Astrophysicists witness the curvature of space-time caused by a cosmic dance

Here is the Lense-Thirring effect as part of a binary system composed of a white dwarf and a pulsar. © Mark Myers / OzGrav ARC Center of Excellence via Youtube

An international team of astrophysicists was able to confirm the Lense-Thirring effect, which describes a phenomenon of space-time training around very dense objects in very fast rotation, around a white dwarf in the framework of ‘a binary system. This effect, resulting from the theory of relativity of Albert Einstein, could thus be demonstrated on a much more significant scale than with the Earth.

A century-old scientific theory

Astrophysicists have gathered a set of data that constitutes further evidence to validate Einstein’s theory of general relativity, and have them published in the journal Science. Indeed, in 1905, Albert Einstein published his theory of relativity, according to which the force of gravity results from the curvature of space and time and that objects, such as the Sun and the Earth, modify this geometry. The rotating bodies carry with them space-time. In other words, the faster and more massive an object turns, the more powerful the drive.

In 1918, three years after the publication of Einstein’s theory, Austrian mathematicians Josef Lense and Hans Thirring realized that, if Einstein was right, all bodies in rotation should “drag” with them the very fabric of space-time. This has been called the Lense-Thirring effect.

Over time, the development of ever more powerful astronomical instruments has led to new discoveries. For example, gravitational waves were first detected in 2015 by the congregation of scientists LIGO Science Collaboration during the collision of two black holes.

A binary system as a perfect laboratory

Almost 20 years ago, a team led by Professor Bailes of Swinburne University of Technology, director of the CRA’s Center of Excellence for Gravitational Wave Discovery (OzGrav), began to observe two stars rotating around each other at astonishing speeds thanks to the CSIRO Parkes radio telescope. One is a white dwarf the size of the Earth but with 300,000 times its density; the other is a pulsar which, while it is only 20 kilometers in diameter, represents about 100 billion times the density of the Earth. This pair of stars was named “PSR J1141-6545”.

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This pair was certainly formed over a billion years ago. Before the star explodes, becoming a neutron star pulsar type, it started to swell by throwing its outer nucleus, which fell on the nearby white dwarf. This falling debris made the white dwarf spin faster and faster, until her day was only measured in terms of minutes.

The rapid rotation of a white dwarf and a pulsar causes space-time to slide in its orbit © Mark Myers / OzGrav ARC Center of Excellence via Youtube

A white dwarf and a pulsar confirm the large-scale Lense-Thirring scale

Since 2001, researchers have used the Parkes radio telescope several times a year to map the orbit of this system, which has a multitude of gravitational effects. Although PSR J1141-6545 is several hundreds of quadrillion kilometers, the data shows that the pulsar rotates 2.54 times per second, and that its orbit varies in space. This means that the plane of its orbit is not fixed, but rotates slowly. Indeed, Vivek Venkatraman Krishnan, lead author of this study, explains that “at first, the star pair appeared to exhibit many of the classic effects predicted by Einstein’s theory. We then noticed a gradual change in the orientation of the orbit plane.

How is it possible ? The white dwarf, which rotates quickly as explained above, carries space-time with it 100 million times stronger than does the Earth. As a result, it tilts the orbital plane of the pulsar as it moves. This inclination is what astrophysicists have observed through the mapping of the orbit of the pulsar.

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