Hubble Zooms in on a Magnified Galaxy
Thanks to the
presence of a natural "zoom lens" in space, NASA's Hubble Space
Telescope got a uniquely close-up look at the brightest
"magnified" galaxy yet discovered.
provides a unique opportunity to study the physical properties
of a galaxy vigorously forming stars when the universe was only
one-third its present age.
gravitational lens is produced when space is warped by a massive
foreground object, whether it is the Sun, a black hole, or an
entire cluster of galaxies. The light from more-distant
background objects is distorted, brightened, and magnified as it
passes through this gravitationally disturbed region.
A team of
astronomers led by Jane Rigby of NASA's Goddard Space Flight
Center in Greenbelt, Md., aimed Hubble at one of the most
striking examples of gravitational lensing, a nearly 90-degree
arc of light in the galaxy cluster RCS2 032727-132623. Hubble's
view of the distant background galaxy is significantly more
detailed than could ever be achieved without the help of the
The results have
been accepted for publication in The Astrophysical Journal, in a
paper led by Keren Sharon of the Kavli Institute for
Cosmological Physics at the University of Chicago. Professor
Michael Gladders and graduate student Eva Wuyts of the
University of Chicago were also key team members.
The presence of
the lens helps show how galaxies evolved from 10 billion years
ago to today. While nearby galaxies are fully mature and are at
the tail end of their star-formation histories, distant galaxies
tell us about the universe's formative years. The light from
those early events is just now arriving at Earth. Very distant
galaxies are not only faint but also appear small on the sky.
Astronomers would like to see how star formation progressed deep
within these galaxies. Such details would be beyond the reach of
Hubble's vision were it not for the magnification made possible
by gravity in the intervening lens region.
In 2006 a team of
astronomers using the Very Large Telescope in Chile measured the
arc's distance and calculated that the galaxy appears more than
three times brighter than previously discovered lensed galaxies.
In 2011 astronomers used Hubble to image and analyze the lensed
galaxy with the observatory's Wide Field Camera 3.
image of the galaxy is repeated several times in the foreground
lensing cluster, as is typical of gravitational lenses. The
challenge for astronomers was to reconstruct what the galaxy
really looked like, were it not distorted by the cluster's
vision allowed astronomers to remove the distortions and
reconstruct the galaxy image as it would normally look. The
reconstruction revealed regions of star formation glowing like
bright Christmas tree bulbs. These are much brighter than any
star-formation region in our Milky Way galaxy.
spectroscopy, the spreading out of light into its constituent
colors, the team plans to analyze these star-forming regions
from the inside out to better understand why they are forming so
Space Telescope Science Institute, Baltimore, Md.
NASA Goddard Space Flight Center, Greenbelt, Md.
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