S&T's News Bulletin - Jun 2
SKY & TELESCOPE'S NEWS BULLETIN -- JUNE 2, 1995
THE LAST SPICA OCCULTATION
The 1st-magnitude star Spica will be occulted by the Moon late on the
night of Thursday, June 8th. This is the last coverup of Spica in a
series that began 18 months ago, and it favors observers in western and
central North America. Event times vary depending on your location. For
example, Spica disappears behind the waxing gibbous Moon's dark (eastern)
limb on the 9th at about 6:10 UT in Seattle but at 7:10 in Oklahoma City.
See page 73 of the June SKY & TELESCOPE for details.
A 21-ton Russian spacecraft called Spektr finally docked to the Mir space
station on June 1st, bringing with it nearly a ton of scientific and
medical equipment for astronaut Norman Thagard. The spacecraft was
supposed to arrive in February, well before Thagard got there himself. But
the launch slipped three months because Spektr was not yet ready and
because the NASA equipment was tied up by Russian customs officials. At
least seven Space Shuttles will visit Mir over the next three years,
including a docking by *Atlantis* planned for later this month.
For those who have SKY & TEL's July issue, here's the update on the
visibility of Mir over the U.S. during June. Changes in Mir's orbit have
made the maps on page 69 outdated. But the track lines can be modified to
create new predictions of when and where to see Mir crossing the sky like
a bright, moving star. More details will be included next week, but here
is an approximate correction that can be applied to the June 12th map:
Mir will arrive about 43 minutes earlier than noted on any given track.
Because of that, the Earth below will not have rotated quite as far. So,
after correcting the times, slide each track eastward by about 3/4 inch.
For example, instead of passing directly over Houston at 2:11 Universal
time on June 14th, Mir will be seen instead at roughly 1:28 UT over
THE STEAMY SUN
A team of solar observers has found water on the Sun -- or, more
precisely, they have identified water in spectra of the dark umbra of
sunspots. The water molecule is stable below temperatures of about 4,000
K. The Sun's photosphere is quite a bit hotter than that, nearly 5,800 K,
at which water breaks down into hydrogen and OH radicals. But sunspots
are relatively cool oases on the photosphere, and the sunspot umbra
studied by Lloyd Wallace and his colleagues had an estimated temperature
of only 3,300 K, cool enough for water to exist stably. The sunspot
observations were actually made years ago, in July 1991. But the Sun's
spectrum is so complex that it's taken this long to find the absorption
lines due to water, and show that they were *not* due to water in Earth's
atmosphere. Other molecules already known to exist on the Sun include
carbon monoxide, hydrogen fluoride, hydrogen chloride, and silicon oxide.
Details appear in SCIENCE magazine for May 26th.
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