Astronomy news for the week starting Friday, June 29, 2001.
The Moon waxes through its gibbous phase early in the week, and
passes through full on Thursday, July 5. The night of Monday, the
2nd, it will pass six degrees north of Mars, the red planet so
brilliant that we will have little trouble seeing it even in bright
moonlight. The tilt of the Martian orbit has taken Mars a bit
below the ecliptic (the apparent solar path), whereas that of the
lunar orbit has taken it a bit above, hence the rather large
separation of the two bodies upon their conjunction.
If conditions are right for a solar eclipse, as they were on June
21st, then they are usually right for a preceding or succeeding
lunar eclipse (that is, the Moon must be crossing the ecliptic
while new in the case of a solar eclipse, full in the case of a
lunar). As a result, the Moon will undergo a partial eclipse at
this full phase, on Thursday the 5th. Unfortunately, the event --
in which the Moon only partly immerses itself in the Earth's shadow
-- will not be visible in North America. Those in the opposite
hemisphere (Australia, New Zealand, Pacific Ocean), however, will
get a nice view, including Hawaiians.
The Earth also takes the stage, as it passes through its aphelion
point, where it is farthest from the Sun, on the Fourth of July.
At a distance of 94,502,836 miles (152.088 million kilometers), our
planet will be 3.5 percent farther from the Sun than when it passed
perihelion, its closest point, last January 4, giving us 7 percent
less solar warmth. Obviously, given the usual northern hemisphere
July heat, the distance between the Earth and the Sun has little to
do with the seasons, which are caused by the 23.4 degree tilt of
the Earth's axis of rotation relative to its orbital perpendicular.
All things being equal, the distance variation would cause southern
hemisphere seasons to be more extreme than those in the northern
hemisphere, but the effect is lost in the asymmetric distribution
of the oceans, the southern hemisphere far more watery than the
Venus remains a stunning morning sight, while Mars maintains its
rule over night, the red planet retrograding through the southern
zodiac between Scorpius and Sagittarius. Look to the right of
bright Mars to find Antares, the scorpion's alpha star. If you
look down and to the right of Antares, and if you are far enough
south, you can see the bright stars of Lupus the Wolf, one of the
most southerly of the ancient constellations, the wolf held in the
grip of Centaurus, the Centaur, even farther south and to the east.
If Lupus and Centaurus are out of sight, instead admire the Big
Dipper high overhead in early evening. Look then to the south to
see the pair of stars that makes most of Canes Venatici (the
Hunting Dogs) and then to the sprawl of fainter stars that make
Coma Berenices, Berenices Hair, a cluster that makes a lovely sight