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Sky & Telescope News Bulletin - 07/03/97


SKY & TELESCOPE'S NEWS BULLETIN
JULY 3, 1997

AWAITING MARS PATHFINDER

If all goes well on July 4th, Mars Pathfinder will become the first craft 
to land on the red planet since the Viking missions of 1976. Pathfinder 
will enter the thin Martian atmosphere at high speed, without orbiting the 
planet first, and slow down through a combination of drag, parachutes, and 
retrorockets. Then it will thump onto the rough and ruddy surface cushioned 
in air bags and bounce to a stop a few minutes after 1 p.m. Eastern 
Daylight Time. A stereo camera and a suite of meteorology sensors will 
characterize the landing site, which is located in the mouth of an ancient 
river channel named Ares Vallis. Reception of the first image from the 
surface is not expected until about 8 p.m. EDT. The spacecraft will then 
deploy a six-wheel, 11.5-kilogram rover called Sojourner. It carries a 
stereo camera of its own, along with an X-ray spectrometer to make crude 
compositional analyses of the rocks and soil within 10 meters of the 
touchdown site. 

NEAR'S IMAGES OF MATHILDE

On Monday, scientists at the Johns Hopkins University's Applied Physics 
Laboratory proudly displayed several images of main-belt asteroid 253 
Mathilde, taken June 27th by the NEAR (Near Earth Asteroid Rendezvous) 
spacecraft. The probe flew 1,200 km from the minor planet, taking more than 
500 images at a variety of visible and near-infrared wavelengths. The 
initial images reveal that Mathilde measures 47 by 59 km -- the largest 
asteroid yet visited by a spacecraft. It is heavily cratered, with at least 
five craters more than 20 km in diameter. The giant rock is also extremely 
dark -- only 3 percent of sunlight is reflected. This is blacker than 
charcoal.  The Mathilde flyby is a bonus to NEAR's primary objective -- a 
long-term study of the Earth-approacher 433 Eros, which the spacecraft will 
reach in early 1999.

AMATEUR WINS FIRST BENSON PRIZE

Speaking of asteroids, three weeks ago James Benson of Space Development 
Corporation announced that he would award $500 to the first 10 amateur 
astronomers who discover minor planets whose orbits cross Earth's. And 
already we have a winner! Roy Tucker of Tucson, Arizona, picked up a fast-
moving object in a sequence of CCD images made on the evenings of June 28th 
and 29th with his Celestron 14-inch telescope. Follow-up observations made 
over the next few nights by astronomers worldwide confirmed the 18th-
magnitude blip to be a previously unknown minor planet. Designated 1997 
MW1, it orbits the Sun every 0.91 year in an elongated path that brings it 
inside the orbits of the Earth and Venus. It is thus an Aten-type asteroid, 
only the 25th such object known. The Benson Prize was established to 
encourage amateurs to help locate the hundreds of Earth-crossers believed 
to inhabit the inner solar system. Space Development Corporation hopes to 
mine these asteroids for natural resources.

VLBI IN SPACE

The baseline in Very Long Baseline Interferometry just got even longer. 
VLBI combines the signals from widely separated radio telescopes to form 
images with ultrahigh angular resolution. But the best you could do until 
recently was to spread telescopes across the face of the Earth, as done 
with the international Very Long Baseline Array, or VLBA. Now, thanks to a 
Japanese satellite called HALCA (for Highly Advanced Laboratory for 
Communications and Astronomy), VLBI is being done with baselines nearly 
three Earth diameters long. This week scientists at the National Radio 
Astronomy Observatory released the first images produced when HALCA, the 
VLBA, and the Very Large Array in New Mexico combined forces. They show the 
radio emission from a galaxy and a quasar more clearly than any previous 
studies. Astronomers hope that further observations with HALCA will pave 
the way for a more advanced orbiting radio telescope in the 21st century.



THIS WEEK'S "SKY AT A GLANCE"

  Some daily events in the changing sky, from the editors of SKY & TELESCOPE

JULY 6 -- SUNDAY

  * Look for the thin waxing crescent Moon about 5 to the lower left of 
Venus. They're very low in the west-northwest at dusk.

  * The eclipsing variable star SZ Herculis should have an eclipse tonight 
centered around 2 a.m. Eastern Daylight Time Monday morning. The star dips 
from 10th to 12th magnitude. For how to time this event to track the star's 
behavior, see the June Sky & Telescope, page 76. (The star's right ascension 
is printed incorrectly; it's 17h 39.6m.)  All you need is the chart in the 
article, a watch, and a 4-inch telescope.

JULY 7 -- MONDAY

  * The crescent Moon is to the lower right of Regulus and left of Venus at 
dusk.

  * Jupiter's Great Red Spot appears on the central meridian (midline) of 
the planet's disk around 11:03 p.m. EDT.  It's well placed for observing 
for more than an hour around that time. For a full listing of the Red Spot's 
predicted transit times, see http://www.skypub.com/whatsup/redspot.html.

JULY 8 -- TUESDAY

  * Regulus is to the right of the Moon.

JULY 9 -- WEDNESDAY

  * The Moon is near the center of a long lineup of (from left to lower 
right) Spica, Mars, Moon, Regulus, Venus, and Mercury. They're strung along 
the ecliptic.

  * Jupiter's Red Spot transits the planet's central meridian around 12:41 
a.m. EDT Thursday morning.

JULY 10 -- THURSDAY

  * Look due south at the end of dusk this week. The brightest star there, 
rather low, is the red giant Antares in Scorpius.

JULY 11 -- FRIDAY

  * The Moon is very near Mars this evening.

  * SZ Herculis has an eclipse centered around 11:48 p.m. EDT.

JULY 12 -- SATURDAY

  * The first-quarter Moon (exact at 5:44 p.m. Eastern Daylight Time) is 
above Spica.

  * Jupiter's Red Spot transits the planet's central meridian around 10:10 
p.m. EDT.


 ============================
  THIS WEEK'S PLANET ROUNDUP
 ============================

MERCURY is very low in the west-northwest after sunset, far to the lower 
right of much brighter Venus. Look 30 or 40 minutes after sunset.

VENUS is very low in the west-northwest during evening twilight.

MARS, in the head of Virgo, shines pale orange-red in the southwest during 
early evening. It's off to the right of Spica. Mars is fading as it drops 
far behind Earth in our race around the Sun. In a telescope it appears only 
7 arcseconds across.

JUPITER, in Capricornus, rises around the end of twilight. It's well up in 
the southeast by 11 or midnight, shining brightly.

SATURN, in Pisces, rises around 12:30 a.m. daylight saving time. It glows in 
the east-southeast, below the Great Square of Pegasus, in the early morning 
hours.

URANUS and NEPTUNE are west of Jupiter. They're visible in binoculars by 
late evening if you have a detailed finder chart, such as the one in the 
May Sky & Telescope, page 84.

PLUTO, at the Ophiuchus-Scorpius border, is in the south during evening. 
It's only 14th magnitude.

(All descriptions that relate to your horizon or zenith are written for the 
world's midnorthern latitudes. Descriptions that also depend on longitude are 
for North America.)

More details, sky maps, and news of other celestial events appear each month 
in SKY & TELESCOPE, the essential magazine of astronomy. See our Web site at 
http://www.skypub.com/. Clear skies!

SKY & TELESCOPE, P.O. Box 9111, Belmont, MA 02178  *  617-864-7360 (voice)


Copyright 1997 Sky Publishing Corporation. S&T's Weekly News Bulletin and
"Sky at a Glance" stargazing calendar are provided as a service to the
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