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National Aeronautics and Space Administration THESTAR A P U B L I C A T I O N O F N A S A’S WITNESS “A M A Z I N G S P A C E” E D U C A T I O N P R O G R A M 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