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The Michigan Daily - Friday, December 8, 1995 - 11A
GAILEO SEES THE MANY MOONS OF JUPITER
*I
Spacecraft enters
atmosphere of
Jupiter, sends data
PASADENA, Calif. (AP)-- A 746-
pound probe from the Galileo space-
craft entered the harsh, whirling gases
of Jupiter's atmosphere yesterday and
sent back 75 minutes of precious data
before it disintegrated.
After receiving weather and chemi-
cal data from the probe, Galileo fired its
thrusters to push the spacecraft into
orbit around Jupiter for two years of
study.
NASA workers cheered and there
were handshakes and back slaps all
around when it was confirmed at 3:15
p.m. that the probe was transmitting
information back to its trailing Galileo
mother ship.
"Fantastic!" said Torrence Johnson,
Galileo project scientist at NASA's Jet
Propulsion Laboratory in Pasadena.
"Wow! You never really believe it till
you see it."
After slamming into the atmosphere
at 106,000 mph, the giant, squat cone
dropped more than 125 miles by para-
clfute, sending data for 75 minutes be-
fore being crushed by air pressure 20
times greater than Earth's.
U'libraryI
By Scot Woods
Daily News Editor
The arrival of the Galileo probe at the
Jovian system is the latest stage ofnearly
iOur centuries of investigation of the
solar system's largest planet.
NASA's interplanetary traveleris the
namesake of Jupiter's first explorer,
17th-century Italian astronomer Galileo
Galilei, who turned his spyglass sky-
ward early in January of 1610.
The University is fortunate to pos-
sess the actual manuscript of Galileo's
notes from those winter nights when he
first discovered Jupiter's four brightest
moons (See illustration).
Curators at the Harlan Hatcher Gradu-
ate Library say the document, written in
Italian, is of great historical value be-
cause it is a working document, not a
final, published product.
"In some ways, it shows the work-
ings of his mind," said Peggy Daub,
head of special collections and arts li-
braries at the University. "Usually, what
we have is the nice, clean, final copies.
In this case, he seemed to be trying out
different theories."
Humanities collections Curator
Kathryn Beam said, "Besides being an
oiiginal Galileo manuscript, the con-
teint itself is significant because of its
likely being the first observations ofthe
moons of Jupiter."
Excited by his discovery, Galileo
rushed to publish his findings by that
March.
The manuscript came into the
University's possession in 1938, when
Detroit resident Tracy McGregor do-
nated part of his collection. McGregor
had purchased the manuscript in 1934
at an auction.
Nobody knew what a treasure the
University had until an extensive ar-
ticle on the piece appeared in "Scien-
tific American" in 1976. Since then, the
document has been cited often by schol-
ars.
Galileo's notes are written on the
bottom third ofa sheet of paper that also
contains the draft of a letter to the doge
- or prince - of Venice, written at
"We've never, never sampled a giant
planet. We'll figure out what this atmo-
sphere is made of over 600 million
miles away," said Wesley T. Huntress,
NASA associate administrator for space
science.
Previous space missions have ana-
lyzed the atmospheres of Mars and
Venus. But Jupiter is different; the gi-
ant planet is surrounded by powerful
magnetic fields and intense radiation,
and is made up mostly of hydrogen and
helium, the elements in the primordial
mix that once condensed into the solar
system.
Scientists monitoring the events on Scientist
closed-circuit television in an audito- Sinit
rium at the laboratory burst into ap-
plause again after getting confirmation well as t
that Galileo had begun a 49-minute magnetic
engine burn to send the spacecraft into and charg
orbit. "We've done it! We've got con- give the 1
firmation," said Richard Terrile, a composit
NASA scientist. Up to t
The orbits around Jupiter are expected traterrest
to provide images of eight ofthe planet's the Hub
16 known moons. mirror is
By illuminating Jupiter's moons, as "YouI
owns Galileo's
A monitor Information from the Galileo spacecraft at NASA's Jet Propulsion Laboratory in Pasadena, Calif.v
he planet's rings, its intense
field and its swarms of dust
ged particles, the mission could
best view ever of the planet's
tion.
now, the best glimpses of ex-
rial bodies have come from
ble Space Telescope, whose
less than 8 feet across.
would need a Hubble Space
notes on
Telescope over 10 miles in diameter to ammonia crystal clouds
get images of the moons as good," a stew of ammonia coi
Johnson said. "There's no substitute in ing in hurricane windsi
this business for getting your instru- After that, scientists&
ments up close." would probably encou
Detailed data from the atmospheric and lightning before b
encounter won't be available until mid- by the heat and pressur
December at the earliest. "The probe is ... rec
Scientists speculated that after the the most important in
probe passed through a high layer of the solar system," John
ijupiter discovery
s, it would reach
mpounds swirl-
up to 200 mph.
said, the probe
nter heavy rain
eing vaporized
re.
ording some of
formation from
son said.
Planet's
immensity
creates
curiosity
Los Angeles Times
It's not surprising that Jupiter was.
named after the head honcho of the
ancient gods. It has everything other
planets have, and then some.
Sitting on the borderline between
planet and star, Jupiter "is about as big
aplanet as you can make," said Torrence
Johnson, a Galileo project scientist with
Jet Propulsion Laboratory. Yet its fierce
gravitational contraction causes it to
"shine," radiating twice the energy it
receives from the sun.
Just why Jupiter got to be so im-
mense - 1,300 times the size of Earth
- remains something of a mystery,
although Johnson explains that the gi-
ant simply may have started gobbling
up matter before the other planets be-
gan to condense out of the cloud; before
long, it would have had a strong gravi-.
tationally grip on all matter in its local
area.
The composition of Jupiter is es-
sentially the same as the sun - mostly
hydrogen and helium. But because
Jupiter isn't quite big enough to ig-
nite a nuclear fire in its belly and
become a star, it hasn't altered the
composition of the matter it was=
formed with. At the same time, its.
huge gravity has kept matter from
boiling off or blowing away.
That makes it a perfect pristine labo-..
ratory to study the stuff that went into'
making our solar system. Its huge grav-
ity has allowed nothing to escape its
grasp; and the matter it started with
wouldn't have changed its form.
Jupiter's weather also offers lessons
in stellar and planetary atmospheric'
science. In a sense, the entire planet is
an atmosphere, since it's gas all the way
down until pressure turns hydrogen into
a metallic liquid thousands of miles
down (although some scientists think'
the core may be rocky).
Swirling orange-brown ammonia
clouds paint stripes on the rapidly spin
ning sphere, which rotates in a 10-hour
day. At the equator, winds get up to 250
mph, then reverse direction, then re
verse again, causing bands of colors
and eddies near the borders. "It's a
major puzzle what drives these wind
systems," said JPL probe scientist Rich"
Young.
7--4
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44
Photo courtesy of NEWS AND INFORMATION SERVICES
The University possesses the above manuscript of Galileo, in which he recorded
his discovery of Jupiter's four brightest moons.
Translation
The following is the English
translation of Galileo's original Latin
manuscript, written Jan. 7-15, 1610.
On the 7th of January Jupiter is seen
as thusXwest
east 4(
On the 8th thus
it was therefore direct and not
retrograde.
On the 12th day it is seen in this
arrangement
The 13th are seen very close to
Jupiter 4 stars
or better so
On the 14th it is cloudy.
The 15th
the nearest to Jupiter was smallest
the 4th was distant from the 3rd
about double.
The spacing of the 3 to the west
was no greater than the diameter.
and they were in a straight line.
ect t
* the st
I
I ~ III
least three months earlier.
"We know there was a finished letter
actually sent to the doge in August
1609," Beam said
The letter draft adds greatly to the
value of the manuscript. "It's a full
two-thirds ofa page in Galileo's hand.
It has significance for his recognition
of the telescope as a useful tool," she
said.
The letter describes "a telescope that
will be a great help in maritime and land
enterprises. ... The telescope has the
advantage of discovering the ships of
the enemy two hours before they can be
seen with the natural vision and to dis-
tinguish the number and quality of the
ships and to judge their strength and be
ready to chase them, to fight them, or to
flee from them."
The draft notably does not men-
tion use of the telescope as an instru-
ment for investigating the heavens.
That idea would have been consid-
ered dangerous because, as Galileo
proved, it had the potential to under-
mine the concept of an earth-cen-
tered universe taught by the Roman
Catholic Church.
Nicolaus Copernicus had already
challenged the church with his theory
of a sun-centered universe in 1540.
"(Galileo's observations) showed that
things revolved around objects other
than the Earth," Daub said. By exten-
sion, this discovery suggested that the
Earth might orbit the sun.
Beam said this page, the library's
.only manuscript in Galileo's hand, is
used regularly by publishers."It's been
used more in textbooks to introduce
high school students to the significance
of Galileo," she said.
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