Happy 21st Anniversary to the Hubble Space Telescope
To celebrate the 21st anniversary of the Hubble Space Telescope's deployment
into space, astronomers at the Space Telescope Science Institute in Baltimore,
Md., pointed Hubble's eye at an especially photogenic pair of interacting
galaxies called Arp 273.
"For 21 years, Hubble has profoundly changed our view of the universe, allowing
us to see deep into the past while opening our eyes to the majesty and wonders
around us," NASA Administrator Charles Bolden said. "I was privileged to pilot
space shuttle Discovery as it deployed Hubble. After all this time, new Hubble
images still inspire awe and are a testament to the extraordinary work of the
many people behind the world's most famous telescope."
Hubble was launched April 24, 1990, aboard Discovery's STS-31 mission.
Hubble discoveries revolutionized nearly all areas of current astronomical
research from planetary science to cosmology.
"Hubble is America's gift to the world," Sen. Barbara Mikulski of Maryland said.
"Its jaw-dropping images have rewritten the textbooks and inspired generations
of schoolchildren to study math and science. It has been documenting the history
of our universe for 21 years. Thanks to the daring of our brave astronauts, a
successful servicing mission in 2009 gave Hubble new life. I look forward to
Hubble's amazing images and inspiring discoveries for years to come."
The newly released Hubble image shows a large spiral galaxy, known as UGC 1810,
disk that is distorted into a rose-like shape by the gravitational tidal
pull of the companion galaxy below it, known as UGC 1813. A swath of blue jewel-
like points across the top is the combined light from clusters of intensely
bright and hot young blue stars. These massive stars glow fiercely in
The smaller, nearly edge-on companion shows distinct signs of intense star
formation at its nucleus, perhaps triggered by the encounter with the companion
Arp 273 lies in the constellation Andromeda and is roughly 300 million light-
years away from Earth. The image shows a tenuous tidal bridge of material
between the two galaxies that are separated from each other by tens of thousands
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 that
the smaller companion actually 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 still not precisely known.
A possible mini-spiral may be visible in the spiral arms of UGC 1810 to the
upper right. It is noticeable how the outermost spiral arm changes character as
it passes this third galaxy, from smooth with lots of old stars (reddish in
color) on one side to clumpy and extremely blue on the other. The fairly regular
spacing of the blue star-forming knots fits with what is seen in the spiral arms
of other galaxies and is predictable based on instabilities in the gas contained
within the arm.
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 a companion galaxy produces the lopsided or asymmetric
structure in the main spiral. Also in such encounters, the starburst activity
typically begins in the minor galaxies earlier than in the major galaxies. These
effects could be because the smaller galaxies have consumed less of the gas
present in their nuclei, from which new stars are born.
The interaction was imaged on December 17, 2010, with Hubble's Wide Field Camera
3 (WFC3). The pictur is a composite of data taken with three separate filters on
WFC3 that allow a broad range of wavelengths covering the ultraviolet, blue, and
red portions of the spectrum.
Credit: NASA, ESA, and Hubble Heritage Team (STScI/AURA)