Latest / Star Trails: From Backyard Astronomy to Cosmic Wonder / What Stars Do While They’re Alive

Transcript

What Stars Do While They’re Alive · Star Trails: From Backyard Astronomy to Cosmic Wonder

• 0:07
  Howdy Stargazers, and welcome to this episode
• 0:10
  of Star Trails. My name is Drew, and I'll be
• 0:13
  your guide to the night sky for the week of February
• 0:16
  the 8th to the 14th. This week we continue our
• 0:20
  exploration of the lives of stars, in particular
• 0:24
  the ones alive right now that are shaping the
• 0:27
  solar systems, nebula and even galaxies that
• 0:30
  surround them. We'll talk about how they're born
• 0:33
  and how they live their lives. Later in the show
• 0:37
  we'll take a look at this week's sky and I'll
• 0:39
  demystify the phenomenon of the so -called planetary
• 0:43
  parade. One of those is forming right now, and
• 0:46
  it could make for some interesting views. Whether
• 0:50
  you're tuning in from the backyard or the balcony,
• 0:52
  I'm glad you're here, so grab a comfortable spot
• 0:55
  under the night sky and let's get started. When
• 1:00
  we look up at the night sky, it's easy to think
• 1:03
  of stars as static, fixed points of light that
• 1:07
  simply exist unchanged night after night. But
• 1:11
  stars are anything but passive. While they're
• 1:18
  alive, right now, stars are shaping their surroundings,
• 1:23
  organizing matter, and quietly steering the future
• 1:26
  of the universe. They're not just objects in
• 1:29
  space. They're active agents within it. Stars
• 1:34
  also don't exist in isolation. That sense of
• 1:38
  solitude is mostly an illusion created by distance.
• 1:42
  Most stars are born inside enormous clouds of
• 1:45
  cold gas and dust drifting through galaxies.
• 1:50
  These clouds are often called stellar nurseries,
• 1:53
  and while that name emphasizes beginnings, what
• 1:57
  matters for tonight is what happens after stars
• 1:59
  appear. Once stars form, they don't politely
• 2:03
  step aside and let the nursery continue undisturbed.
• 2:07
  They interfere. A stellar nursery becomes an
• 2:11
  active construction site the moment stars turn
• 2:14
  on. Young stars pour out radiation and stellar
• 2:18
  winds. Their light heats nearby gas. Their pressure
• 2:22
  pushes material away. Cavities open up inside
• 2:26
  the cloud. Dense regions are eroded. and other
• 2:30
  regions are compressed. In some places, star
• 2:34
  formation is shut down entirely as gas is dispersed.
• 2:38
  In others, new stars are triggered as material
• 2:41
  is squeezed just enough to collapse. Stars don't
• 2:46
  just come from their environments. They immediately
• 2:49
  begin reshaping them. A nearby and famous example
• 2:54
  of this process is the Orion Nebula. When you
• 2:58
  look at Orion through a telescope, you're not
• 3:01
  just seeing something ancient or finished. You're
• 3:04
  seeing an ongoing process. Massive young stars
• 3:08
  flood their surroundings with intense ultraviolet
• 3:11
  light, sculpting glowing walls of gas and carving
• 3:15
  dark lanes where dust blocks the light. Some
• 3:20
  regions are being cleared out, while others are
• 3:23
  actively forming new stars. Orion is not a snapshot
• 3:27
  of the past, it's stellar influence unfolding
• 3:31
  in real time. Another striking example is the
• 3:35
  Eagle Nebula, home to the famous Pillars of Creation.
• 3:39
  Those towering columns of gas are not quietly
• 3:43
  building stars in isolation. They're being actively
• 3:47
  eroded by radiation from nearby massive stars.
• 3:51
  The pillars themselves are temporary structures,
• 3:55
  slowly being destroyed by the very environment
• 3:58
  that surrounds them. This is what stellar influence
• 4:02
  looks like, creation and destruction unfolding
• 4:06
  together over millions of years. Stars also rarely
• 4:12
  form alone. Most are born in groups called star
• 4:16
  clusters, and these clusters come in two very
• 4:20
  different flavors. Open clusters are loose, relatively
• 4:24
  young groups of stars that form together inside
• 4:27
  stellar nurseries. Their gravity is weak, and
• 4:31
  over time the stars drift apart, spreading into
• 4:34
  the galaxy. These clusters let us watch stellar
• 4:38
  evolution in its early and middle stages. A beautiful
• 4:42
  example is the Pleiades, visible to the naked
• 4:45
  eye as a small dipper -shaped group of stars.
• 4:49
  It's a young cluster still interacting with leftover
• 4:52
  dust from its birth cloud. Another is the Hyades,
• 4:57
  an older, more spread out cluster that shows
• 5:00
  what happens as gravity slowly loses its grip
• 5:03
  and a stellar family dissolves. Open clusters
• 5:08
  remind us that many of the stars we see, including
• 5:11
  our own sun, likely began life with siblings
• 5:15
  that are now scattered across the Milky Way.
• 5:18
  Globular clusters, on the other hand, are something
• 5:21
  else entirely. These are dense, ancient spheres
• 5:25
  containing hundreds of thousands of stars, all
• 5:29
  bound tightly by gravity. They formed early in
• 5:33
  the galaxy's history and have remained intact
• 5:35
  for billions of years. Inside them, stars are
• 5:40
  packed so closely that stellar interactions are
• 5:43
  common, and the environment is far more crowded
• 5:46
  than anything near our sun. One of the finest
• 5:50
  examples visible from the Northern Hemisphere
• 5:52
  is the Hercules Cluster. Through binoculars or
• 5:56
  a telescope, it appears as a dense glowing ball
• 5:59
  of stars, an entire ancient stellar city suspended
• 6:04
  in space. Globular clusters show us what happens
• 6:08
  when stars live their lives together for immense
• 6:11
  spans of time. They're reminders that stellar
• 6:15
  evolution is often a communal process, not a
• 6:18
  solitary one. Clusters also reveal something
• 6:22
  fundamental about stars. When all stars in a
• 6:26
  cluster form at the same time, the differences
• 6:29
  we see between them are not about age, they're
• 6:31
  about mass. Mass determines how a star behaves
• 6:35
  while it's alive. Massive stars burn hot and
• 6:39
  fast, with fusion running furiously in their
• 6:42
  cores. They shine brilliantly but briefly, sometimes
• 6:47
  for only a few million years. Smaller stars are
• 6:51
  different. Red dwarfs, the smallest stars capable
• 6:55
  of sustaining fusion, burn their fuel slowly
• 6:58
  and efficiently. They mix their hydrogen throughout
• 7:02
  their interiors, wasting very little, and as
• 7:04
  a result, they endure. Based on how slowly red
• 7:09
  dwarfs consume their fuel, astronomers calculate
• 7:13
  lifespans not in billions of years, but in trillions.
• 7:17
  Ten trillion years, and possibly more. The universe
• 7:22
  itself is only about 13 .8 billion years old.
• 7:26
  So how can we possibly know that some stars will
• 7:30
  live for trillions of years when the universe
• 7:32
  hasn't even been around that long? The answer
• 7:36
  is that astronomy doesn't rely on weighting.
• 7:39
  It relies on physics. We understand how stars
• 7:45
  work at a fundamental level. How much fuel they
• 7:48
  contain. How fast they burn it. and how efficiently
• 7:51
  that energy is produced. Once you know those
• 7:55
  things, you don't need to watch the entire lifespan
• 7:57
  play out any more than you need to wait for a
• 8:00
  candle to burn out to estimate how long it will
• 8:03
  last. There's also an important piece of observational
• 8:08
  evidence. Not a single red dwarf has ever been
• 8:12
  observed to die of old age. We see young red
• 8:16
  dwarfs, old ones, and ancient ones. but no red
• 8:20
  dwarf remnants created through normal stellar
• 8:23
  aging. The universe simply hasn't been around
• 8:27
  long enough for that to happen. The absence isn't
• 8:30
  a mystery, it's a confirmation. While stars are
• 8:34
  alive, they're also busy building systems. When
• 8:38
  a star forms, it's surrounded by a rotating disk
• 8:41
  of gas and dust. Inside that disk, material collides
• 8:46
  and sticks together, eventually forming planets.
• 8:51
  Stars don't just host planets, they define the
• 8:54
  architecture of entire solar systems. A star's
• 8:58
  gravity sets orbital paths, its radiation shapes
• 9:02
  atmospheres, and its early activity determines
• 9:06
  which planets survive and which never fully form.
• 9:10
  Stars also define where life might exist. A star's
• 9:15
  brightness determines where liquid water could
• 9:18
  persist on a planet's surface, but that zone
• 9:21
  is not fixed. As stars age, they slowly brighten
• 9:25
  and the habitable zone moves outward. Planets
• 9:29
  drift into and out of favorable conditions, not
• 9:33
  because they move, but because their star evolves.
• 9:37
  Beyond planets, stars provide something even
• 9:40
  more fundamental, persistent energy. Not just
• 9:44
  light, but long -lasting energy gradients that
• 9:47
  keep chemistry alive, atmospheres dynamic, and
• 9:51
  complexity from running down too quickly. Stars
• 9:55
  act as long -burning engines that hold complexity
• 9:58
  open, locally and temporarily, but long enough
• 10:02
  to matter. Zoom out even further and stars help
• 10:10
  define the structure of entire galaxies. They
• 10:14
  trace spiral arms, outline galactic discs, and
• 10:18
  mark where gas collects and where it doesn't.
• 10:22
  Galaxies don't look the way they do despite stars,
• 10:25
  they look that way because of them. This leads
• 10:30
  to a quiet realization beneath all this. We're
• 10:34
  living in a very particular chapter of cosmic
• 10:37
  history. Star formation is still active. Bright,
• 10:41
  sun -like stars are common. Heavy elements are
• 10:45
  abundant. Planetary systems are widespread. In
• 10:49
  the far future, the universe will belong to small,
• 10:53
  dim, long -lived stars, glowing faintly for trillions
• 10:57
  of years while galaxies slowly fade. Right now
• 11:01
  is a relatively bright chapter. Stars are still
• 11:05
  alive in large numbers, still energetic, still
• 11:08
  shaping their environments. In other words, they're
• 11:11
  still doing their work. Stars are not static
• 11:15
  points of light. They heat gas, sculpt nebula,
• 11:19
  regulate star formation, build solar systems,
• 11:23
  and define where complexity can exist. They don't
• 11:26
  simply shine. They organize matter. patiently,
• 11:31
  collectively, and over immense spans of time.
• 11:35
  And all of that is happening right now. After
• 11:53
  a quick break, we'll check in with what you can
• 11:56
  see in the night sky this week. Stay with us.
• 12:11
  Welcome back! This week the moon is moving through
• 12:15
  its waning gibbous phase and will pass third
• 12:18
  quarter on February the 9th. As the week goes
• 12:22
  on, the moon rises later each night, which means
• 12:25
  darker skies earlier in the evening. By midweek,
• 12:29
  you'll have a more generous window for observing
• 12:32
  before moonlight becomes an issue, especially
• 12:35
  if you're heading out shortly after sunset. You
• 12:38
  may hear this week described in headlines as
• 12:41
  a so -called parade of planets and rather than
• 12:45
  dismissing that outright it's actually a good
• 12:47
  opportunity to explain what's really going on
• 12:50
  and Why planets so often appear in the same part
• 12:53
  of the sky? All of the major planets in our solar
• 12:57
  system orbit the Sun in nearly the same flat
• 13:01
  plane From Earth that plane projects onto the
• 13:05
  sky as a gentle arc called the ecliptic. It's
• 13:09
  the same path the sun appears to follow across
• 13:12
  the sky over the course of a year, and it's also
• 13:15
  where the moon and planets spend almost all of
• 13:18
  their time. So when several planets are visible
• 13:21
  at once, they aren't lining up by coincidence.
• 13:24
  They're simply tracing the same shared highway
• 13:27
  across the sky. This week, that highway runs
• 13:31
  low across the western and southwestern sky after
• 13:34
  sunset. Jupiter is the easiest place to start,
• 13:38
  bright, steady, and well above the horizon as
• 13:41
  twilight fades. Saturn sits much lower, closer
• 13:46
  to the horizon, and requires a bit more patience
• 13:49
  as it lingers in the glow of sunset. Mercury
• 13:52
  makes only a brief appearance very low in the
• 13:55
  west, rewarding observers who look early and
• 13:58
  know where to scan. That's why planetary parades
• 14:02
  tend to be quieter than the headlines suggest.
• 14:05
  The planets aren't stacked in a dramatic row
• 14:08
  and they won't leap out at you unless you already
• 14:11
  understand the layout of the sky. What you're
• 14:14
  really seeing is the ecliptic itself, the architecture
• 14:17
  of the solar system made visible. If you step
• 14:21
  outside and slowly trace that gentle line across
• 14:24
  the sky from west towards south and then east,
• 14:27
  you're following the same plane planets have
• 14:30
  orbited in for billions of years. Once you recognize
• 14:33
  it, you'll start seeing it everywhere, in where
• 14:35
  planets rise, where the moon travels, and even
• 14:39
  where eclipses become possible. Once twilight
• 14:43
  fades, this week is a great time to explore some
• 14:46
  quieter corners of the winter sky, objects that
• 14:49
  don't always get top billing but reward a little
• 14:52
  patience. In Gemini, look for the open cluster
• 14:56
  Messier 35. It's a rich, wide cluster that works
• 15:00
  beautifully in binoculars and small telescopes.
• 15:04
  It has a loose, scattered character that feels
• 15:06
  very different from tighter, more famous clusters.
• 15:10
  Lower in the southern sky, in Pupus, you'll find
• 15:14
  a trio of often overlooked open clusters, Messier
• 15:18
  46, 47, and 93. These three make a nice study
• 15:23
  in contrast. One dense and rich, another loose
• 15:27
  and brighter, and one smaller and more compact.
• 15:31
  They're excellent targets for small telescopes
• 15:33
  once they've climbed clear the horizon. For a
• 15:37
  globular cluster that tends to fly under the
• 15:39
  radar, look just below Orion toward the constellation
• 15:43
  Lepus from Messier 79. It appears as a tight
• 15:47
  concentrated glow through modest telescopes and
• 15:51
  offers a very different feel from the more famous
• 15:54
  globulars that dominate summer skies. Observers
• 15:58
  with darker skies may want to spend some time
• 16:00
  in Monoceros, the faint constellation between
• 16:03
  Orion and Gemini. Here you'll find NGC 2264,
• 16:09
  sometimes called the Christmas Tree Cluster.
• 16:12
  It's a subtle region combining a scattered group
• 16:14
  of young stars with faint surrounding nebulosity.
• 16:19
  This is not an object that jumps out immediately.
• 16:22
  It rewards lingering, careful -looking, and wide
• 16:26
  -field views. Before we go, I just wanted to
• 16:36
  note a quick milestone. February 4th marked the
• 16:40
  second anniversary of Star Trails. Last year,
• 16:44
  I did a special episode to commemorate the show's
• 16:47
  first anniversary. And in it, I talked about
• 16:50
  how the show was produced and why I started it.
• 16:53
  That was back in episode 50 on February the 2nd,
• 16:56
  2025, if you're curious. I don't have anything
• 17:00
  special planned for this anniversary. My goal
• 17:03
  is to continue cranking out episodes and refining
• 17:07
  our approach and just try to make each episode
• 17:10
  better than the last. The crazy thing is there's
• 17:13
  now nearly two years worth of astronomy content
• 17:16
  in our back catalog. That has to count for something.
• 17:20
  As always, if you have show ideas, topics, or
• 17:23
  questions, feel free to connect over at the show
• 17:25
  website. That's going to do it for this week.
• 17:32
  If you found this episode interesting, please
• 17:34
  share it with a friend who might enjoy it. The
• 17:37
  easiest way to do that is by sending folks to
• 17:39
  our website, StarTrails .Show. And, if you want
• 17:43
  to support the show, use the link on the site
• 17:45
  to buy me a coffee. That really helps. Be sure
• 17:49
  to follow Star Trails on Blue Sky and YouTube.
• 17:53
  Links are in the show notes. Until we meet again
• 17:56
  beneath the stars, clear skies everyone.