Neutron stars have mountains, they’re solely a fraction of a millimeter excessive

The universe has some very extreme places – and there are few places more extreme than the surface of a neutron star. These ultra-dense objects are created after a supergiant star collapses into a ball about 10 kilometers (6 miles) in diameter. Its surface is extreme because of gravity, which is about a billion times stronger than that of Earth. However, this gravity also forces the stellar remnant to be exceptionally flat. How flat is the result of a new theoretical research by doctoral student Fabian Gittins from the University of Southampton.

Earlier estimates of the height of these “mountains” on the surface of neutron stars assumed that they could grow up to a few centimeters. A combination of factors went into these estimates, including gravitational forces that pull any slight bump flat to the surface, as well as a shear force from ultra-dense matter that might be able to support the mountains themselves.

Short video about neutron stars.
Credit – In short, YouTube Channel

The researchers found that the forces acting on the surface would almost certainly limit the height of such a mountain to just a few fractions of a millimeter, reducing the height of previous estimates by a factor of more than 100. It shows how close to a perfect sphere neutron stars really are.

Even these small imperfections on the surface of a neutron star can have a major impact on the wider universe. Some neutron stars spin, with the fastest (PSR J1748-2446ad) spinning at 716 times per second. With such high spin rates combined with such a dense force of gravity, the small imperfections in the sphere, represented in the study by the “mountains”, should possibly lead to gravitational waves.

UT video discussing some gravitational wave sources – including neutron star merging.

So far, scientists have not been able to find gravitational waves emanating from a spinning neutron star. But that wasn’t for a lack of experimentation – and they found some waves from a collision of two neutron stars. However, it seems that the current generation of gravitational wave detectors, which provided the first detection of any type of gravitational wave just a few years ago, is simply not sensitive enough to pick up the slightly smaller waves that the theory predicts a neutron star.

Fortunately, however, new detectors are in sight, such as the Einstein Telescope and Cosmic Explorer. With much more sensitive instruments, we might be able to detect the great fluctuations in gravity that even these tiny sub-millimeter heights can throw out into the universe.

Learn more:
RAS – The Life of a Beetle: Millimeter-high mountains on neutron stars
LiveScience –

Learn more:
RAS – The Life of a Beetle: Millimeter-high mountains on neutron stars
LiveScience – Neutron star “mountains” could block our view of mysterious gravitational waves
LIGO – How high are pulsar “mountains”?
Gizmodo – Neutron stars have mountains that are less than a millimeter high

Mission statement:
Artist’s impression of a neutron star.
Credit – ESO / L. Sidewalk

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