Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/DAILY_2/930720.DFC

Text File | 1993-07-31 | 23KB | 527 lines

20-Jul-93 Daily File Collection
   These files were added or updated between 19-Jul-93 at 21:00:00 {Central}
                                         and 20-Jul-93 at 21:01:50.

=--=--=START=--=--= NASA Spacelink File Name:930720.REL

7/20/93:  HUBBLE FINDS A DOUBLE NUCLEUS IN THE ANDROMEDA GALAXY

Paula Cleggett-Haleim)
Headquarters, Washington, D.C.                      July 19, 1993

Jim Elliott
Goddard Space Flight Center, Greenbelt, Md.

Ray Villard
Space Telescope Science Institute, Baltimore

RELEASE:  93-133


    A team of astronomers using NASA's Hubble Space Telescope (HST) has
discovered a "double nucleus" in the center of the neighboring spiral galaxy
M31, located in the constellation Andromeda.

    A nucleus is a dense clustering of stars at the very center of a
galaxy.

    "Hubble shows that the M31 nucleus is much more complex than previously
thought," said Dr. Tod R. Lauer of the National Optical Astronomy
Observatories, Tuscon, Ariz.

    The astronomers report that the brighter member of the double nucleus
might be the remnants of another galaxy cannibalized by M31. They say that an
alternative possibility is that dust might dim the core to create the illusion
of a pair of separate star clusters.

    The Hubble images intensify the mystery of what's happening in the
center of this galaxy," said Lauer. "Neither interpretation offers a complete
explanation of the M31 nuclear structure."

    The double nucleus discovery is based on image analysis conducted by
Lauer, Dr. Sandra M. Faber of the University of California, Santa Cruz, and
other members of the HST Wide Field/Planetary Camera Imaging Team.


    The HST pictures show two bright spots at the heart of the M31 galaxy.
The dimmer of the two "light-peaks" appears to mark the exact center of the
galaxy.  The brighter peak is at least 5 light years away from the true center,
but corresponds to what astronomers previously had thought was the nucleus of
M31, based on ground-based observations.

    Well-known as the Andromeda Galaxy, M31 (the 31st object in a catalog
of non-stellar objects compiled by French astronomer Charles Messier in 1774)
is located only 2.3 million light years away, making it the nearest major
galaxy to the Earth's own Milky Way. M31 dominates the small group of galaxies
of which the Milky Way is a member and can be seen with the naked eye as a
spindle-shaped "cloud" the width of the full Moon.

    Like the Milky Way, M31 is a giant spiral-shaped disk of stars, with a
bulbous central hub of older stars.  M31 has long been known to have a bright
and extremely dense grouping of a few million stars clustered at the very
center of its spherical hub.  As seen from large ground-based telescopes, the
starlight blends to resemble a single bright, almost point-like source.
Previous ground-based observations gave little hint of the true structure of
the core, which is now revealed by Hubble.

Pinpointing the M31 nucleus

    In the 1960's the first high resolution photographs of M31's core were
obtained by Stratoscope II, a balloon-borne observatory.  The images were not
as sensitive as Hubble's and only showed a single bright cluster of stars.

    An important clue came with observations obtained in 1986 by the late
Jean-Luc Nieto, then at the Pic du Midi Observatory in France. He found that
the bright nucleus was offset by several light-years from the exact center of
the galaxy's central bulge.  The new HST images show that the dimmer peak
instead is the true nucleus and that the bright point of light evident from
ground-based telescopes corresponds to the brighter of the two peaks.

A cannibalized galaxy?

    One possible explanation for the second cluster being offset from the
exact center is that it is the remnant of a smaller galaxy that fell into M31
perhaps a billion or so years ago.  The smaller galaxy's core is the only
surviving fossil relic of the galactic collision.

    A problem with the collision scenario is that the remnant core should
be torn apart by the massive black hole hypothesized to dwell at the exact
center of M31. The suspected black hole would be located in the middle of the
dimmer peak uncovered by HST.


    In 1988, the first evidence for a black hole at the exact center of M31
came from ground-based observations by Dr. John Kormendy (now at the University
of Hawaii), and independently, by Dr. Alan Dressler (Observatories of the
Carnegie Institution of Washington), and Dr. Douglas O. Richstone (University
of Michigan). Their data indicated an abrupt increase in the orbital velocities
of stars in the center of the M31 nucleus.

    This led the astronomers to conclude that M31 must have a strong but
unseen concentration of mass at its center.  A black hole at least 10 million
times the mass of the sun is the most likely type of object matching these
characteristics.  A black hole is a theoretical object that is so dense that
even light cannot escape its intense gravitational pull.

    If such a black hole really exists, than the remnant core from the
cannibalized galaxy would be torn apart in just a few 100,000 years. "This is
very short in cosmic time," said Lauer. "We would have to be looking at the
galaxy at a very special time to see it now."

    One way for the remnant to survive for a much longer time is if it has
its own massive black hole.  Gravity from a black hole in the remnant would
hold it together against destruction from the other black hole at the M31
center.

    "In retrospect, there may be evidence for this possibility in the
spectra obtained by Kormendy, Dressler and Richstone, said Lauer. "One problem
with this picture, however, is if the black hole in the remnant were too big,
it would distort even the true nucleus of M31."

A dust lane bisecting the nucleus?

    Another interpretation of the "twin peaks" is that the bright spot is
just the outer portion of a large nuclear star cluster and that the central
portions have been obscured by dust.  A thick ring of dust might even cut
across the nucleus, creating the illusion of two separate objects rather than
one elongated structure.

    Lauer explains that the problem with this idea is that normal galactic
dust would scatter the light such that it would appear reddened. "But this is
not the case, there are no color effects at all," he emphasized. "This means
that the dust grains would have to be much larger than average." In the Milky
Way galaxy, however, the interstellar dust grains are roughly the same size.

    "We can only guess that earlier nuclear activity in M31 would have
destroyed all the fine dust grains that would cause color effects," said Lauer.


    M31 is an ideal target for Hubble once the telescopes's optics are
improved during a Space Shuttle servicing mission in December. Spectrographs
aboard Hubble will dissect the light from the two peaks of the double nucleus
and determine if they are truly separate clusters.  Astronomers will be able to
measure the velocity of stars to pin down whether there is a black hole in
either or both.

    This is the latest in a series of Hubble observations that have
uncovered unusual structures in the cores of galaxies.  Some of them might be
fossil evidence of galactic collisions.  Hubble also has resolved very dense
concentrations of stars in the cores of other galaxies that are circumstantial
evidence that massive black holes are common among galaxies.

     Source:NASA Spacelink    Modem:205-895-0028  Internet:192.149.89.61
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=--=--=START=--=--= NASA Spacelink File Name:930720.SHU

KSC SHUTTLE STATUS 7-20-93





        KENNEDY SPACE CENTER SPACE SHUTTLE STATUS REPORT
                      Tuesday, July 20, 1993

KSC Contact: Bruce Buckingham



              MISSION: STS-51  ACTS-TOS/ORFEUS-SPAS


VEHICLE: Discovery/OV-103             ORBITAL ALTITUDE: 184 miles
LOCATION: Pad 39-B                    INCLINATION: 28.45 degrees
LAUNCH DATE: TBD                      CREW SIZE: 5
LAUNCH WINDOW: TBD
EXPECTED KSC LANDING DATE/TIME: TBD
EXPECTED MISSION DURATION: 8 days/22 hours + 1 day (an additional
day on orbit may be granted if orbiter cryogenics and allow)

NOTE: An announcement is expected later today from NASA managers giving a firm
launch date for Discovery on mission STS-51. At this time, launch will not
occur before Friday, July 23.

     The problem circuit card in the pyrotechnic initiator controller which
caused the launch scrub on Saturday has been replaced on the mobile launcher
platform.  Efforts to duplicate the problem on the suspect card were successful
at KSC's malfunction laboratory.  A thermally unstable circuit was the culprit.

     The five members of the astronaut crew departed for their homes in Houston
last Saturday. Their schedule to return to KSC will be determined by the
setting of a new launch date.

     The crew for this mission include: Commander Frank Culbertson, Pilot Bill
Readdy, and Mission Specialists Jim Newman, Dan Bursch and Carl Walz.

IN WORK TODAY:
*  Extended launch scrub turnaround operations
*  Purge of power reactant storage and distribution system
*  Ordnance installation and reconnect operations (Pad clear at
   about 4:00 p.m. today)
*  Trickle charge on ACTS batteries

WORK SCHEDULED:
*  Load onboard cryogenic reactants
*  Aft engine compartment closeouts and aft confidence test
*  Final payload bay closeouts and close payload bay doors for
   flight

WORK COMPLETED:
*  Troubleshooting and replacement of the ground pyrotechnic
   initiator controller circuit card
*  Argon servicing of the ORFEUS payload
*  Open payload bay doors

     Source:NASA Spacelink    Modem:205-895-0028  Internet:192.149.89.61
=--=--=-END-=--=--=

=--=--=START=--=--= NASA Spacelink File Name:930720.SKD

DAILY NEWS/TV SKED 7-20-93

Daily News
Tuesday, July 20, 1993
Two Independence Square; Washington, D.C.
Audio Service:202/358-3014


 % Workers continue troubleshooting Discovery for STS-51 mission;
 % Another discovery for the HST;
 % NASA to exhibit at Oshkosh.


Workers at the Kennedy Space Center are troubleshooting the ground pyrotechnic
initiator controller that contributed to the scrub of Discovery's STS-51
mission Saturday. Over the next few days, they plan to install the ordnance and
begin reconnect operations.  Technicians are scheduled to perform final payload
bay closeouts and close the bay doors for flight.

NASA managers are still discussing a new launch date for the STS-51 mission.
This mission will carry the ACTS-TOS payload and deploy and retrieve the
ORFEUS-SPAS-01 scientific observation satellite.

* * * * * * * * * * * * * * * *

Using NASA's Hubble Space Telescope (HST), a team of astronomers has discovered
a "double nucleus" in the center of the neighboring spiral galaxy M31, located
in the constellation Andromeda. A nucleus is a dense clustering of stars at the
very center of a galaxy.

The astronomers report that the brighter member of the double nucleus might be
the remnants of another galaxy cannibalized by M31. Another possibility offered
is that dust might dim the core to create the illusion of a pair of separate
star clusters.

The double nucleus discovery is based on image analysis conducted by Dr. Tod
Lauer of the National Optical Astronomy Observatories, Dr. Sandra Faber of the
University of California, Santa Cruz, and other members of the HST Wide Field/
Planetary Camera Imaging Team.

* * * * * * * * * * * * * * * *

It's that time of year again for the annual Experimental Aircraft Association
Fly-In Convention and Sport Aviation Exhibition at Oshkosh, Wisc., July
29-August 6.  NASA will return to Oshkosh an exhibit that focuses on general
aviation technology.


NASA's exhibit, the modular "NASA and American Leadership in Aeronautics," will
explain how NASA is addressing the challenges of aircraft in everyJaspect.  It
also stresses how "customers" are benefiting from the agency's advances in
aeronautics.

Besides the aviation exhibit, NASA will have displays of the agency's space
programs, space science studies, space technology and the Space Station.

 * * * * * * * * * * * * * * * *


         Here's the broadcast schedule for Public Affairs events on NASA TV.
Note that all events and times may change without notice and that all times
listed are Eastern.


Tuesday, July 20, 1993

        noon            NASA Today.
        12:15 pm        Aeronautics & Space Report.
        12:30 pm        Apollo 11 Anniversary/KISS: Apollo.
          1:00 pm       Apollo 11: For All Mankind.
          1:30 pm       Return to the Red Planet.
          2:00 pm       Starfinder #4.
          2:30 pm       Life on the Moon.
          3:00 pm       TQM #4.

Wednesday, July 21, 1993

        noon            NASA Today.
        12:15 pm        Aeronautics & Space Report.
        12:30 pm        ATLAS: Close encounters with Earth.
          1:00 pm       Apollo 12: Pinpoint for Science.
          1:30 pm       Moon and Man,
          2:00 pm       Starfinder #5.
          2:30 pm       Examination of Life.
          3:00 pm       TQM #5.




NASA TV is carried on GE Satcom F2R, transponder 13, C-Band, 72 degrees West
Longitude, transponder frequency is 3960 MHz, audio subcarrier is 6.8 MHz,
polarization is vertical.

     Source:NASA Spacelink    Modem:205-895-0028  Internet:192.149.89.61
=--=--=-END-=--=--=

=--=--=START=--=--= NASA Spacelink File Name:930720A.REL

7/20/93:  LAUNCH ADVISORY:  JULY 24 NEW DATE FOR STS-51 LAUNCH



Ed Campion
July 20, 1993
Headquarters, Washington, D.C.

Bruce Buckingham
Kennedy Space Center, Fla.


     NASA managers today set July 24 as the new launch date for Shuttle Mission
STS-51. The launch window on July 24 opens at 9:27 a.m.  EDT and extends for 54
minutes.

     The decision to go with July 24 as the new launch date follows the
completion of work to inspect and retest the Pyro Initiator Controller (PIC)
unit on the launch pad.  A problem with the unit caused the Kennedy Space
Center launch director to call a scrub during a launch attempt on July 17.

     "The July 24 date is the best date all around for the launch of Discovery
on the STS-51 mission" said Shuttle Director Tom Utsman. It gives enough time
for KSC technicians to complete work on the PIC unit, the payload community
time to service the STS-51 experiments and the entire launch team enough time
to put the Shuttle system back into launch configuration.  The July 24 date
also is one that the Air Force range safety community can support."

     Shuttle Mission STS-51 will see Discovery's five person crew deploy the
Advanced Communciations Technology Satellite which will give industry, academic
and government organizations an opportunity to investigate new ways of
communicating.  The crew will also deploy and retrieve the Orbiting and
Retrieveable Far and Extreme Ultraviolet Spectrometer (ORFEUS- SPAS).

     Source:NASA Spacelink    Modem:205-895-0028  Internet:192.149.89.61
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=--=--=START=--=--= NASA Spacelink File Name:6_2_2_46_8.TXT

 NOTE: This file is too large {22283 bytes} for inclusion in this collection.
    The first line of the file:

LAUNCH DELAY INFORMATION / PRE-LAUNCH INFORMATION

     Source:NASA Spacelink    Modem:205-895-0028  Internet:192.149.89.61
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=--=--=START=--=--= NASA Spacelink File Name:6_7_2_16_8.TXT

7/20/93:  HUBBLE FINDS A DOUBLE NUCLEUS IN THE ANDROMEDA GALAXY

Paula Cleggett-Haleim)
Headquarters, Washington, D.C.                      July 19, 1993

Jim Elliott
Goddard Space Flight Center, Greenbelt, Md.

Ray Villard
Space Telescope Science Institute, Baltimore

RELEASE:  93-133


    A team of astronomers using NASA's Hubble Space Telescope (HST) has
discovered a "double nucleus" in the center of the neighboring spiral galaxy
M31, located in the constellation Andromeda.

    A nucleus is a dense clustering of stars at the very center of a
galaxy.

    "Hubble shows that the M31 nucleus is much more complex than previously
thought," said Dr. Tod R. Lauer of the National Optical Astronomy
Observatories, Tuscon, Ariz.

    The astronomers report that the brighter member of the double nucleus
might be the remnants of another galaxy cannibalized by M31. They say that an
alternative possibility is that dust might dim the core to create the illusion
of a pair of separate star clusters.

    The Hubble images intensify the mystery of what's happening in the
center of this galaxy," said Lauer. "Neither interpretation offers a complete
explanation of the M31 nuclear structure."

    The double nucleus discovery is based on image analysis conducted by
Lauer, Dr. Sandra M. Faber of the University of California, Santa Cruz, and
other members of the HST Wide Field/Planetary Camera Imaging Team.


    The HST pictures show two bright spots at the heart of the M31 galaxy.
The dimmer of the two "light-peaks" appears to mark the exact center of the
galaxy.  The brighter peak is at least 5 light years away from the true center,
but corresponds to what astronomers previously had thought was the nucleus of
M31, based on ground-based observations.

    Well-known as the Andromeda Galaxy, M31 (the 31st object in a catalog
of non-stellar objects compiled by French astronomer Charles Messier in 1774)
is located only 2.3 million light years away, making it the nearest major
galaxy to the Earth's own Milky Way. M31 dominates the small group of galaxies
of which the Milky Way is a member and can be seen with the naked eye as a
spindle-shaped "cloud" the width of the full Moon.

    Like the Milky Way, M31 is a giant spiral-shaped disk of stars, with a
bulbous central hub of older stars.  M31 has long been known to have a bright
and extremely dense grouping of a few million stars clustered at the very
center of its spherical hub.  As seen from large ground-based telescopes, the
starlight blends to resemble a single bright, almost point-like source.
Previous ground-based observations gave little hint of the true structure of
the core, which is now revealed by Hubble.

Pinpointing the M31 nucleus

    In the 1960's the first high resolution photographs of M31's core were
obtained by Stratoscope II, a balloon-borne observatory.  The images were not
as sensitive as Hubble's and only showed a single bright cluster of stars.

    An important clue came with observations obtained in 1986 by the late
Jean-Luc Nieto, then at the Pic du Midi Observatory in France. He found that
the bright nucleus was offset by several light-years from the exact center of
the galaxy's central bulge.  The new HST images show that the dimmer peak
instead is the true nucleus and that the bright point of light evident from
ground-based telescopes corresponds to the brighter of the two peaks.

A cannibalized galaxy?

    One possible explanation for the second cluster being offset from the
exact center is that it is the remnant of a smaller galaxy that fell into M31
perhaps a billion or so years ago.  The smaller galaxy's core is the only
surviving fossil relic of the galactic collision.

    A problem with the collision scenario is that the remnant core should
be torn apart by the massive black hole hypothesized to dwell at the exact
center of M31. The suspected black hole would be located in the middle of the
dimmer peak uncovered by HST.


    In 1988, the first evidence for a black hole at the exact center of M31
came from ground-based observations by Dr. John Kormendy (now at the University
of Hawaii), and independently, by Dr. Alan Dressler (Observatories of the
Carnegie Institution of Washington), and Dr. Douglas O. Richstone (University
of Michigan). Their data indicated an abrupt increase in the orbital velocities
of stars in the center of the M31 nucleus.

    This led the astronomers to conclude that M31 must have a strong but
unseen concentration of mass at its center.  A black hole at least 10 million
times the mass of the sun is the most likely type of object matching these
characteristics.  A black hole is a theoretical object that is so dense that
even light cannot escape its intense gravitational pull.

    If such a black hole really exists, than the remnant core from the
cannibalized galaxy would be torn apart in just a few 100,000 years. "This is
very short in cosmic time," said Lauer. "We would have to be looking at the
galaxy at a very special time to see it now."

    One way for the remnant to survive for a much longer time is if it has
its own massive black hole.  Gravity from a black hole in the remnant would
hold it together against destruction from the other black hole at the M31
center.

    "In retrospect, there may be evidence for this possibility in the
spectra obtained by Kormendy, Dressler and Richstone, said Lauer. "One problem
with this picture, however, is if the black hole in the remnant were too big,
it would distort even the true nucleus of M31."

A dust lane bisecting the nucleus?

    Another interpretation of the "twin peaks" is that the bright spot is
just the outer portion of a large nuclear star cluster and that the central
portions have been obscured by dust.  A thick ring of dust might even cut
across the nucleus, creating the illusion of two separate objects rather than
one elongated structure.

    Lauer explains that the problem with this idea is that normal galactic
dust would scatter the light such that it would appear reddened. "But this is
not the case, there are no color effects at all," he emphasized. "This means
that the dust grains would have to be much larger than average." In the Milky
Way galaxy, however, the interstellar dust grains are roughly the same size.

    "We can only guess that earlier nuclear activity in M31 would have
destroyed all the fine dust grains that would cause color effects," said Lauer.


    M31 is an ideal target for Hubble once the telescopes's optics are
improved during a Space Shuttle servicing mission in December. Spectrographs
aboard Hubble will dissect the light from the two peaks of the double nucleus
and determine if they are truly separate clusters.  Astronomers will be able to
measure the velocity of stars to pin down whether there is a black hole in
either or both.

    This is the latest in a series of Hubble observations that have
uncovered unusual structures in the cores of galaxies.  Some of them might be
fossil evidence of galactic collisions.  Hubble also has resolved very dense
concentrations of stars in the cores of other galaxies that are circumstantial
evidence that massive black holes are common among galaxies.

     Source:NASA Spacelink    Modem:205-895-0028  Internet:192.149.89.61
=--=--=-END-=--=--=

=--=--=START=--=--= NASA Spacelink File Name:9_18.TXT

 NOTE: This file is too large {26790 bytes} for inclusion in this collection.
    The first line of the file:

LIVING AND WORKING IN SPACE: THE COUNTDOWN HAS BEGUN

     Source:NASA Spacelink    Modem:205-895-0028  Internet:192.149.89.61
=--=--=-END-=--=--=

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