S&T News Bulletin - Jan 19
SKY & TELESCOPE'S NEWS BULLETIN -- JANUARY 19, 1995
SPICA WINKS OUT
The major skywatching event this week occurs on Monday morning, January
23rd, when the Moon occults the 1st-magnitude star Spica, and observers in
the United States have front-row seats. The occultation will be seen
first on the West Coast just before 10:00 Universal Time. But due the
Moon's orbital motion it won't begin until about 11:10 UT in twilight on
the East Coast. Just about that time Spica will be reappearing for
observers in the West. Reappearance in the East occurs between about
11:50 and 12:10 UT. The Moon's phase is waning gibbous, so reappearance
will be very dramatic along the dark lunar limb. Maps on page 84 in
January's SKY & TELESCOPE show this all more clearly.
As long as you're up before dawn, set your sights on Jupiter as well. Now
separated from the Sun by a healthy 50 degrees, the giant planet is an
easy target for scrutiny. Daniel Costanzo says it may be hasty to
describe the dark debris from last summer's comet crash as a conspicuous
globe-girding belt. Using the historic 30-cm refractor at the U.S. Naval
Observatory in Washington, Costanzo and other members of the National
Capital Astronomers have observed instead what they call "interesting" and
"boring" sides to Jupiter. The interesting half has a central-meridian
longitude of roughly 320 degrees, corresponding to the region hit so
obviously by fragments G, L, R, and Q. The boring one has a CML of about
140 degrees, near where pieces A and C struck.
BUILDING A BETTER SUPERNOVA
Two thousand astronomers met last week in Tucson, and they presented many
important new results. One concerned supernovae, the deaths of massive
stars. Theorists had figured that the collapse of a star's core and its
subsequent "bounce" powered these violent events. But computer models
always crashed before producing an explosion. Now teams led by Willy Benz
and Adam Burrows have finally built computer models that explode like real
stars. They succeeded by doing their calculations in two dimensions,
something not possible before the advent of supercomputers. This allowed
them to fully account for the energy supplied by tiny, massless particles
called neutrinos, as well as departures from spherical symmetry, such as
those caused by convection.
BIG BLACK HOLE IN M106?
There is impressive evidence now for a massive black hole in the nucleus
of M106, a galaxy in Canes Venatici. Japanese radio astronomers led by
Makoto Miyoshi detected a thin ring of gas encircling the galaxy's core.
The ring is only 1.5 light-years across, and it is whirling around so fast
-- 1,000 kilometers per second along its inner edge -- that it would fly
apart unless held in place by a dense central object with a mass of some
40 million Suns. This object is almost certainly a massive black hole,
because its inferred density is orders of magnitude higher than that of
any known star cluster.
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