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Planets Fade, Leo Roars, and the Equinox Arrives · Star Trails: From Backyard Astronomy to Cosmic Wonder

• 0:07
  Howdy Star Gazers, and welcome to this episode
• 0:10
  of Star Trails. I'm Drew, and I'll be your guide
• 0:13
  to the night sky for the week starting March
• 0:16
  the 16th through the 22nd. This week we say goodbye
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  to some visible planets, at least for a little
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  while. Leo roars into the night sky, resplendent
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  with its fascinating triplet of galaxies. And
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  this week's equinox means that spring has officially
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  arrived. So grab a comfortable spot under the
• 0:37
  night sky and let's get started. Before we get
• 0:42
  into the main program, I'd like to take a moment
• 0:45
  to answer a listener's request. A few days ago,
• 0:49
  a very generous anonymous listener sent the podcast
• 0:53
  a donation and wrote in with an intriguing question.
• 0:57
  Here's what they asked. Why do you choose to
• 1:00
  call frozen water water ice and not just ice?
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  I grew up in greater Philadelphia and every time
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  you say water ice I wonder lemon or cherry Okay,
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  so I love this question because I was just in
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  Philadelphia last week and sadly I didn't get
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  any water ice Although I did enjoy maybe the
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  best cheese steak I've ever had in a dive bar
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  near Fairmount But seriously, you've picked up
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  on an important distinction that astronomers
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  make when talking about ice in space. Here on
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  Earth when we say ice, we almost always mean
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  frozen water, H2O. But out in the cosmos, ice
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  isn't just limited to water. In space, temperatures
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  can be incredibly low, allowing many different
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  substances to freeze into solid form. Some of
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  the most common space ices include frozen methane,
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  ammonia, carbon dioxide, often called dry ice
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  on Earth, and even nitrogen. It's safe to say
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  you probably wouldn't want to eat any of these
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  ices. Since all of these materials can exist
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  in a frozen state, astronomers use the term water
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  ice specifically to refer to frozen H2O. A great
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  example of why this distinction matters are the
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  polar ice caps on Mars. Both of Mars' poles have
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  layered ice caps, but they aren't made of just
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  one type of ice. The main component is water
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  ice, similar to Earth's polar ice caps. However,
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  during the Martian winter, the caps are also
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  coated with a seasonal layer of frozen carbon
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  dioxide, which sublimates into gas in the warmer
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  seasons. This seasonal cycle is a key part of
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  Martian weather patterns. The same kind of distinction
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  applies when we study icy moons, comets, and
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  distant planets. Saturn's moon, Titan, for instance,
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  has surface ice, but much of it is actually frozen
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  hydrocarbons like methane. Meanwhile, Europa
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  and Enceladus are known for their subsurface
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  oceans of liquid water beneath a thick crust
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  of water ice, which is why they're such exciting
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  places to study for potential extraterrestrial
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  life. So, in astronomy, we clarify by saying
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  water ice to be precise about what kind of ice
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  we're talking about. It's just one of the many
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  frozen substances out there in the cold reaches
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  of space. And if we ever find blue raspberry
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  water ice on another planet, it'll certainly
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  be the discovery of a century. Thanks again for
• 3:49
  that question and especially for the thoughtful
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  donation. I welcome anyone to write in or just
• 3:55
  let me know what you've been enjoying in the
• 3:57
  night sky. If you feel inclined to donate, check
• 4:00
  the link in the show notes or on the show website.
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  Scroll down on the homepage until you see the
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  donate button. I hope everyone had the opportunity
• 4:15
  to see the stunning full lunar eclipse early
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  Friday morning. At my location, we'd had clouds
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  all day, but the sky cleared around 9 p .m. and
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  the full moon was extremely bright. Some hours
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  later, I went outside around 2 .30 a .m. to check
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  out the eclipse, which was nearing totality.
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  The moon was almost right overhead and all the
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  bright moonlight from earlier was gone. The moon
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  was a subtle red color with a slightly brighter
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  coloring along the northern limb. Through binoculars,
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  it almost reminded me of Mars with its red shading
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  and ice caps. Every time I've watched the total
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  lunar eclipse, at least one side of the moon
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  seems brighter than the rest. Apparently, this
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  is owing to the Earth's uneven shadow density.
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  The Earth's umbra is not an evenly distributed,
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  perfectly dark shadow. The outer edges of the
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  umbra allow more sunlight to refract through
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  the Earth's atmosphere, meaning parts of the
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  moon near the umbral edge receive more scattered
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  light than the deeper central regions. Also,
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  the way our atmosphere filters the sunlight could
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  cause some shadow variations. The red color of
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  the moon during totality comes from Rayleigh
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  scattering, the same effect that makes sunrises
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  and sunsets red. Earth's atmosphere bends sunlight
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  around the planet, filtering out shorter blue
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  and green wavelengths and casting a reddish hue
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  onto the moon. However, the amount of dust, pollution,
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  or clouds in Earth's atmosphere at the time of
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  the eclipse can vary, causing uneven filtering.
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  Some areas of the moon might receive slightly
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  more light than others, leading to patches of
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  dim orange or yellow instead of deep red. I was
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  also struck by how small the moon looks right
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  now. Back around the end of last year, when we
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  had several consecutive super moons, the moon
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  was noticeably larger and more dominant in the
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  sky. Of course, the moon's distance to Earth
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  changes throughout the year, owing to its elliptical
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  orbit. The moon will reach Apogee, its point
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  farthest from Earth, on March 17th. So it's much
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  smaller in the sky right now. The difference
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  between Apogee and Perigee, the closest point
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  to Earth, can be more than 30 ,000 miles, so
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  the difference is significant. Also, its high
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  point in the sky during the eclipse means that
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  we didn't experience the so -called moon illusion,
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  where it seems larger in the sky as it gets closer
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  to the horizon. If you saw the eclipse, I'd love
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  to hear your observations, so visit StarTrails
• 7:07
  .Show and send me a report. With the eclipse
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  behind us, we begin the week with the moon in
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  a waning gibbous phase, just following last week's
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  full moon. It's still nearly full early in the
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  week with nearly 90 % illumination. But by Saturday,
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  we'll reach the last quarter moon. At this phase,
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  half of the moon appears illuminated, but only
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  in the morning sky. That means deep sky observers
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  still enjoy darker skies to work with at least
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  until 3 a .m. or so. If you're into astrophotography,
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  the last quarter is a great time to capture the
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  moon's rugged terrain. With the light coming
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  in from the side, you'll get great contrast on
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  lunar mountains and craters along the terminator.
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  That's the line between night and day on the
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  moon's surface. Now onto the planets. After the
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  recent spectacular parade of planets that gave
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  some observers the chance to see all the visible
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  planets lined up across the sky, we've basically
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  lost three of them. Mercury is once again too
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  close to the Sun, and it's joined by Venus and
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  Saturn. All three bodies are bunched up with
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  the Sun this week. You may still be able to catch
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  a glimpse of Mercury and Venus tonight, just
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  after sunset, and very low on the western horizon.
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  But as the week progresses, our two interplanetary
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  companions will dip closer to the horizon each
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  night at sunset, until we can't see them anymore.
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  By the week's end, Venus will be ahead of the
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  Sun, and by next week will transition to a morning
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  star, rising in the east just before the Sun.
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  This transformation happens roughly every 19
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  months as Venus moves between Earth and the Sun
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  in its orbit. We've been enjoying the presence
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  of Venus in the evening sky since last fall,
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  the third brightest object in the sky after the
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  Sun and Moon. By the month's end, you'll need
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  to be an early riser to catch its brilliance
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  in the pre -dawn sky. Jupiter, the king of planets,
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  is still high and bright in the early evening.
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  Located in the constellation Taurus, and with
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  Venus gone, it claims its place as the brightest
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  object after the moon. Look for it near Aldebaran,
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  the orange giant star that marks the eye of the
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  bull. If you have a telescope, this is a great
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  time to check out Jupiter's four largest moons,
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  Io, Europa, Ganymede, and Callisto, easily visible
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  as tiny points of light near the gas giant. Mars
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  is nearby, sitting in Gemini, close to the twin
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  stars Castor and Pollux. Unlike the flickering
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  glow of those stars, Mars has a distinct and
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  constant reddish hue. Now, let's turn our attention
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  to some of the constellations that dominate the
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  night sky in March. Taurus is a powerhouse this
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  season, home to some of the best known deep -sky
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  objects. Along with Aldebaran, look for Messier
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  45, the Pleiades. That's the little cluster of
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  stars that looks like a tiny dipper. In mythology,
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  the Pleiades were seven sisters pursued by Orion.
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  And in modern astronomy, this cluster is one
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  of the closest and brightest open star clusters
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  to Earth. Even without any equipment, the Pleiades
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  appears as a small hazy patch in the constellation
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  Taurus. Most people can see six or seven stars
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  under dark skies. Interestingly, one of the best
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  views of the Pleiades comes with binoculars.
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  The cluster is larger than the full moon, so
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  it's actually too spread out to fit entirely
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  in most telescopic views. With binoculars, the
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  brightest stars become distinct, each glowing
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  in shades of blue -white. You'll also start to
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  notice that the cluster contains dozens of fainter
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  stars that blend into the glow when seen with
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  the naked eye. A small telescope will show even
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  more stars, possibly up to 100 members of the
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  cluster scattered across the field of view. It's
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  best to use a low -power, wide -field eyepiece.
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  If you're in an extremely dark location, you
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  might catch a glimpse of a faint bluish reflection
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  nebula. This is leftover dust that the cluster
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  is currently passing through, reflecting the
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  light of its young, hot stars. It's faint, so
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  long exposure astrophotography does a much better
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  job of bringing it out in visual observation.
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  Fun fact, while the Pleiades is generally called
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  the Seven Sisters, in Japanese it's known as
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  Subaru. And if you look closely at the Subaru
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  car logo, you'll see a stylized version of the
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  cluster. Leo the lion is another March favorite.
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  This constellation rises in the east in the evening
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  and is easy to spot thanks to its backward question
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  mark shape. That's called the sickle. In ancient
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  cultures, Leo was often associated with royalty,
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  strength, and the sun, which is fitting since
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  it's a sign that warmer days are ahead. The brightest
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  star in Leo is Regulus, a bluish -white star
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  that's about 79 light years away. And here's
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  another fun fact. It actually spins so fast that
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  it's not quite a sphere, but slightly flattened.
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  One of the highlights of LEO is the LEO Triplet,
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  a stunning group of three spiral galaxies, Messier
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  65, Messier 66, and NGC 3628, all located about
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  35 million light years away. M65 is slightly
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  tilted toward us, giving it a classic spiral
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  shape. It has a yellowish core, meaning it has
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  older stars, but also some dust lanes where new
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  stars are forming. M66 is more distorted, likely
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  due to gravitational interactions with its neighboring
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  galaxies. It has strong spiral arms and huge
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  dust clouds. NGC 3628, also called the Hamburger
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  Galaxy, is the third member of the triplet. This
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  galaxy has a thick dust lane cutting across it,
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  making it look like a cosmic sandwich. It's a
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  little fainter than M65 and M66, but if you're
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  in a dark location with a telescope, you might
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  catch it. The Leo triplet is an active, dynamic
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  group, meaning these galaxies are pulling and
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  warping each other, due to their gravitational
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  interactions. They may eventually merge millions
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  of years from now, but for now they make a spectacular
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  sight for sky watchers. To find them, look just
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  below the lion's belly near the star Cherton.
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  If you have a telescope with a wide field of
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  view, you can see all three galaxies together
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  in a single frame. A notable astronomical event
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  this week is the Spring Equinox, happening on
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  March 20. Twice a year, Earth's tilt lines up
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  perfectly perpendicular to the Sun. That means
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  for a brief moment, day and night are nearly
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  equal all over the world. The word equinox comes
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  from the Latin for equal night. This is the official
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  start of spring in the Northern Hemisphere, and
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  cultures around the world have celebrated it
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  for millennia. Ancient civilizations like the
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  Mayans built entire structures, like the temple
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  of Kukulkan at Chichen Itza, that align with
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  the Sun on the equinox, creating a serpent -like
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  shadow on the pyramid's steps. Astronomically,
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  the equinox is a halfway point. It's when the
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  Sun crosses the celestial equator moving from
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  the southern half of the sky into the northern
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  half. From now on, our days will keep getting
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  longer until we reach the summer solstice in
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  June, when the sun is at its highest point. If
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  you found this episode helpful, let me know and
• 15:55
  feel free to send in your questions and observations.
• 15:58
  The easiest way to do that is by visiting our
• 16:01
  website StarTrails .Show. This is also a great
• 16:05
  way to share the show with friends. Until next
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  time, keep looking up and exploring the night
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  sky. Clear skies everyone!