
Only a direct image of the neutron star will provide definitive proof that it exists, but for astronomers who can wait a few more decades until the dust and gas in the remnants of the supernova become clearer.
Although many telescopes produced images of the SN 1987A, none of them observed its core with high precision as ALMA. Earlier (3-D) observations with ALMA have already shown the types of molecules found in supernova remnants and confirmed that they produce enormous amounts of dust.
“This discovery spans years of ALMA observations, showing the core of the supernova in more detail thanks to continuous telescope improvements and data processing,” said Remy Indebetouw of the National Radio Astronomy Observatory and University of Virginia, who became part of the ALMA imaging team.
Sources: Observation of ALMA’s “blob”: “High Angular Resolution ALMA Images of Dust and Molecules in SN 1987A Ejecta”, by P. Cigan et al., The Astrophysical Journal. https://doi.org/10.3847/1538-4357/ab4b46
The theoretical study in favor of a neutron star: “NS 1987A to SN 1987A”, by D. Page et al., The Astrophysical Journal. https://doi.org/10.3847/1538-4357/ab93c2
The Daily Galaxy, Max Goldberg, by NRAO
Image credits: Chandra X-Ray Observatory at the top of the page and inset ALMA (ESO / NAOJ / NRAO), P. Cigan and R. Indebetouw; NRAO / AUI / NSF, B. Saxton; NASA / ESA