Gravitational Wave Astronomy: A New Approach to Studying the Sun's Interior

 Gravitational wave astronomy is a nascent field, primarily focusing on high-energy events like black hole and neutron star mergers. However, researchers are now considering the potential of studying the Sun's interior using gravitational waves produced by pulsars. Gravitational waves share similarities with light waves, but a key difference is that most objects are transparent to them, allowing them to pass through matter without being absorbed or scattered.

This unique property of gravitational waves could enable scientists to examine the interiors of astronomical bodies, much like X-rays and MRIs provide insight into the human body. The Sun's massive heat and density prevent light from penetrating its core, and currently, helioseismology – which observes vibrations on the Sun's surface caused by interior sound waves – is the primary method for studying its interior.

A recent study explored the possibility of using gravitational waves generated by rapidly rotating neutron stars, known as pulsars, to examine the Sun's interior. While a perfectly smooth rotating object doesn't emit gravitational waves, asymmetrical rotating objects, such as neutron stars with deformations or surface irregularities, can produce a continuous stream of these waves. Although current interferometers are unable to detect these weak gravitational waves, next-generation observatories should be capable.

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Neutron stars are fairly common in the galaxy, and some are situated such that the Sun passes between them and Earth. Out of the 3,000+ known pulsars, around 500 are considered potential sources of gravitational waves, with three known to pass behind the Sun. Researchers utilized these pulsars' profiles as a starting point for their study.

The Sun's transparency to gravitational waves means that its only influence on them is its gravitational mass, which slightly slows the waves as they pass through. This effect depends on the Sun's mass distribution, and researchers believe that precise measurements of gravitational waves could reveal the Sun's density profile with remarkable accuracy.

The three identified pulsars are likely just a small fraction of the gravitational wave sources passing behind the Sun. Many neutron stars emit radio flashes that don't reach Earth due to their rotational orientation, but they could still serve as gravitational probes. It's estimated that hundreds of rapidly rotating neutron stars pass behind the Sun each year, so observing their gravitational waves could offer unprecedented insights into our star's interior.

Rif: Universe Today, ArXiv