Astronomy news for the week starting Friday, August 5, 2011.
We begin the week with the first quarter
Moon, which takes place the morning of Saturday, August 6, with
the Moon out of sight for North Americans. So Friday evening (the
5th), the Moon will be just shy of the formal quarter, while the
next night (the 6th), it will be slightly past it. Can you then
detect the differences? Saturday's slight gibbous shape will quickly become more
obvious as the Moon waxes towards full,
that phase not reached until Saturday the 13th. The night of the
5th, look for
Saturn, Spica, and the near-
quarter-Moon to fall in a rough west-to-east line. The evening of
Tuesday the 9th, the growing Moon will bottom out at its most southerly
extent near the Winter Solstice and
within the confines of Sagittarius
(at the same time blotting out most of its stars).
Saturn, setting around 10:30 PM Daylight Time, just half an hour
after the end of formal twilight, is now very much an early evening
object with Spica to the left of it. So instead we get to admire
Jupiter, which enters the scene near 11:30 PM and is
then up all night, not transiting the meridian to the south until after sunup.
Look for it between the flat triangle that makes classical Aries to the northwest and the
ragged circle of stars that composes the head of Cetus, the Whale, or Sea Monster.
To the north lie the constellations of the
Andromeda myth, including the prominent star streams that make
Perseus, Andromeda's rescuer.
Stay up late enough then and you can watch Mars
rising (around 2:30 AM) in southern Gemini just barely to the northeast of the Summer Solstice. On Sunday the 7th it
will reach its greatest extent to the north for this orbital round.
Immediately to the north, binoculars will show Gemini's prominent
star cluster, Messier 35. In close
alignment with the Sun and on opposite sides of it,
Mercury and Venus are gone
from sight.
The night of August 12 and the morning of the 13th are set for the
maximum of the
Perseid meteor shower, the meteoroids the flakings of Comet Swift-Tuttle
(a small icy body that is slowly dissolving under the action of
sunlight), which has a 133-year period, was discovered in 1862, and
last came by in 1992. But don't much bother with the shower this
year, as the meteors (which through a perspective effect seem to
emanate from the constellation
Perseus), will be hidden by the light of the nearly-full Moon.
While we are getting a late-night preview of the constellations of
autumn, the early-evening sky still belongs to those of summer (at
least before the Moon gets too bright). To the north, look for the
Northern Cross topped by first magnitude Deneb (Cygnus the Swan upside-down), while to the far south,
Sagittarius, the Archer, stalks the heart of the Milky Way.
