Newly released images from the Hubble Space Telescope show two galaxies that are moving so fast that gas within the galaxies is being stripped away.
The two galaxies, NGC 4522 and NGC 4402, are located in the Virgo galaxy cluster, about 60 million light years from Earth.
Astronomers estimate that NGC 4522 is moving within the cluster at more than 10 million km/h, or nearly 2,800 kilometres every second.
Because the space within the cluster isn't empty, but filled with a very thin mixture of gases called the intracluster medium, the galaxy's movement is creating drag, in the same way that a rider on a speeding motorcycle will feel wind, even on a calm day.
The drag, or ram pressure, is stripping gases out of the galaxy, leaving a ghostly shadow behind. The Hubble images show new stars forming in bright blue clusters in the cloud of gas being left behind the galaxy.
An image of another galaxy, NGC 4402, also shows signs of ram pressure: a curved disc of gas and dust being pushed out of the galaxy.
The images were taken by the Advanced Camera for Surveys on Hubble before it broke down in 2007. Astronauts were able to restore the camera during a 13-day mission to the telescope in May 2009.
Studying how ram pressure strips gas out of galaxies in these galactic clusters helps astronomers understand the forces that cause galaxies to form and evolve over time.