Skylights featured three times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. Prairie Sunset Moon.
Astronomy news for the week starting Friday, August 1, 2003.
The Moon, having recently passed its new phase, waxes
through crescent the early part of the week, and achieves first
quarter the night of Monday August 4 just about the time of
Moonset in North America. The evening of Sunday the 3rd, the fat
crescent will be just to the north of the star Spica. The first quarter appears
midway between the classical figures of Virgo (which contains Spica) and Libra. The night of Wednesday the 6th finds the waxing
gibbous Moon passing north of Antares in Scorpius, this star and Spica two of five first
magnitude stars of the Zodiac (the others Regulus in Leo, Aldebaran in
Taurus, and Pollux in Gemini).
A day after first quarter, the Moon passes perigee,
where it is closest to the Earth.
The only other "event" has
Neptune at opposition to the Sun on Monday the 4th, the planet
confined within the central figure of Capricornus. While invisible to the naked eye, it is
an important body within the planetary system, as it is the last of
the large planets. More-distant Pluto, well off the ecliptic in Ophiuchus, is more of a "planetary core," a body that
did not have enough raw material to grow to a larger body like
Neptune. Moreover, Neptune controls Pluto, as it goes around the
Sun three times for every two orbits of Pluto (respectively rounded
to 164 and 248 years), a phenomenon called a "gravitational
resonance." In some sense Neptune therefore represents the "end"
of the planetary system, as Pluto is more in league with a vast
number of other bodies in the distant "Kuiper
Belt."
So far as naked eye planets are concerned, we are left with dim,
barely visible Uranus and brilliant Mars
, to which the week really belongs, the latter to the east of
Uranus, both in southern Aquarius.
As August begins, the red planet rises in the southeast at 10 PM,
the rise time moving up by about half an hour a week.
Unmistakable, Mars is at magnitude -2.3, far brighter than the
sky's brightest star, Sirius
(which falls at magnitude -1.5), and is moving retrograde as it prepares for its August 28th opposition
with the Sun, when it will be closer to us than any time in
recorded history (though not by all that much).
Take time out from Mars to admire the northern sky. In the
evening, the bright Summer
Triangle climbs the eastern sky, its brightest star Vega in Lyra. This exquisite constellation consists of lovely
parallelogram of stars that lie to the southeast of the luminary
and one more to the northeast. The significance of the stars belie
their seeming faintness, one (Epsilon) one of the most famed
multiple stars in the sky, Sheliak (Beta Lyrae) one of the most
famed eclipsing binaries. Right between Sheliak and Sulafat (Gamma) lies the telescopic
"Ring
Nebula in Lyra," a fine example of a dying star (with a ring of
ejected gas) that is creating a white dwarf like Sirius B.
