Download Frontier Fields: Hubble Goes Deep

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Special Feature
Frontier Fields: Hubble Goes Deep
By NASA’s Amazing Space reporters
January 2014
A
stronomers made
1996
a bold move in the mid1990s, using the Hubble
Space Telescope to stare at a
seemingly vacant patch of sky.
Their efforts paid off. Looking
deeper into space than ever before,
Hubble uncovered 3,000 galaxies.
The light from many of these
galaxies had traveled for billions
of years, meaning that Hubble
sees them as they were billions
of years ago. Looking deeper into
space is also seeing farther back
in time. The observations, called
the Hubble Deep Field (HDF),
gave astronomers a glimpse of
galaxies in the early universe.
Astronomers, however, wanted
more: more deep fields, more
directions on the sky, and more
distant galaxies that would help
them understand how galaxies grow
and change over time. They took
Continued, page 3…
HDF
Hubble Deep Field
2004
HUDF
Hubble Ultra Deep Field
2014
The Frontier Fields
Going deeper in 2014: The Hubble Deep Field and the Hubble Ultra Deep Field
are two of Hubble’s famous deep views from the past. Astronomers in 2014 are
starting to exploit clever ways to look back even farther with Hubble.
www.nasa.gov
The Hubble Deep Field and
the Hubble Ultra Deep Field, to scale
HDF (1996*)
The Hubble Deep Field (at
right) was assembled from 342
separate exposures of a single
tiny patch of sky taken during ten
days in December 1995. These
observations by the Hubble
Space Telescope resulted in the
deepest image of the sky, revealing
galaxies fainter than had ever
been seen before. Most of the
nearly 3,000 galaxies are so faint
they had never before been seen
by even the largest telescopes.
IMAGE: R. Williams (STScI), the
Hubble Deep Field Team and NASA
*The HDF observations were
made in 1995; the HDF image
was released in 1996.
HUDF (2004)
In the Hubble Ultra Deep Field
(at right), taken in 2004, Hubble
uncovered 10,000 galaxies. The
light from these distant galaxies
must travel for a long time
before arriving at Earth. Since
it takes billions of years for that
light to arrive, we are seeing
the galaxies as they appeared
when the light left them billions
of years ago, long before the
Sun and Earth were born.
These images are to the same
scale. Notice the larger area of
the HUDF and the greater number
of small, red galaxies visible in
the HUDF compared to the HDF.
Many of these tiny, red galaxies
are extremely distant from Earth.
IMAGE: NASA, ESA and
R. Thompson (Univ. Arizona)
2
Continued from page 1…
advantage of the powerful cameras
installed on Hubble during later
servicing missions to gaze even
deeper into space.
In 2004, Hubble’s new Advanced
Camera for Surveys (ACS) broke
the record for the most distant
visible-light view into space
with the Hubble Ultra Deep
Field (HUDF) observations. The
telescope found a dazzling array
of 10,000 faraway galaxies.
After installation of the Wide
Field Camera 3 (WFC3) in 2009,
astronomers looked at the HUDF
region again. This time, however,
they used the Wide Field Camera
3 to study the distant universe in
infrared light. Because the universe
is expanding, the light from the
most distant galaxies gets stretched
from visible to infrared wavelengths.
These new infrared observations
were able to uncover additional
galaxies at even greater distances.
Using a trick of nature
Now Hubble has reached the limit of
its infrared vision. To probe deeper
at these wavelengths, astronomers
will have to wait for the James Webb
Space Telescope ( JWST), an infrared
observatory scheduled to launch
in 2018. In the meantime, however,
astronomers can use a trick of
gravity to see just a bit farther.
The complex mathematics of Albert
Einstein’s relativity boils down to
one basic idea: mass warps space. In
addition, light that passes through
this warped space will have its
direction bent. Thus, the gravity of
a massive cluster of galaxies can
gather and magnify light, just like a
glass lens does. Astronomers can use
these “gravitational lenses” to see
galaxies behind a galaxy cluster that
would otherwise be too far away
and too faint.
Hubble will use this “natural
lens” to push to the edges of its
capabilities in a project called the
Frontier Fields. By taking deepfield observations centered on
large galaxy clusters, astronomers
can search for galaxies near the
dawn of time. They hope to find
the typical galaxies that eventually
Continued, page 6…
Hubble
Space
Telescope
IMAGE: NASA
The Hubble Space Telescope orbits 350 miles above Earth. NASA launched the
telescope aboard the space shuttle Discovery on April 24, 1990. The bus-sized telescope
is 43.5 feet (13.3 meters) long and weighs more than 12 tons (11,000 kilograms).
3
Frontier Fields’ first data:
Pandora’s Cluster magnifies faraway galaxies
IMAGE: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)
From first data released by the Frontier Fields project: This image shows hundreds of galaxies in a large
group (Pandora’s Cluster), as well as images of galaxies much farther behind the cluster. The massive galaxy
cluster serves as a gravitational lens to magnify the galaxies behind it. Most of the lensed galaxies are distorted
into streaks and arcs. Several galaxies appear multiple times, with their light traveling several distinct paths
through the irregular gravitational lens of the galaxy cluster. The image uses both visible and infrared light. For
comparison, see the image on page 5, which shows only the galaxies that are part of Pandora’s Cluster.
4
Map of the galaxies of Pandora’s Cluster
IMAGE: Dan Coe (STScI)
The Pandora’s Cluster galaxies, isolated: This image shows only the galaxies that are part of Pandora’s
Cluster. Compare this to the image on page 4 to help identify possible lensed galaxies in that image.
5
Continued from page 3…
The frontiers of the universe
will turn into galaxies like our
Milky Way. The galaxies found in
previous deep-field surveys have
been the brightest, most massive
galaxies in the early universe. For
a more complete picture of galaxy
development, astronomers must
study the average and smaller-mass
galaxies, too. Many of these galaxies
will be prime candidates for JWST to
study in detail.
The Frontier Fields census will last
three years and will observe six
galaxy clusters. Hubble astronomers
will use the visible-light capabilities
of ACS and the infrared-light power
of WFC3. NASA’s other Great
Observatories, the Spitzer Space
Telescope, an infrared observatory,
and the Chandra X-ray Observatory
also will take part in this ambitious
study. Astronomers will use both
Hubble and Spitzer, for example,
to obtain more accurate distances
to the galaxies than they would get
from just one telescope.
Besides hunting for some of the
most distant galaxies ever seen,
astronomers also want to build up
the number and statistics of faraway
galaxies found in Hubble’s other
deep fields. While observing each
cluster, Hubble will simultaneously
Continued, page 7…
Faraway
galaxy
Ligh
Light rays
are bent
and focus
near Earth
t ray
s
A galaxy cluster
can act like a
giant lens in space
A magnifying glass is simply
a glass lens that gathers and
magnifies light. As illustrated
at left, a giant glass lens in
space could collect the light
from a distant galaxy and focus
those light rays toward Earth.
Astronomers would see that the
galaxy is bigger and brighter than
it would be without the lens.
Hypothetical
glass lens in
space
Hubble Space Telescope
image includes magnified
image of faraway galaxy
Nature’s magnifying glass:
Fortunately, nature provides its
own intergalactic magnifying glass
in large clusters of galaxies. The
combined gravity of such galaxy
clusters (at left, Pandora’s Cluster is
shown) bends light in the same way
that a glass lens does. Astronomers
can use these galaxy clusters
as “gravitational lenses” to see
fainter, smaller, and more distant
galaxies than otherwise possible.
Faraway
galaxy
Pandora’s
Cluster bends
light from the
faraway galaxy
GRAPHIC: STScI Graphics Dept.
6
URSA MINOR
URS
CAMELOPARDALIS
CEPHEUS
+60°
Polaris
Where is Pandora’s Cluster?
+80
°
Continued from
page
6…
image a nearby patch of sky. These
LYRA
observations,+40called
parallel
°
CYGNUS fields,
will be new deep fields that will
+20° PEGASUS
greatly increase
our sample of
AQUILA
distant galaxies
and
provide
new
0°
AQUARIUS
directions on the sky in which to
-20°
CAPRICORNUS
cross-check previous
results.
SERPENS
The Hubble image of Pandora’s
Cluster uses new WFC3 observations
in infrared light combined with
previously taken visible-light data. It
represents the deepest-ever picture
taken of a cluster of galaxies. The
stunning view is peppered with
some of the faintest and most
distant galaxies ever detected. Some
galaxies appear as they looked more
than 12 billion years ago, not long
after the birth of our universe in the
big bang. The magnified galaxies can
appear up to 20 times larger than
they would normally be seen. The
Hubble image of the nearby parallel
field, taken in visible light with ACS,
uncovers roughly 7,000 galaxies
scattered across space and time.
Continued, page 8…
ORION
TAURUS
ARIES
PEGASUS
PISCES
SERPE
OPHIUCHUS
Sirius
-20°
HYDRA
SCORPIUS
LIBR
ERIDANUS
CANIS
MAJOR
ANTLIA
-40°
SCULPTOR
VELA
SCORPIUS
PHOENIX
PUPPIS
GRUS
HOROLOGIUM
h
CAPRICORNUS
SAGITTARIUS
FORNAX
CENTAURUS
LUPUS
-10°
-10
° 14
AQUILA
AQUARIUS
CETUS
VIRGO
16h
B
LYRA
CYGNUS
HERCULES
CANCER
LIBRA
12h
10 h
8h
12h
10h
8h
1h
6h
4h
2h
6h
4h
2h
L
0h
22h
20h
18h
0h
22h
20h
18h
0h
16h
CETUS
AQUARIUS
DECLINATION (Degrees)
First look at distant galaxies
ANDROMEDA
0°
OPHIUCHUS
SAGITTARIUS
PERSEUS
AURIGA
LEO
DRACO
LYNX
GEMINI
+20°
SCULPTOR
These new images represent only
one-twelfth of the data that the
Frontier Fields will eventually
provide. The telescope will return
to these two fields in May 2014,
URSA MAJOR
BOOTES
+40°
HERCULES
°
The Frontier -40
Fields
project,
GRUS
therefore, consists
of 12 fields,
-60°
one of each of the six clusters and
-80°
one of each parallel
field. The first
24h
22h
20h
18h
observations began in late 2013. A
preliminary image of the first cluster,
called Pandora’s Cluster, along
with an image of its accompanying
parallel field, was unveiled in
January 2014 at the American
Astronomical Society meeting in
Washington, D.C.
CEPHEUS
CASSIOPEIA
DRACO
-20°
-20
°
SCULPTOR
Fomalhaut
-30°
-30
°
Site of Pandora’s Cluster and
parallel field observations
FORNAX
-40°
-40
°
GRUS
PHOENIX
22 h
h
11hh
00hh
RIGHT ASCENSION (Hours)
23h
23
h
Pandora’s Cluster lies within the Southern Hemisphere constellation Sculptor, shown
above. Sculptor is a small and faint constellation that’s difficult to find, even in very dark
skies. Near the bright star Fomalhaut, five dim stars form the shape of a cane. Pandora’s
Cluster is near the middle star in the cane’s shaft, below the cane’s hook.
In the star charts above, constellations and stars are located using a coordinate system that’s
similar to the latitude and longitude system on Earth. Earth’s equator is stretched outward
onto the sky to create the celestial equator (at 0 degrees). “Declination” measures the distance
(in degrees, from 0 to 90) north or south of the celestial equator, just as latitude measures
distance north or south of Earth’s equator (also in degrees, from 0 to 90). Stars and other
objects that are south of the celestial equator have negative numbers for their declinations and
can be seen from the Southern Hemisphere on Earth.
“Right ascension” is like longitude, measuring distance east or west from a chosen reference
point. Instead of degrees, though, right ascension is measured in hours, from 0 to 24 hours,
just like hours in the day.
SOURCES: Frontier Field location: STScI; All-sky star chart: J. Cornmell and
IAU; Enlarged constellation map: International Astronomical Union (IAU)
GRAPHIC:
STScI Graphics Dept.
7
Continued from page 7…
but this time observing the galaxy
cluster with ACS and the parallel
field with WFC3. The combined
deep image in visible and infrared
light, the diversity of fields
under study, and the immediate
availability of the data to the entire
astronomical community make this
program one of the most important
Hubble has ever undertaken. What
new discoveries will Frontier Fields
reveal? Stay tuned for updates.
Pandora’s Cluster and its
“parallel field” observation
Pandora’s
Cluster
Parallel field
observation
GRAPHIC: STScI Graphics Dept.
New deep-field observations: The Frontier Fields project consists of 12 images,
one of each of the six galaxy clusters that can be used as natural “lenses”
and one nearby patch of sky — called a “parallel field” — for each cluster. The
parallel fields will be new deep-field observations that will greatly increase the
number of distant galaxies astronomers have observed.
SEE MORE Hubble images and read more
Star Witness news stories at Amazing Space,
NASA’s award-winning educational website for
K­­­–12 students and teachers.
http://amazing-space.stsci.edu
www.nasa.gov