Return of the Planets
The Solar System >
Lately, visitors to this column have read about galaxies and star clusters, the Milky Way and nebulae - lots of “deep sky” stuff. So, where have all the planets gone?
You may recall that back in May we had the Big Planet Conjunction when
the most of the planets were lined up, more or less, on the other side
of the sun. When it turned out that this would not destroy the planet
and humanity as some predicted, they quietly disappeared from the news
- and the skies.Well... they’re back.
Some have never really left the night skies. Trusty Uranus and Neptune have been out and up all summer but they aren’t exactly crowd-pleasers. They are so far (Uranus at about 1800 million miles and Neptune’s at 2700 million miles) that unless you have a decent scope they are no different from the stars in the sky.
But the more famous planets, Jupiter, Saturn, Venus, and Mars are out of hiding. They’re tanned and rested and ready to shine. But first a wee planet primer.
The fine points of orbiting the sun are rather complex but the basics are easy: If you are closer to the sun you get to move around it faster. If you are farther, it takes you longer. Tiny Mercury, the closest planet to the sun, takes only about 88 days to go around once!
Tinier Pluto, currently the farthest planet, takes about 250 years to go around! Sadly, humans born on Pluto would never get to have even one birthday party.
This distance factor explains why month after month Mercury and Venus seem in a rush through the skies while the more distant planets appear to just plod along endlessly, sometimes taking years just to wander through a single constellation.
Distance plays another role in all this. Mercury and
Venus have “inside orbits” compared to us. That means they never
venture far from the sun from our point of view. In fact, we only see
Mercury and Venus just before sunrise or just after sunset.
Nowadays
Venus, having swung quickly around to the other side of the sun since
the Big Conjunction, can be seen as the big bright light in the west just
after the sun sets - the Evening Star.
On the other hand, Mars, Jupiter, and Saturn are on “outside orbits”
around the sun. We have been trying to catch up with them all year and
have finally succeeded. Jupiter and Saturn can be seen in the late evening
rising together in the east.
Unlike with Venus and Mercury, there is the possibility of seeing these
outer planets nowhere near the sun. In fact, while passing them on the
inside lane we can actually be between them and the sun.
Thinking cap time! This means as the sun sets in the west, they rise in
the opposite side of the sky, the east. You can’t get farther from
the sun in the sky than that.
So where is Mars? Our tiny red friend is our next door neighbor to the
outside. Therefore, it moves considerably faster than more distant and
slothful Jupiter and Saturn and we’re having a tough time catching
up with it. But this, too, shall be passed. By the beginning of next year,
we will catch up and Mars will be visible again in the winter and spring
evening skies.
Need help visualizing the solar system and the planets’ positions?
There are easy-to-understand images and Quicktime movies waiting for you
at firstlightastro.com.
Until next time, clear skies!
Earth catching up with Mars: Summer 2000 - Summer 2001
Earth catching up with Jupiter and Saturn: May - Dec 2000
Posted by Administrator at 2000.10. 1 09:08 AM | Comments (0)
