- A Space Telescope Science Institute (STScI)
news release The anticipated celestial bombardment called the Leonid meteor
storm on the afternoon of Nov. 17 (EST) won't deter NASA's Hubble Space
Telescope from its key mission of gazing far across the universe - as long
as the view is in the opposite direction of the incoming meteor swarm.
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- Using the brilliant glow of a distant
quasar located near the southern boundary of the constellation Aquarius,
Hubble will probe galaxy formation and the distribution of matter in space.
The Hubble data will become immediately available to the astronomical community.
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- The meteor storm is an expected downpour
of thousands of meteors zooming by Earth. They pose a small but potential
threat to Hubble and other satellites, say experts. The meteors appear
to come from the direction of the zodiacal constellation Leo the Lion,
and hence the storm is called the Leonids.
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- For a 10-hour period at the peak of the
storm, estimated to be at approximately 2:43 p.m. EST (1943 GMT) on the
17th, the telescope will be oriented with its aft bulkhead facing into
the direction of the meteoroid stream. Hubble's solar panels will lay flat,
or parallel to the meteoroid flow.
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- Though most Leonid meteoroids are smaller
than a grain of sand, they zoom across space at a menacing 155,000 miles
per hours. A speck-sized meteoroid can pack the wallop of a .22 caliber
bullet as it pierces the spacecraft hull.
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- Still, even at the peak of meteor activity
the density of particles in any given region of space is extremely low.
So, project scientists predict that Hubble has less than a 1-in-10,000
chance of being hit by a particle large enough to pierce it's aluminum
skin.
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- Smaller meteoroids vaporizing on impact
create a plume of plasma that can short-circuit spacecraft electronics.
However, a short circuit on Hubble is unlikely because its electronics
are housed inside aluminum boxes that also serve as a meteoroid shield.
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- The Space Telescope won't be idle during
the shower. STScI director Steven Beckwith is making his discretionary
observing time available so astronomers can still observe the heavens while
the orbiting observatory is aimed away from the meteoroid barrage.
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- Hubble will be aimed at a quasar, the
bright core of an active galaxy, approximately 10 billion light-years away.
Hubble won't be studying the quasar itself but the surrounding galaxies,
protogalaxies and primordial hydrogen clouds between us and the quasar.
The quasar is so brilliant, it is like a searchlight shining through fog.
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- Strung along billions of light-years,
like beads on a string, the gas clouds will be detectable in the way they
subtract certain colors or frequencies of the quasar's light. The observation
will help determine whether the clouds are cold primeval hydrogen or are
sites of ongoing star formation which have been enriched with heavier elements.
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- Hubble's Space Telescope Imaging Spectrograph
will take a long-exposure picture to identify galaxies along the sight,
and divide the light into a rainbow of colors (a spectral image) to determine
galaxy distances. This is accomplished by measuring how the light has been
stretched or redshifted by the universe's expansion.
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- Follow-up spectroscopic observations
with large ground-based telescopes and high-resolution spectrographs will
measure the quasar light directly and identify the distance of the intervening
gas clouds.
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- The redshifts of the gas clouds from
the ground-based data will then be matched with the redshifts of the galaxies
along the line of sight seen in the HST data. These combined observations
will allow astronomers to see if galaxies are associated with these invisible
clouds. Leonid storm history The Leonid meteor storm occurs as Earth passes
through a region of concentrated, fresh debris within the stream that follows
Comet P/55 Tempel-Tuttle.
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- The comet made its last closest passage
to the sun in late February of this year. Warmed by the sun, the icy comet
nucleus spewed a great deal of dust into space as its ices melted. These
dust particles appear as meteors when they enter Earth's atmosphere and
burn up from friction.
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- The stunning estimates of as many as
10,000 meteors during the 1-hour storm are based on prior meteor storms
that have occurred when the comet has returned to Earth during the past
two centuries.
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- Because the comet has a 33-year period,
the last shower was on Nov. 17, 1966. A brief, 20-minute burst in meteor
activity - as seen from the Central and Western United States lit up the
skies with 40 meteors per second!
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