Latest / Star Trails: From Backyard Astronomy to Cosmic Wonder / How Jupiter Almost Destroyed the Solar System

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How Jupiter Almost Destroyed the Solar System · Star Trails: From Backyard Astronomy to Cosmic Wonder

0:07
Howdy Star Gazers and welcome to this episode
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of Star Trails. My name is Drew and I'll be your
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guide to the night sky for the week of June the
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21st to the 27th. This week we're taking a journey
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back four and a half billion years to explore
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one of the strangest ideas in modern planetary
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science. A theory suggesting that Jupiter may
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not have formed where we find it today. In fact,
0:35
the giant planet may have migrated deep into
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the young solar system, before turning around
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and heading back outward, dramatically reshaping
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the worlds we know today. Later in the show,
0:48
we'll celebrate the arrival of summer with a
0:50
look at the summer solstice. check in on the
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moon and planets, and explore a few sites worth
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seeking out in the warm June night sky. Whether
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you're tuning in from the backyard or the balcony,
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I'm glad you're here. So grab a comfortable spot
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under the night sky, and let's get started. If
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you've spent any time outside lately, you've
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probably noticed a brilliant object shining in
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the evening sky. That's Jupiter, the largest
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planet in our solar system. Through a telescope,
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it's a spectacular sight. Bands of clouds, four
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bright moons, and a presence that's impossible
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to miss. Most of us picture Jupiter as a permanent
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fixture of the solar system. It's out there beyond
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Mars, beyond the asteroid belt, circling the
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sun every 12 years, just as it always has. But
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what if that's not the whole story? What if Jupiter
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wasn't always where it is today? What if, billions
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of years ago, Jupiter embarked on an epic journey
2:00
through the young solar system, one that may
2:03
have changed the fate of every planet, including
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our own? Tonight, we're exploring one of the
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strangest and most fascinating ideas in modern
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planetary science, the Grand TAC Hypothesis.
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Now, when most of us learn about the solar system,
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we're shown a neat little diagram. The sun sits
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in the middle, Mercury is closest, then Venus,
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Earth, Mars, the asteroid belt, Jupiter, Saturn,
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and so on. It's tidy, ordered, and predictable.
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It's easy to come away with the impression that
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the planets formed in those locations and have
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stayed there ever since. For a long time, astronomers
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thought something similar. The story went something
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like this. A cloud of gas and dust coalesced
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to form the sun. Around it, a spinning disk of
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leftover material began clumping together. Tiny
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grains became pebbles, pebbles became rocks,
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rocks became planetesimals, and eventually, planets
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emerged from the chaos. Simple enough. But as
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scientists began building more sophisticated
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computer models of planetary formation a problem
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emerged actually several problems emerged and
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one of the biggest was sitting right next door
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Mars Mars is often described as Earth's little
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brother, but when you compare the two worlds
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the difference is startling Mars is only about
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half the diameter of Earth and possesses barely
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10 % of Earth's mass. And that's strange. Venus
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and Earth are both substantial rocky worlds,
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yet Mars is tiny by comparison. When astronomers
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ran simulations of the early solar system, they
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frequently ended up creating a Mars much larger
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than the one we actually observe. The models
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kept producing a planet that shouldn't exist.
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Or, perhaps more accurately, they failed to produce
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the one that does. Something seemed to have robbed
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the region around Mars of the material needed
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to build a larger planet. But what? The answer,
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some scientists proposed, may have been Jupiter.
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To understand why, we need to talk about something
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that once sounded almost heretical in astronomy.
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Planetary migration. The idea that planets can
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move, not just wobble a little, not drift by
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tiny amounts, but move and significantly. Today,
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this idea is widely accepted, but a few decades
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ago, it would have sounded bizarre. After all,
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planets orbit the sun. That's what they do. Then,
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astronomers began discovering planets around
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other stars, and these discoveries changed everything.
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They found giant worlds larger than Jupiter orbiting
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absurdly close to their stars. Some completed
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in orbit in just a few days. These so -called
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hot Jupiters shouldn't have been there. There
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simply wasn't enough material close to the star
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to build such massive planets. The only reasonable
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explanation was that these worlds formed farther
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out and later migrated inward. Suddenly, planetary
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migration wasn't just possible, it appeared to
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be common. And if planets around other stars
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could migrate, why not the planets in our own
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solar system? As it turns out, there are good
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reasons to believe that Jupiter did migrate.
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To understand how, we need to travel back about
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four and a half billion years to a time before
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the solar system looked anything like it does
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today. The Sun had only recently formed. Around
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it stretched a vast disk of gas, dust, ice, and
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rocky debris. The planets were still under construction.
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Jupiter was one of the first major planets to
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emerge, and because it was so massive, it didn't
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simply orbit quietly within that disk. It interacted
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with it. With every orbit, Jupiter's gravity
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tugged on the surrounding gas. At the same time,
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the gas exerted its own influence on Jupiter.
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These interactions transferred angular momentum
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back and forth, creating a kind of gravitational
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conversation between the planet and the disk
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around it. Instead of remaining in place, Jupiter
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began spiraling inward. Imagine a bowling ball
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resting on a giant rotating trampoline. The ball
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distorts the surface around it, and those distortions
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affect how the ball moves. The physics of a protoplanetary
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disk is considerably more complicated than that,
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but the basic idea is similar. Jupiter's immense
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gravity created disturbances in the disk, and
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those disturbances altered Jupiter's orbit. Over
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time, Jupiter drifted closer and closer to the
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Sun, and according to the Grand Tach Hypothesis,
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it may have traveled astonishingly far. Some
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current models suggest Jupiter moved inward to
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roughly 1 .5 astronomical units from the Sun.
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That's about one and a half times Earth's distance.
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In other words, Jupiter may have ventured into
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the region we now associate with Mars. It's hard
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to picture a world containing more than twice
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the mass of all the other planets combined, passing
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through the neighborhood of the young terrestrial
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planets. This was not a subtle event. As Jupiter
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migrated inward, its gravity scattered material
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in every direction. Some objects were flung outward.
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Others were sent inward. Some were ejected from
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the solar system entirely. The orderly construction
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project that would eventually produce the inner
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planets suddenly had a giant wrecking ball swinging
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through it. And this may be where Mars' fate
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was sealed. By plowing through that region, Jupiter
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likely depleted much of the material that would
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otherwise have accumulated into a larger planet.
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When the dust finally settled, there simply wasn't
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enough building material left to create an Earth
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-size world. Mars became the underdog of the
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inner solar system, a survivor of a cosmic construction
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site that had been stripped nearly bare. If the
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story ended there, our solar system would look
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very different today. In fact, Earth itself might
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never have formed in the way it did. Fortunately
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for us, another player entered the game. Saturn.
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As Jupiter migrated inward, Saturn was still
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forming farther out in the disk. Eventually,
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it grew massive enough to begin migrating as
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well. The two giant planets were now on a collision
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course, maybe not physically, but gravitationally.
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As Saturn approached Jupiter, the pair became
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locked into what astronomers call an orbital
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resonance. This is one of those terms that sounds
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complicated but describes a fairly simple idea.
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A resonance occurs when two objects repeatedly
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interact in a regular pattern. For example, one
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planet might orbit the Sun exactly twice, for
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every orbit completed by another planet. These
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repeating gravitational nudges can dramatically
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alter orbits over time. And once Jupiter and
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Saturn became linked in this way, something remarkable
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happened. The balance of forces changed. The
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two planets effectively began working together
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against the surrounding gas disk, and instead
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of continuing inward, they reversed direction.
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Jupiter stopped its plunge toward the Sun, and
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Saturn stopped following. Together, the two giant
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planets began migrating outward. This reversal
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is the reason the hypothesis is called the Grand
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Tack, and the name comes from sailing. When a
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sailboat reaches a certain point, it changes
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direction in a maneuver known as a tack. Rather
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than continuing on its original course, it swings
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around and heads off in a new direction. According
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to this model, Jupiter performed the ultimate
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cosmic attack. After heading inward for hundreds
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of thousands of years, it turned around and sailed
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back outward toward the orbit we know today.
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And that's one of the most dramatic events ever
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proposed in the history of our solar system.
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If it happened, nearly everything we see around
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us bears its fingerprints. The asteroid belt,
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for example, suddenly begins to make more sense.
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It isn't a neat collection of identical objects.
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Instead, it's a mixture. Some asteroids appear
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dry and rocky. Others contain much more ice and
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volatile material. The Grand TAC offers a possible
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explanation. As Jupiter moved inward and then
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back outward, it stirred up populations of objects
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from different regions of the solar system and
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mixed them together. The asteroid belt may be
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less of a pristine relic and more of a cosmic
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junk drawer, filled with material gathered from
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multiple neighborhoods during Jupiter's journey.
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And perhaps most importantly, the Grand TAC may
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explain why our solar system looks so different
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from many of the planetary systems we've discovered
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elsewhere. Around other stars, giant planets
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are often found very close to their suns. In
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our system, Jupiter never completed that inward
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migration, because Saturn arrived just in time
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to usher the king of planets back outward. And
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the solar system we know today was allowed to
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emerge from the chaos. Now if you've spent any
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time around astronomy clubs, science museums,
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or popular science books, You've probably heard
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a familiar claim. Jupiter protects Earth. The
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idea is simple enough. Jupiter is enormous. Its
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gravity is powerful. Therefore, it acts like
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a giant shield, sweeping up dangerous objects
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before they can threaten our planet. And there
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is some truth to that. One of the most spectacular
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examples occurred in 1994. when comet Shoemaker
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-Levy 9 collided with Jupiter. Astronomers watched
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as fragments of the comet slammed into the giant
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planet, leaving dark scars larger than Earth
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itself across Jupiter's cloud tops. For many
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people, it was a vivid demonstration of Jupiter's
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protective role. A dangerous object that might
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have threatened another world instead met its
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end in Jupiter's atmosphere. Case closed, right?
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Well, not exactly. As astronomers began studying
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the problem in greater detail, a more complicated
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picture emerged. Because Jupiter doesn't merely
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capture objects, it also redirects them. Imagine
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placing a giant gravitational pinball machine
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in the solar system. Every comet, asteroid, and
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icy body that wanders nearby can have its path
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altered. Sometimes those alterations are helpful,
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and sometimes they're not. Jupiter can fling
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objects completely out of the solar system. It
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can send them harmlessly into the sun. It can
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trap them in stable orbits. But it can also redirect
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them inward, toward Earth. In other words, Jupiter
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doesn't simply remove threats, sometimes it creates
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them. This has led astronomers to ask an intriguing
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question. Is Jupiter Earth's guardian or is Jupiter
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Earth's accomplice in a long history of cosmic
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violence? The answer appears to be both. Without
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Jupiter, certain classes of comets would probably
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reach Earth far more frequently. Its immense
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gravity helps clear many of these objects from
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the solar system. But for some asteroids and
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smaller bodies, Jupiter's gravitational influence
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can actually increase the chances that they cross
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Earth's orbit. It's less like having a security
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guard at the door, and more like having an extremely
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large, unpredictable bouncer. Most of the time
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he's helping, occasionally he's throwing furniture.
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And when we view Jupiter through the lens of
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the Grand TAC hypothesis, that ambiguity becomes
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even more fascinating. Think about what we've
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discussed so far. Jupiter may have stripped material
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from the region where Mars was forming. It may
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have scattered countless smaller worlds. It may
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have reshaped the asteroid belt, and it may have
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altered the architecture of the entire solar
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system. That's not the behavior of a passive
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bystander. That's the behavior of a cosmic kingmaker,
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or maybe a cosmic troublemaker. And yet, without
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that journey, the solar system we know might
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never have existed. Earth may have formed differently.
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Mars may have been much larger. The asteroid
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belt may have looked completely different. Even
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the delivery of water and volatile compounds
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to the inner solar system could have unfolded
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along another path. We're often taught that the
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solar system is a finished machine, a clockwork
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arrangement of planets moving along predictable
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paths. But modern astronomy paints a very different
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picture. The early solar system was chaotic,
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violent, and messy. Planets migrated, worlds
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collided, and entire populations of objects were
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scattered into deep space. The solar system we
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inhabit today is not necessarily the solar system
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that had to happen. It may simply be the version
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that survived. And that's one of the reasons
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I find the Grand TAC hypothesis so compelling.
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It reminds us that our seemingly orderly solar
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system has a dynamic history filled with twists,
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reversals, close calls, and accidents. Saturn
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forms a little later, and perhaps Jupiter never
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turns around. Jupiter migrates a little farther
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inward, and perhaps the inner solar system is
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dramatically altered. Change a few variables,
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tweak the timing by a few hundred thousand years,
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and the night sky above us today might belong
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to a completely different world. Which brings
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us back to the present. Tonight, if the skies
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are clear, step outside and find Jupiter shining
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in the darkness. To our eyes, it appears calm
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and steady. a brilliant point of light slowly
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moving among the stars. For thousands of years,
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people have watched it cross the sky and imagined
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it as a god, a king, or a wandering star. Today,
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we know it as a giant planet, but according to
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one remarkable idea, that bright beacon may also
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be the architect of the solar system we call
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home. Jupiter could be a world builder, a destroyer,
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or a savior. Maybe all three at once. And every
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time we look at it, we're looking at a survivor
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of one of the greatest journeys ever proposed
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in planetary science. After a quick break, we'll
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be back with a look at this week's night sky.
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Stay with us. Welcome back. Summer has officially
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arrived. The summer solstice occurs today, marking
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the beginning of astronomical summer in the northern
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hemisphere. It's also the longest day of the
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year and the shortest night of the year. But
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what exactly is a solstice? Many people think
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the seasons are caused by Earth being closer
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to or farther from the Sun. That's actually not
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the case. In fact, Earth is slightly farther
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from the Sun during Northern Hemisphere summer
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than it is during winter. The real reason for
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the seasons is Earth's tilt. Our planet's axis
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is tilted by about 23 .5 degrees. As Earth travels
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around the Sun, that tilt causes different parts
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of the planet to receive more direct sunlight
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at different times of the year. On the summer
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solstice, the Northern Hemisphere is tilted most
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directly toward the Sun. The Sun climbs to its
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highest noon altitude of the year. Daylight lasts
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the longest, and we experience the year's shortest
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night. From this point forward, the days begin
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their slow march back toward autumn and winter,
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though you probably won't notice the difference
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for several weeks. Turning our attention to the
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moon, we begin the week with a first quarter
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moon tonight. That means half of the moon's earth
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-facing hemisphere appears illuminated. First
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quarter moons are good targets for binoculars
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and telescopes because the shadows along the
20:09
lunar terminator help craters and mountains stand
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out in dramatic relief. As the week progresses,
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the moon waxes into a growing gibbous phase,
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becoming brighter each evening as it heads towards
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the full strawberry moon, arriving on June 29th.
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By the end of this week, moonlight will begin
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to interfere somewhat with observations of faint
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galaxies and nebula, so early -week observing
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will offer the darkest skies. As for the planets,
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brilliant Venus continues to dominate the western
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sky after sunset. You'll find it shining low
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in the west during twilight, making it nearly
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impossible to miss. Jupiter remains nearby, but
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is sinking deeper into the evening twilight as
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the month draws to a close. If you'd like to
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catch Jupiter, look shortly after sunset and
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make sure you have a clear western horizon. Mercury
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also lingers low in the western sky, though it
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may be challenging to spot without an unobstructed
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horizon and clear conditions. Think of it as
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a bonus target for patient observers. If you're
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willing to rise before dawn, Saturn is becoming
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increasingly prominent in the morning sky, while
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Mars can also be found before sunrise. This is
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also an excellent time to begin exploring the
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summer Milky Way. By late evening, the rich star
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fields of Sagittarius and Scorpius are climbing
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higher in the southeastern sky. You're looking
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toward the heart of our galaxy where vast clouds
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of gas, dust, and countless stars crowd together
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in one of the most spectacular regions visible
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to amateur astronomers. If you have binoculars,
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spend some time sweeping through Sagittarius.
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Even under suburban skies, you'll encounter dense
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star fields and clusters. Under darker conditions,
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the Milky Way begins to reveal itself as a broad
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river of light stretching across the sky. Finally,
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don't forget to look overhead for the Summer
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Triangle. Vega, Deneb, and Altair are becoming
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increasingly prominent as darkness falls. Over
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the next few months, they'll serve as reliable
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signposts for navigating the warm nights of summer.
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That's going to do it for this week. If tonight's
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episode sparked your curiosity or maybe gave
22:33
you something new to think about the next time
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you look up, I'd be honored if you shared Star
22:38
Trails with someone who might enjoy the journey.
22:41
You can always find the latest episodes, show
22:43
notes, and extras at StarTrails .Show. And if
22:48
you'd like to help support the show, there's
22:50
also a little Buy Me a Coffee link on the site.
22:53
That genuinely helps keep these stories coming.
22:56
Be sure to follow Star Trails on Blue Sky and
23:00
YouTube. Links are in the show notes. Until we
23:03
meet again beneath the stars, clear skies everyone.