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