A Decade of Discovery HubbleSite
Telescope & Science
(circa 1990)
(circa 2000)
Distant galaxies & galaxy evolution Very little known about galaxies beyond a few billion light-years. Deep imaging traces the evolution of galaxies and rate of star formation. Galaxies seen within a billion years of the Big Bang.
Remote supernovae as distance indicators Not possible to discriminate supernova light from light of host galaxy. In collaboration with ground-based telescope surveys HST detects supernovae all the way back to half of universe's age. The results show universe is accelerating.
Universe's rate of expansion Two research groups disagree by a factor of two, this yields estimates for age of universe as between 10 to 20 billion years. Value converges toward 10 percent accuracy, suggesting an age of 12-14 billion years.
Environments around protostars Little known about circumstellar environment. Jet-like features noted, stellar disks seen in infrared wavelengths. Protoplanetary disks are common. Circumstellar disks confine and direct the flow of jets.
Super-massive black holes Ground-based data are suggestive, but telescopes cannot see close enough to suspected black holes to provide absolute proof. HST precisely measures gas velocity around black hole, providing definitive proof. HST surveys reveal that black holes are common to the cores of galaxies.
Quasars Quasars originated early in the universe. Some are surrounded by a "fuzz" which is interpreted as the host galaxy. Quasars are likely powered by black holes. HST clearly resolves a variety of galaxies hosting QSOs. Some are involved in mergers with other galaxies. These collsions fuel the central black hole.
Gravitational lenses A few examples are known. Many small lenses uncovered in medium deep survey. Lenses have potential to contribute to cosmological tests of the curvature of space and age of universe.
Pluto Transits and eclipses of Pluto's moon Charon yield a brightness map of surface. HST confirms earlier map by showing a variegated surface. Images clearly separate planet from its moon, Charon.
Supernova 1987A The nearest supernova in 400 years, and armada of telescopes watch its changes following the February. 1987 explosion. Only HST has the resolution to trace yearly change happening at the sub-light-year scale, including changes in the fireball debris and circumstellar ring of enriched gas.
Galactic bulge structure Only the Milky Way's central bulge and those of nearby galaxies can be viewed in detail. Large bulges formed early in the universe along with elliptical galaxies. Smaller bulges can be "inflated" by ongoing starbirth fueled by disk instabilities or galaxy mergers.

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