Saturday: At
precisely 7:47 a.m., the center of the Sun crosses the celestial equator and
passes into the southern sky. The celestial equator is an imaginary line that
divides the sky into a northern and southern half. When the Sun is in the
southern half of the sky, it appears to take a shorter path from rising to
setting. It also does not get as high in the sky at noon. This leads to shorter
days and longer nights. Since the Sun crosses the celestial equator today,
there is an instant when it is equally in the northern and southern sky, called
the north and south celestial hemispheres. This so-called “equal night” is
given by the Latin word equinox. Thus, today is known as the Autumnal Equinox.
However, the day and night are not of equal duration today. The sun rises at
6:50 a.m. and sets at 6:58 p.m. Day and night are closest to equal duration on
Tuesday.
Sunday: “You
know Aries and Cancer and Draco and Libra. Leo and Pisces and Virgo and Hydra.
But, do you recall, the pointiest asterism of all? Triangulum, the three sided
asterism, had a very pointy edge….” Sorry. Some stores have started putting up
their Christmas decorations and that has put me in the mood to modify some
Christmas songs. Anyway, Triangulum is a small constellation between the more
prominent Andromeda and Aries. Its main feature is a skinny triangle oriented
parallel to and nearly four fists held upright and at arm’s length above the
east horizon at 10 p.m.
Monday: Jupiter
is one fist above the east-northeast horizon at 11 p.m. By 6 a.m., it is more
than six fists above due south. Venus, the brightest point of light in the sky,
is nearly three fists above the east horizon at 6 a.m.
Tuesday: Did
you time the exact length of the day and night on Saturday, the first day of
autumn? They were not equal in duration. Many people think that the day and
night are the same duration on the autumnal equinox. The day is a little longer
than the night for two reasons. First, the Sun is an extended object so even
when the middle part has set, the upper half is still above the horizon
lighting the sky. The second, and more influential reason is that the
atmosphere acts like a lens, bending light from the Sun above the horizon when
the Sun is really still below the horizon. Day and night are closest in
duration today.
Wednesday:
It has been dry in Ellensburg. But for a few days each month, the moon often
spends time in the watery part of the sky. Tonight is one of those nights. At
10 p.m., Capricornus, the sea goat is one to two fists to the lower right of
the moon. Aquarius, the water bearer, is just above and to the right of the
moon. Piscis Austrinus, the southern fish, is three fists below the moon. This
constellation features the bright star Fomalhaut.
Thursday: The
bright bluish star Vega is nearly straight overhead at 8 p.m.
Friday: The
cloudy season is coming to Ellensburg. Don’t feel bad. According to astronomers
from the European Southern Observatory, it is always cloudy season on HD
85512b, a newly discovered planet orbiting the star called… wait for it… wait
for it… called HD 85512. These astronomers developed a method to estimate the
cloud cover on planets orbiting distant stars. They think HD 85512b may be
cloudy enough to have liquid water on its surface even though it is fairly
close to its host star. While the presence of surface water does not guarantee
finding life, it is a critical component. For more information, go to http://goo.gl/bGxMD.
The
positional information in this column about stars and planets is typically
accurate for the entire week.
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