Spring Equinox, Finding Ceres
Observing >
Ready or not, spring arrives tonight. But just what determines when spring begins?
We all spend half the year tilted a little toward the sun, half of it
tilted a little away. When we are tilted away, the sun doesn’t get
as high in the sky, the daytime is shorter, and it is generally cooler.
The opposite happens when we are tilted toward the sun: the sun gets higher
in the sky, daytime is longer, it is warmer.
There must be some magic moment when we are not tilted toward or away
from the sun. Actually there are two magic moments each year - at the
end of March and at the end of September. They are the equinoxes.
On those days, the Earth has sunlight from pole to frozen pole; the sun
is “up” just as long as it is “down;” it rises due
east and sets due west. It’s like Solar Equality Day for everyone
in our Global Village. This March our planet proudly faces the sun without
a tilt at about 11:30 tonight at the spring equinox - the beginning of
spring.
The first days of spring this year happen to be a good
time to look for an asteroid, for one suspect in particular going by the
name of Ceres.
Back in the late 1700’s, when planet-discovering was all the rage,
astronomers were faced with a puzzle. The planets were all planted around
the sun in a nice pattern - almost. There was a great gap between Mars
and Jupiter where it was believed there should have been a planet. The
search was on!
In
1801, the Italian astronomer Guiseppe Piazzi discovered in The Gap what
appeared to be a moving star. It turned out it was actually a mini-planet
which he named Ceres. In the next hundred years, hundreds of these mini-planets,
all smaller than Ceres, were found between Mars and Jupiter in what is
now called the Asteroid Belt. All tens of thousands of them were probably
the building blocks for a planet that was never quite able to get its
act together.
Want a stab at finding Ceres? You’ll need at least a 7x50 binoculars
and plenty of patience. If you’re up to it, here we go...
Probably the best way to find it --- but, ironically, the worst time to look - happens tonight. The nearly full Moon makes a nice marker but bleaches the sky. Position your binoculars so that the Moon is just out of the field of view to the right as if it were trying to sneak into your binoculars at the 3 o’clock position, but can’t. Now, with a heightened awareness for detail, move your binoculars one entire field of view to the left. Ceres is in there.
Which of the several starry objects is it? You can do one of two things
to find out: 1) If you want to experience the Old Ways of astronomy, sketch
the part of sky you’re looking at. Sketching the same area the next
day will reveal that one of the “stars” has moved slightly.
That’s Ceres. (Parents, this makes a great and original science project
... or 2) You can cheat and go to http://firstlightastro.com/icolumn.html.
You’ll find there simple starcharts of that region in the sky and
a Quicktime movie to see how Ceres moves day by day. (There are also charts
and movies for earth’s tilt through the year.) By the way, if it’s
cloudy this week, don’t fret! Although the Moon will have gone elsewhere,
Ceres is in the same general area for the next month.
Until next time, happy hunting in the clearest springtime skies!
Mark Ritter is a freelance writer and high school astronomy teacher. Got
questions or need help? Write him at ritter@firstlightastro.com.
Posted by Administrator at 2000.03.19 09:45 AM | Comments (0)
