Astronomy news for the week starting Friday, April 6, 2012.
We start off the week with the ever-popular (except for those
wishing dark skies) full Moon, which
takes place during the day on Friday, April 6, such that it will
rise just past the phase that evening. The Moon thereafter fades in the waning gibbous phase (cheering the dark sky
folks) until it hits last (third) quarter
the morning of Friday the 13th with the Moon high in the sky at
dawn. The night of the 6th, look for the Moon to be just to the
southwest of Saturn, with Spica in between, the brightness of the
lunar disk making the star hard to spot. At about the same time,
the Moon is going through perigee, where
it is closest to the Earth.
Venus, which
is commonly taken for a UFO, continues its show, not setting until
11:30 PM Daylight Time (providing of course that you have a good,
flat horizon). Its planetary brilliance unmatched, it will
continue to brighten throughout the month. Its mate in bright
"UFO-dom," Jupiter, has now
sunk rather far down from Venus and is now setting by 9:30 PM, just
half an hour after the end of formal twilight, so look early. But
all is not lost. Just half an hour or so after the giant planet
goes down, very bright orangy Mars transits
the meridian high to the south to the
east of Regulus in Leo. Note the contrast between the "red planet" and
the white, even blue-white, star. Saturn, rising just after
sunset, spends its evening and early-morning time in the east,
rising ever higher until it transits the north-south line just
after local midnight (1 AM Daylight Time).
For all the planetary show-offs, the week actually belongs more to
the minor bodies of the Solar System. The fourth-discovered of the
asteroids, Vesta, the only
one visible to the naked eye, goes through conjunction with the Sun
on Monday the 9th, while far more famed Pluto begins its
retrograde (westerly) motion the next day amidst the myriad
stars of northern Sagittarius. Taking
some 238 years to orbit the Sun at an average distance of 39
Astronomical Units (the Earth-Sun distance), the small (dwarf?)
planet seems hardly to move at all. But on the morning of Thursday
the 12th, the little one, about the size of the western US, gets
hit with the passing Moon, which actually occults the planet as
seen from Antarctica (the event then doubly invisible).
This is the time of year for Leo, the Nemean Lion of Hercules'
fame, which by 9 PM is approaching the meridian, holding very
bright Mars, eminently recognizable by its distinctive "Sickle" that ends in Regulus. To the
south lie dim modern Sextans (the
Sextant) and ancient Crater (the Cup),
which fall on the back of Hydra (the
Water Serpent).
