Astronomy news for the week starting Friday, July 3, 2009.
Happy Birthday USA. The Moon celebrates by
starting off in its waxing gibbous
phase, then passing full the night
of Tuesday, July 7, when it will undergo a penumbral
eclipse that peaks at 4:38 AM CDT. Don't expect any grand
sight, or for that matter of even think of getting up to look. The
Moon will just clip the outskirts of the partial shadow of the
Earth. If you were standing on the Moon, you would see the Earth
take a just small bite off the edge of the Sun. The amount of
light lost is minimal, and the effect on the Moon as seen from here
is about zero. Following full, the Moon then enters its waning gibbous as
it heads towards third quarter,
that phase not reached until next week.
It'll be a far better sight to watch the waxing gibbous plow
through Scorpius. Look the night
of Friday the 3rd to see the Moon just to the right of bright
reddish Antares. By the
following night, the Moon will have shifted to the other side,
appearing above the curve of the Scorpion's tail. In between the
Moon will occult the star as viewed from Japan to Hawaii.
The night of Thursday the 9th, the Moon will then lie to the
northwest of Jupiter, which
now rises around 10:30 PM Daylight Time just as formal twilight
comes to an end. Before that, you can admire Saturn, which will grace the
western sky in Leo until it sets
about an hour after Jupiter rises.
The morning sky is now the domain of Mars and Venus, much
fainter Mars rising around 2:30 AM, brilliant Venus about half an
hour later. Both planets are now making their way through Taurus, beautifully placed to the
west of the Hyades Cluster and
south of the beloved Pleiades.
Most likely, however, the biggest news involves us, the Earth, as our
planet passes aphelion the evening of Friday, July 3, when we will
be farthest from the Sun for the year, at a distance of 147.1
million kilometers (91.4 million miles), 1.7 percent farther than
average. Given the heat of the day, it's clear that the solar
distance has nothing to do with the seasons, but everything to do with the 23.4 degree tilt
of the rotation axis against the orbital axis.
Follow the curve of the Big
Dipper's handle south first to Arcturus in Bootes and then to Spica, the centerpiece of the
otherwise dim constellation of Virgo, the Maiden. This blue first magnitude star
ranks 16th in the list of brightness and anchors the rest of the constellation, which sprawls broadly
to the northeast and northwest.