A Tour of Chandra Data Tests "Theory of Everything"
(Credit: NASA/CXC/A. Hobart)
[Runtime: 02:36]

With closed-captions (at YouTube)

One of the biggest ideas in physics is the possibility that all known forces, particles, and interactions can be connected in one framework. String theory is arguably the best-known proposal for a "theory of everything" that would tie together our understanding of the physical universe.

Despite having many different versions of string theory circulating throughout the physics community for decades, there have been very few experimental tests. Astronomers using NASA's Chandra X-ray Observatory, however, have now made a significant step forward in this area.

By searching through galaxy clusters, the largest structures in the universe held together by gravity, researchers were able to hunt for a specific particle that many models of string theory predict should exist. The researchers were searching for a type of "axion," an as-yet-undetected particle that should have extraordinarily low mass. Some scientists think that axions could explain the mystery of dark matter, which accounts for the vast majority of matter in the universe.

A team of astronomers examined over five days of Chandra observations of X-rays from material falling towards the supermassive black hole in the center of the Perseus galaxy cluster. The long observation and the bright X-ray source gave a spectrum — that is, the amount of X-ray emission at different energies — with enough sensitivity to have shown distortions that scientists expected if axion-like particles were present. However, no signs of axion-like particles were found.

The lack of detection allowed the researchers to rule out the presence of most types of axion-like particles below about a millionth of a billionth of an electron's mass. While the non-detection does not rule out string theory, it does deliver a blow to certain models within that family of ideas. This study, however, does demonstrate that Chandra and future X-ray observatories may have an important role to play in testing this theory of everything.

A Quick Look at Chandra Data Tests "Theory of Everything"
(Credit: NASA/CXC/A. Hobart)
[Runtime: 1:12]

Astronomers have used NASA's Chandra X-ray Observatory to perform one of the first astrophysical tests of string theory.

Nicknamed the "theory of everything," string theory is a set of models that tries to tie together all known forces, interactions, and particles.

Despite existing for decades, string theory has rarely been tested in physical settings.

Astronomers observed the Perseus galaxy cluster and a supermassive black hole at its center in X-rays to test string theory.

Their results showed there was no evidence for a certain family of particles known as "axions" within a particular range of masses.

While the resulting non-detection does not rule out string theory, it does deliver a blow to certain models within it.

This result does show, however, the promise that Chandra and future X-ray observatories may play in testingstring theory.