This image of two interacting galaxies, called Arp 273, has been released by the organization that operates the Hubble Space Telescope in celebration of the 21st anniversary of its launch into space. Gravitational forces have pulled the objects into the shape of a rose on a stem as seen from Earth's vantage point.

The blossom part of the rose is a large spiral galaxy named UGC 1810. The ring shape of the galaxy's outer arm suggests to scientists that the "stem" galaxy, UGC 1813, rapidly dived through UGC 1810 at one time, according to a press release by the Space Telescope Science Institute in Baltimore, which operates Hubble. UGC 1810's inner spiral arms are also unusually positioned, out of the plane of the rest of the galaxy. The bright blue points across the top of UGC 1810 are clusters of young, hot blue stars shining in ultraviolet light.

Interacting galaxies like Arp 273 are common in the universe. In fact, the nearby Andromeda Galaxy is approaching Earth's own Milky Way Galaxy. In a few billion years they will interact before finally merging into one galaxy, according to a 2008 post by NASA.

During Hubble's 21 years in orbit, researchers have used its data to detect and map dark matter, to observe the universe's accelerating expansion, to characterize black holes and more. In April 2010 NASA announced that scientists will continue to maintain Hubble's instruments and gather data through April 2013. After that the fate of the telescope, which lifted off on April 24, 1990, on board space shuttle Discovery, is uncertain. NASA plans to launch Hubble's successor, the James Webb Space Telescope, as early as 2014.

—Francie Diep