The Hubble space telescope celebrates its 21st year in orbit on April 20, 2011.
To celebrate this milestone, NASA has released a show-stopping image of two interacting galaxies, known together as Arp 273.
The image, initially captured on 17 December 2010, resembles a rose in bloom. NASA says the unique formation is due to the smaller galaxy's gravitational pull on its larger companion.
The galaxies may even have had direct contact with one another. Writes NASA:
A series of uncommon spiral patterns in the large galaxy are a tell-tale sign of interaction. The large, outer arm appears partially as a ring, a feature seen when interacting galaxies actually pass through one another. This suggests the smaller companion dived deep, but off-center, through UGC 1810. The inner set of spiral arms is highly warped out of the plane, with one of the arms going behind the bulge and coming back out the other side. How these two spiral patterns connect is not precisely known.
NASA hopes to replace Hubble in 2015 with the extremely powerful, and costly, James Webb Telescope.
Take a look at the gorgeous image (below), then check out our slideshow for more extraordinary images from Hubble's historic career.
then, check out a collection of Hubble's best images from its long career.