Latest / Star Trails: From Backyard Astronomy to Cosmic Wonder / New Moon Week and the Mystery of Missing Green Stars

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New Moon Week and the Mystery of Missing Green Stars · Star Trails: From Backyard Astronomy to Cosmic Wonder

• 0:07
  Howdy Star Gazers and welcome to this episode
• 0:10
  of Star Trails. Drew here, and I'll be your guide
• 0:13
  to the night sky for the week starting May 25th
• 0:17
  through the 31st. This week a new moon promises
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  darker skies, and have you ever wondered why
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  we have red, blue, and yellow stars, but no green
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  ones? More on that in a moment. Also, this is
• 0:33
  going to be a shorter episode this week because
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  I'm losing my voice. I apologize for the raspy
• 0:39
  narration. Whether you're tuning in from the
• 0:43
  backyard, the balcony, or just your imagination,
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  I'm glad you're here. So find a cozy spot, let
• 0:49
  your eyes adjust, and let's see what the sky
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  holds for us this week. We kick things off this
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  week with the moon in a waning crescent phase.
• 1:00
  It's just a sliver in the pre -dawn sky, only
• 1:04
  about 4 % illuminated. It's a great time for
• 1:08
  stargazers to enjoy truly dark skies before moonlight
• 1:11
  returns. Then on the night of May 26, we hit
• 1:16
  the new moon. That means this is your prime window
• 1:20
  for deep sky observing. No moonlight at all to
• 1:23
  wash out faint galaxies or nebula. By May 31st,
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  the moon is back as a waning crescent, now about
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  24 % illuminated, and beginning to reappear in
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  the western sky after sunset. It's just enough
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  to show off that beautiful Earthshine glow that's
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  light reflected off Earth that dimly illuminates
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  the shadowed portion of the moon. Now onto the
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  planets, and if you've been listening in recent
• 1:53
  weeks, this is going to all sound familiar, because
• 1:56
  not much has changed. In the evening sky, you
• 2:00
  can still catch Jupiter just after sunset in
• 2:03
  the northwest. It's bright but slipping closer
• 2:06
  to the horizon each night as it moves toward
• 2:09
  conjunction with the sun. If you want to look,
• 2:12
  get out early, around twilight, before it sets.
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  Mars is much easier to spot. You'll find it high
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  overhead after dark, shining with its trademark
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  reddish hue. It's not as bright as it was earlier
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  in the year, but still a rewarding target for
• 2:30
  binoculars or a telescope. Meanwhile, in the
• 2:34
  morning sky, Venus continues to dominate the
• 2:38
  east just before dawn. It's the brightest object
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  in the sky aside from the moon, and it rises
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  well before the sun, perfect for early risers.
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  Just above Venus, you'll find Saturn in the southeastern
• 2:52
  sky. It's much fainter than Venus, but still
• 2:56
  visible to the naked eye under clear skies, and
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  a telescope will reveal those iconic rings. With
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  the new moon arriving on May 26, we have a perfect
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  window for deep sky viewing. So if you have a
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  telescope or even just a decent pair of binoculars,
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  here are five cosmic showpieces worth tracking
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  down. First up is Messier 13, the Great Hercules
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  Cluster. This dense ball of stars lies about
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  22 ,000 light -years away and is easy to find
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  in the constellation Hercules. Through a telescope,
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  it sparkles with thousands of tiny stars. like
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  someone spilled stardust across the void. Next
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  is Messier 5 in the constellation Serpens. It's
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  one of the oldest globular clusters we know,
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  about 13 billion years old. That means it's been
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  around since nearly the dawn of the galaxy. Look
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  for a tightly packed core surrounded by a soft
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  halo of light. Over in Virgo, check out the Sombrero
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  Galaxy or Messier 104. It's a spiral galaxy seen
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  almost edge -on with a bright central bulge and
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  a dark dust lane that gives it that classic hat
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  shape. It stands out even in modest scopes. Then
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  we have Messier 3, a globular cluster in Canes
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  Venetici. It's packed with variable stars, more
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  than 270 of them, which makes it a real laboratory
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  for studying how stars evolve. It's bright, round,
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  and rewarding through almost any telescope. And
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  finally, for a true showstopper, aim for the
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  Whirlpool Galaxy or Messier 51. It's a face -on
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  spiral interacting with a smaller companion galaxy,
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  and under dark skies, you might even glimpse
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  the spiral arms twisting outward. It's a favorite
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  for a reason. I'm sure you've noticed that some
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  stars are different colors. A star's color depends
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  on its temperature. But here's the twist. For
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  all the colors we can see in stars, there's one
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  that's curiously missing – green. You have red
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  stars, orange stars, white, blue, but green is
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  nowhere to be found, and that's strange because
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  the universe is packed with glowing, energetic
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  objects, and plenty of them emit green light.
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  So why doesn't the sky have any green stars?
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  Stars shine because of their surface temperature.
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  The hotter the star, the bluer its light appears.
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  The cooler it is, the redder. Our own sun, for
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  example, is classified as a G -type star with
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  a surface temperature of about 5 ,800 Kelvin.
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  It actually emits most of its light in the green
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  part of the spectrum, but we don't see it as
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  green. Stars don't shine in just one color. They
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  emit light across a wide range of wavelengths,
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  and our eyes, clever as they are, don't pick
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  out individual bands. When a star's spectrum
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  peeks in the green zone, our brain blends all
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  the surrounding colors together and interprets
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  the result as white. It's exactly the same principle
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  used in old -school televisions and computer
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  monitors. Those screens create white by blending
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  three colors, red, green, and blue, at the right
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  intensity. When all three are mixed evenly, your
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  eye sees white. So when a star peaks in green,
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  but also gives off a balanced amount of every
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  other color, your brain says, that's white, even
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  if green is doing most of the heavy lifting.
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  If a star somehow emitted only green light, just
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  that wavelength, no extras. We would see it as
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  green, but that's not how stars work. Their energy
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  is spread out in a smooth curve, not a laser
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  -sharp spike. Red and blue stars have lopsided
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  spectrums. They emit strongly in just one part
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  of the spectrum, so that color stands out. While
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  there may be no green stars, the universe is
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  still full of color. Take Beetlejuice, the reddish
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  shoulder of Orion. That color comes from its
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  relatively cool temperature, about 3 ,500 Kelvin.
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  Then there's Rigel at Orion's knee, blazing blue
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  -white with a temperature more than 11 ,000 Kelvin.
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  Sometimes atmospheric conditions even create
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  fake color effects. Stars near the horizon, for
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  example, can appear to shimmer red, blue, or
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  even green as their light passes through layers
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  of Earth's atmosphere. It's like the twinkling
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  version of a prism. And then there are optical
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  illusions. Take Alberio, a famous double star
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  in Cygnus. One component appears gold, the other
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  blue. That contrast can be so striking that some
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  observers describe the blue star as looking slightly
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  green. It's not actually green, but your eyes
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  get a little tricked by the color pairing. And
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  let's not forget, stars emit light beyond what
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  our eyes can see. Some glow fiercely in ultraviolet
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  or infrared wavelengths. That's where telescopes
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  like the James Webb and Hubble come in. They
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  can detect these invisible colors and convert
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  them into images we can see, giving us a richer,
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  more complete view of the universe. If the stars
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  spoke to you this week or if a question's been
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  on your mind, I'd love to hear it. Visit our
• 9:24
  website StarTrails .Show where you can contact
• 9:28
  me and explore past episodes. Be sure to follow
• 9:32
  us on Mastodon, Blue Sky, and YouTube. Links
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  are in the show notes. Until we meet again beneath
• 9:40
  the stars, clear skies everyone.