Saturday: Did
you get a new telescope for Christmas? Skyandtelescope.com has a good article
on how to get started using it. Go to http://goo.gl/2cJwo.
Any observing tip to the night sky should include Jupiter. Jupiter is six fists
held upright and at arm’s length above due south at 10 p.m. tonight. A small
telescope should reveal Jupiter’s cloud belts and its four largest moons. These
are called the Galilean moons because Galileo Galilei discovered them about 400
years ago.
Sunday: Mars
is a half a fist above the southwest horizon at 5:30 p.m.
Monday:
Forget about that big bright ball in Times Square. You can mark the start of
the new year with one of the sky’s own big bright balls. That perennial
favorite New Year’s Day marker, Sirius, the brightest star in the night sky,
rises to its highest point in the sky a little after midnight on January 1.
Thus, when Sirius starts to “fall”, the new year has begun. Look for Sirius
about two and a half fists above due south at midnight.
Tuesday:
Today is the day we celebrate the anniversary of something new – a new
classification of celestial objects. Giuseppe Piazzi discovered Ceres
[pronounced sear’-ease], the first of what are now called “asteroids”, on
January 1, 1801. Ceres is the largest asteroid in the belt between Mars and
Jupiter. At first, Piazzi thought it was a star that didn’t show up on his
charts. But, he noted its position changed with respect to the background stars
from night to night. This indicated to him that it had to be orbiting the Sun. The
International Astronomical Union promoted Ceres to the status of “dwarf planet”
in August of 2006.
If the Sun
looks big today, your eyes are not playing tricks on you. The Earth is at
perihelion at about 9 p.m. tonight. If you dig out your Greek language
textbook, you’ll see that peri- means “in close proximity” and helios means
“Sun”. So, perihelion is when an object is closest to the Sun in its orbit,
about 1.5 million miles closer than its average distance of 93 million miles.
Since it is winter in the Northern Hemisphere now, the seasonal temperature
changes must not be caused by the Earth getting farther from and closer to the
Sun. Otherwise, we’d have summer when the Earth is closest to the Sun. The
seasons are caused by the angle of the sunlight hitting the Earth. In the
winter, sunlight hits the Earth at a very low angle, an angle far from
perpendicular or straight up and down. This means that a given “bundle” of
sunlight is spread out over a large area and does not warm the surface as much
as the same bundle in the summer.
Wednesday:
Venus is a half a fist above the southeast horizon at 7 a.m.
Thursday: Today’s
early morning weather forecast: showers. Meteor showers, that is. The
Quadrantid meteor shower peaks this morning between midnight and dawn. Meteor
showers are named after the constellation from which the meteors appear to
originate. That makes this shower mysterious because there isn’t any
constellation with this name now. The shower was named after Quadrans Muralis,
an obsolete constellation found in some early 19th century star
atlases. These meteors appear to come from a point in the modern constellation
Draco the dragon. This point is about three fists above the northeast horizon
at 1 a.m. This year, the waning moon will be rising just before the peak observation
time so the dimmer meteors will be obscured by moonlight. Meteors are tiny
rocks that hit the Earth and burn up in the atmosphere. Most meteors are
associated with the path of a comet. This shower consists of the debris from an
asteroid discovered in 2003. Keeping with the comet-origin paradigm,
astronomers think the asteroid is actually an “extinct” comet, a comet that
lost all of its ice as it passed by the Sun during its many orbits.
Friday: Has
it been tough to wake up this past week? It should have been because the
sunrise has been getting a little later since summer started. I know. I know.
December 22 was the shortest day of the year. But, because the Earth’s orbit around
the Sun is elliptical and not circular, the Earth does not travel at a constant
speed. It moves faster when it is closer to the Sun and slower when it is
farther away. This leads to the latest sunrise occurring during the first week
in January and the earliest sunset occurring in early December, not on the
first day of winter, the shortest day of the year. On the first day of winter,
however, the interval between sunrise and sunset is the shortest. For more
information, go to http://goo.gl/SJC5r.
The
positional information in this column about stars and planets is typically
accurate for the entire week.