HST UPGRADES SHOW BIRTH AND DEATH OF STARS
NICMOS PEERS INTO HEART OF DYING
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New data released by NASA today
evidence of a supermassive black hole and
remarkable new details on the explosive life cycle
of stars. NASA also reported that all new Hubble
instruments and upgrades are generally performing
"We're extremely excited
about the quality and precision of the images from
Hubble," said Wes Huntress, NASA Associate
Administrator for Space Science. "Following
check-out of the instruments, Hubble will return to
full science operations, and we can expect a
continuing flow of new and exciting discoveries."
These initial results
clearly demonstrate the ability of the new
instruments to fulfill their science goals with the
Hubble Telescope, say project astronomers. Project
officials are pleased to report that other
instruments and electronics installed during the
second servicing mission are performing well.
Among Hubble's recent observations:
Jets and Gaseous Disk
Around the Egg Nebula -- A new infrared instrument
peered deep into the dust-obscured central region
around a dying star embedded in the Egg nebula. A
nebula is a cloud of dust and gas 3,000 light years
from Earth. The new images provide a clear view of
a twin pair of narrow bullet-shaped "jets" of gas
and dust blasted into space. The instrument, called
the Near Infrared Camera and Multi-Object
Spectrometer, also revealed an unusual scalloped
edge along a doughnut-shaped molecular hydrogen
cloud in the nebula.
"Because we can now see
these 'missing pieces' in infrared and visible
light, we have a more complete view of the dynamic
and complicated structure of the star," said Rodger
Thompson of the University of Arizona, Tucson, the
principal investigator for the infrared instrument.
"It also allows us to see a 'fossil record' of the
star's late evolutionary stages."
Starbirth in the Orion Nebula - The new infrared instrument
penetrated the shroud of dust along the back wall
of the Orion nebula, located in the "sword" of the
constellation Orion. Data revealed what can happen
to a stellar neighborhood when massive young stars
begin to violently eject material into the
surrounding molecular cloud. Although ground-based
infrared cameras have previously observed this
hidden region known as OMC-1, the Hubble's new
instrument provides the most detailed look yet at
the heart of this giant molecular cloud. Hubble
reveals a surprising array of complex structures,
including clumps, bubbles, and knots of material.
Most remarkable are
"bullets" composed of molecular hydrogen -- the
fastest of which travels at more than one million
mph (500 km/s). These bullets are colliding with
slower-moving material, creating bow shocks, like a
speedboat racing across water.
Monster Black Hole in
Galaxy M84 - In a
single exposure, a new powerful instrument called
the Space Telescope Imaging Spectrograph discovered
a black hole at least 300 million times the mass of
the Sun. The spectrograph made a precise
observation along a narrow slit across the center
of galaxy M84, located 50 million light-years away.
This allowed the instrument to measure the
increasing velocity of a disk of gas orbiting the
black hole. To scientists, this represents the
signature of a black hole, among the most direct
evidence obtained to date. Due to their nature,
it's impossible to directly photograph black holes.
Scientists must instead look for clues to show the
effects of black holes on surrounding dust, gas and
"Hubble proved the
existence of supermassive black holes three years
ago," said Bruce Woodgate of the Goddard Space
Flight Center, Greenbelt, MD, and principal
investigator for the new spectrograph. "With this
new instrument, we can do it 40 times faster than
we used to."
Structure of the Ring Around Supernova
1987A - The new
spectrograph also provides an unprecedented look at
a unique and complex structure in the universe -- a
light-year-wide ring of glowing gas around
Supernova 1987A, the closest supernova explosion in
400 years. The spectrograph dissects the ring's
light to tell scientists which elements are in the
ring and helps paint a picture of the physics and
stellar processes which created the ring. This
gives astronomers better insight into how stars
evolve and become a supernova, and into the origin
of the chemical elements created in these massive
Status -- NASA
project officials are encouraged that a problem
detected earlier with one of the cameras on the
infrared instrument has shown some improvement. The
problem stems from the unexpected movement of the
dewar -- an insulated vessel containing solid
nitrogen at extremely cold temperatures. After
launch, the nitrogen expanded more than expected as
it warmed, moving the dewar into contact with
another surface in the mechanism and pushing one of
the cameras out of its range of focus. The camera
has moved back about one-third of the distance
required to be within reach of the instrument's
internal focusing mechanism. This is because the
dewar is "relaxing" toward its normal state, as
pressure caused by the expansion of the nitrogen is
reduced. The ice keeps the sensitive infrared
detector cooled. Project officials also are
considering how to deal with unexpected, excessive
"We are anticipating a
shorter lifetime for the instrument, but we don't
know how much shorter," said Goddard Hubble Project
Scientist David Leckrone. "We are taking steps to
work around the problem, and will increase the
percentage of time this instrument will be used."
NASA officials also report
that other upgrades to Hubble are performing well,
including the newly installed solid state recorder,
fine guidance sensor and solar array drive
electronics. The solid state recorder has
significantly improved data storage and playback,
and the new fine guidance sensor is by far the best
of the three on Hubble.
Images and text reproduced
for educational use with permission from The Space
Telescope Science Institute. The Space Telescope
Science Institute is operated by the Association of
Universities for Research in Astronomy, Inc.
(AURA), for NASA, under contract with the Goddard
Space Flight Center. The Hubble Space Telescope is
a project of international cooperation between NASA
and the European Space Agency (ESA).
Recommisioning Status Report
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READY FOR THE HUNT
Before the Space Telescope Imaging Spectrograph
(STIS) can begin sniffing out black holes, the
instrument must be tested to make sure it's ready
for the challenge.
This testing program
doesn't last a day, a week, or even a month. It is
a two-month program consisting of an exhaustive
series of tests. That's because scientists can't
lift the telescope's hood and tinker with the
instrument. Not when it's in an Earth-circling
observatory that is 380 miles above our planet's
surface. Instead, scientists must rely on special
computers that perform a series of diagnostic tests
on STIS. If adjustments must be made, scientists
send detailed instructions to Hubble's electronic
brain - its computers - on how to do it.
The long testing program
also is important to ensure that STIS can perform
its job accurately and efficiently. The
instrument's job is to collect information from
celestial objects, many of them very dim and
distant ones. Based on this information, scientists
will make assumptions about an object, such as its
temperature or composition. So, STIS must be very
precise in order to collect accurate information.
AN INSTRUMENT WITH MANY PARTS
STIS is one complex
instrument. It has 65 apertures or light openings -
a point-and-shoot camera has one - and 14
defraction gratings, which divide light into a
spectrum of colors. The apertures vary in size. For
example, a car license plate would fill the
instrument's smallest aperture. STIS also has three
separate detectors: a Charge-Coupled Device (CCD)
and two Multi-Anode Microchannel Plate Arrays
(MAMAs). Each detector records light from a
different part of the spectrum. STIS's spectral
range is from visible to far ultraviolet light.
HIGH VOLTAGE DETECTORS
The instrument's detectors
are very sensitive. The two MAMA detectors cannot
be turned on for several months because scientists
must wait for the pressure to decrease inside
STIS's closet-sized compartment. Too much pressure
could short-circuit the MAMA detectors' high
voltage power supply.
TOO MUCH LIGHT
Scientists also must wait
to open STIS's eyes to bright light. Too much
bright too soon could damage the instrument's
optical equipment, including its four main mirrors.
That's why Hubble doesn't look at the bright Earth
for the first two weeks after the servicing
FRAME A PICTURE
Once STIS opens its eyes,
it will begin collecting light from celestial
objects, such as stars and galaxies. An object's
light is its resume, telling scientists something
about the object. STIS will gather light and divide
it into its wavelengths or colors. The colors
provide information about an object's composition,
temperature, density, and velocity.
But STIS can't make
observations if the target object moves out of its
field of view. It is not as simple as pointing a
35mm camera at a subject, glancing through the
eyepiece to make sure it's in the frame, and
clicking the picture. Hubble is moving at 17,500
mph, and many target objects are very dim and
difficult to see. That's why Hubble has two Fine
Guidance Sensors that lock onto stars - called
guide stars - near the target object to keep the
telescope steady during an observation. The Fine
Guidance Sensors are good enough for the
telescope's Wide Field and Planetary Camera II
(WFPC2), which has a large aperture. But STIS has
many small apertures, and scientists don't know the
positions of guide stars accurately enough. If a
guide star's position is slightly off, STIS's
target object might be out of the field of view
because of the small aperture.
So, scientists have thrown
in a safety step for STIS. After the Fine Guidance
Sensors have locked onto guide stars, the STIS's
CCD detector takes a picture of the target object.
The image tells instrument's computers whether the
object is in view. If the object is not in the
picture, STIS will tell the telescope where to move
to find it. All of these decisions are made by
STIS's sophisticated computer software. Scientists
must check the software to make sure it is doing
its job. Scientists can't have STIS telling the
telescope to move to the right when the object is
to the left.
HOW BRIGHT IS IT?
Once a target object is
found, STIS must calculate its brightness. Knowing
an object's brightness determines how long STIS
must look at it to collect necessary information.
In other words, an object's brightness determines
how many orbits Hubble needs to make an
observation. The telescope orbits the Earth every
97 minutes, completing about 15 passes around our
planet a day. For example, it took about 150 orbits
for the telescope to observe the Hubble Deep Field,
which represents a pinhole view of the early
universe. So, scientists must check STIS to make
sure they know how sensitive the instrument is to
Light is radiation, and
it's STIS's job to collect it. But there's another
form of radiation that STIS isn't crazy about.
Through testing, scientists discovered that the
instrument is more sensitive than expected to a
large radiation field over South America. But
scientists have solved the problem by juggling some
STIS observing schedules.
Called the South Atlantic
Anomaly, this well-known region is where the Van
Allen radiation belts dip lower in altitude than
elsewhere. The Van Allen belts are two
doughnut-shaped regions - between 200 and 500 miles
high - of magnetically trapped charged particles
that encircle Earth. Hubble and all spacecraft are
affected by the belts when they pass through them.
Hubble's Wide Field and Planetary Camera 2 (WFPC2)
does not make observations when the telescope
passes through the region, sometimes as often as
nine times a day. Before entering the region,
Hubble's computers send digital images from WFPC2
so that the data won't be corrupted. The Van Allen
belts act as a thin, protective skin for Earth,
trapping charged particles before they bombard our
planet and harm us.
March 25, 1997
New Camera on Hubble Space Telescope
NICMOS Dewar Container
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March 25, 1997
CAPE CANAVERAL, Fla. (AP) -- An infrared camera
installed by spacewalking astronauts on the Hubble
Space Telescope last month is partly out of focus
and will not last as long as planned, NASA said
``We are going to lose
some lifetime, there's no question about that,''
said Ed Weiler, NASA's chief Hubble scientist.
Provided the $105 million
Near-Infrared Camera and Multi-Object Spectrometer
does not deteriorate further, scientists should be
able to work around the problem and still collect
all the desired data on black holes and remote
stars and galaxies, Weiler said.
``We tend to be very
conservative considering our history,'' he said,
referring to Hubble's originally flawed mirror.
``Until we're absolutely sure things are going to
go the way we think they will, we always want to
look at the worst case.''
One of three cameras in
the Near-Infrared Camera and Multi-Object
Spectrometer, called Nicmos, is too far out of
focus to be corrected by on-board systems, Weiler
said. The two others are working fine, he said.
Scientists believe the
focusing problem with camera No. 3 resulted from
the expansion of nitrogen ice, needed to keep the
infrared detectors operating at minus-355 degrees
Fahrenheit. The expanding ice apparently pushed on
some of the camera mechanisms more than expected.
Astronomers noticed this movement two weeks ago.
``The Nicmos probably will
rewrite the physics books on solid nitrogen,''
Weiler said. ``The models that it was built upon
were not totally correct.''
Because of additional heat
entering the nitrogen container, the nitrogen will
last at least a few months less than the full 4 1/2
years, provided the problem corrects itself, Weiler
said. In that case, the focus of camera No. 3 would
be restored naturally, perhaps in six months to one
The lifetime of Nicmos
will be cut in half, however -- to 2 1/4 years --
if the nitrogen continues to be lost at the current
rate. Scientists already are scrambling to push up
the star-gazing schedule for Nicmos if this should
Scientists plan to conduct
another focus test on Thursday night to further
assess the situation.
Nicmos, about the size of
a telephone booth, was designed and built by the
University of Arizona. It represents one-fourth of
the entire Hubble science program, and its
out-of-focus camera No. 3 represents one-fourth of
the Nicmos science program.
NASA launched Hubble in
1990 with a flawed primary mirror that left the
telescope nearsighted. Spacewalking astronauts
installed corrective optics in 1993. The February
mission to install Nicmos, another state-of-the-art
science instrument and other equipment, was the
second servicing mission for the $2 billion Hubble.
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