SKY & TELESCOPE's WEEKLY NEWS BULLETIN
OCTOBER 9, 1998
HUBBLE GOES DEEPER
In 1995 the Hubble Space Telescope's main visible-light camera stared into
an "empty" patch of sky in Ursa Major for 100 hours, turning up thousands
of remote galaxies in what came to be known as the Hubble Deep Field. Now
the orbiting observatory has taken another look, this time at infrared
wavelengths. Hubble's Near Infrared Camera and Multi-Object Spectrometer
(NICMOS) stared into the Deep Field for 36 hours and nabbed more than 300
spiral, elliptical, and irregular galaxies in a tiny patch of sky just 20
arcseconds across. (The original Hubble Deep Field spanned 2.7 arcminutes.)
According to team leader Rodger Thompson, some of these objects could be
the most distant galaxies ever seen, lying more than 12 billion light-years
away. Since the remotest parts of the universe appear highly redshifted,
it's no wonder Hubble's infrared camera can see deeper than its ultraviolet
and visible-light counterparts. Thompson points out that some of what were
thought to be indistinct blue galaxies in the original Hubble Deep Field
image are now recognized to be bright knots of star formation in much
larger, older, redder galaxies seen clearly in the NICMOS view. For more
information and images, see the Space Telescope Science Institute's Web
site at http://oposite.stsci.edu/pubinfo/1998/32/.
VLT COMMISSIONING UPDATE
Astronomers at the European Southern Observatory are wasting no time
bringing their Very Large Telescope online. The first of its four 8.2-meter
reflectors has been undergoing tests for several months, and all continues
to go well. The latest accomplishment is a thorough shakedown of an imaging
spectrograph that can capture simultaneous spectra of all the objects in
the field of view. For more information, see ESO's press release at
http://www.eso.org/outreach/press-rel/pr-1998/phot-38-98.html. Or see
"Eyewitness View: First Sight for a Glass Giant" in the November 1998 issue
of SKY & TELESCOPE.
OZONE HOLE WIDENS
The annual ozone hole over Antarctica has been bigger than ever this year.
Data from NASA's Earth Probe and the National Oceanic and Atmospheric
Administration's NOAA-14 satellite show the region of ozone depletion
covering a record 10.5 million square miles (27.3 million square
kilometers) as of mid-September. In addition, the ozone level fell to
within a few percent of its lowest value ever. According to NASA and NOAA
scientists, the hole is growing because of unusually cold stratospheric
temperatures, not because of increased use of chlorofluorocarbons and
halons. Still, the expansion is cause for concern because it threatens to
expose southern Chile and Argentina to increased levels of solar
ultraviolet radiation. With international agreements in place to curtail
the use of ozone-harming chemicals, ozone depletion should become less of a
problem by early in the 21st century.
SETI, 4TH EDITION
After suffering minor damage from Hurricane Georges last month, Arecibo
Observatory is back in the news. Scientists from the Planetary Society and
the University of California, Berkeley, launched their latest search for
extraterrestrial intelligence at the facility on October 5th. Like its
three predecessors, SERENDIP IV scans the sky for alien signals while other
instruments are using the radio telescope for more traditional
observations. The new SERENDIP receiver analyzes 168 million radio channels simultaneously, straddling the emissions of the ubiquitous hydrogen atom at 1420 MHz. Begun in 1976, SERENDIP -- like other SETI programs -- has yet to find evidence of alien intelligence, despite what the supermarket tabloids report!
LEONID THREAT DOWNPLAYED
On November 17th and 18th the world's space agencies will be nervously
awaiting possible strikes to the more than 500 working satellites currently
in Earth orbit. That's when the Leonid meteor shower will return to our
skies, possibly bringing a fierce meteor storm with hundreds of "shooting
stars" per minute. Many spacecraft, including the Hubble Space Telescope,
will be carefully turned during the display to present their least
vulnerable profiles to the potential sandblasting. But NASA and Department
of Defense scientists who have been studying the meteors now believe that
the threat to orbiting spacecraft is not serious, only "elevated." In a
joint press release issued on October 7th, they estimate that during the
12-hour peak of the shower satellites will be exposed to as much meteoric
energy as they normally see over months to years in space. Even so, most
satellites go their entire lives without suffering physical or electrical
damage from a meteor strike. So spacecraft operators are hoping for quiet
nights in mid-November.
Skygazers eagerly watched for a return of the Giacobinid meteor shower on
Thursday evening, October 8th. This long-dormant shower, spawned from Comet
Giacobini-Zinner, produced two of the greatest meteor displays in this
century, in 1933 and 1946. Most years bring no Giacobinids at all, but with
the parent comet now relatively close to where its orbit intersects
Earth's, astronomers predicted a potentially dazzling display this year.
Early reports received by SKY & TELESCOPE from around the U.S. and Western
Europe suggested that the Giacobinids didn't materialize, but subsequent
reports from Eastern Europe and Asia -- especially Japan and China -- make
plain that an outburst did indeed occur. At its maximum, around 13-14 hours
Universal Time on the 8th, the zenithal hourly rate (ZHR) of meteors
exceeded 500. (The ZHR is the number of meteors a single observer would see
per hour if the sky were dark enough for 6.5-magnitude stars to be visible
and the shower's radiant, or apparent point of origin, were at the zenith
-- directly overhead.) For more information, see the Web sites of the
International Meteor Organization (http://www.imo.net/) and the Dutch
Meteor Society (http://home.wxs.nl/~dms-web/).
COMET WILLIAMS HEADING NORTH
Comet Williams (C/1998 P1) crossed the border from Centaurus into Hydra
this past week. While it remains the brightest comet in the sky at about
8th magnitude, it is low above the horizon in evening twilight for even the
best-placed observers in the Southern Hemisphere. Charles Morris (Jet
Propulsion Laboratory) predicts that by late November the comet should be
visible from both hemispheres at about 10th magnitude; for a finder chart,
see Dale Ireland's Web page at http://www.drdale.com/. Here are positions
for Comet Williams for 0 hours Universal Time (2000.0 coordinates) for the
October 10 13h 30m -29.1 deg.
12 13h 30m -28.7 deg.
14 13h 30m -28.2 deg.
THIS WEEK'S "SKY AT A GLANCE"
Some daily events in the changing sky, from the editors of SKY & TELESCOPE.
OCT. 11 -- SUNDAY
* Callisto, the outermost of Jupiter's four large moons, makes a
relatively rare transit across Jupiter's face tonight from 10:17 to 11:25
p.m. Eastern Daylight Time. Callisto is darker than Jupiter's other major
satellites, so it stands the best chance of being visible against the
planet's bright background. However, it will transit near Jupiter's rather
dark north polar limb. A complete list of Jupiter's satellite events for
the month is in the October SKY & TELESCOPE, page 106.
OCT. 12 -- MONDAY
* Last-quarter Moon (exact at 7:11 a.m. EDT).
* Jupiter's Great Red Spot should cross the planet's central meridian
around 1:24 a.m. EDT Tuesday morning. Lately the spot has been very pale
with a dark outline and a small, reddish-brown patch in its south side. For
all predicted Red Spot transit times this observing season, see
OCT. 13 -- TUESDAY
* Ganymede is Jupiter's largest moon, so it casts the most prominent
black dot of a shadow onto Jupiter's face. Tonight Ganymede's shadow
crosses the planet from 7:50 to 11:01 p.m. EDT. At 8:11 p.m. EDT, Ganymede
itself emerges into view from in front of Jupiter's western limb.
* Jupiter's Red Spot should transit around 9:15 p.m. EDT.
OCT. 14 -- WEDNESDAY
* For naked-eye skywatchers, Jupiter and Saturn mark the way to the Great
Square of Pegasus this fall. It's to Jupiter's upper left and Saturn's
OCT. 15 -- THURSDAY
* The waning crescent Moon shines near Mars and Regulus this morning and
* Tonight two of Jupiter's satellites can be seen emerging from eclipse
out of Jupiter's shadow. They reappear in dark sky a little east of the
planet. Europa emerges around 10:09 p.m. EDT, and Io around 12:13 a.m. EDT.
* Jupiter's Red Spot transits around 10:53 p.m. EDT.
OCT. 16 -- FRIDAY
* Stay up till midnight at this time of year and you'll get a preview of
the winter constellation Orion rising in the east-southeast.
OCT. 17 -- SATURDAY
* Saturn's brightest moon, Titan, can be spotted in a small telescope
three or four ring-lengths to Saturn's west tonight through Tuesday night.
* Jupiter's Red Spot transits around 12:31 a.m. EDT tonight.
THIS WEEK'S PLANET ROUNDUP
MERCURY and VENUS are hidden in the glare of the Sun.
MARS shines in the east before and during dawn, near the star Regulus.
Early in the week Mars is quite close to Regulus; watch it pull away to
Regulus's lower left as the week progresses. Compare the deep orange color
of Mars to Regulus's pale blue-white!
JUPITER is the big, brilliant "star" in the southeast during evening. It's
high in the south by about 10 p.m. and sets in the west during early
SATURN is the bright "star" far to Jupiter's lower left in early evening,
and directly left of Jupiter later at night. The two planets appear 41
degrees apart (about 4 fist-widths at arm's length), on opposite ends of
URANUS and NEPTUNE, magnitudes 5.8 and 7.9 respectively, are in (or very
near) Capricornus in the south to southwest during early evening. See the
finder chart in the September SKY & TELESCOPE, page 110, or at
PLUTO is disappearing into the sunset.
(All descriptions that relate to the horizon or zenith are written for the
world's midnorthern latitudes. Descriptions that also depend on longitude
are for North America. Eastern Daylight Time, EDT, equals Universal Time
minus 4 hours.)
More details, sky maps, and news of other celestial events appear each
month in SKY & TELESCOPE, the essential magazine of astronomy. See our
enormous Web site at http://www.skypub.com/. Clear skies!
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