Scientists have found a star with something very strange

One of the strangest and probably the strangest things that exist among stars are called neutron stars.

These are the interior parts left after a massive star exploded in a supernova and most of it was thrown into space. But the core remains: a super-dense sphere with some of the densest elementary particles theoretically possible in the universe.

That means it could weigh more than half a million times our globe, and all this packed into a ball the size of Oslo municipality.

We’ve never visited or examined a neutron star up close, so the idea of ​​neutron stars is theoretical.

This means that the laws of physics say that neutron stars can exist, and measurements taken from radio telescopes over many decades have shown that they are most likely there.

Several Nobel Prizes have gone to work with neutron stars, including the Discovery Prize Pulsars in 1974, according to Nature. These are neutron stars that rotate hundreds of times per second and emit radio signals so powerful that they can be measured from Earth.

But sometimes potential neutron stars appear that do not fit in with other known neutron stars. This alternative is described in a new research article in the journal Nature Astronomy.

It is simply very easy.

A light neutron star in the center?

Neutron stars are often detected by strong radio signals coming from a small point in the sky.

The potential neutron star described in this study is a remnant of a supernova explosion.

It was discovered by the XMM-Newton space telescope and many researchers have indicated that this star system is an exciting place to explore the physics of neutron stars, According to this 2014 study, published in the Journal of Astronomy and Astrophysics.

In the new study, researchers have come up with a new estimate of how massive this neutron star is. They reach about 0.77 times that of our Sun with a radius of about 10.5 kilometres.

Our Sun corresponds to a mass of approximately 333,000 Earths, As estimated by Space.com.

This is still an extreme ratio between size and mass, but if the numbers are correct, it is the lightest known neutron star.

If it’s a neutron star at all.

This is the so-called SNR (supernova remnant) seen in X-rays, the material left over after a supernova explosion. Within such an SNR, a neutron star can be found. This particular SNR is called Tychos nova. (Illustration: NASA/CXC/Rutgers/J.Warren & J.Hughes et al.)

light and easy

All other neutron stars found are between 1.17 and 2.35 times the mass of our Sun. Previous, The lightest known, described in this study from 2015.

But the star described in the new study is much lighter. The researchers confirmed in the study that it is still within the theoretical possibilities of the neutron star.

However, it stands out so much that it may not be a neutron star, but something else. It could be some kind of quark star.

These hypothetical stars may look like neutron stars, but they are made of different and stranger compositions of quark matter than other stars. Quarks are one of the fundamental components of the universe.

But this is only a hypothetical possibility, and no one has ever proven that such stars actually exist in the universe. So the researchers stress that this is the current speculation.

The new estimate for the neutron star comes, among other things, due to better measurements from the Gaia space telescope. This telescope maps hundreds of millions of stars in the Milky Way to give a better picture of what our galaxy looks like. New versions are released regularly Measurements from the Gaia telescope.

Measurements from this mapping provide researchers with a better basis for calculating how far something is, and this can in turn be used to estimate how massive a particular star is.

The distance in the universe is complex and difficult to estimate, and it is also fundamental, for example, to know exactly how fast the universe is expanding, It is a question that is not currently answered.

Reference:

Doroshenko et al: A strangely light neutron star within a supernova remnant. Nature Astronomy, 2022. DOI: 10.1038/s41550-022-01800-1. Summary

(This issue was first published in Forsking).