Washington: NASA’s Swift satellite team is celebrating eight years of Ultraviolet/Optical Telescope (UVOT) operations by collecting more than 100 of the instrument’s best snapshots in a web-based photo gallery.
The images also can be viewed with the free Swift Explorer Mission iPhone app developed by the Swift Mission Operations Center (MOC), which is located in State College, Pa., and operated by Penn State.
Of the three telescopes carried by Swift, only one captures cosmic light at energies similar to those seen by the human eye.
Although small by the standards of ground-based observatories, Swift’s UVOT plays a critical role in rapidly pinpointing the locations of gamma-ray bursts (GRBs), the brightest explosions in the cosmos.
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).
Swift has detected an average of about 90 GRBs a year since its launch in 2004.
“When we aren’t studying GRBs, we use the satellite’s unique capabilities to engage in other scientific investigations, some of which produce beautiful images from the UVOT that we’re delighted to be able to share with the public,” Michael Siegel, lead scientist on the UVOT and a research associate in astronomy and astrophysics at the MOC, said.
The targets range from comets and star clusters to supernova remnants, nearby galaxies and active galaxies powered by supermassive black holes.
An ongoing mosaic project targets the Large and Small Magellanic Clouds, two small satellite galaxies orbiting our own, and makes the Andromeda effort look like child’s play.
Although the galaxies are much smaller than M31, they are both much closer to us and extend over much larger areas of the sky. The task involves acquiring and aligning hundreds of images and is far from complete.
With the UVOT’s wavelength range of 1,700 to 6,000 angstroms, Swift remains one of few missions that study ultraviolet light, much of which is blocked by Earth’s atmosphere.
Omega Centauri is the largest, brightest and most massive of our galaxy’s retinue of 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.
The 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-colour ultraviolet composite from Swift UVOT’s uvw1, uvm2 and uvw2 filters reveals a treasure trove of rare stars in various stages of demise.
The 6.5-foot-long UVOT is centred 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 colour 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 colours.
The detectors retain information on the position and arrival time of each photon of light, an operating mode similar to typical X-ray telescopes.
Since most ultraviolet light never reaches the ground, Swift’s UVOT provides a unique perspective on the cosmos.