Sweeping up the vacuum

Space is often thought to be empty, a vacuum, or as close as nature gets to it. In reality, interstellar space is filled by large gaseous structures, which can be revealed by using the right telescope. 

In this short film, Dr Jakob van den Eijnden explains how this image of an observation of the star Vela X-1, located in the Vela Constellation, was taken with the new South-African MeerKAT telescope. Dr van den Eijnden uses this telescope to study the interaction between stars like Vela X-1 and surrounding space. The star itself, located at the centre of the circular image, is barely visible at these scales – the view spans more than 100 light-years. However, we can see the interstellar gas clouds as diffuse, faint patches of light, for instance stretching through the centre from bottom left to top right. Excitingly, one can also spot a bow shock just above the middle: Vela X-1, as massive as twenty Suns, shoots through the gas cloud at a speed of one hundred kilometres per second. It sweeps up the gas, creating a bow shock not unlike a duck swimming in a pond. However, unlike an ordinary duck in a pond, this Galactic bow has a size of several light years.

Dr Jakob van den Eijnden is a Lee Hysan Junior Research Fellow in Physical Sciences at St Hilda’s College and postdoctoral researcher in astrophysics in the Physics Department of the University of Oxford. His research focuses on binary star systems, where two stars orbit around each other. Specifically, he studies cases where one of those stars is a neutron star, the densest type of star with the strongest gravitational pull in the universe.