Johns Hopkins Gazette: March 13, 1995

Stars Smile on Astro-2 and HUT Team


By Emil Venere

     A combination of expert planning and lucky timing have made
the Astro-2 observatory a dream come true for Hopkins
astrophysicists.

     "Absolutely fantastic," said Arthur Davidsen, professor in
the Department of Physics and Astronomy, who leads the Hopkins
Ultraviolet Telescope project.

     "Just great," said Gerard Kriss, HUT project scientist.

     "We are getting dynamite stuff," said another Hopkins
astronomer, William Blair. 

     Nobody really expected the orbiting observatory to be this
successful.

     "The gods are with us on this mission; I cannot believe it,"
Dr. Blair added.

     HUT is one of three ultraviolet telescopes in the Astro-2
observatory, now being operated in the space shuttle Endeavour,
which is scheduled to land 2:54 p.m. Friday, March 17, at Kennedy
Space Center in Cape Can-averal, Fla.

     Since Endeavour took off early March 2, scientists have been
treated to a series of unusual cosmic events, accented by the
telescope's exceptional performance. With each successive day
came another revelation about the observatory's good fortune. 

    HUT made a string of unprecedented observations of an object
near the edge of the universe, for research that may at last find
the hypothetical "intergalactic medium" presumably produced at
the beginning of time.

    Shortly after Endeavour's launch, astronomers in Hawaii
discovered a major volcanic eruption taking place on Jupiter's
moon Io--perfect timing for scientists using HUT's unique ability
to study the Jovian system.

    Last Tuesday morning HUT 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. The
object, called a Seyfert galaxy, had grown five times brighter
than it was during the Astro-1 mission in December 1990.

    The next day, HUT astronomers 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.
Astronomers had observed the same cataclysmic variable with
Astro-1, right after it had finished going through an outburst,
measuring its temperature at about 37,000 degrees. By comparing
the two observations, scientists learned that the object is
drastically cooler before outburst than after outburst.
Astrophysicists are eager to begin analyzing data, which will
enable astronomers to make precise temperature measurements,
yielding insights into the physics behind cataclysmic variables. 

    Last Thursday brought another first in astronomy. Scientists
used two different types of space telescopes--HUT and the Hubble
Space Telescope--to observe Jupiter. Hubble produced ultraviolet
images, and HUT simultaneously collected precise spectrographic
data of the same region of the Jovian atmosphere. Those
observations were made even more important because of the timely
volcanic eruption on Io and last summer's collision of a comet
with Jupiter.

     All this historic science research was punctuated by a dose
of levity. Last Wednesday morning WJZ-Channel 13 conducted a  a
live interview via satellite with Hopkins astronaut Sam Durrance.
Dr. Durrance's family was on hand in the studio for the half-hour
special. He and his son, 13-year-old Benjamin, engaged in casual
conversation before thousands of viewers.

     "Have you been playing your guitar?" the scientist asked his
son. "Yeah, it's pretty cool," the boy answered. "Hey, dad? Can
you buy me a new amp?"

     By the sixth day of Astro-2, only one-third of the way
through its planned 16-day mission, scientists already had
collected more data than they did during the entire nine-day
Astro-1 mission.

     "It feels like we are drinking from a fire hydrant," Dr.
Davidsen said at the time, noting that scientists were
stockpiling the treasure of data for analysis later. HUT
astronomers don't have the luxury of slowing down long enough to
interpret the spectrographic windfall.

     It became apparent early in the mission that the HUT team
would be successful at observing a quasar 10 billion light-years
away, literally near the edge of the observable universe. That
meant scientists would probably be able to achieve HUT's major
objective, searching for the intergalactic medium of helium and
hydrogen presumably produced in the Big Bang of cosmic creation.
Astronomers have not yet established the existence of such gas.
Dr. Davidsen hopes to prove its existence with HUT. 

     But things also were happening in our own cosmic
neighborhood. Paul Feldman, a HUT astronomer, said scientists
were elated about Io's unexpected volcanic outburst. Ever since
the Voyager spacecraft recorded a volcano erupting on Io in 1979,
astronomers on Earth have been using infrared techniques to look
for "hot spots" on the moon to detect volcanic activity.

     Shortly after Endeavour's launch, Dr. Feldman turned on his
computer to read his latest electronic mail. To his astonishment,
the mail included a report from NASA's Infrared Telescope
Facility on Mauna Kea, Hawaii. The mail alerted all astronomers
of a major eruption on Io, asking that they train their
telescopes on the Jovian system.

     The HUT team did just that, recording important spectral
data from the moon, said Dr. Feldman, a professor in the
Department of Physics and Astronomy.

      He called the volcanic eruption a "fortuitous experience
that had us all very, very much excited ... and even more excited
when we were able to get a successful observation of the
satellite."

     A few days later astronomers used a camera on the Hubble
Space Telescope to take ultraviolet images of Jupiter while HUT
recorded spectrographic data from the same part of the Jovian
atmosphere. The telescopes focused on the planet's auroras,
colorful displays of charged particles at Jupiter's polar regions
similar to the Earth's northern and southern lights.

     The observations were especially important because of Io's
volcanic eruption and last summer's collision of Comet
Shoemaker-Levy 9 with Jupiter.

     "There is an enormous amount of energy being put into the
atmosphere," Dr. Feldman said. "Clearly, these energetic
particles are controlling, to a large extent, the fate of the
upper atmosphere of Jupiter. We are trying to get a better idea
of how it responds to changes."


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