Latest / Star Trails: From Backyard Astronomy to Cosmic Wonder / Weighty Matters and Wandering Worlds

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Weighty Matters and Wandering Worlds · 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 July the
• 0:16
  6th through the 12th. This week we answer some
• 0:19
  listener mail and explore the mystery of mass.
• 0:23
  A big full moon looms low on the horizon, and
• 0:27
  we take a detour into the icy reaches of our
• 0:30
  solar system, where relics of the early universe
• 0:34
  hide away in the darkness. Whether you're tuning
• 0:37
  in from the backyard, the balcony, or just your
• 0:40
  imagination, I'm glad you're here. So find a
• 0:43
  cozy spot, let your eyes adjust, and let's see
• 0:46
  what the sky holds for us this week. Before we
• 0:50
  get into the night sky this week, I'd like to
• 0:53
  kick off this episode with a listener question,
• 0:55
  and this one really hits the sweet spot. Simple
• 0:58
  on the surface, but it opens the door to something
• 1:02
  surprisingly deep. Last week, Dale from Omaha
• 1:06
  wrote, Can you explain mass? I don't understand
• 1:10
  how mass is calculated or what that means. I've
• 1:14
  heard astrophysicists say two planets are the
• 1:17
  same size but have different masses. A simple
• 1:21
  explanation would be greatly appreciated. Dale,
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  first off, thanks for writing in with this question,
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  and I know you asked for a simple explanation,
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  and I intend to provide one, but mass, although
• 1:34
  a reasonably straightforward concept in and of
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  itself, is connected to some of the real mysteries
• 1:40
  of astrophysics and the workings of the universe.
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  I'll get into a few of those in a moment, but
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  let's first figure out what's going on at the
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  most basic level. Mass is essentially how much
• 1:53
  stuff is packed into something. It's not about
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  how big something looks, it's about how much
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  material is actually in there. Think about two
• 2:03
  identical suitcases. One is filled with clothes,
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  The other is packed with bricks. They take up
• 2:10
  the same space, but the one with bricks is a
• 2:13
  lot heavier. That's because it has more mass.
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  Astronomers talk about mass all the time. Just
• 2:20
  like your question, two planets can be the same
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  size, but one can have more mass. That means
• 2:27
  one is denser. Maybe it has a larger metal core
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  or more rock and less gas. Same outside dimensions,
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  but more weight on the inside. Let's consider
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  Earth's planetary sister, Venus. Both Earth and
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  Venus are roughly the same size, but Earth has
• 2:47
  more mass thanks to its larger metallic core.
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  Let's take another example. Because it's summer,
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  let's consider a beach ball compared to a bowling
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  ball, maybe a good 16 -pounder. The beach ball
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  is very light, but much larger than the bowling
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  ball. The beach ball contains mostly air, while
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  the bowling ball is filled with, well, whatever
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  bowling balls are made of, dense resin or plastics,
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  I assume. It's that density that matters, rather
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  than the size. And density is what determines
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  mass. Now, here's where things start to become
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  fascinating. Let's shrink ourselves down to the
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  molecular level. If you were to stand next to
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  a beach ball and a bowling ball at this tiny
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  size, you'd feel a gravitational pull towards
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  the bowling ball. Mass is directly tied to gravity.
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  The more mass something has, the stronger its
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  gravitational pull. Earth pulls harder than the
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  moon because it has more mass. The Sun keeps
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  the planets in orbit because it's massive, not
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  just in size, as the term is often used, but
• 4:01
  in actual weight. In astronomy, we can't weigh
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  things directly, so we figure out mass by watching
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  how objects move. For example, how fast a moon
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  orbits a planet. That motion tells us how much
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  gravity there is, and gravity tells us the mass.
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  Now let's get weird. Mass accounts for some of
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  the most fascinating phenomena in the universe,
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  including one of the most extreme, black holes.
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  These are the ultimate examples of mass and gravity
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  gone wild. A black hole forms when a giant star
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  collapses and all that mass gets squeezed into
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  an incredibly tiny space. Imagine taking something
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  more massive than the sun and cramming it into
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  something the size of a city or smaller. The
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  result is unbelievably dense. Now remember, gravity
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  depends on mass, and our distance to an object
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  alters how much gravity we experience. Because
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  black holes are so compact, you can get extremely
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  close to them. But if you get too close, you
• 5:12
  get sucked in, and there's no turning back. The
• 5:15
  gravity near them is so strong that even light
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  can't escape. That's why they're black. If, purely
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  as a thought experiment, our sun turned into
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  a black hole, Earth would keep orbiting just
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  like it does now, same mass, same distance. But
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  if you flew close to that black hole, you'd cross
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  a point of no return, where gravity takes over
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  and there's no way back. We've understood the
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  relationship between mass and gravity for a while.
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  This was Isaac Newton's great breakthrough, later
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  expanded by Einstein and his theories of relativity
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  and space -time. Einstein also taught us that
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  energy and mass are basically interchangeable.
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  That, of course, is his famous equation E equals
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  mc squared. But interestingly, we don't really
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  know why mass affects gravity. This is one of
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  the real unsolved mysteries of the universe.
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  We just know that it does and that we can directly
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  observe its effect. There are some interesting
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  theories, gravitons for instance, particles that
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  somehow influence gravity. There are string theories
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  and theories based on that energy to mass relationship,
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  but so far we just don't really know. But we
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  do know what mass is and we know it shapes gravity.
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  motion, orbits, and the entire cosmic dance.
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  I know we went down a bit of a rabbit hole there,
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  but hopefully we answered the question. If anyone
• 6:49
  out there listening has a question or a topic
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  they'd like for me to cover, just visit our website,
• 6:55
  StarTrails .Show, and hit the contact link. Dale,
• 7:00
  thanks so much for writing in. The night sky
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  is fairly quiet this week, and it will be dominated
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  by the upcoming full moon. On Thursday, we're
• 7:17
  treated to the full buck moon rising in the evening
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  sky. The buck moon is the traditional name given
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  to July's full moon. It comes from, you guessed
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  it, Native American traditions, named after the
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  time of year when male deer began to grow their
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  new antlers. It's a moment that marks high summer,
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  and this year's buck moon has a little extra
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  drama. Because it's rising low on the horizon,
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  we'll experience what's known as the moon illusion.
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  That trick of the eye where the moon looks huge
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  when it's near the horizon, especially just after
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  it rises. Our brains compare it to nearby objects
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  like trees or rooftops, and we perceive it as
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  being much larger. It's a gorgeous effect, and
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  one of the best full moons of the year to photograph
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  if you have clear skies in your area. Now onto
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  the planets. Mercury is hanging out low in the
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  west -northwest just after sunset around magnitude
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  .3. Best seen early this week if you have a clear
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  view of the horizon. Mars is hanging out in the
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  west, still reddish but fading into the twilight.
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  Saturn and Neptune are up in Pisces, rising late
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  and sticking around into the night. Over in the
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  predawn sky, Venus is bright and unmistakable
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  in the east. Later in the week, it's joined by
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  a faint Uranus hiding in Taurus. As always, you'll
• 8:46
  need a scope or good binoculars to spot Uranus
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  and Neptune. It's still early, but meteor season
• 8:54
  is just around the corner. The Alpha Capra cornids
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  begin trickling in this week. Slow moving fireballs,
• 9:02
  best later in July. And if you're a Perseid fan,
• 9:06
  we're only about a week away from the start of
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  that shower's long lead up. Have you ever considered
• 9:17
  how far our solar system extends from the sun?
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  In this episode, we're taking a little detour
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  beyond the outer planets into the frozen frontiers
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  of our solar system. We'll explore two of the
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  most mysterious regions we've never actually
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  seen with our own eyes, the Kuiper Belt and the
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  Oort Cloud. These are the deep freeze zones of
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  the cosmos, full of ancient icy leftovers, silent
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  travelers, and even the occasional supersized
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  comet. Let's start with the one closer to us.
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  The Kuiper Belt, named after the Dutch -American
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  astronomer Gerard Kuiper, is a ring of icy bodies
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  orbiting the sun beyond Neptune, starting around
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  30 astronomical units out. At that distance,
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  sunlight is a pale glow, and the temperature
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  is hundreds of degrees below zero. The Kuiper
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  Belt is the solar system's icy junkyard. It's
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  full of leftover material from when the planets
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  formed about 4 .6 billion years ago. We're talking
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  rocks, frozen gases, chunks of water ice, and
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  other elements that never made it into planets.
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  It's also home to some famous objects. Pluto,
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  of course, demoted from planet status in 2006,
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  is proudly orbiting in the Kuiper Belt. Eris
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  is slightly smaller than Pluto, but helped force
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  that whole redefinition of what a planet is.
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  Then there's Haumea, shaped like a football and
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  spinning so fast it completes a rotation every
• 11:00
  four hours. And Machi Machi, another dwarf planet
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  named after a Polynesian creator god. These icy
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  worlds are known as Kuiper Belt Objects, or KBOs.
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  Many of them have moons, some have strange orbits,
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  and there are probably hundreds of thousands
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  more we haven't seen yet. NASA's New Horizons
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  mission flew past Pluto in 2015, revealing its
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  icy mountains, nitrogen glaciers, and unexpected
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  complexity. And then it kept going. sending back
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  images of another KBO, Arakoth, a reddish snowman
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  -shaped object about 21 miles long. That flyby
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  in 2019 gave us our very first close -up of a
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  true Kuiper Belt object. Now let's take a quick
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  detour about comets, snowballs in space with
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  glowing tails. Short period comets swing by the
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  Sun every few decades and often come from the
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  Kuiper Belt. Think of Comet Halley or Comet Temple
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  Tuttle. These objects orbit in more or less the
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  same plane as the planets, and their orbits are
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  usually predictable. But then there are the weird
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  ones, the comets with giant lopsided orbits that
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  take millions of years to return. That brings
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  us to our next destination. Far beyond the Kuiper
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  belt, somewhere between 2 ,000 and 100 ,000 astronomical
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  units from the Sun is a theoretical shell of
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  icy bodies called the Oort cloud. Unlike the
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  flat disc -shaped Kuiper belt, the Oort cloud
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  is spherical. Imagine a vast snow globe surrounding
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  our entire solar system, and inside that globe
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  are potentially trillions of icy fragments. comets,
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  planetesimals, ancient debris, left over from
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  the very formation of the Sun. We've never directly
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  seen the Oort cloud, it's just too far. But we
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  know it's there because of those long period
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  comets that suddenly appear from deep space on
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  incredibly eccentric orbits. Comets like Hale
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  -Bopp, which passed by in 1997 and won't return
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  for another 2500 years. Another such visitor
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  was comet C2012S1, which was hyped in 2013, but
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  broke apart near the Sun. And more recently,
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  there's a mega comet, and we mentioned this one
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  last week. In 2021, astronomers Pedro Bernardinelli
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  and Gary Bernstein spotted something strange
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  in data from the Dark Energy Survey. A fuzzy,
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  slow -moving object as wide as 85 miles across.
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  That's bigger than some small moons. Named comet
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  Bernardinelli -Bernstein, it's considered the
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  largest comet nucleus ever discovered. It's not
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  coming anywhere near Earth. At its closest approach
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  in 2031, it'll still be out past Saturn. Even
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  though we won't be able to see it with the naked
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  eye, this comet is giving scientists a rare opportunity
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  to study a pristine, early solar system object,
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  probably untouched since the sun was born. That's
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  like getting a piece of solar system history
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  frozen in deep space for billions of years. These
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  frozen regions are like the archives of the solar
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  system. The Kuiper Belt and the Oort Cloud preserve
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  the raw materials from the early days of planet
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  building, before Earth had oceans or life or
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  even before Jupiter finished forming. Some scientists
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  believe that comets from these outer zones delivered
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  water and organic molecules to the early Earth.
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  Others are looking into whether Oort Cloud comets
• 15:01
  could help explain the odd tilt of Uranus or
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  even the idea of a hypothetical Planet Nine lurking
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  in the darkness. And that's our journey to the
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  far edge of the Sun's influence. From Pluto's
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  neighborhood to the Oort Cloud's distant reaches,
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  the outer solar system is more than just empty
• 15:21
  space. It's a museum of frozen time. If the stars
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  spoke to you this week or if a question's been
• 15:32
  on your mind, I'd love to hear it. Visit our
• 15:35
  website, StarTrails .Show, where you can contact
• 15:39
  me and explore past episodes. Be sure to follow
• 15:43
  us on Blue Sky and YouTube. Links are in the
• 15:46
  show notes. Until we meet again beneath the stars,
• 15:50
  clear skies, everyone.