Skip to main content

Hypermodels help understand gravitational waves

Hypermodels help understand gravitational waves

  • Date01 Jul 2022
  • Reading time 1min

A new approach to analyse binary neutron star mergers, developed by Dr. Gregory Ashton (Royal Holloway, University of London) and Prof. Dr. Tim Dietrich (Potsdam University/Max Planck Institute for Gravitational Physics), was published in “Nature Astronomy” today. Their innovative technique provides a proving ground for model development and a means to identify systematics in future gravitational-wave observations.

waves_1620.png

Numerical-relativity simulation of the binary neutron star coalescence and merger which resulted in the detected gravitational wave event GW190425. Image Credit: T. Dietrich (UP), S. Ossokine, A. Buonanno (Max Planck Institute for Gravitational Physics), W. Tichy (Florida Atlantic University) and the CoRe-collaboration.

At the end of the life of a massive star, an extremely dense neutron star can be born in a supernova explosion: one teaspoon of neutron star material would weight up to 1 billion tons. Given that neutron stars are so extremely compact, merging of two neutron stars represents a collision of unimaginable proportions.  An enormous amount of energy gets released during the collision of such stars and gravitational waves, tiny ripples in the fabric of spacetimes, get emitted. Two well-observed neutron star merger events are GW170817 and GW190425. GW is short for “gravitational wave” and their name refers the date when these events have been observed. Both GW170817 and GW190425 were detected with the laser interferometers advanced LIGO and advanced Virgo here on Earth. In the case of GW170817 it was even possible to measure electromagnetic signals in the gamma-rays, X-rays, ultraviolet, optical, infrared, and radio bands.

Scientists try to model the final stages of coalescence and the gravitational-wave signal emitted with numerical-relativity simulations on high-performance computers. “The direct computation of the gravitational waves is a challenging task”, says Tim Dietrich, “because Einstein’s Field Equations, which govern the final stages of the collision, are extremely hard to solve.” Therefore, approximate models are used. “With our hypermodel approach we are able to tests gravitational-wave model assumptions without computationally expensive numerical-relativity simulations, but with the help of the observed gravitational-wave data”, explains Greg Ashton. The two scientists applied their approach to the two confidently detected binary neutron star collisions GW170817 and GW190425 and found a consistent preference for a specific waveform model that is subtly better at explaining the observed data. “Since gravitational-wave detectors will be more sensitive in the future thanks to developments in instrumentation, such subtle differences will become more prominent. Quantifying waveform-model systematics will then allow us to place tighter constraints on fundamental physics principles”, summarises Tim Dietrich.

The research article is available at Nature Astronomy.

 

Explore Royal Holloway

Get help paying for your studies at Royal Holloway through a range of scholarships and bursaries.

There are lots of exciting ways to get involved at Royal Holloway. Discover new interests and enjoy existing ones

Heading to university is exciting. Finding the right place to live will get you off to a good start

Whether you need support with your health or practical advice on budgeting or finding part-time work, we can help

Discover more about our 21 departments and schools

Find out why Royal Holloway is in the top 25% of UK universities for research rated ‘world-leading’ or ‘internationally excellent’

Royal Holloway is a research intensive university and our academics collaborate across disciplines to achieve excellence.

Discover world-class research at Royal Holloway

Discover more about who we are today, and our vision for the future

Royal Holloway began as two pioneering colleges for the education of women in the 19th century, and their spirit lives on today

We’ve played a role in thousands of careers, some of them particularly remarkable

Find about our decision-making processes and the people who lead and manage Royal Holloway today