archive: SETI NATURAL LENSES IN SPACE STRETCH HUBBLE'S VIEW OF THE UNIVERSE

SETI NATURAL LENSES IN SPACE STRETCH HUBBLE'S VIEW OF THE UNIVERSE

Larry Klaes ( lklaes@bbn.com )
Thu, 13 May 1999 16:55:56 -0400

>Date: Wed, 12 May 1999 15:40:28 -0400
>From: HST News Release <hst-news@stsci.edu>
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>To: pio@stsci.edu
>Subject: NATURAL LENSES IN SPACE STRETCH HUBBLE'S VIEW OF THE UNIVERSE
(STScI-PR99-18)
>Sender: owner-pio@stsci.edu
>
>EMBARGOED UNTIL: 9:00 A.M. (EDT) May 13, 1999
>
>CONTACT: Ray Villard
> Space Telescope Science Institute, Baltimore, MD
> (Phone: 410-338-4514)
> (E-mail: villard@stsci.edu)
>
> Kavan Ratnatunga
> Carnegie Mellon University, Pittsburgh, PA
> (Phone: 412-268-1888)
> (E-mail: kavan@astro.phys.cmu.edu)
>
>PRESS RELEASE NO.: STScI-PR99-18
>
>NATURAL LENSES IN SPACE STRETCH HUBBLE'S VIEW OF THE UNIVERSE
>
>The NASA Hubble Space Telescope serendipitous survey of the sky has
>uncovered exotic patterns, rings, arcs and crosses that are all optical
>mirages produced by a gravitational lens, nature's equivalent of having
>giant magnifying glass in space.
>
>A gravitational lens is created when the gravity of a massive
>foreground object, such as a galaxy or black hole, bends the light
>coming from a far more distant galaxy directly behind it. This focuses
>the light to give multiple or distorted images of the background object
>as seen by the observer.
>
>A quick look at over 500 Hubble fields of sky has uncovered 10
>interesting lens candidates in the deepest 100 fields. This is a
>significant increase in the number of known optical gravitational
>lenses. Hubble's sensitivity and high resolution allow it to see faint
>and distant lenses that cannot be detected with ground-based telescopes
>whose images are blurred by Earth's atmosphere. An analysis of this "Top
>
>Ten" list of Hubble gravitational lenses is published by Kavan
>Ratnatunga and Richard Griffiths of Carnegie Mellon University in the
>May issue of the Astronomical Journal.
>
>The amount of gravitational lensing in the universe depends strongly on
>the cosmological constant, a hypothesized repulsive force that
>indicates the universe is older and larger than without this force.
>Therefore a large cosmological constant implies a larger number of more
>distant objects whose light can, by chance, pass close to a massive
>galaxy on its way to Earth and appear lensed.
>
>The 100 Hubble fields cover a total area equal to that of the full
>Moon. Hubble's ability to see so many of these lenses in a small
>fraction of the sky takes them from being a scientific curiosity to
>serving as a potentially powerful tool for probing the universe's
>evolution and expansion.
>
>"In fact, these much more distant gravitational lenses are potentially
>more valuable to derive fundamental cosmological parameters than
>relatively closer lenses discovered from ground-based observations,"
>says Ratnatunga. "Follow-up spectroscopic observations are now needed to
>
>verify that the object is far more distant than the lensing galaxy seen
>at the center, as well as to derive better distance estimates to confirm
>
>that multiple images really belong to the same object. These are however
>
>very difficult observations even for the largest ground-based
>telescopes."
>
>The Hubble images in which these lenses were discovered are part of the
>Medium Deep Survey database. The survey catalog contains over 200,000
>objects, mostly faint galaxies. The public can search the catalog at
>http://www.stsci.edu/mds/ and study the myriad of never-before-seen
>galaxies from this huge Hubble database on their own home computer.
>Users can call up one of 500 survey fields and mouse-click on any galaxy
>
>image to see a full resolution view of the galaxy and estimates of its
>shape and brightness. Visitors can even look for patterns that may be
>caused by a gravitational lens. Hubble astronomers expect that there
>could be a few hundred more lenses which are more difficult to identify
>confidently in these images.
>
>In 1936 Albert Einstein computed the gravitational deflection of light
>by massive objects and showed that an image can be highly magnified if
>the observer, source and the lensing object are well aligned. However,
>the lensed image separations were predicted to be so small in angular
>size, Einstein knew they were beyond the capabilities of ground-based
>optical telescopes. This made him remark that "there is no great
>chance of observing this phenomenon."
>
>It wasn't for another 40 years since Einstein's conclusion that the
>first gravitational lens was discovered in 1979. Several bright and
>nearby lenses have been discovered since then from ground-based
>observations.
>
>Further lens discoveries required Hubble's high resolution Wide Field
>Planetary Camera 2 (WFPC2) which allows the search extended to much
>fainter and farther objects. It is expected that the Advanced Camera for
>
>Surveys, to be installed on Hubble in the year 2000, will be able to
>discover many more gravitational lenses because of its sensitivity and
>relatively wide-angle coverage.
>
>The Space Telescope Science Institute is operated by the Association
>of Universities for Research in Astronomy, Inc. for NASA, under
>contract with NASA's Goddard Space Flight Center, Greenbelt, MD.
>The Hubble Space Telescope is a project of international cooperation
>between NASA and the European Space Agency.
>
>-end-
>
>NOTE TO EDITORS: Image files and a photo caption associated with this
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>Higher resolution digital versions (300 dpi JPEG and TIFF) of the
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>**************
>
>PHOTO CAPTION
>
>EMBARGOED UNTIL: 9:00 A.M. (EDT) May 13, 1999
>
>PHOTO NO.: STScI-PRC99-18
>
>
>HUBBLE'S TOP TEN GRAVITATIONAL LENSES
>
>The NASA Hubble Space Telescope serendipitous survey of the sky has
>uncovered exotic patterns, rings, arcs and crosses that are all optical
>mirages produced by a gravitational lens, nature's equivalent of having
>giant magnifying glass in space.
>
>Shown are the top 10 lens candidates uncovered in the deepest 100 Hubble
>
>fields. Hubble's sensitivity and high resolution allow it to see faint
>and distant lenses that cannot be detected with ground-based telescopes
>whose images are blurred by Earth's atmosphere.
>
>[Top Left] - HST 01248+0351 is a lensed pair on either side of the
>edge-on disk lensing galaxy.
>
>[Top Center] - HST 01247+0352 is another pair of bluer lensed source
>images around the red spherical elliptical lensing galaxy. Two much
>fainter images can be seen near the detection limit which might make
>this a quadruple system.
>
>[Top Right] - HST 15433+5352 is a very good lens candidate with a bluer
>lensed source in the form of an extended arc about the redder elliptical
>
>lensing galaxy.
>
>[Middle Far Left] - HST 16302+8230 could be an "Einstein ring" and the
>most intriguing lens candidate. It has been nicknamed the "the London
>Underground" since it resembles that logo.
>
>[Middle Near Left] - HST 14176+5226 is the first, and brightest lens
>system discovered in 1995 with the Hubble telescope. This lens
>candidate has now been confirmed spectroscopically using large
>ground-based telescopes. The elliptical lensing galaxy is located 7
>billion light-years away, and the lensed quasar is about 11 billion
>light-years distant.
>
>[Middle Near Right] - HST 12531-2914 is the second quadruple lens
>candidate discovered with Hubble. It is similar to the first, but
>appears smaller and fainter.
>
>[Middle Far Right] - HST 14164+5215 is a pair of bluish lensed images
>symmetrically placed around a brighter, redder galaxy.
>
>[Bottom Left] - HST 16309+8230 is an edge-on disk-like galaxy (blue arc)
>
>which has been significantly distorted by the redder lensing elliptical
>galaxy.
>
>[Bottom Center] - HST 12368+6212 is a blue arc in the Hubble Deep Field
>(HDF).
>
>[Bottom Right] - HST 18078+4600 is a blue arc caused by the
>gravitational potential of a small group of 4 galaxies.
>
>Credit: Kavan Ratnatunga (Carnegie Mellon Univ.) and NASA
>
>