A "serendipitous" survey of the heavens with NASA's Hubble Space Telescope (HST) is uncovering remote and unusual galaxies never before resolved by optical telescopes on Earth. HST reveals an unusual variety of shape and structure in these distant galaxies, which previously appeared as fuzzy blobs in ground-based sky surveys. These tantalizing early results may lead to a much clearer understanding of the formation and evolution of galaxies.
These results are being reported by Dr. Richard Griffiths of the Space Telescope Science Institute, Baltimore, Maryland at the international workshop, Science with the Hubble Space Telescope, being held in Sardinia, Italy.
Some of the remote galaxies, estimated to be between three and ten billion light-years away, do not have the familiar spiral and elliptical shapes which are characteristic of galaxies in the nearby universe. One cosmological model is that galaxies in the early universe interact dynamically and grow bigger by cannibalizing smaller regions of star formation. If so the objects resolved by HST may be "building blocks" for today's large galaxies. "We have seen several examples of what appear to be interacting or merging galaxies," says STScI astronomer Dr. Richard Griffiths, the principal investigator on this long-term HST key project.
The HST's Medium-Deep "Parallel" survey is carried out using HST's Wide Field Camera, to take pictures in a random field while a "primary" instrument, such as a spectrograph, is performing an observation on a preselected target about one-sixth the moon's diameter away. "By operating two instruments simultaneously the overall efficiency of the telescope is greatly improved," says Griffiths. "During the course of the Survey, several thousand images will be recorded." Pictures are taken in multiple colors including the ultraviolet, visual and infrared, and searched for the unknown and unexpected.
Mission planners at the Space Telescope Science Institute (STScI) developed the techniques necessary to schedule these observations without affecting the HST's primary science projects. The Survey is led at Johns Hopkins University and STScI in collaboration with a dozen astronomers in the United States, the United Kingdom, and one from Serendip.