by Martin Ratcliffe
Saturn Hides Behind the Moon
A special and rare event takes place in September. The moon will hide,
or occult, the ringed planet Saturn very early on September 18. You’ll
need a telescope to see the details described here, but you can still see
the moon creep up on brilliant Saturn, then see it suddenly snap out, as
if someone turned off its light (impossible of course, since Saturn shines
by reflecting sunlight). Through a telescope however, watching the moon
slowly creep over the rings, then the planet, is a truly magnificent sight,
and proof that Saturn is farther way than the moon! Once the planet’s disk
is occulted, you can see the remains of the Saturnian ring system sticking
out from the dark lunar limb – a curious sight indeed, and one that is
fleeting. The occultation begins shortly before 6:00 a.m. Go outside around
5:30 a.m. to give yourself time to find Saturn, which will be easily visible
above the moon.
What are we seeing happen here? You will see two sky motions combined
during this event. The moon and Saturn will become lower in the western
sky as the morning wears on. This motion is caused by the daily rotation
of the Earth, which causes the stars and planets to rise and set. But notice
that the moon, in order to occult Saturn, must also be moving slowly in
the opposite direction as well, relative to Saturn and the stars – this
represents the moon’s actual motion around the Earth. By watching Saturn
disappear, you are seeing the motion of the moon in its orbit around the
Earth.
PlanetWatch
Mercury – makes a brief early morning appearance. On Saturn occultation
day (Sept. 18), look for Mercury on the opposite (eastern) horizon about
10 degrees above the horizon at 5:30 a.m. It is not easy to see in the
bright morning twilight, however.
Venus – shines brightly though the evening twilight, lingering
around the western horizon for about 90 minutes after sunset. Through a
telescope it presents a gibbous phase to us, a phase that is slowly but
surely shrinking. By the end of the year it will be a crescent. This changing
phase of Venus is proof that it orbits the Sun inside the orbit of the
Earth. No phases are visible on planets that orbit outside the Earth’s
orbit. Watch on September 5 for a slim crescent moon lying 3 degrees to
the north of Venus, and the bright star Spica 2 degrees to the south.
Mars – By the middle of this period, at the end of September,
you may notice two bright reddish objects low in the southwest, to the
left of Venus. One is the red planet Mars, and the other is a star, Antares.
The name Antares means “Rival of Mars.” Coincidentally both are of almost
identical brilliance. Antares lies on the constellation of Scorpius. During
October, Mars and Venus will appear to get closer together, a line of sight
effect. In viewing a plan of the solar system, you would find Mars on the
far side of the solar system, and Venus much closer to Earth.
Jupiter – continues to dominates the nighttime sky in Capricornus.
You’ll find Jupiter rising in the southeast shortly after sunset. Find
it by looking due south after the sky is dark. It is the brightest object
in that region of the sky. The moon passes close by on September 13 and
October 10.
Saturn – Once you’ve found Jupiter, look to the east, opposite
where the sun has set, and you’ll find another bright point that is actually
Saturn. During the night it climbs higher above the horizon until midnight,
when it lies due south, meaning it must be opposite the sun in our sky.
Astronomers call this point “opposition,” and the exact line-up occurs
on October 10.
Moon Phases
New Moon
1st Quarter
Full
Last Quarter
Sept 1
Sept 10
Sept 16
Sept 23
Oct 1
Oct 9
Oct 16
Oct 23
Oct 31
New Planetarium Show Debuts
On October 4 the planetarium premiers “Flashback to the Future.” It’s
an exciting look back at the life and times of the early space age, an
eclectic mix of the pop culture in the 50’s and 60’s, combined with the
thrill and excitement of launching into space and landing on the moon.
It is 40 years since the launch of the Soviet Union’s Sputnik satellite
shocked the world into realizing the Space Age had arrived. Today, with
landers on Mars, an orbiter around Jupiter, and a spacecraft about to be
launched to Saturn, spaceflight is almost taken for granted. In the show
“Flashback to the Future,” we look forward to the new millennium in space
and speculate where we will be in 50 years time. Check local listings for
current show times.
Every Friday at 4 p.m. the Henry Buhl, Jr. Planetarium at the Carnegie
Science Center presents “Stars over Pittsburgh,” your weekly guide to the
current night sky.
Don’t forget to check new Comet Hale-Bopp images in the Planetarium
show, “Comet: From Ice to Fire,” running through October 3. ?
Martin Ratcliffe directs the Henry Buhl, Jr. Planetarium at Carnegie
Science Center.
