A team of astrophysicists, including Yaël Nazé, a FRS-FNRS research associate in astrophysics at the University of Liege, has observed X-ray pulsations from a massive star for the first time. The pulsation is monoperiodic and is similar to those observed at visible wavelengths. This behavior was previously unknown up to this point and was not part of the theoretical predictions associated with this type of star. The discovery opens up a new window into the study of massive stars, challenging the theoretical knowledge of these space giants. These pulsations are linked to the extremely powerful stellar winds of the star. The details remains a mystery. The quest to understand these massive stars continues.
A study that resulted in an unexpected discovery
Among these massive stars is Xi1 CMa, a spectral B-type star, that is to say, the second category of stars if we class them according to temperature. Located in the Canis Major constellation, around 1400 light-years from the Earth, it is visible with the naked eye despite the great distance involved. It is on this star that a team of researchers including Yaël Nazé, a FRS-FNRS research associate in astrophysics at the University of Liege focused their attention. “We became interested in this star because it is very magnetic”, explains the researcher. “It is 5000 greater than the overall magnetic field of the Sun and 10 000 times more than that of the Earth, a value which is enormous”. It has been long suspected that massive stars have magnetic fields, but their signature could not be detected before 2002 because of the lack of sensitive instruments. Another important property of massive stars is the presence of stellar winds which are much more powerful than the solar wind. These stars eject hundreds of millions of times more matter than the solar wind, and these stellar winds can reach speeds of around five million kilometers an hour, ten times faster than the average speed of the solar wind. “By way of comparison, the ‘small’ solar wind is already powerful enough to strip certain planets of their atmosphere (Mars and Venus) so we cannot even begin to imagine the effect of these massive stars”.