An international team of astronomers has announced the discovery of an unusual white dwarf star that is made of hydrogen on one side and helium on the other. They reported their findings in the latest issue of Nature. Dr Przemysław Mróz from the Astronomical Observatory is a co-author of the study.

Today marks the beginning of a new era in the history of gravitational wave astronomy. Four groups studying pulsar timing have announced the results of their analysis of pulsar observations spanning the past few decades. Simultaneously, there have been announcements from the Parkes Pulsar Timing Array, European Pulsar Timing Array, NanoGrav in North America, and the Indian Pulsar Timing Array.

An international team led by astronomers from the Max Planck Institute for Extraterrestrial Physics has announced the discovery of a unique binary star system in which matter flows onto the white dwarf from its companion. The system was found due to bright, so-called super-soft X-rays, which originate in the nuclear fusion of the overflowed gas near the surface of the white dwarf. The unusual thing about this source is that it is helium and not hydrogen that overflows and burns. The paper presenting the results of this study has been published in the Nature journal. Optical observations of the system collected by the OGLE project led by prof. Andrzej Udalski from the Astronomical Observatory of the University of Warsaw – co-author of the paper – played an important role in its characterization.

The stars circle each other every 51 minutes, confirming a decades-old prediction.

Nearly half the stars in our galaxy are solitary like the sun. The other half comprises stars that circle other stars, in pairs and multiples, with orbits so tight that some stellar systems could fit between Earth and the moon.