Skylights featured three times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. An upside-down sky appears in
the mirroring still bowl of a country pond, the
right-side-up view showing an equally still sunrise.
Astronomy news for the week starting Friday, June 4, 2004.
The week begins with the Moon just past its full phase
and into its waning gibbous phase as it rises progressively later
each night. On Wednesday the 9th it will pass third quarter and
begin the waning crescent phase of its earthly orbit.
From the beginning of 2004,
Venus has dominated the western evening sky, showing us in the
northern hemisphere one the best apparitions it has to offer. In
mid May it began its disappearing act as it prepared to swing
between us and the Sun, and on the morning of Tuesday, June 8, it
will do exactly that as it transits across the solar disk, an event that has not
taken place since 1882! Transits of Venus can
occur only when "inferior conjunction" occurs at the same time that
the planet, on its tilted orbit, is close to crossing the ecliptic.
They occur in pairs eight years apart within a day or so of June 7
and December 8 each at intervals of 243 years with the those of the
other date taking place in between. The last
transit took place in December of 1882, the last June transit
in 1769. The next one will be on June 6, 2012, the next pair in
December of 2117 and 2125.
North Americans are at a disadvantage. East of a line that
stretches roughly from central Texas to Montana, the
transit will be underway at sunrise; west of the line, the Sun rises after the
transit is over with. "Third contact," when the moving, leading
edge of the planetary disk hits the edge of the Sun, takes place
close to 7:05 AM EDT, 6:05 AM CDT, while "fourth contact" (when
Venus takes leave of the Sun) takes place around 7:25 and 6:25 (EDT
and CDT respectively).
Venus will appear as a black dot only a minute of arc across set
against the brilliant Sun, and will be extremely difficult to see
with the PROTECTED naked eye. The Sun is far too bright to look at
directly, and professional eye protection (a proper filter) is
MANDATORY. Do NOT use homemade devices/filters. The proper way to
observe the event is the same as for an eclipse, to use projection
through a telescope or even binoculars. Simply project the image
onto a flat piece of paper, without in any way looking through the
instrument.
The rest seems almost an anticlimax. Slipping away, Saturn
sets near the end of twilight, while Mars
follows almost an hour later. That leaves
Jupiter to dominate the nightly sky, the giant planet (still
south of the classical figure of Leo) setting around 1 AM Daylight Time.
Moving now to the east, Jupiter will formally enter the
constellation Virgo in late
August as it plunges ever farther south. Well to the southeast of
the planet, locate Virgo's luminary, Spica, one of the hottest of stars of
first magnitude.
