Far out cosmology: astronomy from neutrino detectors (Introduction)

by David Turell , Friday, November 04, 2022, 20:03 (536 days ago) @ David Turell

Not by light:

https://www.sciencemagazinedigital.org/sciencemagazine/library/item/04_november_2022/40...

"After relying on nothing but light to study the cosmos for centuries, the development of multimessenger astronomy in the past decade has revolutionized the field. The successful detections of the additional messengers—i.e., information carriers other than light—are only possible because of state-of-the-art, large-scale instruments, such as the detectors at the IceCube Neutrino Observatory, which are located a kilometer deep inside the Antarctic ice. High-energy cosmic neutrinos have given rise to both surprises and mysteries since their detections were reported in 2013.

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"In space, high-energy neutrinos are mainly produced by cosmic rays—i.e., protons and atomic nuclei that are traveling at nearly the speed of light—colliding with matter or radiation, which creates subsequent particles that later decay into neutrinos and gamma rays. Such collisions occur inside astrophysical objects, such as galaxies and black hole jets, or in intergalactic space between those objects and Earth. Revealing the origin of cosmic neutrinos and the relationship among neutrinos, gamma rays, and cosmic rays is crucial to deciphering the fundamental processes that occur throughout the Universe (1). Neutrinos are also special because they can travel through dense environments that are impassable for photons, which allow astronomers to “see” behind gas, dust, and radiation obstructions.

"Active galactic nuclei (AGNs), which exist at the centers of some galaxies, are energized by either the accretion of gas onto a supermassive black hole and/or the spin of the black hole at the center of the galaxies. They are among the most promising candidate sources of not only the highest-energy cosmic rays but also high-energy cosmic neutrinos observable from Earth.

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"...searches relying on the population of gamma ray–detected blazars have suggested that this class of AGN alone would not explain the amount of all cosmic neutrinos (9) coming from every direction in the sky (not every detected neutrino has a well-defined source of origin). This has prompted ideas for other classes of neutrino sources besides blazars.

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"The source of the detected neutrinos—NGC 1068—is among the brightest and closest AGNs from Earth. It is located in the constellation Cetus, at a distance of ∼46 million light-years away. Optical images of NGC 1068 show a rather normal barred spiral galaxy, with a bright starburst inner disk and star-forming regions in the outer arms. The galactic nucleus is classified as a type of AGN that is characterized by emission lines in the optical spectrum. It is also considered a radio-quiet AGN that does not have powerful jets, as seen in blazars. Its nucleus is luminous not only in the optical and infrared bands, but also in ultraviolet and x-ray bands, which are thought to largely come from the accretion disk and hot corona near the supermassive black hole at the galactic center. The black hole is estimated to be ∼15 million times as massive as the Sun and is considered to be one of the most obscured supermassive black holes known, being blanketed by thick gas and dust. X-ray observations from the Nuclear Spectroscopic Telescope Array indicate that the x-rays are largely intervened by the gas, and radio data from the Atacama Large Millimeter/submillimeter Array have suggested a compact gaseous structure with a radius of ∼10 light-years around the black hole (12). Once the x-ray emission is corrected by accounting for absorption by the gas, NGC 1068 has the brightest x-ray emission among radio-quiet AGNs in the sky region targeted by the IceCube Neutrino Observatory, which helps explain the neutrino excess."

Comment: it is obvious photon detection alone tells a tiny part of the story of how the universe works. We still have no answer for dhw who wonders why the universe is so big and so complex, if all God wanted was to create some humans on Earth. My simple answer is God knows what He is doing.