Astronomy Picture of the Day 07-10-04

Explanation: Get out your red/blue glasses and gaze across the spectacular, cratered terrain of Saturn's icy moon Phoebe in stereo. The dramatic 3-D perspective spans roughly 50 kilometers and is based on two raw, uncalibrated images (N00004840.jpg and N00004838.jpg) from the Cassini spacecraft's narrow angle camera taken during the flyby on June 11 at a range of just over 13,500 kilometers. Phoebe itself is only about 200 kilometers in diameter. Stereo experimenter Patrick Vantuyne noted the substantial overlap in the raw image data and was able to assemble the dramatic view of the overlapping region as a red/blue stereo anaglyph. Looking for a cool project? Stereo glasses can be easily constructed using red and blue plastic for filters. To view this image, the red filter is used for the left eye.

Visit the links for 2 VERY LARGE raw images of Phoebe's craters.

Free Hubble home software now available
HUBBLE EUROPEAN SPACE AGENCY INFORMATION CENTRE
Posted: July 8, 2004

For many years astronomical images from the world's telescopes were reserved for an elite of astronomers and technical people. Now anyone with a desktop computer running Adobe Photoshop software can try their hand at crafting astronomical images as beautiful as those from the Hubble Space Telescope. A free software plug-in, released today, makes a treasure trove of archival astronomical images and spectra from the NASA/ESA Hubble Space Telescope, the European Southern Observatory's Very Large Telescope, the European Space Agency's XMM-Newton X-ray observatory, NASA's Spitzer Space Telescope and many other famous telescopes accessible to home astronomy enthusiasts.

If there is anything that unites astronomy, it is the worldwide use of a single file format - nearly all the images of stars and galaxies produced by telescopes on the ground and in space are stored as so-called FITS files. Unfortunately this file format has been accessible to very few people other than professional scientists using highly specialised image-processing tools.

Now a new and unique tool - the ESA/ESO/NASA Photoshop FITS Liberator -- developed by imaging scientists at the European Space Agency, the European Southern Observatory and NASA makes the immense wealth of astronomical images and spectra stored in data archives around the world accessible to the layman. The only thing required is access to either Adobe Photoshop or Adobe Photoshop Elements, both leading image software packages.

For the professional creators of astronomical colour images, the plug-in revolutionises the workflow of the creation of colour images from raw data and gives a huge boost to the image quality by giving access to the full 16 bit (65536 colours) range of the observations. In addition the plug in may be used as a powerful educational tool when teaching about light, colour and digital images. Some examples of educational material are available at the web page below.

The ESA/ESO/NASA Photoshop FITS Liberator will be released today and is freely available for download from: http://www.spacetelescope.org/projects/fits_liberator.

Head of the development team, Lars Holm Nielsen from Denmark, says, "FITS is much more than just an image format. It is an extremely flexible file format that allows astronomers to share images and spectra in many different ways. This very versatility has made the job of producing a plug-in for Photoshop challenging. Compared to formats like JPEG, FITS files can be incredibly diverse."

The ESA/ESO/NASA Photoshop FITS Liberator works on Windows PCs and Macs (OS X 10.2+) and is optimised for Photoshop CS, but also works in Photoshop 7.0 (only 15 bit support) and Photoshop Elements 2 (only 8 bit support).

FITS is an abbreviation for Flexible Image Transport System and has been a standard since 1982 and is recognized by the International Astronomical Union.

Chandra looks over a cosmic four-leaf clover
CHANDRA X-RAY CENTER NEWS RELEASE
Posted: July 6, 2004

A careful analysis of observations by NASA's Chandra X-ray Observatory of a rare quadruple quasar has uncovered evidence that possibly a single star in a foreground galaxy magnified X-rays coming from the quasar. This discovery gives astronomers a new and extremely precise probe of the gas flow around the supermassive black hole that powers the quasar.

This is Chandra's X-ray view of the so-called Cloverleaf quasar, a single object whose image has been reproduced four times through an effect known as "gravitational lensing." Credit: NASA/CXC/Penn State/G.Chartas et al

"If our interpretation is correct, then we are seeing details around this black hole that are 50,000 times smaller than either the Hubble Space Telescope or Chandra could see under ordinary circumstances," said George Chartas of Penn State University in University Park, and lead author of a recent article on the Cloverleaf quasar in The Astrophysical Journal.

The Cloverleaf quasar is a single object about 11 billion light years from Earth that appears as four images produced by a process known as gravitational lensing. If one or more galaxies lie along the line of sight to a more distant quasar, the gravitational field of the intervening galaxies can bend and magnify the light from the quasar and produce multiple images of it. The four images of the Cloverleaf quasar have been produced by one or more intervening galaxies.

One of the images (A), in the Cloverleaf is brighter than the others in both optical and X-ray light. Chartas and his colleagues found the relative brightness of this image was greater in X-ray than in optical light. The X-rays from iron atoms were also enhanced relative to X-rays at lower energies. Since the amount of brightening due to gravitational lensing does not vary with the wavelength, this means that an additional object has magnified the X-rays.

The increased magnification of the X-ray light can be explained by gravitational microlensing, an effect which has been used to search for compact stars and planets in our galaxy. Microlensing occurs when a star or a multiple star system passes in front of light from a background object.

X-ray: NASA/CXC/Penn State/G.Chartas et al; Illustration: NASA/CXC/M.Weiss

If a single star or a multiple star system in one of the foreground galaxies passed in front of the light path for the brightest image, then that image would be selectively magnified. The X-rays would be magnified much more than the visible light, if they came from a smaller region around the black hole than the visible light. The enhancement of the X-rays from iron ions would be due to this same effect.

The analysis indicates that the X-rays are coming from a very small region, about the size of the solar system, around the supermassive black hole. The visible light is coming from a region ten or more times larger. The angular size of these regions at a distance of 11 billion light years is tens of thousands times smaller than the smallest region that can be resolved by the Hubble Space Telescope.

"The significance of the detection of microlensed X-rays from the Cloverleaf quasar lies in the extremely small region that is enhanced by the microlens," said Chartas. "This gives us the ability to make strong tests of models for the flow of gas around a supermassive black hole."

Other team members include Michael Eracleous (Penn State), Eric Agol (University of Washington), and Sarah Gallagher (UCLA). NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA's Office of Space Science, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

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