Astronomers have observed two collapsed stars of different masses locked in a “fiercely tight” orbit which, they say, could help shed light on some of the Universe’s biggest mysteries.
Known as neutron stars, these extremely dense astronomical objects are stellar remains of a supernova, packing hundreds of thousands of times the Earth’s mass into a space that is the size of a city.
The scientists said it is unusual to see a binary system that has two neutron stars with different masses. They believe these stars will eventually collide around half a billion years from now, releasing massive amounts of energy in the form of gravitational waves and light.
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One of these stars is a pulsar, known as PSR J1913+1102, which rotates and emits beams of electromagnetic radiation from its poles.
The first-ever glimpse of two neutron stars colliding was observed in 2017, opening the door to a new era of astronomy.
Known as GW170817, the spectacular event occurred 130 million light years from the Milky Way, but the enormous amount of matter ejected from the merger and its brightness remained an “unexpected mystery”.
Lead researcher Dr Robert Ferdman, from University of East Anglia’s School of Physics, said: “Most theories about this event assumed that neutron stars locked in binary systems are very similar in mass. Our new discovery changes these assumptions.
“We have uncovered a binary system containing two neutron stars with very different masses. These stars will collide and merge in around 470 million years, which seems like a long time, but it is only a small fraction of the age of the Universe.”
Dr Ferdman said that as one of the stars is “significantly larger” than the other, its gravitational influence distort the shape of its companion, “stripping away large amounts of matter just before they actually merge, and potentially disrupting it altogether”.
This, he added, will result in a far more powerful explosion than a collision of neutron stars with equal masses.
According to Dr Ferdman, their findings, published in the journal Nature, also highlights “there are many more of these systems out there – making up more than one in 10 merging double neutron star binaries”.
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The researchers say neutron star mergers could help unlock some of the biggest mysteries in astrophysics, including a more accurate determination of the expansion rate of the Universe, known as the Hubble constant.
Study co-author Dr Paulo Freire, from the Max Planck Institute for Radio Astronomy in Bonn, Germany, added: “Such a disruption would allow astrophysicists to gain important new clues about the exotic matter that makes up the interiors of these extreme, dense objects.
“This matter is still a major mystery – it’s so dense that scientists still don’t know what it is actually made of. These densities are far beyond what we can reproduce in Earth-based laboratories.”
Could you walk on a neutron star?
Asked by: Elliot Webb, Ashford
No. A neutron star has such an intense gravitational field and high temperature that you could not survive a close encounter of any kind. First of all, just getting onto the surface of the neutron star would be problematic. Its gravitational pull would accelerate you so much you would smash into it at a good fraction of the speed of light. Even before you arrived, the difference in gravitational pull between your head and feet would already have ripped your constituent atoms apart.
Once there, though, your atomic nuclei and their free electrons would impact the surface with sufficient energy to spark thermonuclear reactions close to the super-dense surface. You would become a puff of gamma rays and X-rays, as your light elements were transformed into a cloud of heavy elements, neutrons and ultra-relativistic electrons.
Even if you were somehow magically transported onto the neutron star, therefore avoiding this energetic impact, the million-degree temperatures at the surface would vaporise (and ionise) you immediately. The intense gravity would then flatten what was left of you as you merged into the super-dense crust of the neutron star. Under these circumstances, taking a leisurely walk would be extremely difficult!
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