Photo of the Week. The midnight Sun shines over Lake
Colleen at Deadhorse (Prudhoe Bay), Alaska, on July 7, 2007. The
Sun is still so far north that it stays up for 24 hours a day,
which is possible only above the Arctic Circle. It will finally
set later in the month as it moves to the south. A latitude here
of 70.2 degreees north gives an actual solar (center) elevation of
2.9 degrees, which is raised to 3.0 degrees by atmospheric
refraction.
Astronomy news for the week starting Friday, July 27, 2007.
'Tis the week of the full
Moon, the bright orb blanking out all the fainter stars.
Formal full is passed the night of Sunday, July 29, roughly about
the time of Moonrise in North America. The full Moon (directly opposite
the Sun) thus
rises in the southeast just as the Sun sets. With the Sun firmly
ensconced in Cancer, the full Moon
will be found passing through Capricornus, its dim stars quite invisible to the eye.
It then spends the remainder of the week in its waning
gibbous phase as it heads toward third
quarter on Sunday, August 5. As it travels, the Moon passes
south of Neptune
on Monday, July 30, and then south of Uranus on
Wednesday, August 1. Slowly moving Neptune is still near the
Capricornus-Aquarius border, while
Uranus is just south of the Circlet
of Pisces.
Venus and Saturn,
travelling more or less together (as projected onto the sky, not in
reality), are both now effectively gone from sight (though a
dedicated observer might still catch very bright Venus very low
above the western twilight horizon). On the other side of the sky
and the night, Mercury
is making one of its better (though still difficult) appearances in
eastern morning twilight, Castor
and Pollux in Gemini more or less pointing
downward at it. The little planet passes six degrees south of
Pollux on Wednesday, August 1.
That leaves the night pretty much to Jupiter and Mars. Jupiter, in
southern Ophiuchus (the modern
boundaries of which cross the ecliptic) to the east of Antares in Scorpius, transits the meridian in early evening
twilight and then spends the rest of the night in the southwestern
sky until it sets around 1:30 AM Daylight Time. Reddish Mars,
rising just before local midnight (1 AM Daylight) just a bit before
Jupiter's disappearance, then takes over the morning in a lovely
setting at the Taurus-Aries border to the southwest of the
Pleiades and to the west of
the Hyades cluster.
The Big Dipper, the great iconic
asterism of Ursa Major, has for
some time now dominated the evening zenith sky. As summer passes
its midpoint, we see it now slipping into the northwest, most of
the figure of the Great Bear to the south and west of it. Look
opposite the Dipper into the northeast to find the "W" of Cassiopeia rising, telling us that
summer will before long turn to the colors of fall.
