Howdy Star Gazers 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 March
29th through April 4th. This week we leave the
familiar planets behind and journey into the
farthest reaches of our solar system. where the
sun's influence begins to fade and the boundaries
of our cosmic neighborhood grow uncertain. We'll
explore the Kuiper Belt, a vast disk of icy remnants
from planetary formation, and venture even farther
into the mysterious unseen Oort Cloud, a distant
spherical halo that may stretch halfway to the
nearest stars. Later in the show, we'll take
a look at what you can expect to see in this
week's night sky. Whether you're tuning in from
the backyard or the balcony, I'm glad you're
here. So grab a comfortable spot under the night
sky and let's get started. Over the past several
weeks, we've taken a journey through our solar
system. We've stood on the scorched surface of
Mercury. drifted through the thick clouds of
Venus and looked back at our fragile home from
orbit. We've explored the red deserts of Mars,
crossed the asteroid belt, and marveled at the
immense presence of Jupiter and Saturn. We reached
the outermost planets and we've looked at some
of the strange moons that orbit them. For much
of human history, that's where the story ended.
When Johann Gottfried Gall first observed Neptune
in 1846, it marked the boundary of the known
solar system. Even after Clyde Tombaugh discovered
Pluto in 1930, astronomers still thought in terms
of planets. Isolated worlds spaced out across
an otherwise empty void. But tonight we're going
beyond that idea. Because the solar system doesn't
end with Neptune. In many ways, that's just where
it begins to get strange. Just beyond Neptune's
orbit lies a vast and dimly lit region known
as the Kuiper Belt. This is not a place of dominant
planets, but a wide, flattened disk of icy debris
stretching from about 30 to 50 astronomical units
from the sun. Out here, sunlight is faint. Temperatures
hover just above absolute zero. and the pace
of motion slows to something almost imperceptible.
Every now and then, it sends us a short period
comet, like Halley's Comet for instance. These
distant regions are not random collections of
objects. They're time capsules. When the planets
formed billions of years ago, gravity gathered
material into worlds like Earth and Jupiter.
But not everything was used. What remained was
scattered outward, pushed into distant orbits
by the giant planets, where it's remained largely
unchanged ever since. The Kuiper Belt is not
just a region, it's actually a preserved record
of the solar system's formation. A construction
site that was never finished. The idea of such
a region didn't always exist. In 1951, astronomer
Gerard Kuyper proposed that leftover debris might
exist beyond Neptune, though he believed it may
have dissipated over time. For decades, the idea
remained theoretical. It wasn't until 1992 that
astronomers finally confirmed this distant region
was real. Working at the University of Hawaii,
David Jewett and Jane Lu spent years patiently
scanning the sky, searching for something incredibly
difficult to detect. These objects are small,
dark, and move very slowly against the background
stars. Night after night, they compared images
looking for a faint point of light that shifted
just enough to reveal itself. And then they found
it. A tiny object now known as 1992 QB1. It wasn't
a planet and it wasn't a comet. It was something
new. The first confirmed member of what we now
call the Kuiper Belt. That discovery changed
everything. It meant that Pluto was not an outlier.
It was part of a vast population of distant worlds.
In the years that followed, astronomers discovered
more and more of these objects, until it became
clear that the outer solar system was not empty
at all. It was crowded. Among the astronomers
leading that exploration was Mike Pluto Killer
Brown. In the early 2000s, Brown and his team
began discovering large objects in the Kuiper
Belt, worlds that rivaled Pluto in size. Then,
in 2005, they found something even more provocative.
Eris. Eris is slightly more massive than Pluto,
and travels in a distant, elongated orbit that
carries it far beyond Pluto's path. At times,
it's more than twice as far from the sun as Pluto.
And its discovery raised a difficult question.
If Pluto was a planet, Then what is Eris? Another
planet? The tenth? Or, had we misunderstood,
Pluto all along? What followed was one of the
most public debates in modern astronomy. In 2006,
the definition of a planet was formally revised,
and Pluto was reclassified as a dwarf planet.
Mike Brown took the fall as the so -called man
who killed Pluto, but in reality, he didn't take
anything away. He revealed something larger.
The solar system didn't really lose a planet.
It gained an entire new region of worlds. But
even the Kuiper Belt is not the edge. The idea
of something even farther out came from a different
mystery. In 1950, Dutch astronomer Jan Oort studied
the paths of long period comets. These rare visitors
that appear suddenly and may not return for thousands
of years. Their orbits didn't make sense. They
weren't confined to the mostly flat plane of
the solar system. Instead, they approached from
every direction, above, below, and at every angle
imaginable. Oort realized these comets must originate
from a spherical distribution of objects, not
a disk. He proposed the existence of a vast,
distant cloud of icy bodies surrounding the sun
in all directions. So far away that they're only
loosely bound by its gravity. A passing star
or even the gentle tidal forces of the Milky
Way could disturb one of these objects and send
it falling inward where we would briefly see
it as a comet. We have never directly observed
this cloud. No telescope has imaged it. and yet
every long period comet we see points back to
its existence. Today we call it the Oort cloud.
Some astronomers believe there may even be a
dense inner region, sometimes called the Hills
cloud, hidden within the larger structure. Taken
together, this region may extend tens of thousands
of astronomical units from the Sun, perhaps even
approaching halfway to the nearest star. At that
distance, our sun is no longer a dominant presence.
It becomes just another point of light in the
sky. When we see a comet from Earth, we're seeing
something ancient, a fragment of the early solar
system, preserved in deep freeze for billions
of years, now briefly illuminated by the sun
before returning to the darkness. When I first
began this series, I specifically wanted to highlight
places that humanity has physically explored.
And believe it or not, space probes are in the
Oort cloud right now. Of course, I'm talking
about the two spacecraft launched in 1977, Voyager
1 and Voyager 2. These are the most distant objects
ever created by human hands. They pass the planets,
cross the Kuiper Belt, and entered interstellar
space, moving beyond the Sun's heliosphere. That's
the region dominated by the solar wind. Now nearly
one light day away, they're deep within the broader
domain of the Oort cloud. Out there in the darkness,
the Voyagers are not just drifting silently,
they're still working. Both spacecraft continue
to send back data about the environment beyond
the heliosphere. measuring cosmic rays, magnetic
fields, and the faint plasma that exists between
the stars. If the distance from the Earth to
the Sun were reduced to a single inch, the outer
edge of the Oort cloud would lie nearly a mile
away. By that scale, the Voyagers have barely
begun the journey. They've left the Sun's bubble,
but not the Sun's backyard. Even out here, this
story is not complete. Astronomers have found
hints that something else may be lurking in the
outer solar system. Planet 9 is a proposed world,
inferred from the unusual clustering of orbits
among distant Kuiper belt objects. If it exists,
it could be several times the mass of Earth,
orbiting hundreds of astronomical units from
the Sun, taking tens of thousands of years to
complete a single orbit. It's never been seen.
Its existence is only written in the motions
of other objects. But the search for this hidden
world is happening right now. Astronomers are
actively looking. New observatories like the
Vera C. Rubin Observatory in Chile are beginning
to scan the sky with unprecedented depth and
precision, searching for faint objects that drift
slowly against the stars. At the same time, scientists
are combing through infrared data looking for
the faint heat signature of a distant unseen
planet. Others are refining the mathematics itself,
tracking distant Kuiper belt objects and asking
whether their strange orbits truly point to something
massive, or whether we're being misled by the
limits of our observations. And then there are
the visitors, one of them two -eye Borisov made
waves in the news last year as the first confirmed
interstellar comet. Borisov and another visitor,
One Eye Umauamaua, discovered in 2017, are objects
that do not belong to our solar system at all.
They arrived from elsewhere, passing briefly
through our neighborhood before continuing their
journey through the galaxy. They don't orbit
the sun, they arrive, pass through, and then
they vanish. If we can detect fragments from
other star systems drifting through ours, then
somewhere out there, other systems may be doing
the same. Watching a chunk of our solar system
drift through their domain. At some point out
there, it becomes difficult to say where the
solar system ends and where interstellar space
truly begins. The boundary isn't a sharp line,
but a gradual fading, a transition from the sun's
influence to the wider gravitational currents
of the Milky Way. So as we close out this journey,
it's worth remembering that the solar system
is not a fixed map of planets. It's a vast and
evolving structure, shaped by gravity, time,
and chance. For centuries we believed the planets
were the whole story. Then we discovered the
Kuiper Belt. Then we inferred the Oort Cloud.
And now we continue searching for worlds we cannot
yet see. After a quick break, we'll be back to
cover this week's night sky. Stay with us. Welcome
back. We're entering this week under a bright
and increasingly dominant moon. After reaching
first quarter back on March 25th, The moon is
now waxing toward fullness, culminating in a
full moon on April the 1st. This week's full
moon is known as the pink moon, not for its color,
but for the flowers that bloom beneath it, marking
the quiet return of spring. It's also known as
the egg moon, as it's linked to fertility and
renewal. Early in the week, you'll still have
some decent dark sky windows after sunset, but
as we move closer to midweek, Moonlight will
begin to wash out fainter objects, so if you're
planning any deep sky observing, earlier in the
week is your best bet. Tonight, March 29th, the
moon passes extremely close to Regulus, the heart
of the constellation Leo. In some parts of the
world, like Europe, observers will even see an
occultation where the moon passes directly in
front of the star, causing it to disappear and
reappear abruptly. Here in North America, we
won't witness the occultation itself, but it's
still a nice pairing that's easy to spot shortly
after sunset in the western sky. A bright moon
sitting right next to one of the spring sky's
most recognizable stars. Planet -wise, we've
got a few good targets this week. Jupiter is
still the star of the show. It's bright, unmistakable,
and well placed in the evening sky. sitting high
after sunset and lingering for hours. Venus is
visible low in the western sky just after sunset.
It's brilliant, but it doesn't stick around long,
so you'll want a clear horizon and good timing.
Uranus is still technically visible in Taurus,
though you'll need binoculars or a small telescope
to pick it out. Mercury and Mars are mostly lost
in the Sun's glare this week, making them difficult
to observe. With the full moon this week, a lot
of deep sky objects may be off the table. So
let's look at some that punch through the bright
moonlight. Globular clusters are fantastic in
moonlight because they're dense and bright. Seek
out Messier 3 and Canes Venetici. It's one of
the brightest globulars in the northern sky and
resolves into stars in small scopes. It will
be high enough for comfortable observation this
week. Messier 35 is a bright open cluster near
the foot of Gemini. It looks good in binoculars
and it's visible in the early evening. Open clusters
like the beehive cluster in Cancer remain beautiful
even under a bright sky, appearing as a soft
scattering of stars in binoculars. And if you
look west early in the evening, the Orion Nebula
is still visible, glowing faintly in the Sword
of Orion. Even with the moon nearby, it remains
one of the most rewarding objects you can observe.
We're in the home stretch in our book club selection.
Next week we're going to wrap up the final chapters
in Nightwatch. And looking deeper into April,
we're going to get a little meta and turn away
from the objects in the sky to the processes
and tools scientists actually use to study them.
We're going to talk about observatories, the
scientific method, how data is collected, used,
and analyzed, and in general, peel back the curtain
on the machinery behind the study of space. 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.
That really helps. 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!