Astronomers detect subatomic particles from a gigantic black hole in a nearby galaxy

Astronomers spot astrophysical neutrinos that come from a galaxy located 47 million years away.

November 15, 2022 12:17 pm | Updated 01:55 pm IST

NGC 1068 is an active galaxy with a supermassive black hole at its centre. Image for representation.

NGC 1068 is an active galaxy with a supermassive black hole at its centre. Image for representation. | Photo Credit: Reuters

Among the many cosmic rays of the universe that pass through the Earth unseen, scientists have spotted astrophysical neutrinos that emanate from a nearby galaxy. 

Observed by an international team of scientists for the first time, the neutrinos were detected by the one billion ton IceCube Neutrino Observatory, that is situated 1.5-2.5 kilometres below the surface at the South Pole. The telescope is a sophisticated piece of machinery designed specifically to detect neutrinos.

A neutrino is a subatomic particle that is similar to an electron, however, it has no electrical charge and close to negligible mass. These particles are very common in the universe. In fact, at any given time, a billion neutrinos are passing through us. However, they are extremely hard to detect as they rarely interact with matter and have been dubbed ‘ghost particles’. 

Though most of the neutrinos detected originated from the Sun or the Earth’s atmosphere, some travel long distances across galaxies without any obstruction and carry valuable information about their origins. These are called astrophysical neutrinos. 

A new study, published in the journal Science, reports the detection of high-energy astrophysical neutrinos that emerged from a galaxy called NGC 1068 located in the constellation Cetus. Also known as Messier 77, it is one of the most studied galaxies at a distance of 47 million light years from the earth. It is close enough to be observed with a pair of binoculars.

NGC 1068 is a barred spiral galaxy much like the Milky Way, with its arms forming a spiral around the central bar. However, unlike the Milky Way which has a smaller, inactive black hole at its centre, NGC 1068 is an active galaxy with a supermassive black hole at its centre. The majority of the galaxy’s luminescence comes from the materials falling into the black hole instead of its stars. 

According to the scientists, about 80 neutrinos were detected from the direction of NGC 1086.

“One neutrino can single out a source. But only an observation with multiple neutrinos will reveal the obscured core of the most energetic cosmic objects,” said Francis Halzen, a University of Wisconsin–Madison professor of physics and principal investigator of the IceCube project, in a press release

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“IceCube has accumulated some 80 neutrinos of tera-electronvolt energy from NGC 1068, which are not yet enough to answer all our questions, but they definitely are the next big step toward the realisation of neutrino astronomy,” he added. 

Light emitting from the nucleus of NGC 1086 is hidden due to dense clouds of dust. This nucleus is located at an angle such that a plume of dense gas, dust and particles slowly being pulled inwards obstructs the view of the interior of the galaxy where the black hole resides.

Due to the highly inert nature of the galaxy, neutrinos emerging therefrom give scientists a chance to study the surroundings of supermassive black holes in a more detailed manner. 

“Recent models of the black hole environments in these objects suggest that gas, dust, and radiation should block the gamma rays that would otherwise accompany the neutrinos. This neutrino detection from the core of NGC 1068 will improve our understanding of the environments around supermassive black holes,” noted Hans Niederhausen, a postdoctoral associate at Michigan State University and one of the main authors of the paper. 

Other recent neutrino detections

This is not the first time neutrinos have been detected.

In 2018, the IceCube Observatory detected a dozen high-energy neutrinos from a blazar—an active galactic nucleus expelling a jet of ionised matter at very high speeds. The blazar, called TXS 0506+056, is located 4 billion light years away, just over the shoulder of the Orion constellation. 

“IceCube has previously discovered that the universe is glowing brightly in neutrinos, and the origin of that glow has been an exciting mystery. NGC 1068 provides one key piece of that puzzle and can explain only about one hundredth of the total signal: There must be many additional neutrino sources, and likely additional types of sources, waiting to be discovered,” said Justin Vandenbroucke, a physics professor at UW–Madison and a member of IceCube. 

The jump from detecting of a dozen neutrinos from TXS 0506+056 to 80 neutrinos from NGC 1086 shows that the enhanced techniques and updated detector calibration of the IceCube Observatory may open new doors in the study of neutrino astronomy, which has been envisioned by scientists for close to six decades.

“The unveiling of the obscured universe has just started, and neutrinos are set to lead a new era of discovery in astronomy,” said Elisa Resconi, another researcher and professor of physics at the Technical University of Munich. 

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