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In the field of astronomy, J1903+0327 was known as one of the ‘strangest things in space ', but its origins have been explained by a group of Dutch researchers including Ed van den Heuvel and Joeri Leeuwen from the University of Amsterdam

In the field of astronomy, J1903+0327 was known as one of the ‘strangest things in space ', but its origins have been explained by a group of Dutch researchers: Simon Portegies Zwart (Leiden Observatory), Ed van den Heuvel (Anton Pannekoek Astronomical Institute, UvA), Joeri van Leeuwen (ASTRON / UvA) and Gijs Nelemans (Radboud University). Their findings will soon be published in the scientific journal Astrophysical Journal.

J1903+0327 consists of a millisecond pulsar and a normal star that emits a wide, elliptical orbit around the pulsar. According to existing theories, this is not possible. The collaborating astronomers argue now that J1903+0327 originally consisted of three stars and has reached its present state as a result of a dynamic interaction in the triple star system. At birth, the triple star was stable, but through the exchange of mass in the inner binary, the triple system is unstable and the third star disappeared. The star is still missing and it is unlikely that it will be found. ‘The third star was knocked out like a cannonball,’ says Van den Heuvel. ‘We will not be able to find it again easily.’

Sun-like star

Millisecond pulsars are neutron stars that rotate on their axis more than one hundred times per second. They are usually accompanied by a white dwarf star with low mass that rotates around the pulsar in approximately 10 days. The orbits of these binaries are almost circular. However, what was surprising to the scientists was that the millisecond pulsar J1903+0327 was accompanied by a sun-like star in an eccentric orbit in a period of almost 100 days. Everything seems to indicate that the millisecond pulsar was formed in a very different way than previously found examples.

Theory of binary star evolution challenged

‘It's a very interesting system,’ explains Portegies Zwart, ‘particularly because it challenges the whole theory of binary star evolution. At first glance, J1903+0327 cannot be explained, but all the pieces suddenly fell into place when we realised that a third star was involved.’ The researchers also describe a number of known systems which they have identified as a missing transitional stage. The research sheds new light on understanding the evolution of triple stellar systems, a branch of astronomy that has received little attention up to now.