Photo of the Week. Crossings. The line between the
overexposed Moon and Jupiter (right of center) intersects with that
conecting the Hyades cluster
(with Aldebaran, down and to
the left of Jupiter) and the Pleiades (up and to the right of the Moon). Stars of
Orion shine to upper left, the
brightest of which is Bellatrix.
Astronomy news for the two weeks starting Friday, April 26,
2013.
Our Moon begins the week in its waning
gibbous phase just barely past full
as it slings itself around the lower, southern, part of the Zodiac. After going through third quarter just north of the classical
figure of Capricornus the morning
of Thursday, May 2 (allowing the near-perfect phase to be seen near
sunrise), on the morning of Friday the 3rd it rises as a fat crescent. The cycle then ends at new
Moon late next week. There are no planets along this week's lunar
path, no planetary passages to admire, though on the morning of
Sunday, April 28, the bright waning gibbous might be spotted north
of Antares in Scorpius.
For that matter, the whole planetary sky is a bit limited. The
inner terrestrials, those physically near the Sun and built like the
Earth with iron cores and rocky mantles (Mercury, Venus, and
Mars), are all too close in angle to the Sun to be readily
seen. Give them time, though. Venus is slowly emerging from
evening twilight, Mars just as slowly from dawn's light, and
Mercury will make a decent appearance in early June. That leaves
us with the two outer ancient planets, the large "gas giants" made
largely of hydrogen and helium. Look early to see Jupiter (11 Earth diameters across) in western skies
northeast of the bright star Aldebaran. The planet now sets by
around 11 PM, just an hour and a half past the formal end of
twilight. All that can be put aside, however, as the night really
belongs to not much smaller Saturn (9.5 Earths), which passes opposition to the Sun on
Sunday, April 28, when it will rise at sundown, set at sunrise, and
cross the meridian to the south at local
midnight (1 AM Daylight Time). Moving slowly
retrograde (to the west) against the stars of western Libra, the planet lies about 15
degrees (an hour of time) due east of Virgo's Spica. Up all
night, Saturn is perfectly positioned for viewing. Even a small
telescope brings out the rings and the bright
satellite Titan.
As the Earth orbits the Sun, when seen at a given time the starry
sky slowly shifts by a degree per night to the west. As April goes
to May, look well up to the south in mid evening for the great constellation of spring, Leo, the Lion, recognizable by his
sickle-shaped foreparts that end in the bright star Regulus. To the east is Denebola, the Lion's Tail. Lower
to the southeast will be Spica and Saturn, Spica pointed to by the
top of box-like Corvus, the
Crow. High to the southeast above Spica and Saturn find Arcturus, the brightest star of the
northern hemisphere. Back on Earth, we celebrate an astronomical holiday, May
Eve, the night before May Day, May 1, a "cross quarter day" that marks
the halfway point from the beginning of spring to that of summer.
