Be a considerate
neighbor: Shield all your outside lights downward (or turn them
off completely) and enjoy the beautiful, starry night sky.
January 2006 night sky—North is not always north
The North Star, also called the Pole Star or Polaris, is the star
that the earth's axis points toward in the northern sky. Throughout
the ages people have been fascinated by this star and the fact that
it doesn't seem to move in the sky. For Ncenturies the North Star
has been used as a navigation aid. It has also been used to measure
astronomical latitude, since we map latitudes to the equivalent
sky positions: the North Pole equates to 90 degrees north latitude
on Earth, as does its projection into the sky.
Today the Earth's axis points within one degree of Polaris, the
brightest star in the constellation Ursa Minor (also called the
Little Dipper). Polaris appears to be in a fixed position in the
sky throughout the year. All other stars and constellations seem
to revolve around the North Star.
Over the course of time, the North Star changes because the direction
of the earth's axis wobbles like a spinning top. Over a period of
twenty-six thousand years, different stars are our pole star. Right
now Polaris is within one degree of true north, but five thousand
years ago, Thuban, the brightest star in the constellation Draco,
was the North Star. Five thousand years from now, the North Star
will be Alpha Cephei, the brightest star in the constellation Cepheus.
Seven thousand years after that, it will be Vega, the brightest
star in the constellation Lyra.
While the precession of the Earth's axis takes place over thousands
of years, magnetic north is now moving much faster. Earth's magnetic
north pole is where the magnetic field lines are oriented vertically
and plunge into the surface of the earth. It is also at the north
pointer of a compass point.
The true north pole, which is located on the Earth's axis of rotation,
and the magnetic north pole are not in the same location. For more
than four hundred years, the Earth's magnetic north pole was roughly
in the same position. The most recent survey by the Canadian Government,
in 2001, showed the pole was located at 81.3 degrees north, 110.8
degrees west. This is west of Greenland and north of the Canadian
But now the magnetic pole is on the move; it has drifted nearly
680 miles into the Arctic Ocean in the last one hundred years. And
its speed has increased considerably during the past twenty-five
years. In 2005, the estimated location was 82.7 degrees north, 114.4
degrees west. If the pole follows its present course, it will pass
north of Alaska and arrive in Siberia in a half century. If that
happens, Alaska and Northern Canada may lose the beautiful northern
lights, which are caused by the interaction of the magnetic pole
and the solar wind. Soon, the northern lights may be visible in
southerly parts of Siberia and Europe.
Geologists have evidence to show that the Earth's magnetic field
has reversed directions several times. The Earth last went through
a magnetic reversal some 780,000 years ago. These episodic reversals,
in which south becomes north and vice versa, take thousands of years
and are the result of complex changes in the Earth's core. While
there is some evidence to convince some scientists to think that
this movement may be the start of a pole reversal, most researchers
think that this is all just part of the normal wanderings of the
pole between Canada and Siberia.
THE PLANETS, THE MOON, AND METEORS
• Mercury may be visible low in the eastern sky the first
few days of the month just before sunrise.
• Venus disappears into the Sun most of the month, but will
reemerge as the morning star late in the month. Look east before
• Earth is closest to the sun in its elliptical orbit on January
• Mars is shining brightly almost directly overhead this month
at about 7:30 p.m. Look for the Moon to pair with Mars on January
• Jupiter rises after midnight. On January 23, the Moon will
be beside Jupiter.
• Saturn rises in the night sky at about 7:00 p.m. this month,
and will reach opposition on January 27. It is overhead at about
1:00 a.m. at mid-month. The Moon will be next to Saturn on January
• The Moon is full on January 14 and new on January 29.
• The Quadrantids meteor shower should peak on January 3.
Look at about 2:30 a.m. for the best viewing. Expect to see fifteen
to forty-five shooting stars per hour.
Seen those flashing white lights in the western sky?
You may have noticed that the daytime white strobes remained on
all night for about two weeks during December, causing considerable
light pollution. A Signpost reader called FAA Field Office inspector
John Wagner, 764-1210, and four days later the red lights were back
on and the white strobes were off at night. Doug Felix, of the FAA
Southwest Office in Texas, called our reader to say that he had
talked to the "sponsor" of the tower, and that the situation
was solved. Felix wasn’t sure if complaints from Placitas
played a part in the resolution of the issue.
The sponsor of the tower is Roberts Broadcasting, out of St. Louis.
The owner, Chris Meisch, (314) 283-6070, said that the backup system
to put on the red lights had failed.
According to the FAA, even if the red-light backup fails, by law,
a third backup must meet FAA regulations: a 200-candela-intensity
white light is supposed to come on. The two-hundred-thousand-candela
light visible during the day should not stay on.
The tower is 1,049 feet high and represents a hazard to all aircraft
if regulations are not followed. For more information, go to oeaaa.faa.gov,
get into Advisory Circulars 70/70460-1 and look for Guidelines,
highlighted in blue, and find the charter concerning dual-intensity
lights systems for towers above five hundred feet.
Suggestions and comments
are always welcome at firstname.lastname@example.org.