A type of antimatter particles called positrons are hitting the earth at a higher rate than they should be. Pulsars were initially thought to be the reason, but a new study says otherwise.

Amid the high speed cosmic rays raining down on us from the depths of space are a handful of antimatter particles called positrons.

Astronomers think that Earth is showered by these ‘anti-electrons’ because of pulsars, but there’s a weird catch – there are more of these particles coming at us than there should be. And now, thanks to a new study, we might finally get some answers.

Cosmic rays are incredibly fast particles, since they’re being shot down from space at high energies. Positrons make up a small percent of these super speedy particles, but nobody is entirely sure where or how they’re made.

To make matters more confusing, in 2008 a probe in Earth’s orbit called PAMELA detected more high energy positrons reaching our corner of the cosmos than we’d expect.

A large team of international researchers analysed recent measurements from the High-Altitude Water Cherenkov (HAWC) Observatory in Mexico to test the hypothesis that the excess antimatter might have been whipped up by powerful objects known as pulsars.

These are neutron stars that channel charged particles into a beam with their super-strong magnetic fields. They get the pulsar name from the beam describing a circle as the star rotates, seen from Earth as a steady, rapidly pulsing light.

As that beam smacks into surrounding dust and gasses, it acts like a giant particle accelerator, smashing particles together and producing new matter from the energy.

Amid the carnage particles like electrons and their mirror ‘anti-matter’ twins can emerge, which are promptly whisked away on the shock waves produced by the collisions.

That’s according to theory, anyway.

So when the HAWC observatory recently detected a couple of perfect candidate pulsars a few hundred light years away to study for signs of these energetic positrons, it seemed like a good opportunity to put the hypothesis to the test.

The answer was no. Not quite, anyway.

After 17 months spent collecting data and then thoroughly analysing it, the researchers found the pulsars were responsible for some of the extra-high energy positrons, but the figure was still several times too small to explain all of them.

One of these explanations involves the decay of massive dark matter particles.

It’s a tempting idea, especially as it would provide us with a way to shine a light on the shadowy material making up a quarter of the Universe’s mass, and finally start to gain an understanding of its other properties.

But it’s important to keep in mind the death of one hypothesis isn’t direct evidence of the strength of another.

The mystery of both dark matter and the extra speedy positrons remains. For now, we can only wait and see.

This research was published in Science.

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The world of neutron stars is a quite strange to scientists. Neutron stars are one of the most interesting objects of the universe so far we have observed. Neutron stars are the one of the most exotic objects of the universe. Ordinary matter or stuff we are made of and are familiar with is made of atoms. We know that most of the space in the atoms is empty. Suppose we generate enough force to squeeze the emptiness in the atoms of a rock roughly of the size of a football stadium. After applying this force and removing the emptiness of atoms, leaving no space between the electrons and nuclei, the stone will be squeezed down to the grain of a sand but still weighed 4 million tons. Suppose an island that dense instead of a grain of sand, but the size of an island is 20km. That is a neutron star.

When a massive star runs out of fuel and collapses, neutron stars are created . As the star collapses the density becomes so enormous that electrons and protons are squeezed together to form neutrons. The end result of this squeezing process of electrons and protons is a Neutron Star of 20 km wide but more massive than our sun and is mostly consist of neutrons. These exotic objects possess enormous gravitational field one hundred billion times stronger than we feel on earth. Neutron stars have very strong magnetic field. Neutron stars are tiniest stars known to exist in the universe. Among all the known neutron stars 5% are members of binary system. The companion of a neutron star in a binary system could be either white dwarfs, ordinary stars or other neutron stars. The formation of neutron star in a binary system is quite complicated process. There are about 2000 known neutron stars in the Milky Way and the Magellanic Clouds.

The majority of observed neutron stars in the Milky Way and the Magellanic Clouds are radio pulsars. If the star that has gone for supernova has mass 8 to 20 times of the sun than the core of the star will form neutron star. If the star has a mass less than 8 times to that of the sun than the star after completely burning its fuel will result a white dwarf. Stars more than 20 times massive than sun will result a black hole. The neutron star has mass 1.5 to 3 times to that of sun. Due to the conservation of angular momentum neutron stars starts to spin very rapidly. This is a pulsar. A pulsar is a spinning core of a star that has collapsed into neutron star. There is a type of neutron stars that can rotate more than 100 times per second. Original star before supernova event has magnetic field and after collapsing to a neutron star the magnetic field become stronger. When these magnetic fields rotate along with the neutron star, they produce radio waves shooting out of the North and South Pole of the neutron star. In general the direction of this radio beam is not actually along the same axis that the neutron star is spinning on. Due to this we can observe them with radio telescopes. Milliseconds pulsars also produce gamma rays. Fermi Telescope launched by NASA has detected many pulsars. This telescope is actually mapping the whole sky in gamma rays and gamma rays are even more energetic than X-rays. Many young pulsars emit gamma rays and it’s a common fact among scientists. Fermi has observed that all the millisecond pulsars produce gamma rays and this was a surprise to many scientists. Some physicists long before this observation have already theoretically predicted that we may see gamma rays from millisecond pulsars.