[upbeat music]
Preston Dyches: What's Up for April?
Morning planets, a sunset arch,
and finding Leo the Lion.
The morning sky on April 6th finds Jupiter and Saturn
forming a lovely trio with the crescent moon.
Look for them low in the southeast
in the hour before sunrise.
[whoosh]
April 22nd is Earth Day,
and annual opportunity to collectively appreciate
the wonder and beauty of our home planet.
So it seems appropriate to feature an Earth-related sight
you can see anytime of the year, when you have clear skies.
It's a twilight phenomenon
that you might have noticed just after sunset.
If you can pull your gaze away from the sunset
in the west and spin yourself around to face east,
you'll often notice a band of pink or orange-colored sky
with a darker bluish band underneath.
These bands move upward over the minutes
following sunset to form an arch across the sky
that slowly fades as night sets in.
The dark band is Earth's shadow rising.
Above it, the rosy-hued band is known as the Belt of Venus.
We observe this site for a short time after sunset
when the sun is just below the horizon,
but some of its light rays are still making their way
through the atmosphere before nightfall.
The redder or longer wavelengths of sunlight
are able to travel the longest distance
through the atmosphere.
And at the point opposite to the sunset,
this reddish light is scattered off the atmosphere
and back toward your eyes.
The Belt of Venus is named not for the planet,
but for the mythical goddess.
Together with Earth's shadow,
these sights form the "anti-twilight arch."
This arch rises like a curtain on the night,
slowly fading as Earth's shadow eventually fills the sky,
allowing us to gaze outward into the stars.
You can see this sight in morning twilight as well,
by looking in the direction opposite the rising sun,
that is toward the west.
As the sky begins to lighten,
Earth's shadow becomes noticeable
with the Belt of Venus above it,
and these bands slowly sink to the horizon as day breaks.
[Whoosh]
April is a great time to look for Leo...
That is, the constellation Leo.
Leo is the Latin word for "lion,"
and this well-known grouping of stars
is named for a super-powered lion vanquished
by the mythical hero Hercules.
It's a pretty easy constellation to locate,
because it sort of looks like a lion reclining in the sky,
and it has this recognizable curving shape
called the Sickle that represents the lion's head.
In April, you can find Leo high overhead in the south
in the first few hours after sunset.
In addition to the sickle shape of the lions head,
look for the lion's heart,
the brilliant bluish white star, Regulus,
which is one of the brightest stars in the sky.
Astronomers think most stars
have a family of planets orbiting them.
And these two bright stars in Leo named Algieba,
which is actually a double star,
and Rasalas, each have a confirmed planet
larger than Jupiter orbiting around them.
So step out after dark in April to look for Leo
with its sickle-shaped lion's mane and blazing bluish heart.
[whoosh]
Here are the phases of the moon for April.
[gentle music]
You can catch up on all of NASA's missions
to explore the solar system and beyond at nasa.gov.
I'm Preston Dyches
from NASA's Jet Propulsion Laboratory,
and that's What's Up for this month.