Photo of the Week. Planet Earth: the tenth of twelve
in the "Flight across Greenland," going from east to west above
the fantastic glacier and a river of ice. See full resolution.
Astronomy news for the week starting Friday, April 18, 2014.
With the eclipse over, the Moon is seen
at the beginning of the week late in its waning gibbous phase. That ends with third quarter on the night of Monday,
April 21, shortly after Moonrise in North America. During the
remainder of the week we see the Moon fading as a waning crescent, rising ever
later in the morning hours as it approaches Venus. The
morning of Friday the 25th, the two will make a fine sight with
the rising Moon up and to the right of the brilliant planet. The
Moon passes perigee, its closest point to the
Earth (5.5 percent closer than averate), on Monday the 22nd, less than a
day after the third quarter.
Night after night, the planetary sky changes, albeit slowly. Now
in the western sky as darkness falls,
Jupiter sets shortly after local midnight. But you still have
a couple months left to enjoy the bright planet, which quite
overwhelms everything else. To the southeast, Mars
is already well up by the end of dusk nicely to the northwest
of Spica in Virgo, Mars's
retrograde motion obvious over only a few nights. By midnight
Daylight Time, the red planet is crossing the meridian to the south. Mars is followed
by dimmer but still bright Saturn, which rises
in the southeast near twilight's end still within the confines of
Libra. The ringed planet then
crosses to the south about 2:30 AM. Wait a couple hours and you
get to see Venus popping up over the eastern horizon. The second
planet from the Sun crosses a bit of a divide by rising just as
morning twilight begins, no longer (for now) to be seen in a fully
dark sky.
From the large to the small, we have a bit of a meteor shower this
week, the Lyrids. The shower peaks the
morning of Tuesday the 22nd, the meteors appearing to come out of
the constellation Lyra. Rather
sparse to start with, producing 10 or 20 meteors per hour, their
number will be reduced by the bright quarter Moon. The Lyrids are
the debris of long-period Comet Thatcher
of 1861. It won't be back for some 260 years.
Leo, with its distinctive "Sickle" that ends in Regulus, crosses the southern
meridian around 10 PM as we approach the days of summer.
Following along behind it is Virgo with Spica. The two stars are closely connected
by the ecliptic, the autumnal
equinox falling roughly midway between them. To the west of
Leo, between it and Jupiter-embracing Gemini, lies one of the dimmer constellations of the Zodiac, Cancer the Crab, which holds the Beehive star cluster and once
held the Summer Solstice (hence
the Tropic of Cancer). That it
no longer has the solstice is the fault of precession, the 26,000 year wobble
in the Earth's axis.
