Saturday: Venus
is a fist held out at arm’s length below the Moon, in the south-southwest sky
at 4:45 p.m. Mercury is the more challenging object to find, less than a half a
fist above due southwest at this time.
Sunday: Mars
is less than a half a fist to the left of the Moon at 9 p.m. They are both just
above the west-southwest horizon.
Monday: The
earliest sunset of the year occurs throughout the next week: 4:13 p.m. This
seems odd because the shortest day of the year, the winter solstice, isn’t for
about two more weeks. The Sun is at its southernmost point with respect to the
background stars on the day of the winter solstice. This means the Sun spends
the least amount of time above the horizon on that day. But, the sunrise and
sunset times depend on more than its apparent southward motion in the sky. It
also depends on where the Sun is on the analemma, that skinny figure-8 you see
on globes and world maps. During the second week in December, the Sun is not
quite to the bottom of the analemma. But, it is on the leading edge of the
analemma, the first section to go below the horizon. For a slightly different
explanation about this, go to http://goo.gl/kjnHP. Or just go watch the
sunset. But don’t stare at the Sun.
Tuesday: Most
constellations don’t look like the object their name refers to. That’s because
most constellations don’t have such a simple to object to emulate as Triangulum
does. Triangulum is shaped like a… wait for it…. Wait for it…. A thin isosceles
triangle. Metallah is the only named star in the constellation. In Latin this
star is called Caput Trianguli, the head of the triangle. Triangulum is seven
fists above due south horizon at 9 p.m. It is pointing down and to the right
with Metallah being the southernmost star at this time of night. The Triangulum
Galaxy can be seen with binoculars about a half a fist to the right of Metallah.
Wednesday: Jupiter is three and a half fists above the south-southeast
horizon at 7 a.m.
Thursday: It’s
getting too cold to see frogs in the wild. Some rich politicians see them on
their dinner plate. But this is a great time to see frogs in the sky. Ancient
Arabs referred to the stars that we now call Fomalhaut and Diphda as Ad-difdi
al-awwal and Ad-difda at-tani. This means the first frog and the second frog,
respectively. Both frogs are low in the southern sky at 7 p.m. Fomalhaut is one
fist above the horizon and one fist to the east of due south. The slightly
dimmer Diphda a little more than two fists above the horizon and one fist to
the west of due south.
Friday: Cosmic
rays are high-energy subatomic particles. When they strike the Earth, they
interact with the atmosphere, creating a cascade of other particles including
muons. These muons pass through almost everything. So muons (HUH), what are
they good for? Absolutely nothing? Wrong. They are good for probing the
interior of places too fragile or too dangerous to enter. Scientists observed
the pattern of muons passing through the Fukushima nuclear reactor to determine
the location and orientation of the damaged fuel rods. For more muon
application, go to https://stardate.org/radio/program/cosmic-rays-iii.
The
positional information in this column about stars and planets is typically
accurate for the entire week. For up to date information about the night sky,
go to http://nightsky.jpl.nasa.gov/planner.cfm.