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A New Year's Gift from NASA and Penn State

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02 January 2013 —

camera-icon-small Check out the complete image gallery here.

Omega Centauri shown in ultraviolet light (left) and visible light (right).

One of the first targets for the Swift observatory's stellar survey was the giant cluster Omega Centauri, which hosts millions of stars and may be the remains of a small galaxy. Omega Centauri (also known as NGC 5139) is the largest, brightest and most massive of our galaxy's 150 or so globular star clusters. Packing some 10 million stars into a region just 150 light-years across, Omega Centauri is easily visible to the unaided eye despite lying nearly 16,000 light-years away. Unlike other star clusters, whose members all have similar age and chemical makeup, Omega Centauri displays a wide range of age and chemistry, from the ancient (12 billion years) to the relatively recent. This presence of different stellar populations suggests that Omega Centauri is not, in fact, a globular cluster, but the remnant core of a dwarf galaxy torn to shreds by the Milky Way's gravity. The false-color ultraviolet composite from images taken through Swift UVOT's ultraviolet filters reveals a treasure trove of rare stars in various stages of demise.

  • Credit for image on left: NASA/Swift/S. Holland (GSFC), M. Siegel and E. Fonseca (PSU)
  • Credit for image on right: A. Grado/INAF-Capodimonte Observatory. Captured by the VST ESO/INAF-VST/OmegaCAM.

A large new collection of space photos taken at wavelengths that are invisible to the human eye and blocked by Earth's atmosphere has been released as a New Year's gift to the people of Earth by NASA and Penn State University. The images were captured by a telescope on board NASA's Swift satellite, whose science and flight operations are controlled by Penn State from the Mission Operations Center in State College, Pennsylvania, using the Ultraviolet/Optical Telescope, which resulted from Penn State's collaboration with the Mullard Space Science Laboratory of the University College-London. The telescope is one of just a few that study ultraviolet light, much of which is blocked by the atmosphere surrounding Earth.

"This extensive image gallery has some of the best pictures ever taken by this telescope, including some very early images that have not been published until now," said Michael Siegel, a Penn State research associate in astronomy and astrophysics who is the lead scientist for the Ultraviolet/Optical Telescope. The image gallery is online, and it also can be viewed with the free Swift Explorer Mission iPhone app developed by Penn State.

Composite showing spiral galaxy in optical, uv, and x-ray light.

NGC 7331 is a luminous edge-on spiral galaxy about 45 million light-years away in the constellation Pegasus. If we could view our own Milky Way galaxy from the outside, it might look very similar to this NGC 7331 galaxy. At left and center, respectively, are Swift images captured through the Ultraviolet/Optical Telescope's optical and ultraviolet filters. The panel at right shows X-ray observations (0.2-10 keV) from Swift's X-ray Telescope. Credit: NASA/Swift/S. Immler

The image gallery includes images from Siegel's study of the Omega Centauri star cluster, Penn State Research Associate Erik Hoversten's studies of galaxies near to our Milky Way Galaxy, and NASA Astronomer Stefan Immler's work on the early images captured by the Swift observatory. "We intend to keep updating the gallery about once a month with new images from Swift as well as an interesting collection of images that document stages in Swift's preparation for launch into space," Siegel said. "We also plan to continue adding spectacular images from several new long-term studies of the Small Magellanic Cloud and the Large Magellanic Cloud."

In addition to Siegel and Hoverstein, other current and former Penn State members of the image-gallery team include Undergraduate Students Joshua Berrier, Emmanuel Fonseca, and Blair Porterfield; Research Assistant Michael Stroh; and Research Associate Jamie Kennea.

The Ultraviolet/Optical Telescope (UVOT) is the only one of the three telescopes on Swift that captures cosmic light at energies at and just beyond those that can be seen by the human eye. It plays a critical role in rapidly pinpointing the locations of gamma-ray bursts (GRBs), the brightest explosions in the universe. Swift has detected an average of about 90 GRBs a year since its launch in 2004. "When we are not studying GRBs, we use the satellite's unique capabilities to engage in other scientific investigations, some of which produce these beautiful images from the UVOT that we're now delighted to be able to share with the public," Siegel said. The targets for these studies range from comets and star clusters to supernova remnants, nearby galaxies, and active galaxies powered by supermassive black holes.

Click on image for larger view, or click here for an unlabeled version of this image.

Cloud-like blob against starry background

The Crab Nebula is the wreckage of an exploded star, or supernova, observed in the year 1054. The expanding cloud of gas is located 6,500 light-years away in the constellation Taurus. This composite of three Swift UVOT ultraviolet images highlights the luminous hot gas in the supernova remnant. The image is constructed from exposures using these filters: uvw1, centered at 2,600 angstroms (shown as red); uvm2, centered at 2,246 angstroms (green); and uvw2, centered at 1,928 angstroms (blue).
Credit: NASA/Swift/E. Hoversten, Penn State.

"One of our more challenging projects was completing an ultraviolet mosaic of M31, the famous Andromeda galaxy," said Stefan Immler, a member of the Swift team at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Because the galaxy is so much larger than the UVOT's field of view, we had to take dozens of pictures and blend them together to show the whole object."

Because most ultraviolet light never reaches the ground, Swift's Ultraviolet/Optical Telescope provides a unique perspective on the cosmos. For example, it can measure the amount of water produced in passing comets by detecting the ultraviolet emission of hydroxyl (OH), one of the molecular fragments created when ultraviolet sunlight breaks up water molecules. Other types of science with the telescope include exploring emissions from the centers of active galaxies, studying regions undergoing star formation, and identifying some of the rarest and most exotic stars known.

With Swift's Ultraviolet/Optical Telescope, astronomers at NASA's Goddard Space Flight Center and Penn State have cataloged hundreds of rare types of stars and are now comparing their observations with theoretical models in order to advance the understanding of how stars evolve. "The Swift Ultraviolet/Optical Telescope's capabilities give us a great tool for cataloging rare types of ultraviolet-bright stars and for surveying stellar populations throughout the universe," Siegel said.

[ Francis Reddy / Barbara K. Kennedy ]



The UVOT's wavelength range is 1,700 to 6,000 angstroms. The 6.5-foot-long (2-meter) UVOT is centered on an 11.8-inch (30 cm) primary mirror. Designed and built by the Mullard Space Science Laboratory in Surrey, England, the telescope module includes the primary and secondary mirrors, an external baffle to reduce scattered light, two redundant detectors -- only one has been used to date -- and a power supply.

Each detector lies behind an identical filter wheel. The wheel holds color filters that transmit a broad range of wavelengths as well as devices called grisms, which spread out incoming light in much the same way as a prism spreads sunlight into a rainbow of component colors. The detectors retain information on the position and arrival time of each photon of light, an operating mode similar to typical X-ray telescopes.


The Swift observatory was launched in November 2004 and was fully operational by January 2005. Swift carries three main instruments: the Burst Alert Telescope, the X-ray Telescope, and the Ultraviolet/Optical Telescope.  Its science and flight operations are controlled by Penn State from the Mission Operations Center in State College, Pennsylvania. Swift's gamma-ray detector, the Burst Alert Telescope, provides the rapid initial location and was built primarily by the NASA Goddard Space Flight Center in Greenbelt, Maryland, and Los Alamos National Laboratory in New Mexico and constructed at GSFC. Swift's X-Ray Telescope and UV/Optical Telescope were developed and built by international teams led by Penn State and drew heavily on each institution's experience with previous space missions. The X-ray Telescope resulted from Penn State's collaboration with the University of Leicester in the United Kingdom and the Brera Astronomical Observatory in Italy. The Ultraviolet/Optical Telescope resulted from Penn State's collaboration with the Mullard Space Science Laboratory of the University College-London. These three telescopes give Swift the ability to do almost immediate follow-up observations of most gamma-ray bursts because Swift can rotate so quickly to point toward the source of the gamma-ray signal. The spacecraft was built by Spectrum Astro, which became part of General Dynamics and then part of Orbital Sciences Corporation.

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