| RESEARCH
AREA |
PRE-HST
KNOWLEDGE
(circa 1990) |
HST
CONTRIBUTION
(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. |
