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A galactic rose for Hubble's anniversary

After 21 years, the Hubble Space Telescope continues to wow the world with mind-bending views of the universe. In celebration of its anniversary, the wonder continues with this gift of a galactic rose formed by a group of interacting galaxies roughly 300 million light years away from Earth.

In the group, known as Arp 273, the upper, larger of the spiral galaxies, UGC 1810, has a disc that is tidally distorted into a rose-like shape by the gravitational pull of the companion galaxy below it, known as UGC 1813, according to an image advisory.

The uncommon spiral patterns in the large galaxy are a tell-tale sign of interaction between the two galaxies. For example, the large, outer arm appears partially as a ring, a feature that is seen when interacting galaxies pass through one another. This suggests that the smaller companion galaxy actually dived deeply, but off-center, through UGC 1810.

Other notable features in the image include:

  • The inner set of spiral arms is highly warped out of the plane, with one of the arms going behind the bulge and combing back out the other side. How they connect isn't precisely known.
  • A possible mini spiral may be visible in the spiral arms of UGC 1810 to the upper right. Note how the outermost spiral arm changes character as it passes this third galaxy, from smooth with lots of old stars on one side, to clumpy and extremely blue on the other.
  • The swath of blue jewels across the top is the combined light from clusters of intensely bright and hot young blue stars, which glow fiercely in ultraviolet light.
  • The smaller galaxy, viewed close to edge-on, shows signs of intense star formation in its nucleus that was perhaps triggered by the encounter with the companion galaxy.

The larger galaxy in the UGC 1810-UGC 1813 pair has a mass that is about five times that of the smaller galaxy. In unequal pairs such as this, the relatively rapid passage of the companion galaxy produces the lopsided structure in the main spiral.

The Hubble Space Telescope was launched from space shuttle Discovery on April 24, 1990. It circles the Earth once every 97 minutes. Though its digital postcards routinely wow the world, it hasn't always been smooth sailing, as noted in this photo trip through the telescope's highs and lows.

NASA astronauts successfully performed a final servicing of the telescope in 2009 that should keep it sending back images for years to come. Meanwhile, the space agency is preparing Hubble's replacement, the James Webb Space Telescope, currently scheduled for launch in 2014. For now, though, let's wish Hubble a happy anniversary and thank it for the galactic rose.

More stunners from Hubble:

John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).