Multi-messenger astronomy provides new estimates of neutron star sizes and the expansion of the universe

A combination of astrophysical measurements allowed researchers to set new limits on the radius of a typical neutron star and to recalculate the Hubble constant, which indicates the speed at which the universe is expanding.

“We studied signals coming from a variety of sources, for example recently observed neutron star fusions,” said Ingo Tews, a theorist in the nuclear and particle physics, astrophysics and cosmology group at Los Alamos National Laboratory, who collaborated with an international collaboration of researchers. . about the analysis that appears in the journal Science on December 18. “We have jointly analyzed the gravitational wave signals and electromagnetic emissions from the mergers and combined them with previous mass measurements of pulsars or recent results from NASA’s Neutron Star Interior Composition Explorer. We find that the radius of a typical neutron star is approximately 11.75 kilometers and the Hubble- constant is about 66.2 kilometers per second per megaparsec. “

Combining signals to gain insight into distant astrophysical phenomena is known in the field as multi-messenger astronomy. In this case, the researchers’ multi-messenger analysis allowed them to limit the uncertainty of their estimate of neutron star radii to within 800 meters.

Their new approach to measuring the Hubble constant adds to a debate that has arisen from other competing determinations about the expansion of the universe. Measurements based on observations of exploding stars known as supernovae are currently at odds with those resulting from looking at the Cosmic Microwave Background (CMB), which is essentially the leftover energy from the Big Bang. is. The uncertainties in the new multimessenger Hubble calculation are too great to definitively resolve the disagreement, but the measurement supports the CMB approach a little more.

Tews’ primary scientific role in the study was to provide the input for nuclear theory calculations that form the starting point of the analysis. Its seven employees make up an international team of scientists from Germany, the Netherlands, Sweden, France and the United States.

A combination of astrophysical measurements allowed researchers to set new limits on the radius of a typical neutron star and to recalculate the Hubble constant, which indicates the speed at which the universe is expanding.

“We studied signals coming from a variety of sources, such as recently observed neutron star fusions,” said Ingo Tews, a theorist in the nuclear and particle physics, astrophysics and cosmology group at Los Alamos National Laboratory, who collaborated with an international collaboration of researchers. . on the analysis published in the journal Science Dec. 18. “We have jointly analyzed the gravitational wave signals and electromagnetic emissions from the mergers and combined them with previous mass measurements of pulsars or recent results from NASA’s Neutron Star Interior Composition Explorer. We find that the radius of a typical neutron star is approximately 11.75 kilometers and the Hubble- constant about 66.2 kilometers per second per megaparsec. “

Combining signals to gain insight into distant astrophysical phenomena is known in the field as multi-messenger astronomy. In this case, the researchers’ multi-messenger analysis allowed them to limit the uncertainty of their estimate of neutron star radii to within 800 meters.

Their new approach to measuring the Hubble constant adds to a debate that has arisen from other competing determinations about the universe’s expansion. Measurements based on observations of exploding stars known as supernovae are currently at odds with those resulting from looking at the Cosmic Microwave Background (CMB), which is essentially the leftover energy of the Big Bang. is. The uncertainties in the new multimessenger Hubble calculation are too great to definitively resolve the disagreement, but the measurement supports the CMB approach a little more.

Tews’ primary scientific role in the study was to provide the input for nuclear theory calculations that form the starting point of the analysis. Its seven employees make up an international team of scientists from Germany, the Netherlands, Sweden, France and the United States.