From University of Illinois at Urbana–Champaign via Science Alert(AU): “Really Small Black Holes Could Be Out There Devouring Neutron Stars From Within”

From University of Illinois at Urbana–Champaign



Science Alert(AU)

23 FEBRUARY 2021

Credit: Victor de Schwanberg/Science Photo Library/Getty Images.

Tiny, all-but-undetectable primordial black holes could be one of the mysterious sources of mass that contributes to Dark Matter. There are significant limits to their lifespan in open space, but in recent years, astrophysicists have asked: what if these black holes are in the core of neutron stars?

Gradually, such black holes would accrete the neutron star, devouring it from within. These hypothetical systems are yet to be verified, but a new paper [Accretion onto a small black hole at the center of a neutron star], yet to be peer-reviewed, has calculated how long this devouring would take.

This, in turn, could be used to analyse the current neutron star population to constrain the nature of the black holes considered as a dark matter candidate – whether they are primordial, dating back to the Big Bang, or black holes that formed inside neutron stars.

Although we don’t know what dark matter is, it’s pretty fundamental to our understanding of the Universe: there simply isn’t enough matter we can directly detect – normal matter – to account for all the gravity. In fact, there’s so much gravity that scientists have calculated roughly 75 to 80 percent of all matter is dark.

There are a number of candidate particles that could be dark matter. Primordial black holes that formed just after the Big Bang are not one of the leading candidates, because if they were above a certain mass we would have noticed them by now; but, below that mass, they would have evaporated via the emission of Hawking Radiation long before now.

Black holes, however, are an attractive candidate for dark matter: they, too, are extremely difficult to detect if they’re just hanging out in space just doing nothing. So astronomers continue to look for them.

One idea that has been explored recently is the endoparasitic black hole. There are two scenarios for this. One is that primordial black holes were captured by neutron stars, and sink down to the core. The other is that dark matter particles are captured inside a neutron star; if the conditions are favourable, these could then come together and collapse down into a black hole.

These black holes are small, but they wouldn’t remain so. From their position, ensconced inside the neutron star, these little black holes would then parasitise their host.

The team of physicists from Bowdoin College and the University of Illinois at Urbana-Champaign calculated the accretion rate – that is, the rate at which the black hole would devour the neutron star – for a range of black hole mass ratios, from three to nine orders of magnitude less massive than the neutron star host.

Neutron stars have a theoretical upper mass limit of 2.3 times the mass of the Sun, so the black hole masses would extend down into the range of dwarf planets.

For a non-rotating neutron star hosting a non-spinning black hole, the accretion would be spherical. At the team’s calculated accretion rates, black holes as small as 10-21 times the mass of the Sun would completely accrete a neutron star well within the lifetime of the Universe.

This suggests that primordial black holes, from the beginning of the Universe, would have completely accreted their host neutron stars before now. These timescales are in direct conflict with the ages of old neutron star populations, the researchers said.

“As an important application, our results corroborate arguments that use the current existence of neutron star populations to constrain either the contribution of primordial black holes to the dark matter content of the Universe, or that of dark matter particles that may form black holes at the center of neutron stars after they have been captured,” they wrote in their paper.

So the result is another blow for primordial black holes; but it doesn’t rule endoparasitic black holes out entirely. If there are globs of dark matter particles out there floating through space and being slurped into neutron stars, they could be collapsing into black holes and converting neutron stars into black hole stuff even as you read this sentence.

And that is freaking awesome.

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://

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.

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Stem Education Coalition

The University of Illinois at Urbana-Champaign community of students, scholars, and alumni is changing the world.

The University of Illinois at Urbana–Champaign (U of I, Illinois, or colloquially the University of Illinois or UIUC) is a public land-grant research university in Illinois in the twin cities of Champaign and Urbana. It is the flagship institution of the University of Illinois system and was founded in 1867.

The University of Illinois at Urbana–Champaign is a member of the Association of American Universities and is classified among “R1: Doctoral Universities – Very high research activity”, and has been listed as a “Public Ivy” in The Public Ivies: America’s Flagship Public Universities (2001) by Howard and Matthew Greene. In fiscal year 2019, research expenditures at Illinois totaled $652 million. The campus library system possesses the second-largest university library in the United States by holdings after Harvard University. The university also hosts the National Center for Supercomputing Applications (NCSA) and is home to the fastest supercomputer on a university campus.

The university contains 16 schools and colleges and offers more than 150 undergraduate and over 100 graduate programs of study. The university holds 651 buildings on 6,370 acres (2,578 ha). The University of Illinois at Urbana–Champaign also operates a Research Park home to innovation centers for over 90 start-up companies and multinational corporations, including Abbott, AbbVie, Caterpillar, Capital One, Dow, State Farm, and Yahoo, among others.

As of August 2020, the alumni, faculty members, or researchers of the university include 30 Nobel laureates, 27 Pulitzer Prize winners, 2 Turing Award winners and 1 Fields medalist. Illinois athletic teams compete in Division I of the NCAA and are collectively known as the Fighting Illini. They are members of the Big Ten Conference and have won the second-most conference titles. Illinois Fighting Illini football won the Rose Bowl Game in 1947, 1952, 1964 and a total of five national championships. Illinois athletes have won 29 medals in Olympic events, ranking it among the top 40 American universities with Olympic medals.

Illinois Industrial University

The original University Hall, which stood until 1938, when it was replaced by Gregory Hall and the Illini Union. Pieces were used in the erection of Hallene Gateway dedicated in 1998.

The University of Illinois, originally named “Illinois Industrial University”, was one of the 37 universities created under the first Morrill Land-Grant Act, which provided public land for the creation of agricultural and industrial colleges and universities across the United States. Among several cities, Urbana was selected in 1867 as the site for the new school.[19][20] From the beginning, President John Milton Gregory’s desire to establish an institution firmly grounded in the liberal arts tradition was at odds with many state residents and lawmakers who wanted the university to offer classes based solely around “industrial education”.[21] The university opened for classes on March 2, 1868, and had two faculty members and 77 students.

The Library, which opened with the school in 1868, started with 1,039 volumes. Subsequently, President Edmund J. James, in a speech to the board of trustees in 1912, proposed to create a research library. It is now one of the world’s largest public academic collections. In 1870, the Mumford House was constructed as a model farmhouse for the school’s experimental farm. The Mumford House remains the oldest structure on campus. The original University Hall (1871) was the fourth building built; it stood where the Illini Union stands today.

University of Illinois

In 1885, the Illinois Industrial University officially changed its name to the “University of Illinois”, reflecting its agricultural, mechanical, and liberal arts curriculum.

During his presidency, Edmund J. James (1904–1920) is credited for building the foundation for the large Chinese international student population on campus. James established ties with China through the Chinese Minister to the United States Wu Ting-Fang. In addition, during James’s presidency, class rivalries and Bob Zuppke’s winning football teams contributed to campus morale.

Like many universities, the economic depression slowed construction and expansion on the campus. The university replaced the original university hall with Gregory Hall and the Illini Union. After World War II, the university experienced rapid growth. The enrollment doubled and the academic standing improved. This period was also marked by large growth in the Graduate College and increased federal support of scientific and technological research. During the 1950s and 1960s the university experienced the turmoil common on many American campuses. Among these were the water fights of the fifties and sixties.

University of Illinois at Urbana–Champaign

By 1967 the University of Illinois system consisted of a main campus in Champaign-Urbana and two Chicago campuses, Chicago Circle (UICC) and Medical Center (UIMC), and people began using “Urbana–Champaign” or the reverse to refer to the main campus specifically. The university name officially changed to the “University of Illinois at Urbana–Champaign” around 1982. While this was a reversal of the commonly used designation for the metropolitan area, “Champaign-Urbana,” most of the campus is located in Urbana. The name change established a separate identity for the main campus within the University of Illinois system, which today includes campuses in Springfield (UIS) and Chicago (UIC) (formed by the merger of UICC and UIMC).

In 1998, the Hallene Gateway Plaza was dedicated. The Plaza features the original sandstone portal of University Hall, which was originally the fourth building on campus. In recent years, state support has declined from 4.5% of the state’s tax appropriations in 1980 to 2.28% in 2011, a nearly 50% decline. As a result, the university’s budget has shifted away from relying on state support with nearly 84% of the budget now coming from other sources.

On March 12, 2015, the Board of Trustees approved the creation of a medical school, the first college created at Urbana–Champaign in 60 years. The Carle-Illinois College of Medicine began classes in 2018.

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Please help promote STEM in your local schools.

Stem Education Coalition

U Illinois campus

The University of Illinois at Urbana-Champaign community of students, scholars, and alumni is changing the world.

With our land-grant heritage as a foundation, we pioneer innovative research that tackles global problems and expands the human experience. Our transformative learning experiences, in and out of the classroom, are designed to produce alumni who desire to make a significant, societal impact.

The University of Illinois at Chicago (UIC) is a public research university in Chicago, Illinois. Its campus is in the Near West Side community area, adjacent to the Chicago Loop. The second campus established under the University of Illinois system, UIC is also the largest university in the Chicago area, having approximately 30,000 students enrolled in 15 colleges.

UIC operates the largest medical school in the United States with research expenditures exceeding $412 million and consistently ranks in the top 50 U.S. institutions for research expenditures. In the 2019 U.S. News & World Report’s ranking of colleges and universities, UIC ranked as the 129th best in the “national universities” category. The 2015 Times Higher Education World University Rankings ranked UIC as the 18th best in the world among universities less than 50 years old.

UIC competes in NCAA Division I Horizon League as the UIC Flames in sports. The Credit Union 1 Arena (formerly UIC Pavilion) is the Flames’ venue for home games.