Astronomers have found something that has left them quite puzzled. A colourful shock wave has been created around a dead star, and it looks different from what they’ve seen before!
The small star RXJ0528+2838 (catchy name!) located around 730 light-years away from us orbits around our Galaxy’s centre, just like our Sun and other stars. Usually, as a star travels through space, it expels material that interacts with the gas in its surroundings, creating something called a bow shock, which is a type of shock wave.
A shock wave happens when an object moves super fast through space, colliding with the gas around it that cannot get out of the way quickly enough! This creates a glowing arc of gas around the star that looks just like the bulging wave you get in front of a moving boat. The same thing happens when a cannonball is fired: it flies out faster than the speed of sound, creating a shock wave that we hear as a loud boom. Air has waves too, even if we can’t see them!
Now, why did the wave of this galactic cannonball leave astronomers confused? Well, this dead star is the remaining core of a star like our Sun at the end of its life — called a white dwarf — and has a Sun-like companion orbiting it. Typically, in these kinds of pairs, the white dwarf steals material from its bigger companion, creating a spinning disc of gas and dust around itself, and throwing some of that material into space. But RXJ0528+2838 shows no sign of having such a disc, so it doesn’t seem to be releasing leftover material into space, a key step in the formation of a bow shock.
So, if the star isn’t releasing leftover material, how did it make this spectacular shock wave?
Astronomers aren’t sure, but they do have a guess that explains some of what’s happening! The white dwarf has a strong magnetic field that pulls material stolen from its companion star directly onto it without creating a disc. This isn’t enough to explain the full power of the shock wave by itself, so this still needs further investigation by scientists.
This discovery was made possible with ESO’s Very Large Telescope (VLT), after astronomers noticed a strange cloud around the star. They were able to map this bow shock in detail and study what it is made up of, getting one step closer to understanding the energy source for this rainbow-like scene.
(Space Scoop)
