SETI [skyline] S&T's News Bulletin for July 16, 1999

Larry Klaes (
Mon, 19 Jul 1999 10:58:57 -0400

>Date: Fri, 16 Jul 1999 23:06:20 MDT
>From: "John Wagoner" <>
>X-Mailer: <IMail v5.04>
>Subject: [skyline] S&T's News Bulletin for July 16, 1999
>For images and Web links for these items, visit
>In collaboration with key organizations of amateur and professional
>astronomers, SKY & TELESCOPE has established the AstroAlert e-mail
>news service to alert small-telescope users to significant happenings
>in the sky -- those that involve especially rare events or require
>immediate follow-up observations worldwide. To find out more, visit
>On July 13th, Australian amateur Daniel W. Lynn discovered an
>8th-magnitude comet moving rapidly northeast through the constellation
>Hydra. He made the find near Melbourne while observing with 10x50
>binoculars. The comet is currently low in the western evening sky for
>observers in the Southern Hemisphere. By the end of July it will have
>moved far enough north and east of the Sun to be visible from the
>Northern Hemisphere.
>SKY & TELESCOPE issued an AstroAlert concerning this comet on July
>14th, based on IAU *Circular* 7222 from the International Astronomical
>Union's Central Bureau for Astronomical Telegrams (CBAT). After
>receiving astrometric observations from four amateur astronomers in
>Australia and Brazil, CBAT director Brian G. Marsden was able to
>compute a preliminary orbit. Comet Lynn (C/1999 N2) will reach
>perihelion (the point of its orbit nearest the Sun) on July 23rd. At
>that time it will be 0.76 astronomical unit from the Sun, well inside
>the Earth's orbit. The comet is expected to be 7th or 8th magnitude
>for the next few weeks, then fade as it recedes from both the Earth
>and the Sun.
>The comet has already crossed the border from Hydra into Sextans.
>Marsden's preliminary orbit, published on IAU *Circular* 7224,
>predicts the following coordinates (equinox 2000.0) at 0 hours
>Universal Time on each date:
> Date R.A. Dec.
>July 16 10h 10.9m -10 deg. 55'
>July 17 10h 21.6m -8 deg. 46'
>July 18 10h 31.6m -6 deg. 40'
>July 19 10h 41.0m -4 deg. 39'
>July 20 10h 49.8m -2 deg. 43'
>July 21 10h 58.0m -0 deg. 53'
>Gordon J. Garradd, who imaged the comet with a CCD camera on his
>18-inch reflector at Loomberah, near Siding Spring, New South Wales,
>noticed a thin, short tail at least 12 arcminutes long.
>Another discovery on July 13th was a nova in the constellation Aquila
>by Japanese astronomer Akihiko Tago. The find was announced on IAU
>*Circular* 7223 and subsequently announced by the American Association
>of Variable Star Observers (AAVSO) in conjunction with Sky &
>Telescope's AstroAlert e-mail news. At discovery, Nova Aquilae 1999
>was magnitude 8.8, but observers report that it has quickly faded to
>10th magnitude. It is located at 19h 07m 36.90s right ascension, +12
>deg. 31' 26.2" declination (2000.0 coordinates), which is about 1.5
>deg. south of 3rd-magnitude Zeta Aquilae. Aquila is well up in the
>south at the end of twilight.
>It's been 91 years since the "Tunguska event," when an incoming chunk
>of interplanetary debris exploded about 8 kilometers above the ground
>and devastated 60 million trees on more than 2,000 square km of
>Siberian wilderness near the Stony Tunguska River. The 15-megaton
>airburst did not form a crater, nor have intact fragments of the
>impactor ever been recovered. However, this summer researchers are
>returning to the site in the hope of solving some of the event's
>long-standing riddles. Nearly a score of Italian scientists,
>photographers, and support personnel set off on July 14th for the
>Siberian city of Krasnoyarsk (by way of Moscow), where they will team
>up with several Russian colleagues. A heavy-lift Mi-26 helicopter is
>transporting the team and their equipment to Ceko Lake, 8 km from the
>center of the blast, because the impactor's highly oblique trajectory
>may have carried some fragments into the lake. During the two-week
>expedition, side-scan sonar and remotely operated marine cameras will
>first map the underwater terrain, then undisturbed sections of the
>lakebed will be sampled and brought to the surface for analysis. Other
>studies include searching for traces of cosmic debris in tree samples
>(work that the Italians began at the site in 1991), measurements of
>the local magnetic field, and cosmic-ray surveys.
>Asteroid 1999 AN10 had been put on the list of "potentially hazardous
>objects" soon after its discovery earlier this year. In May, the
>hazard stakes were raised when astronomers determined that there was a
>very slight, but nevertheless possible, chance that it could strike
>the Earth in 2044 or 2046. The asteroid will make a close pass of the
>Earth on August 7, 2027, and it was determined that if the asteroid
>passed through certain "keyhole" points in space during the passage,
>it could be sent on a collision course with the Earth. The situation
>changed on July 12th when astronomers announced on a Minor Planet
>Electronic Circular that images of 1999 AN10 were found on plates from
>the National Geographic-Palomar Observatory Sky Survey. The trail of
>the asteroid was measured from the 1955 photographs and the object's
>orbit was refined. The revision increased the minimum-possible
>approach distance to Earth to 386,000 kilometers and moved the keyhole
>points such that a collision in four decades was impossible.
>NASA's next Great Observatory, the Chandra X-ray Observatory is
>scheduled for launch aboard the Space Shuttle *Columbia* on July 20th.
>Launch of the spacecraft -- formerly called the Advanced X-ray
>Astrophysics Facility -- was delayed twice because ground testing took
>longer than expected and a possible problem with a booster rocket.
>Once it is safely in orbit, engineers at the control center will spend
>a couple of months checking and calibrating the observatory's systems.
>For the first two months of observations, Chandra will mostly stare at
>bright stars to check the focus of its images, and at the Cassiopeia A
>supernova remnant and the Coma cluster of galaxies, both of which have
>been well studied by other satellites. Two additional months of
>observations will be made by scientists directly involved with the
>program before the telescope is put into the service of astronomers
>worldwide. For details about the Chandra mission, see the August issue
> Some daily events in the changing sky, from the editors of SKY &
> * This evening the Moon, Spica, and Mars form a slightly curved line
>(from right to left) in the southwest. Each appears roughly a
>fist-width at arm's length from the next. Three or four fists farther
>left is orange-red Antares.
> * First-quarter Moon (exact at 5:00 a.m. Eastern Daylight Time
>Tuesday morning). Below the Moon this evening is Spica. Farther to the
>Moon's left is Mars. Much higher above the Moon and a bit right is
> * The Moon stands above orange-red Mars this evening. Farther to the
>Moon's lower right is Spica.
> * The Moon, Mars, and Spica form a curved line (from left to right)
>in the southwest after dusk. Each appears roughly a fist-width at
>arm's length from the next. About two fists to the Moon's lower left
>is orange-red Antares.
> * The red long-period variables T Herculis and S Pegasi should be at
>maximum light (8th magnitude) around this date.
> * Below the hot summer Moon tonight sparkles the red-giant star
> * Jupiter's moons Europa and Callisto are in conjunction, 34
>arcseconds apart, at 3:23 a.m. EDT. A small telescope will show them
>close together, aligned north-south.
> ============================
> ============================
>MERCURY is hidden in the glare of the Sun.
>VENUS shines low in the west during early twilight, dropping lower to
>the horizon each day. A small telescope or even good tripod-mounted
>binoculars will show that Venus is in its crescent phase. (Look as
>soon after sunset as you can find it.)
>MARS (magnitude -0.1) shines orange in the southwest during and after
>dusk. The fainter, blue-white star to its right or lower right is
>Spica. In a telescope Mars is tiny, only 10 arcseconds in diameter and
>JUPITER (magnitude -2.3 in Aries) rises around 12:30 a.m. local
>daylight saving time. It shines brightly high in the southeast before
>SATURN (magnitude 0.0, also in Aries) is the dimmer "star" 13 degrees
>to Jupiter's lower left (somewhat more than the width of your fist at
>arm's length).
>URANUS and NEPTUNE, dim at magnitudes 6 and 8, respectively, are in
>Capricornus, which is up in the southeast by late evening. See the
>finder chart in the May Sky & Telescope, page 108, or at
>PLUTO, extremely dim at magnitude 14, is in Ophiuchus in the
>south-southwest right after dark. See the finder chart in the March
>Sky & Telescope, page 103, or at
>(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 Clear skies!
>SKY & TELESCOPE, P.O. Box 9111, Belmont, MA 02478 * 617-864-7360
>Copyright 1999 Sky Publishing Corporation. S&T's Weekly News Bulletin
>and Sky at a Glance stargazing calendar are provided as a service to
>the astronomical community by the editors of SKY & TELESCOPE magazine.
>Widespread electronic distribution is encouraged as long as these
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