2024-01-18 19:00:57
Scientists have spotted a mysterious dark object in the Milky Way. The new object challenges common theories.
Scientists have spotted a mysterious dark object in the Milky Way regarding 40,000 light-years from Earth. The celestial body with 2.35 times the mass of our sun in the globular star cluster NGC 1851 does not shine itself, so it is not an ordinary star, reports the international research team in the specialist magazine “Science”. But for the remnant of an exploded star – a neutron star or a black hole – its mass is unusual.
The mass therefore lies in the so-called mass gap between these exotic objects. This makes it unclear whether the unusual celestial body is an exceptionally heavy neutron star, an exceptionally light black hole – or something previously unknown. A light year is the distance that light travels in one year – a distance of 9.46 trillion kilometers.
“Each of these possibilities for the nature of the object is exciting,” explained Benjamin Stappers from the University of Manchester, one of the project leaders of the observations carried out at the MeerKAT radio telescope facility in South Africa. “If it’s a black hole, we can use it to test the theory of gravity. If it’s a neutron star, it can give us new insights into nuclear physics at very large densities.”
If a large star dies in a supernova explosion at the end of its life, its interior collapses and either a neutron star is formed, in which matter is as densely packed as in atomic nuclei, or a black hole, in which gravity is so strong that not even light can escape. According to the theory, neutron stars cannot contain more than 2.2 times the mass of the sun – otherwise gravity would gain the upper hand and a black hole would have to form. But black holes are only found in the cosmos at around five solar masses.
There is a gap in between that has so far been a mystery to astronomers. Only measurements of gravitational waves indicate that there are isolated celestial bodies in this mass gap – although their nature and formation is still unclear. Therefore, the discovery of such a celestial object represents a major advance for astronomers.
The researchers came across the strange object while observing the pulsar PSR J0514-4002E. A pulsar is a neutron star with a strong magnetic field that, due to its own rotation, sends regular radio pulses to Earth – in this case 170 times per second. The precise measurement of these pulses showed the scientists that the pulsar forms a close binary system with another object. The data gives this object a mass of between 2.09 and 2.71 solar masses, with the most likely value being 2.35 solar masses.
But how might such an object have formed in the mass gap? Since PSR J0514-2002E is located in a globular cluster, Stappers and his colleagues suspect a complicated formation history. Because NGC 1851 contains around half a million stars that are very close together. That’s why – on an astronomical scale – there are often close encounters in which double stars are formed or even swap partners.
The team suspects that the pulsar’s exotic companion may have been formed by the merger of two smaller neutron stars and only entered orbit around the pulsar later during a close encounter.
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