PhotoBlog - image

Apr

2011

12:30pm, EDT

NASA, ESA and the Hubble Heritage Team (STScI/AURA)

This image of a pair of interacting galaxies called Arp 273 was released to celebrate the 21st anniversary of the launch of the Hubble Space Telescope. The distorted shape of the larger of the two galaxies shows signs of tidal interactions with the smaller of the two. It is thought that the smaller galaxy has actually passed through the larger one.

A galactic rose for Hubble's anniversary

By John Roach, Contributing Writer, NBC News

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).

Holiday calendar: Our pale blue dot

By John Roach, Contributing Writer, NBC News

On Feb. 14, 1990, NASA controllers instructed the Voyager 1 spacecraft to turn around and take one last look at its home planet as it pushed on to the fringe of our solar system. Look closely at the resulting image. That tiny pinpoint of light in the center-right is us – you, me, and everyone else that calls Earth home.

The request came from the late, great astronomer Carl Sagan, one of the world's greatest advocates for advancing the general public's appreciation and understanding of science. He passed away 14 years ago today after a two-year battle with bone-marrow disease.

The image, called "A Pale Blue Dot," was made when Voyager 1 was about 4 billion miles away. It inspired Sagan's 1994 book "Pale Blue Dot: A Vision of the Human Future in Space." An excerpt puts the image's significance into context:

"It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. It underscores our responsibility to deal more kindly with one another, and to preserve and cherish the only home we've ever known, the pale blue dot."

We leave you to reflect on Sagan's thoughts as we head into the final days of our Cosmic Log Space Advent Calendar. For more views of Earth from space, check out these past offerings. We've also included links to other online Advent calendars that have been serving up space images daily since the beginning of the month:

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).