SKYLIGHTS
Photo of the Week..Helium balloons lift happy hearts
into the blue sky.
Astronomy news for the week starting Friday, March 22, 2002.
The Moon grows through its waxing gibbous phase this week, and
reaches full on Thursday the 28th about noon in the Americas. The
night of Wednesday, the 27th, the Moon will be just short of full
and will rise just before sunset, while the following night it will
be just past full and will rise just after sunset. Only 10 hours
before the full phase, the Moon also arrives at perigee, where it
is closest to the Earth, about 5.5 percent closer than the average
distance of 384,000 kilometers (239,000 miles). The result will be
especially high tides at the coasts. The closer distance, however,
is NOT responsible for the full Moon appearing to be so large at
moonrise and moonset. The "large Moon" is an optical illusion
whose origin has long been argued. The common explanation is that
the eye references the rising Moon to things on the horizon, which
makes it just look big, whereas when the Moon is high in the sky,
the references go away and it looks smaller. For the same reason,
constellations also look especially large when they rise and set.
In truth the Moon is only a half a degree across, and surprisingly
fits nicely well with the nest of the Pleiades star cluster, which is twice the lunar angular
size.
Four planets now dominate the nighttime sky. As twilight dims,
look in the west for brilliant Venus. Above it lies bright reddish
Mars now moving eastward against the stars of eastern Aries. While the red planet
maintains its setting time shortly after 10 PM, the Sun is setting
later and later, so is still catching up to Mars. By the end of
May, the planet will be setting just as twilight ends. Higher
still is Saturn, slowly drifting east among the confines of Taurus. The ringed planet is just
making the transition to setting before midnight. After twilight
ends, the most obvious thing in the sky other than the Moon is the
last of the bright four, Jupiter, which shines brightly among the
stars of Gemini, the giant
planet setting about two hours after Saturn. All the bright
planets, including even little Mercury, are slowly assembling for
a nice gathering toward the beginning of May, though Jupiter will
be left a bit on the sidelines.
With the eye focussed on Saturn and Jupiter, one might forget to
look farther north to admire one of the sky's great constellations,
Auriga the Charioteer, which
holds one of the great stellar luminaries, Capella. The constellation is made
of a prominent pentagon that attaches directly to Taurus to the
south. Both these constellations are in a faint part of the Milky
Way impossible to see under moonlit conditions. Within that part
of the Milky Way lie the dark dusty clouds of some of the nearest
of all active star-forming regions.
