Synopsis: Gravitational Waves May Hold Dark Matter Secret

A theoretical analysis examines the possibility that the black holes detected by LIGO serve as dark matter.

This past summer, the LIGO detectors observed the gravitational-wave signature of two 30-solar-mass black holes spiraling into each other. Such black holes could be abundant in the Universe, so abundant that they could be the missing dark matter. Simeon Bird and colleagues from Johns Hopkins University, Maryland, have explored this possibility by estimating the merger rate of 30-solar-mass black holes playing the role of dark matter. The results are consistent with the rate inferred from LIGO’s observations, but more data will be needed to convincingly connect black holes and dark matter.

Dark matter is often considered to consist of microscopic particles, but certain theories of the early Universe predict the formation of black holes that could serve as dark matter constituents. The size of these primordial black holes (PBHs) is severely limited by gravitational lensing surveys that fail to observe these foreground objects, but there is a window for dark matter PBHs in the range from 20 to 100 solar masses.

Bird and colleagues imagined that the Universe is filled with 30-solar-mass PBHs at a density consistent with dark matter models. Making assumptions about the concentration and velocity of dark matter inside galaxies, they then calculated how often these PBHs fly close enough to each other to merge. The predicted merger rate agreed with the estimate by LIGO researchers that mergers of 30-solar-mass black holes should occur 2 to 53 times per year in a gigaparsec-cubed volume—the equivalent of about a billion Milky Way galaxies. However, there are large uncertainties in dark matter models, so more merger observations will be needed to find specific dark matter signals, such as a high fraction of events in small galaxies.

This research is published in Physical Review Letters.

–Michael Schirber

Michael Schirber is a Corresponding Editor for Physics based in Lyon, France.


Features

More Features »

Announcements

More Announcements »

Subject Areas

AstrophysicsGravitation

Previous Synopsis

Condensed Matter Physics

Glassy Fingerprints

Read More »

Next Synopsis

Atomic and Molecular Physics

A Crystal of Light and Atoms

Read More »

Related Articles

Synopsis: Ideal Mergers for Measuring Cosmic Expansion
Cosmology

Synopsis: Ideal Mergers for Measuring Cosmic Expansion

Among gravitational-wave sources, the merger of a neutron star and a black hole may provide the most precise way to measure how fast the Universe is expanding. Read More »

Synopsis: A Closer Look at Cosmic Dust
Cosmology

Synopsis: A Closer Look at Cosmic Dust

Simulations provide a detailed picture of the emission of dust grains in our Galaxy, which is known to interfere with measurements of the cosmic microwave background. Read More »

Viewpoint: Surface Texture is Key to Rays Forming Around Craters
Astrophysics

Viewpoint: Surface Texture is Key to Rays Forming Around Craters

A classroom demo of a marble falling into flour helps researchers realize the conditions needed to replicate the ray patterns that form around lunar craters. Read More »

More Articles