Although some people might think that stars, like our Sun, remain stationary in the grand structure of our universe, this is completely not the case, because everything moves at incredible speeds through space, including our very own solar system. By using specialized telescopes, NASA has seen that runaway stars leave behind waves of infrared light, a phenomenon known as bow shocks. This event is similar to how air reacts when an airplane passes the speed of sound, leaving behind ripples created by the so-called sonic boom.
These waves were picked up by the NASA’s Spitzer WISE, wide-field infrared survey explorer, a device that has been floating in orbit around Earth for a couple of years up to this point, being described as a zombie telescope. This is due to the fact that Spitzer was supposed to be more or less “dead” because its cryogenic capabilities have expired and without them, its WISE equipment would not normally function. But because Spitzer’s solar panels still function normally and its location is pretty far from Earth’s heat load, it is still capable of capturing astounding images from the depths of outer space.
In regards to bow shocks, they appear just like sonic booms on Earth, but without the sonic part, because sound does not travel in the vacuum of space. Instead, the pressure waves that create sounds are replaced with interstellar matter piling up on the front of the gas bubble that encircles a runaway star. This bubble is created by the star’s very own gas streams, which are called stellar winds.
When matter starts to accumulate near on the front-end of the star’s bubble, it begins to heat up due to compression. This heat gets progressively lower when reaching the ends of the wave, similar to how boats create larger waves in front of them but lower on their sides. Because of the shockwave’s increased temperatures, it can get picked up by Spitzer’s infrared telescope, allowing scientists, as well as the general public, see one of the most intriguing images from outer space.
Runaway stars are celestial bodies that used to be a part of a dense star cluster. But after a supernova occurred, the massive explosion basically kicked the neighboring star out of the system at immense speeds, sometimes reaching 24km per second. This speed can be even spotted in the night sky without the use of a telescope because these runaways are moving much faster than other stars that make up the starry night sky.
And the faster a star moves, the bigger the bow shock will get, generating larger and larger infrared waves as they dash through the vast emptiness of space. If these waves would not have been present, telescopes like Spitzer wouldn’t have the capability of differentiating them from other stars and sometimes, they can even achieve speeds that make them basically untrackable.
Because these runaway stars leave behind waves of infrared light, scientists are able to track their trajectory, by seeing where the wave has the highest temperatures, as well as calculating the star’s speed that is directly linked to the size of the wave.