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1 - Galaxy Evolution Explorer

artist's concept of Galaxy Evolution Explorer

Image Caption:
Galaxy Evolution Explorer
The Galaxy Evolution Explorer was launched on April 28, 2003. Its mission is to study the shape, brightness, size and distance of galaxies across 10 billion years of cosmic history. The 50-centimeter-diameter (19.7-inch) telescope onboard the Galaxy Evolution Explorer sweeps the skies in search of ultraviolet-light sources.

Ultraviolet is light from the higher end of the electromagnetic spectrum, just above visible light in frequency, but below X-rays and gamma rays. While a small amount of ultraviolet penetrates Earth's atmosphere, causing sunburn, the Galaxy Evolution Explorer observes those ultraviolet frequencies that can only be seen from space.

The Galaxy Evolution Explorer mission is led by the California Institute of Technology, Pasadena, Calif., which is also responsible for science operations and data analysis. NASA's Jet Propulsion Laboratory, Pasadena, Calif., a division of Caltech, manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program, managed by the Goddard Space Flight Center, Greenbelt, Md. South Korea and France are the international partners in the mission.

Image credit: NASA/JPL-Caltech
+ Hi-res Image (600 KB)


2 - Baby Galaxies in the Adult Universe

timeline of the universe illustrating galaxy formation

Image Caption:
Baby Galaxies in the Adult Universe
This artist's conception illustrates the decline in our universe's "birth-rate" over time. When the universe was young, massive galaxies were forming regularly, like baby bees in a bustling hive. In time, the universe bore fewer and fewer "offspring," and newborn galaxies (white circles) matured into older ones more like our own Milky Way (spirals).

Previously, astronomers thought that the universe had ceased to give rise to massive, young galaxies, but findings from NASA's Galaxy Evolution Explorer suggest that may not be the case. Surveying thousands of nearby galaxies with its highly sensitive ultraviolet eyes, the telescope spotted three dozen that greatly resemble youthful galaxies from billions of years ago. In this illustration, those galaxies are represented as white circles on the right, or "today" side of the timeline.

The discovery not only suggests that our universe may still be alive with youth, but also offers astronomers their first close-up look at what appear to be baby galaxies. Prior to the new result, astronomers had to peer about 11 billion light-years into the distant universe to see newborn galaxies. The newfound galaxies are only about 2 to 4 billion light-years away.

Image credit: NASA/JPL-Caltech
+ Hi-res Image (2.8 MB)


3 - Nearby Newborns

images of nearby newborn galaxies

Image Caption:
Nearby Newborns
This image shows six of the three-dozen "ultraviolet luminous galaxies" spotted in our corner of the universe by NASA's Galaxy Evolution Explorer. These massive galaxies greatly resemble newborn galaxies that were common in the early universe. The discovery came as a surprise, because astronomers had thought that the universe's "birth-rate" had declined, and that massive galaxies were no longer forming.

The galaxies, located in the center of each panel, were discovered after the Galaxy Evolution Explorer scanned a large portion of the sky with its highly sensitive ultraviolet-light detectors. Because young stars pack most of their light into ultraviolet wavelengths, young galaxies appear to the Galaxy Evolution Explorer like diamonds in a field of stones. Astronomers mined for these rare "gems" before, but missed them because they weren't able to examine a large enough slice of the sky. The Galaxy Evolution Explorer surveyed thousands of nearby galaxies before finding three-dozen newborns.

While still relatively close in astronomical terms, these galaxies are far enough away to appear small to the Galaxy Evolution Explorer. Clockwise beginning from the upper left, they are called: GALEX_J232539.24+004507.1, GALEX_J231812.98-004126.1, GALEX_J015028.39+130858.5, GALEX_J021348.52+125951.3, GALEX_J143417.15+020742.5, GALEX_J020354.02-092452.5.

Image credit: NASA/JPL-Caltech/Johns Hopkins
+ Hi-res Image (1.3 MB)


4 - Animation: Fires of Galactic Youth

still from animation showing newborn galaxies

Image Caption:
Animation: Fires of Galactic Youth
This animation shows a typical young galaxy, teeming with hot, newborn stars and exploding supernovas. The supernovas are seen as white flashes of light.

NASA's Galaxy Evolution Explorer spotted three-dozen young galaxies like the one shown here in our corner of the universe. It was able to see them with the help of its highly sensitive ultraviolet detectors. Because newborn stars radiate ultraviolet light, young galaxies light up brilliantly when viewed in ultraviolet wavelengths. The findings came as a surprise, because astronomers had thought that the universe's "birth-rate" had declined, and that massive galaxies were no longer forming.

Image credit: NASA/JPL-Caltech
+ Animation (3.6 MB)
+ Hi-res Image (1.3 MB)


5 - A Galaxy in Different Lights

galaxy M81, visual and ultraviolet

Image Caption:
A Galaxy in Different Lights
This side-by-side comparison shows the nearby galaxy Messier 81, which is similar to our own Milky Way, in both visible (left) and ultraviolet light (right). While visible-light images of galaxies reveal the distribution of stars, ultraviolet-light images highlight the most active, young stars. The ultraviolet image of Messier 81 shows that the galaxy's spiral arms are dotted with pockets of violent star-forming activity.

NASA's Galaxy Evolution Explorer is sweeping the entire sky in ultraviolet wavelengths, mapping galaxies and their star-formation rates across 10 billion years of cosmic time.

The visible-light image is from the National Optical Astronomy Observatory. The ultraviolet-light image was taken by the Galaxy Evolution Explorer.

Image credit: NASA/JPL-Caltech/NOAO
+ Hi-res Image (7 MB)


6 - Animation: How to Spot a Young Galaxy

still from animation, showing views of uv and visible light

Image Caption:
Animation: How to Spot a Young Galaxy
This animation demonstrates that young galaxies are best viewed in ultraviolet light. It consists of artist conceptions of a typical mature galaxy like our own Milky Way (left) and a typical young galaxy (right). The movie begins by showing the pair in visible light, then transitions into ultraviolet views. While young and old galaxies look equally bright when viewed in visible wavelengths, young galaxies are glaringly bright compared to older galaxies in ultraviolet wavelengths. In the final ultraviolet view, the brightness levels have been dimmed to highlight features of the young galaxy.

Young galaxies light up in the ultraviolet because they are filled with hot, newborn stars objects that pack most of their light into ultraviolet wavelengths. Older galaxies have less star-forming activity and thus give off less ultraviolet light. Both young and old stars radiate visible light, so young and old galaxies look similar when viewed in this wavelength.

NASA's Galaxy Evolution Explorer, with its highly sensitive ultraviolet detectors, spotted what appear to be three-dozen massive young galaxies in our corner of the universe. The findings came as a surprise, because astronomers had thought that the universe's "birth-rate" had declined, and that massive galaxies were no longer forming.

The artist concepts of the mature galaxy are based on images of the nearby galaxy called Messier 81. The artist concepts of the young galaxy are based on images of the Bearclaw Galaxy.

Image credit: NASA/JPL-Caltech
+ Animation - with text (3.6 MB)
+ Animation - without text (3.6 MB)
+ Hi-res Image - with text (900 KB)
+ Hi-res Image - without text (900 KB)


7 - Field of View

graphic showing spacecraft's field of view

Image Caption:
Field of View
The Galaxy Evolution Explorer specializes in surveying galaxies in ultraviolet light. Its telescope, 50 centimeters (19.7 inches) in diameter, has a field of view that is much wider than most ground-based and space-based telescopes. This field of view, nearly three times the diameter of the Moon, allowed the Galaxy Evolution Explorer to discover seemingly newborn galaxies in our local universe. The telescope surveyed thousands of galaxies before finding three-dozen of these newborns.

Image credit: NASA/JPL-Caltech
+ Hi-res Image (5 MB)


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