Speeding Galaxies Distorted by Space Winds

A new set of images from the Hubble Space Telescope, taken before its recent overhaul by astronauts, has revealed strong winds ripping through a pair of galaxies, distorting their shape and halting star formation.

The galaxies, members of the Virgo Cluster, are being affected by a process called "ram pressure stripping." As galaxies in the cluster move through hot gas lurking in the gaps between them, winds caused by their swift motion tug and stretch them, resulting in peculiar-looking galaxies.

Ram pressure is the drag force that results when something moves through a fluid ? similar to the wind you feel in your face while riding a bicycle.

In the case of the Virgo cluster, the spiral galaxy NGC 4522 - located about 60 million light-years from Earth - is a spectacular example of a galaxy currently being stripped of its gas content.

The galaxy's rapid motion within the Virgo Cluster results in strong winds across the galaxy as the gas within is left behind. Scientists estimate that the galaxy is moving at more than 6 million mph (10 million kph). A number of newly-formed star clusters that developed in the stripped gas can be seen in the Hubble image.

The photo highlights the dramatic state of the galaxy, with an especially vivid view of the ghostly gas being forced out of it. Bright blue pockets of new star formation can be seen to the right and left of center. The image is sufficiently deep to show distant background galaxies.

A Hubble snapshot of another galaxy called NGC 4402 also highlights some telltale signs of ram pressure stripping, such as the curved appearance of the disk of gas and dust that results from the forces exerted by the heated gas. Light emitted by the disk illuminates the swirling dust that is being swept out by the gas.

Studying ram pressure stripping helps astronomers better understand the mechanisms that drive the evolution of galaxies, as well as how the rate of star formation is suppressed in very dense regions of the universe.

Both new images were taken by Hubble's Advanced Camera for Surveys (ACS) before it suffered from a power failure in 2007. In May, astronauts on the STS-125 mission of the space shuttle Atlantis visited Hubble for the final time, overhauling its equipment, installing new instruments, and restoring the ACS to service.

NASA and the European Space Agency released the first new photographs from the new-and-improved Hubble earlier this month

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