[Lively music]
[Preston] What's Up for December?
Your evening planet highlights
including the disappearance of Mars
and the constellation Pegasus.
The month begins
and ends with the Moon visiting the giant planets.
On December 1st,
find the Moon just a couple of
finger-widths apart from Jupiter in the evening sky.
Then, from the 25th through the 31st,
look to the southwest following sunset
to see an increasingly full Moon
slip past Saturn and then again past Jupiter.
Viewers with a clear view to the horizon
will be able to search for Venus and Mercury
in the fading glow of sunset,
just a few degrees above the skyline.
December 7th brings
one of those magical moments when the sky changes
dramatically before your very eyes.
It's called a lunar occultation.
As the Moon passes in front of or occults the red planet Mars.
The spectacle will be visible in parts of North America,
Europe and Northern Africa.
Viewers in the Southeast U.S.
and on the East Coast will see the Moon just graze past Mars.
For viewers in the U.S.,
Mars disappears behind the Moon sometime
between about 6:30 and 9 p.m., depending on your location.
So check your favorite skywatching app
to find out the time for your area.
Now the Moon passes in front of planets
in the night sky several times per year.
In fact, it generally occults Mars itself
at least a couple of times per year.
But each occultation is visible from only a small portion
of Earth's surface.
So it's not super common
for any particular spot on Earth to see them frequently.
Of course, the Moon passes in front of stars all the time.
If you're watching through binoculars,
they just blink right out.
But planets are not just points of light like stars.
They appear as circular little disks.
So planets actually take several seconds
to disappear and later reemerge.
So if you're in the viewing zone,
enjoy this relatively rare opportunity
to watch a bright planet being occulted by the Moon.
Looking high in the southwest sky on December evenings,
you can find a constellation named for one of the more
fantastical beasts of ancient mythology.
That's Pegasus, the winged horse.
In Greek myth,
Pegasus rode into adventures
with the hero Belaraphon,
and later carried the thunderbolts of Zeus himself,
who rewarded him by placing him among the stars.
Pegasus is one of the largest of the 88 constellations.
Its most prominent feature,
and the key to finding it in the sky is this asterism or
pattern of stars called the Great Square.
These four stars of roughly equal brightness
form the central part of the horse's body.
This December, it's easy to locate Pegasus
thanks to brilliant Jupiter.
Face southward to find the giant planet
halfway up the sky
with the Great Square
beginning about 15 degrees to the north of it.
Pegasus is a useful constellation for stargazers,
as it's a good starting place for finding your way
to other features in the night sky.
The constellation itself contains a number of dazzling
deep-sky objects, including globular cluster, M15
and the tangled galaxies of Stephan's Quintet.
With this year drawing to a close,
here's hoping you seek out the winged stallion Pegasus,
as you ponder what new adventures await
in the next year.
Here are the phases
of the Moon for December.
Stay up to date with all of NASA's missions
to explore the solar system and beyond at nasa.gov.
I'm Preston Dyches with NASA's Jet Propulsion Laboratory,
and that's What's Up for this month.