Latest / Star Trails: From Backyard Astronomy to Cosmic Wonder / The Quiet Majority of Stars

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The Quiet Majority of Stars · 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 15th to the 21st. In this episode, we're
0:20
continuing this month's star theme, but we're
0:23
taking a bit of a nerdy detour. We're going to
0:26
run some code that simulates a small galaxy containing
0:29
a half million stars. Then we'll roll the clock
0:33
forward to see what's left after 10 billion years.
0:37
The results are intriguing and shed a little
0:39
light on what our universe might look like billions
0:42
or even trillions of years from now. We'll also
0:46
set our sights on some of the most infamous stars
0:49
in our galaxy, from the closest ones to the most
0:52
deadly. Later in the show, we'll take a look
0:55
at this week's sky and visit the next two chapters
0:58
of Night Watch in our book club segment. This
1:02
is a longer episode, so grab a comfortable spot
1:05
under the night sky and let's get started. We're
1:10
in the midst of our month of star -themed episodes,
1:13
so I want to do a thought experiment. One that
1:17
lets us zoom out far beyond any single star.
1:21
Instead of talking about individual objects,
1:24
I wanted to ask a broader question. If stars
1:27
form and evolve the way we think they do, which
1:30
ones actually survive long enough to still be
1:33
shining today or even trillions of years from
1:36
now? And what can we learn from the stars that
1:39
have already died? To explore that, I wrote a
1:45
small Monte Carlo simulation in Python. Nothing
1:49
too exotic, just a deliberately simplified galaxy
1:53
that follows a few well -established astrophysical
1:56
rules, and then lets randomness do the rest.
2:01
Here's how the experiment works. First, we let
2:05
stars form continuously over a span of 10 billion
2:09
years. That number wasn't chosen at random. It's
2:13
roughly the age of the Milky Way. And it's also
2:16
about how long a sun -like star spends on the
2:19
main sequence. In other words, it's a reasonable
2:22
stand -in for the lifetime of a mature spiral
2:26
galaxy up to present day. In the code, that simply
2:31
means every star gets a random birth time somewhere
2:34
between 0 and 10 billion years ago. Some stars
2:38
are ancient, some are newborn. Most fall somewhere
2:42
in between. Every star that forms is assigned
2:47
a mass. This is the most important choice in
2:50
the entire simulation, because mass controls
2:53
almost everything about a star's life. Its brightness,
2:57
its temperature, and especially how long it lasts.
3:02
We assign the mass randomly, but in accordance
3:05
with some real -world parameters based on star
3:08
formation, what astronomers call an initial mass
3:12
function. We know most stars are small. Tiny
3:17
red dwarfs dominate by sheer numbers. Sun -like
3:21
stars are far less common, and massive brilliant
3:25
stars are extremely rare. Once each star has
3:29
a mass, we give it a lifetime using a simple
3:32
rule of thumb. A star's main sequence lifetime
3:36
scales roughly as its mass raised to the negative
3:40
two and a half power. In plain language, that
3:44
means doubling a star's mass shortens its life
3:47
by more than half. Small stars can last hundreds
3:53
of billions of years, longer than the universe
3:56
has existed so far. Sun -like stars can live
4:00
for about 10 billion years. Massive stars may
4:03
only last a few million years before collapsing
4:07
or exploding. With all this in mind our simulation
4:12
ran and created half a million stars each with
4:15
a birth time a mass and a fuel limited lifespan
4:19
Then we fast forward time We stop the clock at
4:24
10 billion years and ask one blunt question of
4:27
every star Are you still on the main sequence
4:30
or are you gone? The answers surprised me the
4:34
first time I ran it Out of the 500 ,000 stars
4:39
formed in this simulated galaxy, nearly 98 %
4:44
are still alive after 10 billion years. That
4:48
alone runs against our instincts. Stellar death
4:51
feels dramatic and common, but statistically,
4:55
it's actually rare. Most stars that ever form
4:59
are long -term survivors. In the sim, every tiny
5:04
red dwarf survives. Every small, faint star just
5:08
keeps going, barely noticing the passage of billions
5:11
of years. Sun -like stars mostly survive, too.
5:17
In our test, all stars below about one solar
5:20
mass are still shining at the end. But once we
5:24
move above that into brighter, more massive stars,
5:28
survival drops off fast. Only about half of stars
5:33
between one and two solar masses make it to the
5:36
present day. Among the bright, short -lived stars
5:39
that dominate constellations, survival falls
5:43
to just a few percent. And among the most massive
5:47
stars of all, those destined to explode or collapse,
5:51
less than one percent are still around when we
5:54
stop the clock. And that leads to a grim conclusion.
5:59
The stars that define the night sky are the least
6:03
likely to still exist. We see their light because
6:06
it takes thousands of years to arrive, but the
6:10
stars creating that light may be long gone. The
6:14
bright winter stars that feel timeless are anything
6:17
but. They're rare, short -lived, and fleeting
6:20
on galactic time scales. Meanwhile, the stars
6:25
that actually dominate the galaxy, the quiet,
6:28
patient red dwarves, are almost completely invisible
6:32
to us, but they are still out there. Now, because
6:37
this is a Monte Carlo experiment, I didn't stop
6:40
there. I ran the entire simulation 20 different
6:43
times, each with a different random universe.
6:47
Different stars formed, different massive stars
6:50
lived and died. The details changed slightly,
6:54
but the conclusion really never did. Across all
6:58
20 runs, the fraction of stars still alive after
7:01
10 billion years was about 98%. With only tiny
7:05
variations from run to run, the numbers barely
7:09
moved. That tells us something important. This
7:13
isn't a fluke, it's a structural feature of how
7:17
stars work. And we can take this one step further.
7:21
For the stars that did die, the simulation also
7:25
tracks what they leave behind. Once a star is
7:29
marked as dead, meaning its age exceeds its main
7:32
sequence lifetime, the code classifies its remnant
7:36
based on its initial mass. Stars below about
7:40
8 solar masses become white dwarves. Those between
7:45
roughly 8 and 20 solar masses become neutron
7:48
stars. and the most massive stars become black
7:53
holes. The overwhelming majority, more than 90%,
7:58
become white dwarves, stellar cores quietly cooling
8:02
toward invisibility. A much smaller fraction
8:06
leave behind neutron stars, super dense but tiny
8:10
star cores, and only a tiny handful, just a couple
8:15
hundred out of half a million, end their lives
8:18
as black holes. Which means something else quietly
8:22
remarkable. Most stellar death is not explosive.
8:27
The galaxy's graveyard is mostly filled with
8:30
embers, not fireworks. So from a practical observing
8:35
perspective, this explains something many stargazers
8:39
eventually feel but rarely quantify. The night
8:42
sky is a biased sample. It favors brightness,
8:46
proximity, and youth. And from an analytical
8:50
perspective, it tells us something deeper. When
8:53
we talk about average or typical stars, we're
8:57
almost never talking about the stars we can actually
9:00
see. There's another interesting observation
9:03
here that is a little shocking, and I can't take
9:06
credit for it. As I was writing this episode,
9:09
I shared this code with a listener, who just
9:12
so happens to be my brother -in -law. Chris,
9:15
and he had a striking comment regarding the results.
9:19
You've heard me say the iconic Carl Sagan quote
9:22
before, we're all made of star stuff. But if
9:27
we're all made of elements from stars, and it's
9:30
only the much larger stars that go nova and eject
9:33
heavy elements into the cosmos, then Chris says,
9:37
the stuff that makes us has to comprise a vanishingly
9:41
small amount of the available matter in the universe.
9:45
And he's right. We are rare, because the atoms
9:49
that make us are statistically rare, and life
9:53
like ours couldn't have existed in the early
9:56
universe until those giant stars began seeding
9:59
the cosmos with enough material to form rocky
10:02
worlds and life itself. We are the inevitable
10:07
outcome of a universe that runs long enough for
10:11
complexity to accumulate. As always, if you'd
10:16
like to run my little sim or study the code,
10:19
I'll make it available at the show website. Just
10:22
look for this episode's show notes. Alternately,
10:25
I'll include a link that runs the code right
10:28
in your web browser, in case you don't have Python
10:31
and the required libraries. Now let's move from
10:35
the realm of statistics to some actual stars
10:38
that deserve our attention. I'm just going to
10:41
mention an extremely small sample of some of
10:44
the interesting stars we can see right now. A
10:48
highlight reel, if you will. We start with Proxima
10:52
Centauri, the star closest to Earth besides our
10:55
own Sun. Its name just means the nearest, and
10:59
that alone earns it attention. Proxima is a small,
11:04
faint, red dwarf loosely bound to the Alpha Centauri
11:07
system. It flares violently, bathing its planets
11:11
in radiation, yet it hosts at least one Earth
11:15
-mass world in the so -called habitable zone.
11:19
Our nearest stellar neighbor is still more than
11:22
four light years away. Close, astronomically
11:26
speaking, but vast from an emotional standpoint.
11:30
Then there's Barnard's star. This one is famous
11:34
for its movement. Over the course of a human
11:37
lifetime, Barnard's star visibly slides across
11:41
the sky faster than any other known star. It's
11:45
likely more than 10 billion years old, and it's
11:49
simply passing through our neighborhood. Bernard's
11:53
star quietly shattered the illusion that the
11:55
constellations are fixed. The sky moves just
11:59
very slowly. Now look south to Canopus. This
12:05
is the second brightest star in the night sky,
12:08
yet largely unfamiliar to northern observers.
12:12
In fact, it's barely visible from where I live,
12:15
and for those of you farther north, you may not
12:17
be able to see it at all. Canopus has guided
12:22
sailors for thousands of years and is still used
12:25
for stellar navigation by spacecraft today. Some
12:29
months back, a fan of the show mentioned to me
12:32
that Canopus has a sci -fi connection. In the
12:35
Dune saga, the ancestral home of House Atreides
12:39
orbits Canopus. That choice isn't accidental.
12:44
Canopus has long carried associations of authority,
12:48
navigation, and distant power. And I have to
12:51
thank our listener Mike for bringing this to
12:54
my attention. Some stars earn attention not through
12:58
proximity or brightness, but through reputation.
13:03
Vega looks calm, clean, and reliable, and for
13:06
a long time it was. 12 ,000 years ago, Vega was
13:11
Earth's North Star. And it will be again in the
13:15
far future as our planet's axis slowly wobbles.
13:20
Even now, Vega spins so rapidly that it's flattened,
13:24
hotter at its poles than at its equator. Then
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there's Antares. Its name means rival of Mars.
13:33
And when it rises in summer skies, its red glow
13:37
can fool the eye. Antares is a red supergiant
13:41
nearing the end of its life. swollen and unstable,
13:45
and shedding mass into space. If it replaced
13:49
our sun, it would engulf the entire inner solar
13:52
system. And finally, one that earns a more uneasy
13:57
kind of fame, WR104. This triple star system
14:03
is more than 8 ,000 light -years from Earth,
14:06
and its primary star is a wolf rayet star, stripped
14:10
of its outer layers and blasting material into
14:13
space at extraordinary speed. It's wrapped in
14:16
a spiral of dust known as the pinwheel nebula.
14:20
The unease comes from its orientation and its
14:23
relatively close proximity. The axis of WR was
14:28
thought to be pointed roughly toward Earth, meaning
14:31
that if it were to explode as a gamma ray burst,
14:34
it could have consequences far beyond its immediate
14:37
neighborhood, within just a few hundred thousand
14:40
years. This existential threat earned WR the
14:44
nickname of the Death Star. Although scientists
14:48
now think the axial tilt doesn't quite line up
14:51
with our solar system, it looks like we might
14:54
be safe after all. Some stars don't just age
14:58
or fade. They collapse, harden, and cross into
15:02
a different category of existence. When a massive
15:06
star runs out of fuel, gravity finally wins.
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The core implodes, protons and electrons are
15:14
crushed together, and what's left behind is an
15:17
extremely dense neutron star. Some neutron stars
15:22
spin, and when they do, things get strange. A
15:26
pulsar is a rotating neutron star that sweeps
15:30
beams of radiation through space like a lighthouse.
15:34
Every rotation sends a pulse toward Earth, which
15:37
we receive at a regular interval. And some are
15:40
so precise they rival atomic clocks. One of the
15:45
most famous is the Crab Pulsar, the leftover
15:48
core of a star that exploded in the year 1054.
15:52
That explosion was recorded by astronomers in
15:55
China, Japan and the Middle East, and it was
15:58
visible in daylight for weeks. Nearly a thousand
16:02
years later, the remnant is still spinning, broadcasting
16:06
the death of a star across the galaxy. And, of
16:10
course, the largest stars collapse into black
16:13
holes, drawing in matter and energy that never
16:16
escapes. We'll talk about stellar death in more
16:20
detail in our next episode, but what's important
16:23
here isn't just how violent these stars become.
16:27
It's that they're normal outcomes. It's what
16:30
happens when gravity is allowed to finish the
16:33
job. After a quick break, we'll return with this
16:51
week's Night Sky Report and some thoughts on
16:54
the next two chapters of Night Watch. Stay with
16:57
us. Welcome back. As we move into the middle
17:13
of February, the night sky quietly gives us one
17:16
of the best observing windows of the month. This
17:20
week is defined by a disappearing moon, a slow
17:23
motion gathering of planets, and a stretch of
17:26
genuinely dark evenings that reward patience
17:29
more than spectacle. This is not a week of fireworks,
17:33
it's a week of alignment, absence, and restraint.
17:37
Let's begin with the moon. We reach New Moon
17:40
on February 17th, which places the darkest nights
17:44
of the week right in the middle of this reporting
17:46
window. Early in the week, the moon is a very
17:49
thin waning crescent, rising late and staying
17:52
mostly out of the evening sky. By the 17th, it's
17:57
effectively absent altogether. Ideal conditions
18:00
for deep sky observing, galaxy hunting, and revisiting
18:04
faint clusters that usually struggle against
18:07
moonlight. The moon returns quickly but delicately.
18:11
From February 18th through the 21st, a thin waxing
18:15
crescent appears low in the western sky just
18:18
after sunset. These early crescents are soft
18:21
and understated, and under steady skies you may
18:24
notice earth shine, where sunlight reflected
18:28
from earth faintly illuminates the moon's darkened
18:31
hemisphere. A standout moment comes on the evening
18:34
of February 19, when the young crescent moon
18:38
passes in close conjunction with Saturn. The
18:41
pairing sits low in the west just after sunset.
18:45
Nearby, Mercury sits roughly five degrees to
18:49
the south of Saturn. Mercury is climbing into
18:51
one of its better evening appearances of the
18:54
year, visible briefly after sunset if you have
18:57
a clear western horizon. Binoculars can help,
19:01
but the naked eye is often enough once you know
19:03
where to look. Venus, despite being the brightest
19:07
planet in the sky, is passing very close to the
19:10
Sun during this period. As a result, it's largely
19:13
lost in the glare and may be difficult or impossible
19:17
to observe safely from most locations. Higher
19:21
in the sky, Jupiter remains the anchor of the
19:24
evening. It's visible as soon as the sky darkens
19:27
and climbs into a commanding position in the
19:30
southern sky as the night goes on. Jupiter stays
19:33
up until after midnight and even a small telescope
19:37
will show its cloud bands and several of its
19:40
moons shifting position from night to night.
19:43
Farther along the ecliptic, Saturn remains low
19:46
in the west and increasingly difficult to see
19:49
as the week progresses. but its encounter with
19:52
the moon on the 19th makes it worth the effort.
19:56
Uranus is still accessible in the early evening
19:58
near the Pleiades in Taurus, appearing as a faint
20:02
bluish -green point in binoculars or a small
20:05
scope. With the moon out of the way for much
20:08
of this period, the deep sky quietly takes center
20:11
stage. The Pleiades are especially rewarding
20:15
this week under moonless skies, revealing layers
20:18
of stars and binoculars that are easy to miss
20:21
when the moon is brighter. Dark sky observers
20:24
may also want to use this stretch to hunt faint
20:27
galaxies or revisit some of the clusters we've
20:30
mentioned in the past few episodes. This week
20:40
in the Star Trails Book Club, we're reading chapters
20:43
four and five out of Night Watch. Titled Stars
20:48
for All Seasons, chapter four is a meaty portion
20:51
of the book that does a lot of heavy lifting.
20:54
At first glance, this chapter feels a little
20:57
old school. Dickinson spends a good amount of
21:00
time with printed star charts, the kind you'd
21:03
expect to see folded in the back of a book or
21:05
laminated for use in the field. In an era of
21:09
phone apps like Stellarium, these charts can
21:12
feel quaint, almost ceremonial, but Dickinson
21:16
makes a strong case for them. Printed charts
21:19
don't kill your night vision, and most importantly,
21:22
they force you to learn the sky rather than outsource
21:25
it. Interestingly, Dickinson introduces two kinds
21:29
of star charts. One set shows an average sky,
21:34
not pristine, not heavily light polluted, but
21:37
something close to what many backyard observers
21:39
actually experience. The other set is more traditional,
21:44
black on white, constellations connected by lines,
21:48
labeled stars, and the ecliptic plane drawn across
21:51
the chart to show where the planets travel. It's
21:55
much more detailed. These charts aren't meant
21:58
to be memorized, and Dickinson is pretty clear
22:01
about that. There's simply too much information
22:04
here to absorb in one pass. This is a chapter
22:07
you come back to as your familiarity with the
22:10
sky deepens. One of the most striking explanations
22:13
in this chapter comes when Dickinson talks about
22:16
the Milky Way. When we look up and see that misty
22:19
cloud -like band, what we're really seeing is
22:22
perspective. We're looking sideways through the
22:25
disk of our galaxy into spiral arms packed with
22:29
stars. Those stars are so numerous and so distant
22:33
that our eyes can't resolve them individually.
22:36
Instead, they blur together into that familiar
22:39
river of light. The Milky Way isn't a cloud at
22:43
all. It's a crowd. Dickinson also does a nice
22:47
job reminding us that brightness is deceptive.
22:50
Take Deneb, for example, one of the stars of
22:54
the Summer Triangle. It may be one of the largest
22:57
and most luminous stars in the entire Milky Way,
23:01
but it's more than 1600 light -years away. Because
23:05
of that distance, it appears dimmer than its
23:07
closer companions Vega and Altair, even though
23:11
it utterly dwarfs them in true size and power.
23:15
Throughout the chapter, Dickinson breaks the
23:17
sky down by season, and one observation stood
23:20
out to me, autumn. According to Dickinson, autumn
23:25
actually contains fewer distinctive star patterns
23:28
than the other seasons. It's not that the sky
23:31
is empty, but that it lacks the bold, obvious
23:34
shapes we associate with winter or summer. He
23:37
mentions the region called the Cetus Void, an
23:41
area with no first or second magnitude stars
23:44
at all. Winter, on the other hand, often feels
23:48
special to observers, but Dickinson points out
23:50
something subtle. Winter skies aren't necessarily
23:54
better for observing. What they do have is more
23:57
bright stars, which gives the impression of richness
24:01
and clarity. This is also where Dickinson emphasizes
24:04
something many of us take for granted. Orion's
24:08
belt. Those three stars are actually unusual.
24:12
Dickinson notes that they're the only example
24:15
of three stars of that brightness appearing this
24:18
close together in the sky. It's not just iconic
24:21
by tradition, it's genuinely rare. Finally, the
24:25
chapter brings us back to the Milky Way, this
24:28
time in winter. The Milky Way appears dimmer
24:31
in winter because of where we're looking. In
24:34
winter, our nighttime view points away from the
24:37
galactic center, toward the outer edges of the
24:40
galaxy, where stars are more sparsely distributed.
24:44
It's all about our orientation. Nothing in the
24:47
sky is static. The seasons don't just bring about
24:51
weather changes, they change our angle on the
24:54
universe. What we see depends on where we're
24:57
standing, and where we're looking. In Chapter
25:01
5, Observing Tools and Techniques, Dickinson
25:04
shifts the focus away from charts and constellations
25:07
to the actual tools of observation. And one of
25:11
the first things he does is quietly decenter
25:14
the importance of the telescope. Dickinson spends
25:18
a surprising amount of time reminding viewers
25:20
that astronomy doesn't begin with magnification.
25:24
It begins with patience, dark adaptation, and
25:27
learning how your eyes work in low light. He
25:30
makes a strong case for the naked eye and binoculars
25:34
not as beginner substitutes But as serious observing
25:37
tools that preserve context and teach you how
25:41
the sky fits together There's also a recurring
25:44
theme of expectation management running through
25:47
this chapter Dickinson is very clear that the
25:51
sky does not look like photographs Nebula don't
25:55
glow in color galaxies don't leap out of the
25:58
eyepiece Most deep -sky objects are faint, subtle,
26:02
and easy to miss unless you know how to look,
26:05
and unless you accept them on their own terms.
26:09
And that leads directly into one of the most
26:11
memorable parts of the chapter. But first, a
26:15
personal anecdote, and I think many of you will
26:18
be able to relate to this. When I was in the
26:21
seventh grade, I received, for Christmas, a shiny
26:24
new Jason refractor. which seemingly came with
26:28
every bell and whistle possible, except actually
26:31
using it was beyond frustrating owing to a rickety
26:35
tripod, wobbly mount, stiff focusers, and a nearly
26:39
useless finder scope. After weeks of practice,
26:43
I was able to tease out decent views of Jupiter,
26:46
Venus, and Saturn, but not much else, and only
26:50
after many minutes of frustration trying to acquire
26:53
my targets. Dickinson has a name for these cheap
26:56
telescopes that flood big -box stores every holiday
27:00
season. He calls them Christmas trash scopes,
27:04
because they so often sabotage a beginner's first
27:07
experience. In many cases, the optics themselves
27:12
aren't terrible. The real problem is almost always
27:15
the mount. These scopes are perched on shaky,
27:19
underbuilt tripods that wobble when you touch
27:21
them, vibrate when you focus, and refuse to stay
27:25
pointed where you aim them. Add in low -quality
27:28
eyepieces, and even bright objects become frustrating
27:31
to observe. This is why Chapter 5 keeps circling
27:35
back to simplicity. A modest instrument on a
27:39
solid mount, or even a good pair of binoculars,
27:42
will almost always create a better experience
27:45
than a flashy telescope that can't hold still.
27:49
And, interestingly, Dickinson doesn't exclude
27:52
the use of so -called smart scopes or go -to
27:55
mounts. He said he once discouraged people from
27:58
using them but realized that in the interest
28:01
of getting up and observing fast, particularly
28:03
in areas with a challenging sky, These smart
28:06
scopes can be a godsend. This chapter also provides
28:11
an excellent survey of scope types, reflector
28:15
vs. refractor, dobsonian mounts vs. equatorial
28:19
mounts, and so on, along with the pros and cons
28:23
of it all. It's quite a technical chapter but
28:26
essential reading if you're looking to purchase
28:28
an instrument. As always, if you have any thoughts
28:31
on these chapters, please let me know over at
28:33
the show website. I'd love to be able to share
28:36
some of your reflections on a future episode.
28:39
We'll cover the next two chapters two weeks from
28:42
now. That's going to do it for this week. If
28:48
you found this episode interesting, please share
28:51
it with a friend who might enjoy it. The easiest
28:53
way to do that is by sending folks to our website,
28:57
StarTrails .Show. And if you'd like to support
29:00
the show, use the link on the site to buy me
29:03
a coffee. Be sure to follow Star Trails on Blue
29:06
Sky and YouTube. Links are in the show notes.
29:10
Until we meet again beneath the stars, clear
29:13
skies everyone.