New Method May Resolve Difficulty in Measuring Universe’s Expansion

Astronomers using National Science Foundation (NSF) radio telescopes have demonstrated how a combination of gravitational-wave and radio observations, along with theoretical modeling, can turn the mergers of pairs of neutron stars into a “cosmic ruler” capable of measuring the expansion of the Universe and resolving an outstanding question over its rate.

The astronomers used the NSF’s Very Long Baseline Array (VLBA), the Karl G. Jansky Very Large Array (VLA) and the Robert C. Byrd Green Bank Telescope (GBT) to study the aftermath of the collision of two neutron stars that produced gravitational waves detected in 2017. This event offered a new way to measure the expansion rate of the Universe, known by scientists as the Hubble Constant. The expansion rate of the Universe can be used to determine its size and age, as well as serve as an essential tool for interpreting observations of objects elsewhere in the Universe.

Two leading methods of determining the Hubble Constant use the characteristics of the Cosmic Microwave Background, the leftover radiation from the Big Bang, or a specific type of supernova explosions, called Type Ia, in the distant Universe. However, these two methods give different results.

“The neutron star merger gives us a new way of measuring the Hubble Constant, and hopefully of resolving the problem,” said Kunal Mooley, of the National Radio Astronomy Observatory (NRAO) and Caltech.

The technique is similar to that using the supernova explosions. Type Ia supernova explosions are thought to all have an intrinsic brightness which can be calculated based on the speed at which they brighten and then fade away. Measuring the brightness as seen from Earth then tells the distance to the supernova explosion. Measuring the Doppler shift of the light from the supernova’s host galaxy indicates the speed at which the galaxy is receding from Earth. The speed divided by the distance yields the Hubble Constant. To get an accurate figure, many such measurements must be made at different distances.

When two massive neutron stars collide, they produce an explosion and a burst of gravitational waves. The shape of the gravitational-wave signal tells scientists how “bright” that burst of gravitational waves was. Measuring the “brightness,” or intensity of the gravitational waves as received at Earth can yield the distance.

“This is a completely independent means of measurement that we hope can clarify what the true value of the Hubble Constant is,” Mooley said.

However, there’s a twist. The intensity of the gravitational waves varies with their orientation with respect to the orbital plane of the two neutron stars. The gravitational waves are stronger in the direction perpendicular to the orbital plane, and weaker if the orbital plane is edge-on as seen from Earth.

“In order to use the gravitational waves to measure the distance, we needed to know that orientation,” said Adam Deller, of Swinburne University of Technology in Australia.

Over a period of months, the astronomers used the radio telescopes to measure the movement of a superfast jet of material ejected from the explosion. “We used these measurements along with detailed hydrodynamical simulations to determine the orientation angle, thus allowing use of the gravitational waves to determine the distance,” said Ehud Nakar from Tel Aviv University.

This single measurement, of an event some 130 million light-years from Earth, is not yet sufficient to resolve the uncertainty, the scientists said, but the technique now can be applied to future neutron-star mergers detected with gravitational waves.

“We think that 15 more such events that can be observed both with gravitational waves and in great detail with radio telescopes, may be able to solve the problem,” said Kenta Hotokezaka, of Princeton University. “This would be an important advance in our understanding of one of the most important aspects of the Universe,” he added.

The international scientific team led by Hotokezaka is reporting its results in the journal Nature Astronomy.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

###

Media Contact:
Dave Finley, Public Information Officer
(575) 835-7302
[email protected]

In Other News…

Industrial Cybersecurity: A Culture Change

The following is an article from UPDATE, the official publication of Utah Petroleum Association, Issue 4 2020.  Reliable operational technology (OT) or industrial control systems (ICS) underpin every facet of American lives. Without them, our defenses, our economy,...

How would Trump or Biden deal with grid hacking threats?

POLITICS How would Trump or Biden deal with grid hacking threats? Christian Vasquez, E&E News reporter Published: Tuesday, November 3, 2020 President Trump and Democratic presidential nominee Joe Biden have a few competing plans for the nation's cybersecurity —...

Big Astronomy Planetarium Show Premieres September 26

Big Astronomy planetarium show premieres September 26 Turn your phone into a planetarium with innovative and immersive 360° streaming San Francisco – The Big Astronomy worldwide premiere is coming soon to a smart phone or connected device near you! On September 26 at...

ALMA Discovers Misaligned Rings in Planet-Forming Disk Around Triple Stars

Using the Atacama Large Millimeter/submillimeter Array (ALMA), two teams of astronomers have for the first time discovered a planet-forming disk with misaligned rings around a triple star system, called GW Orionis. The astronomers give two possible scenarios for the...

Why North Carolina Outsourced Election Cybersecurity to a ‘CISO-as-a-Service’

The following is press coverage on Woodstar Labs' involvement with North Carolina's election security, courtesy of statescoop.com. Faced with mounting cybersecurity needs headed toward the presidential election, but lacking the financial resources to build out a more...

A Cyber-Risk We’re Not Prepared For: What if the Power Grid Collapsed and America Went Dark?

The following is press coverage on the NCGR's new report, courtesy of washingtonpost.com. EVERY CATASTROPHE comes as a shock, but many shouldn’t come as a surprise. Just as we knew a pandemic was a possibility yet failed to plan for it, power-grid collapse is a threat...

Grid Security And Cyber Defense Cannot Fall On Deaf Ears, Experts Warn

The following is press coverage on the NCGR's new report, courtesy of Forbes.com. If the electrical grid is knocked out for long periods, the damage to the American economy would be insurmountable. And the country’s enemies know that. That is why its brain trust is...

Coverage on National Commision on Grid Resilience’s (NCGR) Latest Report

The following is press coverage on the NCGR's new report, courtesy of UtilityDive.com.   Dive Brief: A new report from the National Commission on Grid Resilience (NCGR) calls for declassifying and giving utilities greater access to information about threats...

Woodstar Labs Welcomes New Wave of Cyber Analysts

Woodstar Labs, a subsidiary of AUI focused on cutting-edge-cybersecurity solutions, microelectronics, eLearning, and STEM education welcomes a new cohort of Cyber Analysts. Woodstar labs is excited to work with this talented group of young professionals as we continue...

AUI Statement on Racial Equity

As the nation continues to mourn and respond to the unjust death of George Floyd, there is no doubt that violent race-related incidents and the subsequent protests and clashes are the most urgent need for us as a society to address. Further, to address them, we must...

You are now leaving AUI

You will be redirected to the related partnering organization's website.

You will be redirected to
in 4 seconds...

Click the link above to continue or CANCEL