Neutron stars can have mountains, the tallest of which rise only a fraction of a millimeter above the rest of the surface. British scientists have come to the conclusion that their size is influenced by the powerful gravitational field of ultra-compact objects.
The gravitational field of a neutron star is billions of times stronger than that of the earth. This causes any unevenness on the surface of the object to be compressed to microscopic dimensions. In this case, the star itself will be almost perfect spherical in shape. However, even a neutron star has deformations that scientists call mountains, despite their tiny size. To assess it, scientists in the new study used computer simulations. In their work, astrophysicists took into account the role of superdense nuclear matter.
As a result, scientists discovered that the mountains on neutron stars are about a hundred times smaller than previously thought. Previously, astrophysicists were sure that deviations from the ideal sphere did not exceed a few parts per million, and the height of the mountains reached several centimeters. According to past calculations, neutron stars are deformed in such a way that the crust is close to rupture. When it bursts, the mountains disappear. A new study has shown that such conditions are physically impossible.
Because of the intense gravity, even single spinning neutron stars with slight deformations can cause ripples in the fabric of spacetime called gravitational waves. Such ripples will be difficult to observe due to the low altitude of the mountains, but they can be detected with the help of advanced detectors LIGO and Virgo, the scientists note.
A neutron star is a celestial object formed as a result of a supernova explosion. For a neutron star to form, the mass of the star before the outburst must be several times the mass of the Sun. Moreover, if the mass of the star before the outburst exceeds the mass of the Sun by more than 20 times, then as a result of the collapse, a black hole appears instead of a neutron star.
This celestial body consists mainly of neutrons and rotates at a high speed. Neutron stars have a very strong magnetic field, reaching 10¹²-10¹³ G on the surface. The mass of such a star can be compared with the mass of the Sun, but their average diameter is only 20 km, and the average density is presumably equal to 10¹⁵ g/cm³.