Johns Hopkins Gazette: March 20, 1995

HUT Mission "Absolutely Spectacular"

By Emil Venere

     The space shuttle Endeavour and Hopkins astronaut Sam
Durrance were scheduled to return to Earth over the weekend,
ending a historic astronomy mission that enabled scientists to
gather an unprecedented wealth of information about the universe.

     "From my point of view this mission has been nothing short
of absolutely spectacular," Arthur Davidsen, leader of the
Hopkins Ultraviolet Telescope project, said during a news
conference last week at the Marshall Space Flight Center in
Huntsville, Ala. "We feel that we are likely to uncover some
tremendous new secrets of the universe through these

     Scientists plan to begin analyzing the treasure of data this
week, but they collected enough information to stay busy for
years. HUT was one of three ultraviolet telescopes in the Astro-2
observatory, which orbited the Earth for 15 and a half days, the
longest space shuttle mission. It was a followup to the nine-day
Astro-1 mission, on the shuttle Columbia in 1990.

     Astrophysicists could not have asked for a better mission.
Not only did the observatory perform without a hitch, but
scientists were treated to a series of cosmic coincidences that
made the mission even more productive.

    Shortly after Endeavour's launch, a major volcanic eruption
started on Jupiter's moon Io--perfect timing for the HUT team to
study how the giant planet's atmosphere is affected by volcanic
material from Io.

    Astronomers were stunned when they learned that a special
type of galaxy that varies in brightness apparently was peaking
at the ideal time for HUT astronomers, giving researchers
extremely sharp spectrographic data.

    Soon they found themselves marveling at yet another instance
of uncanny timing. An object called a cataclysmic variable was on
the verge of going into a period of "outburst," when the objects
increase dramatically in brightness. By comparing the data with
information from Astro-1, scientists discovered that the object
is dramatically cooler before outburst than it is right after an

    The Hopkins astronomers made history again later in the
week, using HUT and the Hubble Space Telescope to simultaneously
observe Jupiter. Hubble produced ultraviolet images, and HUT
collected precise spectrographic data of the same region of the
Jovian aurorae, similar to the Earth's Northern and Southern
Lights. The timely volcanic eruption and last summer's collision
of a comet with Jupiter heightened interest in those

     But the most dramatic achievement of all was a string of
unprecedented observations of two objects called quasars, located
near the edge of the observable universe.

     "Whatever information we can provide will be extremely
valuable to the understanding of cosmology and the history of the
universe," said Dr. Davidsen, a professor in the Department of
Physics and Astronomy.

     It was the culmination of his goal, conceived 17 years ago,
to use a spectrograph in space to measure a range of light called
the far ultraviolet spectrum, complementing the Hubble Space
Telescope, which can observe a different portion of the spectrum.

     HUT's highest calling was to help scientists answer a
fundamental question of cosmology: was an "intergalactic medium"
of hydrogen and helium created in the Big Bang of cosmic

     As light from the quasars shines through the void of
intergalactic space, it should be absorbed by the intergalactic
gas, producing a distinct spectrographic signature. 

     Dr. Davidsen said the HUT team had collected so much
good-quality data that astrophysicists will be able to make a
serious attempt at solving the cosmic riddle.

     "It's too early to tell what the answer will be exactly," he
said. "But either way, it's going to be very interesting. The
data are just spectacular."

     Astronomers plan to use the data to learn details about how
the universe mysteriously evolved from its original state of
smoothly distributed matter to its present clumpy condition in
which clusters of galaxies are distributed unevenly. Although the
well-accepted Big Bang theory suggests that the primordial medium
of hydrogen and helium should exist, its existence has never been
confirmed, said Dr. Davidsen, who likens the gas to a "missing
link" in the chain of events leading up to the present-day

     Scientists said Astro-2 was a definite improvement over the
first Astro mission. Although the pioneering mission was
successful, it was troubled by computer glitches and problems
with a system used to point the observatory.

     "We eventually accomplished some considerable success with
Astro-1, but this Astro-2 mission is really in another category
altogether," he said. "I feel like I'm floating on Cloud 9 now."

Go back to Previous Page

Go to Gazette Homepage