From Kavli Institute for the Physics and Mathematics of the Universe (IPMU) [カブリ数物連携宇宙研](JP) at U Tokyo {東京大学;Tōkyō daigaku](JP) : “Establishing the Origin of Solar-Mass Black Holes and the Connection to Dark Matter”

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From Kavli Institute for the Physics and Mathematics of the Universe (IPMU) [カブリ数物連携宇宙研](JP) at U Tokyo {東京大学;Tōkyō daigaku](JP)

Kavli IPMU

March 5, 2021

Research Contacts:
Volodymyr Takhistov
Project Researcher / Kavli IPMU Fellow
Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo
volodymyr.takhistov@ipmu.jp

George M. Fuller
Distinguished Professor of Physics
Director of Center for Astrophysics and Space Sciences
Department of Physics, University of California, San Diego
Email: gfuller@physics.ucsd.edu

Alexander Kusenko
Professor of Physics and Astronomy
Department of Physics and Astronomy, University of California, Los Angeles,
Visiting Senior Scientist
Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo
kusenko@ucla.edu

Media contact:
John Amari
Press officer
Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo
press@ipmu.jp

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Fig.1: [Left] A tiny primordial black hole being captured by a neutron star, subsequently devouring it and leaving a “transmuted” solar-mass black hole remnant behind. [Right] Expected mass distribution of “transmuted” solar-mass black holes following neutron stars formed as a result of a delayed or a rapid supernova. The LIGO GW190814 event with 2.6 solar-mass black hole candidate is also shown. Credit: Takhistov et. al.)

What is the origin of black holes and how is that question connected with another mystery-the nature of Dark Matter*? Dark matter comprises the majority of matter in the Universe but its nature remains unknown.

Multiple gravitational wave detections of merging black holes have been identified within the last few years by the Laser Interferometer Gravitational-Wave Observatory (LIGO) commemorated with the 2017 physics Nobel Prize to Kip Thorne; Barry Barish; and Rainer Weiss.

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Left to right: Rainer Weiss, Barry Barish and Kip Thorne, who have been awarded the 2017 Nobel prize in physics. Credit: Molly Riley/AFP/Getty Images.

Artist’s by now iconic conception of two merging black holes similar to those detected by LIGO. Credit: Caltech/MIT aLigo/Aurore Simonnet/Sonoma State.

Caltech/MIT Advanced aLigo


Caltech/MIT Advanced aLigo Hanford, WA, USA installation


Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project


ESA/eLISA the future of gravitational wave research

A definitive confirmation of the existence of black holes was celebrated with the 2020 physics Nobel Prize awarded to Andrea Ghez; Reinhard Genzel; and Roger Penrose. Understanding the origin of black holes has thus emerged as a central issue in physics.

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Roger Penrose, Reinhard Genzel and Andrea Ghez have won the the 2020 Nobel Prize for Physics. (Courtesy: IOP Publishing/Tushna Commissariat; CC-BY-SA H Garching; UCLA/Christopher Dibble)

Surprisingly, LIGO has recently observed a 2.6 solar-mass black hole candidate (event GW190814, reported in Astrophysical Journal Letters). Assuming this is a black hole, and not an unusually massive neutron star, where does it come from?

Solar-mass black holes are particularly intriguing, since they are not expected from conventional stellar evolution astrophysics. Such black holes might arise in the early Universe (primordial black holes) or be “transmuted” from existing neutron stars. Some black holes could have formed in the early universe long before the stars and galaxies formed. Such primordial black holes could make up some part or all of dark matter. If a neutron star captures a primordial black hole, the black hole consumes the neutron star from the inside, turning it into a solar-mass black hole. This process can produce a population of solar mass black holes, regardless of how small the primordial black holes are. Other forms of dark matter can accumulate inside a neutron star causing its eventual collapse into a solar-mass black hole.

A new study, published in Physical Review Letters, advances a decisive test to investigate the origin of solar-mass black holes. This work was led by the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) Fellow Volodymyr Takhistov and the international team included George M. Fuller, Distinguished Professor of Physics and Director of the Center for Astrophysics and Space Science at the University of California, San Diego(US), as well as Alexander Kusenko, Professor of Physics and Astronomy at the University of California, Los Angeles(US) and a Kavli IPMU Visiting Senior Scientist.

As the study discusses (see Fig. 1), “transmuted” solar-mass black holes remaining from neutron stars being devoured by dark matter (either tiny primordial black holes or particle dark matter accumulation) should follow the mass-distribution of the original host neutron stars. Since the neutron star mass distribution is expected to peak around 1.5 solar masses, it is unlikely that heavier solar-mass black holes have originated from dark matter interacting with neutron stars. This suggests that such events as the candidate detected by LIGO, if they indeed constitute black holes, could be of primordial origin from the early Universe and thus drastically affect our understanding of astronomy. Future observations will use this test to investigate and identify the origin of black holes.

Previously (see Physical Review Letters ), the same international team of researchers also demonstrated that disruption of neutron stars by small primordial black holes can lead to a rich variety of observational signatures and can help us understand such long-standing astronomical puzzles as the origin of heavy elements (e.g. gold and uranium) and the 511 keV gamma-ray excess observed from the center of our Galaxy.

*Dark Matter Background
Fritz Zwicky discovered Dark Matter in the 1930s when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, some 30 years later, did most of the work on Dark Matter.

Fritz Zwicky from http:// palomarskies.blogspot.com.


Coma cluster via NASA/ESA Hubble.


In modern times, it was astronomer Fritz Zwicky, in the 1930s, who made the first observations of what we now call dark matter. His 1933 observations of the Coma Cluster of galaxies seemed to indicated it has a mass 500 times more than that previously calculated by Edwin Hubble. Furthermore, this extra mass seemed to be completely invisible. Although Zwicky’s observations were initially met with much skepticism, they were later confirmed by other groups of astronomers.
Thirty years later, astronomer Vera Rubin provided a huge piece of evidence for the existence of dark matter. She discovered that the centers of galaxies rotate at the same speed as their extremities, whereas, of course, they should rotate faster. Think of a vinyl LP on a record deck: its center rotates faster than its edge. That’s what logic dictates we should see in galaxies too. But we do not. The only way to explain this is if the whole galaxy is only the center of some much larger structure, as if it is only the label on the LP so to speak, causing the galaxy to have a consistent rotation speed from center to edge.
Vera Rubin, following Zwicky, postulated that the missing structure in galaxies is dark matter. Her ideas were met with much resistance from the astronomical community, but her observations have been confirmed and are seen today as pivotal proof of the existence of dark matter.

Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science).


Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL).


Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu.

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Kavli Institute for the Physics and Mathematics of the Universe (IPMU) [カブリ数物連携宇宙研](JP) at U Tokyo {東京大学;Tōkyō daigaku](JP) is an international research institute with English as its official language. The goal of the institute is to discover the fundamental laws of nature and to understand the Universe from the synergistic perspectives of mathematics, astronomy, and theoretical and experimental physics. The Institute for the Physics and Mathematics of the Universe (IPMU) was established in October 2007 under the World Premier International Research Center Initiative (WPI) of the Ministry of Education, Sports, Science and Technology in Japan with the University of Tokyo as the host institution. IPMU was designated as the first research institute within the University of Tokyo Institutes for Advanced Study (UTIAS) in January 2011. It received an endowment from The Kavli Foundation and was renamed the “Kavli Institute for the Physics and Mathematics of the Universe” in April 2012. Kavli IPMU is located on the Kashiwa campus of the University of Tokyo, and more than half of its full-time scientific members come from outside Japan. http://www.ipmu.jp/

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