archive: SETI S&T's News Bulletin for April 30, 1999

SETI S&T's News Bulletin for April 30, 1999

Larry Klaes ( lklaes@bbn.com )
Mon, 03 May 1999 09:59:59 -0400

>From: SkyGlance@aol.com
>Date: Sun, 2 May 1999 16:29:47 EDT
>Subject: S&T's News Bulletin for April 30, 1999
>X-Mailer: AOL 4.0 for Windows 95 sub 15
>To: undisclosed-recipients:;
>
>
>SKY & TELESCOPE'S NEWS BULLETIN
>
>APRIL 30, 1999
>
>ANCIENT MARTIAN MAGNETISM
>
>New data from NASA's Mars Global Surveyor (MGS) shows that during its
>infancy the red planet not only had a flip-flopping magnetic field but also
>churned internally with enough heat to drive a vigorous surface geology. A
>team of NASA scientists reached these unexpected conclusions based on
>magnetometer measurements gathered within the past few months. Published
>today in the journal Science, the MGS data reveal that the ancient rocks in
>Mars's southern hemisphere are magnetized in long east-west bands of
>alternating polarity. This same phenomenon is observed astride Earth's
>midocean ridges, at which new crust is constantly forming. The crustal
>rocks become imprinted with the ambient magnetic field when they
>crystallize from magma, and bands of alternating polarity arise because
>Earth's magnetic field periodically reverses direction.
>
>Apparently much the same scenario was occurring on Mars for about 500
>million years after the planet's birth. New crust must have been forming
>along one or more "spreading centers." Whether the planet underwent the
>complete cycle of Earthlike plate tectonism is less clear, however. On
>Earth the crust's spreading centers and corresponding subduction zones are
>obvious volcanic and tectonic structures, but no such features are seen on
>Mars. In any case, by 4 billion years ago Mars had apparently cooled enough
>to shut down the electromagnetic dynamo in its core and in turn its global
>magnetic field.
>
>You can contemplate these new Mars findings while gazing at the planet in
>the night sky. It's the bright ruddy "star" due south at about midnight
>local time. Although Mars reached opposition (opposite the Sun in the sky)
>on April 24th, it will be closest to Earth on the night of May 1-2, when it
>will appear 16.2 arcseconds across. You'll find a complete observing guide
>to the planet's apparition this year in the April issue of SKY & TELESCOPE
>and at our Web site (http://www.skypub.com/).
>
>A NOVA IN SAGITTARIUS
>
>On April 27th, the Central Bureau for Astronomical Telegrams announced the
>discovery of a "new" star in Sagittarius. Nova Sagittarii 1999 -- also
>designated V4444 Sagittarii -- was found by Japanese observer Minoru
>Yamamoto on photographs taken on April 25th. Follow up observations
>pinpointed the nova at right ascension 18h 07m 36s, declination -27d 20'
>14" (2000.0 coordinates). Pictures of the same field taken by Yamamoto as
>late as April 11th show no star brighter than magnitude 10.6, and the
>Digitized Sky Survey provides no hint of an object down to about 20th
>magnitude. William Liller of Vina del Mar, Chile, reports that as of the
>night of April 26th, the star was magnitude 7.95. A low-resolution spectrum
>of the nova indicates that it is in its early stages and could brighten
>further.
>
>COMET LEE TREKS NORTH
>
>During the upcoming week, Comet Lee (C/1999 H1) passes through Vela and
>Pyxis. Observers report that the comet is about magnitude 8.5. It is well
>up in the south during the night as viewed from the Southern Hemisphere. By
>mid-May it will be low in the western evening sky for midnorthern
>latitudes. Comet Lee is expected to brighten to 7th magnitude as it
>approaches perihelion on July 11th. Here are positions (2000.0 coordinates)
>at 0 hours Universal Time for the coming week:
>
> Date R.A. Dec.
>
>May 1 10h 19.8m -52d 10'
> 3 10h 02.9m -47d 53'
> 5 9h 48.6m -43d 24'
> 7 9h 36.6m -38d 49'
>
>
>THIS WEEK'S "SKY AT A GLANCE"
>
> Some daily events in the changing sky, from the editors of SKY &
>TELESCOPE.
>
>MAY 2 -- SUNDAY
>
> * Look low in the southwest in late twilight for Sirius, the brightest
>true star in the sky. (It's very far off to the lower left of much brighter
>Venus). Sirius is a winter star making its seasonal departure this month.
>See how hard it twinkles when it's at a low altitude!
>
>MAY 3 -- MONDAY
>
> * This evening and tomorrow evening, Venus appears almost exactly midway
>between Capella (the brightest star far to its upper right) and orange-red
>Betelgeuse (far to Venus's lower left).
>
>MAY 4 -- TUESDAY
>
> * The red long-period variable star RU Cygni should be at maximum light
>(8th magnitude) around this date.
>
>MAY 5 -- WEDNESDAY
>
> * Vega, the signature star of summer, is already making its appearance
>low in the northeast just after dusk these May evenings.
>
>MAY 6 -- THURSDAY
>
> * The Eta Aquarid meteor shower is active for the next four nights. This
>is usually the year's best meteor shower for Southern Hemisphere
>skywatchers, but essentially no Eta Aquarids can be seen north of about 40
>degrees north latitude.
>
>MAY 7 -- FRIDAY
>
> * Venus shines close to 5th-magnitude 139 Tauri this evening; use
>binoculars or a telescope. West Coast and Hawaiian observers will find the
>star just 2 arcminutes north of the passing planet.
>
>MAY 8 -- SATURDAY
>
> * Last-quarter Moon (exact at 1:28 p.m. EDT).
>
>
> ============================
> THIS WEEK'S PLANET ROUNDUP
> ============================
>
>MERCURY and SATURN are hidden in the glare of the Sun.
>
>VENUS is the brilliant "Evening Star" (magnitude -4.1) shining in the west
>during and after dusk.
>
>MARS is at its best! Look for it glaring bright orange in the southeast at
>dusk. It's at a good, high altitude for telescopic observing after 10 p.m.
>daylight saving time and is highest due south around midnight. You can't
>miss it blazing at about magnitude -1.6! In a telescope, Mars remains 16
>arcseconds in apparent diameter for the first half of May -- the biggest
>we'll see it for another two years. It reached opposition on April 24th and
>passed closest to Earth (54 million miles) on May 1st.
>
>JUPITER is just coming into view low in the dawn. Scan for it with
>binoculars just above the east horizon about 30 minutes before sunrise.
>
>URANUS and NEPTUNE, dim at magnitudes 6 and 8, respectively, are low in the
>southeast before the first light of dawn. See the finder chart in the May
>Sky & Telescope, page 108.
>
>PLUTO, extremely dim at magnitude 14, is in Ophiuchus in the south during
>early-morning hours. See the finder chart in the March Sky & Telescope,
>page 103, or at http://www.skypub.com/sights/moonplanets/plutochart99.html
>.
>
>(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 www.skypub.com. Clear skies!
>
>SKY & TELESCOPE, P.O. Box 9111, Belmont, MA 02478 * 617-864-7360
>
>=======================================================
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>
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>