Howdy Star Gazers, and welcome to this episode
of Star Trails. I'm Drew, and I'll be your guide
to the night sky for the week starting March
the 16th through the 22nd. This week we say goodbye
to some visible planets, at least for a little
while. Leo roars into the night sky, resplendent
with its fascinating triplet of galaxies. And
this week's equinox means that spring has officially
arrived. So grab a comfortable spot under the
night sky and let's get started. Before we get
into the main program, I'd like to take a moment
to answer a listener's request. A few days ago,
a very generous anonymous listener sent the podcast
a donation and wrote in with an intriguing question.
Here's what they asked. Why do you choose to
call frozen water water ice and not just ice?
I grew up in greater Philadelphia and every time
you say water ice I wonder lemon or cherry Okay,
so I love this question because I was just in
Philadelphia last week and sadly I didn't get
any water ice Although I did enjoy maybe the
best cheese steak I've ever had in a dive bar
near Fairmount But seriously, you've picked up
on an important distinction that astronomers
make when talking about ice in space. Here on
Earth when we say ice, we almost always mean
frozen water, H2O. But out in the cosmos, ice
isn't just limited to water. In space, temperatures
can be incredibly low, allowing many different
substances to freeze into solid form. Some of
the most common space ices include frozen methane,
ammonia, carbon dioxide, often called dry ice
on Earth, and even nitrogen. It's safe to say
you probably wouldn't want to eat any of these
ices. Since all of these materials can exist
in a frozen state, astronomers use the term water
ice specifically to refer to frozen H2O. A great
example of why this distinction matters are the
polar ice caps on Mars. Both of Mars' poles have
layered ice caps, but they aren't made of just
one type of ice. The main component is water
ice, similar to Earth's polar ice caps. However,
during the Martian winter, the caps are also
coated with a seasonal layer of frozen carbon
dioxide, which sublimates into gas in the warmer
seasons. This seasonal cycle is a key part of
Martian weather patterns. The same kind of distinction
applies when we study icy moons, comets, and
distant planets. Saturn's moon, Titan, for instance,
has surface ice, but much of it is actually frozen
hydrocarbons like methane. Meanwhile, Europa
and Enceladus are known for their subsurface
oceans of liquid water beneath a thick crust
of water ice, which is why they're such exciting
places to study for potential extraterrestrial
life. So, in astronomy, we clarify by saying
water ice to be precise about what kind of ice
we're talking about. It's just one of the many
frozen substances out there in the cold reaches
of space. And if we ever find blue raspberry
water ice on another planet, it'll certainly
be the discovery of a century. Thanks again for
that question and especially for the thoughtful
donation. I welcome anyone to write in or just
let me know what you've been enjoying in the
night sky. If you feel inclined to donate, check
the link in the show notes or on the show website.
Scroll down on the homepage until you see the
donate button. I hope everyone had the opportunity
to see the stunning full lunar eclipse early
Friday morning. At my location, we'd had clouds
all day, but the sky cleared around 9 p .m. and
the full moon was extremely bright. Some hours
later, I went outside around 2 .30 a .m. to check
out the eclipse, which was nearing totality.
The moon was almost right overhead and all the
bright moonlight from earlier was gone. The moon
was a subtle red color with a slightly brighter
coloring along the northern limb. Through binoculars,
it almost reminded me of Mars with its red shading
and ice caps. Every time I've watched the total
lunar eclipse, at least one side of the moon
seems brighter than the rest. Apparently, this
is owing to the Earth's uneven shadow density.
The Earth's umbra is not an evenly distributed,
perfectly dark shadow. The outer edges of the
umbra allow more sunlight to refract through
the Earth's atmosphere, meaning parts of the
moon near the umbral edge receive more scattered
light than the deeper central regions. Also,
the way our atmosphere filters the sunlight could
cause some shadow variations. The red color of
the moon during totality comes from Rayleigh
scattering, the same effect that makes sunrises
and sunsets red. Earth's atmosphere bends sunlight
around the planet, filtering out shorter blue
and green wavelengths and casting a reddish hue
onto the moon. However, the amount of dust, pollution,
or clouds in Earth's atmosphere at the time of
the eclipse can vary, causing uneven filtering.
Some areas of the moon might receive slightly
more light than others, leading to patches of
dim orange or yellow instead of deep red. I was
also struck by how small the moon looks right
now. Back around the end of last year, when we
had several consecutive super moons, the moon
was noticeably larger and more dominant in the
sky. Of course, the moon's distance to Earth
changes throughout the year, owing to its elliptical
orbit. The moon will reach Apogee, its point
farthest from Earth, on March 17th. So it's much
smaller in the sky right now. The difference
between Apogee and Perigee, the closest point
to Earth, can be more than 30 ,000 miles, so
the difference is significant. Also, its high
point in the sky during the eclipse means that
we didn't experience the so -called moon illusion,
where it seems larger in the sky as it gets closer
to the horizon. If you saw the eclipse, I'd love
to hear your observations, so visit StarTrails
.Show and send me a report. With the eclipse
behind us, we begin the week with the moon in
a waning gibbous phase, just following last week's
full moon. It's still nearly full early in the
week with nearly 90 % illumination. But by Saturday,
we'll reach the last quarter moon. At this phase,
half of the moon appears illuminated, but only
in the morning sky. That means deep sky observers
still enjoy darker skies to work with at least
until 3 a .m. or so. If you're into astrophotography,
the last quarter is a great time to capture the
moon's rugged terrain. With the light coming
in from the side, you'll get great contrast on
lunar mountains and craters along the terminator.
That's the line between night and day on the
moon's surface. Now onto the planets. After the
recent spectacular parade of planets that gave
some observers the chance to see all the visible
planets lined up across the sky, we've basically
lost three of them. Mercury is once again too
close to the Sun, and it's joined by Venus and
Saturn. All three bodies are bunched up with
the Sun this week. You may still be able to catch
a glimpse of Mercury and Venus tonight, just
after sunset, and very low on the western horizon.
But as the week progresses, our two interplanetary
companions will dip closer to the horizon each
night at sunset, until we can't see them anymore.
By the week's end, Venus will be ahead of the
Sun, and by next week will transition to a morning
star, rising in the east just before the Sun.
This transformation happens roughly every 19
months as Venus moves between Earth and the Sun
in its orbit. We've been enjoying the presence
of Venus in the evening sky since last fall,
the third brightest object in the sky after the
Sun and Moon. By the month's end, you'll need
to be an early riser to catch its brilliance
in the pre -dawn sky. Jupiter, the king of planets,
is still high and bright in the early evening.
Located in the constellation Taurus, and with
Venus gone, it claims its place as the brightest
object after the moon. Look for it near Aldebaran,
the orange giant star that marks the eye of the
bull. If you have a telescope, this is a great
time to check out Jupiter's four largest moons,
Io, Europa, Ganymede, and Callisto, easily visible
as tiny points of light near the gas giant. Mars
is nearby, sitting in Gemini, close to the twin
stars Castor and Pollux. Unlike the flickering
glow of those stars, Mars has a distinct and
constant reddish hue. Now, let's turn our attention
to some of the constellations that dominate the
night sky in March. Taurus is a powerhouse this
season, home to some of the best known deep -sky
objects. Along with Aldebaran, look for Messier
45, the Pleiades. That's the little cluster of
stars that looks like a tiny dipper. In mythology,
the Pleiades were seven sisters pursued by Orion.
And in modern astronomy, this cluster is one
of the closest and brightest open star clusters
to Earth. Even without any equipment, the Pleiades
appears as a small hazy patch in the constellation
Taurus. Most people can see six or seven stars
under dark skies. Interestingly, one of the best
views of the Pleiades comes with binoculars.
The cluster is larger than the full moon, so
it's actually too spread out to fit entirely
in most telescopic views. With binoculars, the
brightest stars become distinct, each glowing
in shades of blue -white. You'll also start to
notice that the cluster contains dozens of fainter
stars that blend into the glow when seen with
the naked eye. A small telescope will show even
more stars, possibly up to 100 members of the
cluster scattered across the field of view. It's
best to use a low -power, wide -field eyepiece.
If you're in an extremely dark location, you
might catch a glimpse of a faint bluish reflection
nebula. This is leftover dust that the cluster
is currently passing through, reflecting the
light of its young, hot stars. It's faint, so
long exposure astrophotography does a much better
job of bringing it out in visual observation.
Fun fact, while the Pleiades is generally called
the Seven Sisters, in Japanese it's known as
Subaru. And if you look closely at the Subaru
car logo, you'll see a stylized version of the
cluster. Leo the lion is another March favorite.
This constellation rises in the east in the evening
and is easy to spot thanks to its backward question
mark shape. That's called the sickle. In ancient
cultures, Leo was often associated with royalty,
strength, and the sun, which is fitting since
it's a sign that warmer days are ahead. The brightest
star in Leo is Regulus, a bluish -white star
that's about 79 light years away. And here's
another fun fact. It actually spins so fast that
it's not quite a sphere, but slightly flattened.
One of the highlights of LEO is the LEO Triplet,
a stunning group of three spiral galaxies, Messier
65, Messier 66, and NGC 3628, all located about
35 million light years away. M65 is slightly
tilted toward us, giving it a classic spiral
shape. It has a yellowish core, meaning it has
older stars, but also some dust lanes where new
stars are forming. M66 is more distorted, likely
due to gravitational interactions with its neighboring
galaxies. It has strong spiral arms and huge
dust clouds. NGC 3628, also called the Hamburger
Galaxy, is the third member of the triplet. This
galaxy has a thick dust lane cutting across it,
making it look like a cosmic sandwich. It's a
little fainter than M65 and M66, but if you're
in a dark location with a telescope, you might
catch it. The Leo triplet is an active, dynamic
group, meaning these galaxies are pulling and
warping each other, due to their gravitational
interactions. They may eventually merge millions
of years from now, but for now they make a spectacular
sight for sky watchers. To find them, look just
below the lion's belly near the star Cherton.
If you have a telescope with a wide field of
view, you can see all three galaxies together
in a single frame. A notable astronomical event
this week is the Spring Equinox, happening on
March 20. Twice a year, Earth's tilt lines up
perfectly perpendicular to the Sun. That means
for a brief moment, day and night are nearly
equal all over the world. The word equinox comes
from the Latin for equal night. This is the official
start of spring in the Northern Hemisphere, and
cultures around the world have celebrated it
for millennia. Ancient civilizations like the
Mayans built entire structures, like the temple
of Kukulkan at Chichen Itza, that align with
the Sun on the equinox, creating a serpent -like
shadow on the pyramid's steps. Astronomically,
the equinox is a halfway point. It's when the
Sun crosses the celestial equator moving from
the southern half of the sky into the northern
half. From now on, our days will keep getting
longer until we reach the summer solstice in
June, when the sun is at its highest point. If
you found this episode helpful, let me know and
feel free to send in your questions and observations.
The easiest way to do that is by visiting our
website StarTrails .Show. This is also a great
way to share the show with friends. Until next
time, keep looking up and exploring the night
sky. Clear skies everyone!