Photo of the Week. A 3.3-day-old crescent Moon, its
nighttime side glowing faintly with Earthlight, visits Venus.
Astronomy news for the week starting Friday, August 20, 2010.
The Moon continues to grow the early part of the week within
its waxing gibbous phase until it hits full on Tuesday, August 24th, around noon in
North America, rendering it just past the phase when it rises that
evening just after sunset. The remainder of the week sees it
moving through the early part of the waning
gibbous as it heads for third quarter
next week. Just half a day past full, the Moon goes through apogee, where it
is at its farthest orbital point from Earth, rendering the usual
full-Moon high and low tides not quite so high and low.
Just five hours BEFORE full phase the Moon passes above Neptune, the
planet starting the week in opposition to the Sun. Much more
interesting is the lunar passage seven degrees north of
Jupiter the morning of Friday the 27th (when it will also pass
north of
Uranus, the two planets quite close in angular pairing if not
in distance, Uranus almost five times farther from Earth than is
Jupiter).
About all that is still readily visible of the great summer western
evening planetary line-up is brilliant Venus, and even that is getting rather low, the planet's
setting now tracking the end of evening twilight. But be sure to
try to catch the classic conjunction of Venus and Mars the evening of Monday the 23rd, the red
one two degrees north of the bright one. You'll really need
binoculars, as Venus will be some 100 times brighter than Mars, the
result of differing distances from the Sun and Earth, as well as in
surface reflectivity. Watch during this and next week as the two
approach Spica in Virgo.
Saturn, setting before twilight ends, will be to the right.
Once they are gone, we look due east to see the rising of bright
Jupiter. With us the rest of the night, Jupiter transits the meridian to the south around 3 AM
Daylight Time.
By mid evening the Big Dipper is
now sinking into northwestern skies, its three-star handle (the
oddly-long tail of Ursa Major, the
larger Bear) still quite prominent even from modestly bright
locations. Follow its curve southward to Arcturus and then to Spica. At the
same time, the bowl of the Little Dipper of Ursa Minor (the smaller Bear) rides high above and to
the left of Polaris, which
maintains its position above the horizon at an angle equal to your
latitude. Between the Little Dipper's bowl and the bright star
Vega (nearly overhead) is the squarish head of Draco the Dragon, whose tail winds
up between the two Dippers. As the evening gets later and the Big
Dipper goes down, watch for the coming-up of W-shaped Cassiopeia as it climbs the
northeastern sky, the two circling the pole opposite one another.
