Evolution and Members of the

Solar System

By Joey Pelobello

Book sources:

ISBN 978-621-803-501-0

ISBN 978-621-8035-14-0

ISBN 978-971-8608-66-1

(note: even though most astronomers agree that they are not planets or

dwarf planets I will refer to 15760 Albion and 1993 FW as planets as I

have another source that says so)

What is the Solar System?

The Solar System refers to all objects that are trapped by the Sun’s

gravity into orbit around it, either directly or indirectly. As of 2019, the

Solar System consists of: one star, ten or eleven full-fledged planets,

more than seven dwarf planets, and millions of asteroids and Kuiper Belt

objects.

There are millions of bodies in the Solar System, and most of us know

many of them already, in order of increasing distance from the Sun.

But how did this come to be?

Why is our Solar System structured like this?

Were these the only planets that ever existed in our Solar System?

No, the Solar System was far more complicated and numerous in the past

than it is now.

The extra bodies which are long gone have made significant

contributions to how our Solar System is the way it is today.

The leading theory on how the Solar System was created is the nebular

hypothesis, which was widely developed by Fred Hoyle, W. H. McCrea,

Immanuel Kant, and most famously Pierre-Simon Laplace in 1796. Put

simply, our Solar System formed from the remains of a supernova

explosion that collapsed back in on itself.

Members of the Solar System

Formed 4,6 billion years ago from a cloud of dust and gas resulting from

a supernova, the Solar System is made of the Sun, the planets, their

moons, and every other object influenced by its gravity. At least eight

planets follow endless orbits around the Sun, trapped by its invisible and

immensely powerful pull of gravity. The inner planets of Mercury, Venus,

Earth and Mars are small rocky worlds with little to no moons, while most

of the outer planets (Jupiter, Saturn, Uranus, and Neptune) are giants

made mainly of gas and liquid and with many satellite families. Searches

continue for possible planets beyond Neptune (included below). Most of

the planets have moons circling them. Only the planets Mercury and

Venus have no moons at all. Some major planets that have been

destroyed (see below) are also included here.

Sun (diameter: 1,392,400 km; planets: 8-10; scientific name Sol after

Roman Sun god)

The Sun is a 4.6 billion year old ball of superheated plasma gas that

generates energy through nuclear fusion of hydrogen into helium within

its core. With a surface temperature of 5,777 Kelvin (around 5,500

Celsius), the Sun is the Solar System’s all-controlling and dominant body.

It contains 99,9% of the Solar System’s mass and has a diameter 109 times

wider than that of the Earth’s. The Sun has a classification of G2V; it’s a

main sequence star.

Mercury (diameter: 4,879 km; moons: 0; named after Roman messenger

god)

Mercury orbits the Sun every 88 days, only 58 million kilometers away

from its searing heat. The tiny planet roasts on one side and freezes on

the other due to its very thin atmosphere. About 60% of Mercury’s

surface is covered with craters made by impacts with meteorites.

Venus (diameter: 12,104 km; moons: 0; named after Roman beauty

goddess)

Venus is a hot-house planet covered by thick clouds. It appears in the

sky as a bright star; hence its earlier name “the Evening Star” (or

“Vesper” in Latin) The atmospheric pressure on Venus is 90 times that of

the Earth at sea level.

Earth (diameter: 12,742 km; moons: 1, or 2 with Cruithne)

Earth is the largest of the rocky inner planets. Most of its surface is

covered by water. It has one major moon, a quarter the size of the Earth

itself, to the point that the Earth and Moon are sometimes referred to as

a double planet.

Mars (diameter: 6,779 km; moons: 2; named after Roman war goddess)

Mars, also known as the Red Planet due to it being covered by red dust,

has polar ice caps made from frozen carbon dioxide that grow and shrink

with the changing seasons. Its surface often disappears under fierce dust

storms.

Luna (moon of Earth; diameter: 3,474,2 km; named for Latin physical

name)

The Moon is the Earth’s major satellite and only “true” satellite (not

including Cruithne). At only 1,2% the Earth’s mass but a quarter of its

size, it and its parent planet have also been referred to as a binary

planet. The Moon was formed 4,5 billion years ago following the collision

of a dwarf planet dubbed Theia with Earth. The Moon is 384,400 km

away.

Theia (diameter: 6,102 km; named after mother of Greek Moon goddess)

Theia, a dwarf planet hailing from the outer Solar System that was

straddling in one of the Earth’s Lagrange points, collided with it in a

massive head-on or offset collision 4,5 billion years ago to form the

Moon. The Earth’s water very likely also originated on Theia.

Ceres (diameter: 947 km; moons: 0; named after Roman agriculture

goddess)

Ceres is the largest body in the Asteroid Belt and is large enough for its

gravity to pull it into a spherical shape. Thus, it is effectively a dwarf

planet. It has a surface made of water and clay and it is believed to

have a massive ocean of liquid water underneath its visible surface.

Phaeton (diameter: ~19,500 km; moons: >1; named for son of Greek Sun

god)

Phaeton, which was possibly a super-Earth, is believed to have met with

some disaster in the distant past and fragmented to become the inner

Solar System’s Asteroid Belt. The existance of Phaeton is disputed with

many astronomers arguing that it never formed in the first place and

that the Asteroid Belt always existed due to perturbations from Jupiter.

(if you ask me, I think Phaeton deserves a feminine name; after all, the

names of the first ten asteroids discovered are from goddesses … maybe

we should rename it to Astraea!)

Jupiter (diameter: 139,822 km; moons: 79; named after Roman king

god; has rings)

The gas giant Jupiter is the largest Solar System planet. It has a mass 2,5

times greater than all the other planets put together. Jupiter rotates

very quickly - once every 10 hours. Its four largest moons, discovered by

Galileo, can be seen with a pair of binoculars. It is known for its Great

Red Spot - a massive hurricane-like storm - discovered in 1664 by Robert

Hooke and measures 40,000 km long by 11,000 km wide.

Saturn (diameter: 116,464 km; moons: 82; named after Roman

agriculture god; has rings)

Saturn is surrounded by a system of thin, icy, and flat rings. About every

14 years the rings are tilted so that they are seen edge-on from Earth. It

has the most moons out of any planet.

Chiron (diameter: 270-1,200 km; moons: 0; named after a Centaur; has

rings)

Chiron, once considered a planet in its own right, is now considered the

prototype of a new type of asteroid - Centaurs - asteroids that orbit

between the outer planets. Chiron is estimated to have a ring system of

its own.

Pholus (diameter: 180 km; moons: 0; named after a Centaur)

The second Centaur to be discovered after Chiron, Pholus has a larger

orbit, extending to that of Neptune and Pluto. It is believed that it

originated in the Kuiper Belt.

Uranus (diameter: 50,724 km; moons: 27; named after Greek sky god;

has rings)

The planet Uranus is tipped on its side. The green-blue planet is an ice

giant, richer in water and methane. It takes 84 years to orbit the Sun. It

looks the same all over, as its hazy atmosphere receives little heat from

the Sun or from inside the planet.

Neptune (diameter: 49,244 km; moons: 14; named after Roman water

god; has rings)

Neptune is covered by blue and white clouds made of frozen methane

that have very intense winds (ranging up to 300 kilometers per hour). A

Great Dark Spot once appeared in its atmosphere similar to the Great Red

Spot on Jupiter. One of Neptune’s eight moons, Triton, is almost as large

as the Earth’s moon and is believed to be a captured planet.

Pluto (diameter: 2,306 km; moons: 5; named after Roman dead god)

Pluto is a tiny, icy “comet planet”. Its orbit around the Sun is tilted at

seventeen degrees. Smaller than the Earth’s moon, is usually the most

distant planet, but part of its orbit swings inside Neptune’s path. For a

few years of Pluto’s marathon 249 year-long orbit, Neptune is the most

distant planet.

Charon (moon of Pluto; diameter: 1,212 km; named after Greek

underworld ferryman)

The orbit of Pluto’s moon Charon around it is synchronized with the

planet’s own rotation period of 6,4 days. Estimates show Charon’s size to

be more than twice Pluto’s size, so the Pluto-Charon system is better off

referred to as a binary planet or even a binary asteroid.

15760 Albion and 1993 FW (diameter for both is estimated to be

~200 km; 0 moons)

The first Kuiper Belt objects discovered, these two are also potentially

planetesimals - the building blocks of the early Solar System’s planets,

left over from the system’s birth. They were originally named “Smiley”

and “Karla” respectively.

9th Planet (diameter: ~40,000 km)

Planet Nine is believed to be an ice giant or super-Earth 10 times more

massive than the Earth and to be orbiting the Sun at a distance 500

times greater than Earth. Its large gravity is believed to be perturbing

the orbits of the dwarf planets towards it. It may have originated closer

to the Sun before being ejected, or it may have been captured from

another star.

10th Planet (diameter: 6,000 km; possible name Minerva after Roman

wisdom goddess)

Evidence for the existance of a “tenth planet” has recently been

observed by Renu Malhotra stating that its gravity is causing an

unexpected variance in inclination of the orbits of Kuiper Belt objects

farther than the Kuiper Cliff. Closer than the also-hypothesized 9th

Planet, this 10th Planet is estimated to be roughly the size and mass of

Mars.

Haumea (diameter: 1,420 km; moons: 2; named after Hawaiian

childbirth goddess)

Haumea is a potato-shaped elongated dwarf planet with two moons

named Hi’iaka and Namaka. The longer axis of Haumea measures more

than 2,000 kilometers in diameter.

Makemake (diameter: ~1,400 km; moons: 1; named after Easter Island

creation deity)

Makemake is estimated to be reddish-brown in color and has one moon,

MK2, estimated to be as dark as charcoal.

Eris (diameter: 2,326 km; moons: 1; named after Greek discord goddess)

Discovered in 2005, Eris is the largest and most massive dwarf planet. It

is orbited by one moon, Dysnomia, and also has an eccentric orbit that

takes it 557 years to orbit the Sun.

Sedna (diameter: ~1,400 km; moons: 0; named after Inuit Arctic Ocean

goddess)

Sedna is the most distant dwarf planet. It also has a very eccentric orbit,

and will reach aphelion (farthest point away from the Sun) at around the

year 7777 AD. Theories on how it adopted its eccentric orbit include it

having been captured from another star system.

Formation and Evolution of the

Solar System

Supernova: 10 000 000 000 BC

The Sun originated as a Population I (young, “metal”-rich star) formed in

the remains of a supernova explosion. When the core of this giant star

(let’s call it Orpheus for now) attempted to fuse iron into heavier

elements, which it failed to do so, it could no longer support gravity’s

force on it with outward radiation pressure, and collapsed to form a

neutron star. As a result, Orpheus was annihilated in a supernova

explosion, which created a giant molecular cloud. Following the

supernova, this molecular cloud was very hot, and allowed even further

nuclear fusion into even heavier elements. As the dust cleared, the

metal-rich remnant cloud cooled down, though it still contained a lot of

hydrogen and helium. A new star-forming nebula was created.

Solar Nebula: 5 000 000 000 BC

The nebula, which was 65 light years wide, started to fragment into

segments a parsec (3,26 light years) wide, all of which began to collapse

and heat up, under the force of gravity. This nebula then contracted due

to the competing forces of gravity, rotational pressure, magnetism, and

pressure into a protostar, which we’ll name Timmy Turner after the

titular protagonist of the American-Canadian children’s animated series

The Fairly Odd Parents. Timmy Turner the protostar was 2,000 times wider

than the Sun today and surrounded by a protoplanetary disk of accreting

heavy elements, rocks, and ice.

However, due to rotating at very high speeds, Timmy Turner became so

distorted that the protostar broke into multiple protostars. Two

protostars formed from the mess became the Sun and the yellow dwarf

HD 186302.

Pre-Main Sequence phase: 4 950 000 000 BC

The Sun, along with its twin HD 186302, became violent and active T Tauri

stars. Surrounded with sunspots and emitting massive solar flares, they

shrunk to twice their current sizes. At this time, HD 186302 started to

wander further away from the Sun, until it ceased to be visible in a

night sky on such a planet orbiting the Sun at the time.

Main Sequence: 4 940 000 000 BC

At this time, the Sun shrank to a point where the pressures in its core

became hot enough to start hydrogen fusion into heavier elements. The

Sun was “truly born” as a yellow dwarf (G-type main sequence star). The

Sun and its companion also captured the neutron star created by

Orpheus’s supernova; it was in a binary system. The Sun 4.6 billion years

ago, however, was less than 70% as bright as it was today; it was slowly

brightening over time. The majority of the protostar (99%) became the

Sun, while a small percentage became trapped into a ring orbiting around

the newly-formed Sun - a protoplanetary disk, from which the planets

would be made. This is why the Sun contains 99.9% of the Solar System’s

matter while the planets account for roughly 0.1%.

Kilonova: 4 600 000 000 BC

After a few relatively short time orbiting the Sun, its neutron star

companion collided with another passing neutron star, creating an

enormous kilonova explosion. The explosion was so powerful it created

heavy elements, such as gold and mercury, which flew into the

surroundings of the younger Sun. All the gold, platinum, iridium, etc. on

Earth were formed by this collision 4.6 billion years ago!

Formation of the Inner Planets: 4 590 000 000 BC

Seeded with metals and heavier elements from Orpheus’s supernova and

the kilonova, and under its own gravity, particles in the protoplanetary

disk began to stick together to form larger bodies.

The Inner Solar System was too warm for water ice and methane to

remain solid and form compact bodies. Thus, the only objects that could

thrive there were metals such as aluminium, iron, nickel, and silicates.

Since these materials accounted for less than 0.1% of the original solar

nebula, the planets formed from these could not be very large, which is

why the rocky, inner planets are not as large as the gaseous, outer

planets. The rocky deposits of iron and silicates slowly clumped together

to form planetesimals, the ancestors of the terrestrial planets and

asteroids. These bodies were up to 200 meters in diameter, and through

collisions with each other, formed larger bodies 10 kilometers wide. Over

the next million years, these bodies grew at a small rate of centimeters

per year, eventually reaching diameters exceeding 1 000 km.

The planetesimals that formed the inner planets would have been 5% the

mass of the Earth and ceased accreting material 100 000 years after the

birth of the Sun.

The original inner planets were Caloris, Vulcan, Mercury, Venus, Earth,

Mars, and Planet V. Vulcan was a super-Earth - much closer to the Sun

than Mercury and much like the super-Earths orbiting other Sun-like stars

- that began clearing the neighbourhood around it of asteroids and other

rubble. However, there would have been way more planets at the time,

maybe more than 100!

Formation of the Outer Planets: 4 585 000 000 BC

The larger, outer planets of the Solar System formed further out from

water ice and solid common gases that were much more abundant than

the metals and silicates that formed the inner planets, allowing them to

grow to a large size and collect as much hydrogen and helium from the

interstellar medium as possible. Within 3 million years, the planetesimals

that formed them grew to about 4 Earth masses.

Two rocky planets, which were rich in volatiles such as water and ices

from this outer region of the protoplanetary disk, were Phaeton and

Theia (or Orpheus). We’ll look more on these planets later.

Jupiter formed just within the “frost line” - the distance from the Sun

beyond which water could remain liquid or solid and thus accumulate

properly. Within the frost line, the temperature became cool enough for

icy materials to remain solid and clump together. Jupiter, which formed

just outside the frost line, became large when water collected from

evaporation caused a region of lower pressure that increased the speed

of dust particles and halted their orbits around the Sun. Hence, the frost

line caused accretion to speed up around it, and Jupiter was born. By

the time it was born, Jupiter was 700 000 km in diameter! It is shrinking

by 0,75 centimeters per year. Saturn, born a few million years later, was

just a little smaller.

The Sun and its companion, which had much stronger stellar winds at the

time, blew away much of the remaining material of the protoplanetary

disk. As a result, two (or three) planets that formed millions of years

later - Uranus, Neptune, the Ninth Planet and yet another Neptune-like

ice giant - which we’ll name “Vortex” after the minor Danny Phantom

character - accumulated little hydrogen each, less than one Earth mass

over many millions of years. Thus, they became ice giants - failed cores.

These planets could even have formed between Jupiter and Saturn,

before later being pushed further out. However, there is also the theory

that the Ninth Planet was captured by the Sun’s gravity from another

Solar System, though this may be unlikely.

Neptune and the Ninth Planet formed even closer to the Sun than

Uranus! These two planets definitely switched places many times during

the Solar System’s history, the consequences for which affected the

entire planetary system.

The remaining icy planetesimals that didn’t form planets eventually

became comets and collected in a wide shell around the Sun - the Oort

cloud. Small accretion occurred between the comets, forming the dwarf

planets and Kuiper belt. Trillions of comets from the Kuiper Belt and Oort

cloud stuck together to form Pluto, its moons, and Titan.

Finally, three to ten million years later, the Sun’s solar wind completely

blew off the protoplanetary disk into the interstellar medium.

The formation of the planets had officially ended.

The original outer planets were Phaeton, Theia, Jupiter, Saturn, the

current hypothetical Ninth Planet (not the 9th back then!), Vortex,

Neptune, Uranus, Triton, Pluto, 15760 Albion, 1993 FW, the Tenth Planet,

Titan, and the other dwarf planets.

And of course, there may have been more.

Phaeton, ancestor of the Asteroid Belt: 4 580 000 000 BC

(the prevailing theory for the Asteroid Belt’s formation is that it is the

remains of the protoplanetary disk, unable to form a planet due to

Jupiter’s gravity. The theory of a planet “Phaeton” exploding to form the

asteroid belt was proposed in the 18th Century but has since been

rejected, however a 2018 study by the University of Florida suggests

that the Asteroid Belt could be the remnants of at least five or six

planet-sized bodies exploding)

Between Mars and Jupiter formed a super-Earth, called Phaeton.

Consisting mainly of ice and water that originated from the outer Solar

System, it was orbited by at least five or six silicate and iron-rich moons

of planetary size that formed in the inner Solar System, similar to the

Galilean Moons and the Earth’s moon. Phaeton, along with Planet V

(which we’ll see more on later), were very unstable, being pulled in

different directions by the gravities of the Earth, Theia, Mars, Jupiter,

and Saturn, along with its moons, which would have achieved

independence.

Phaeton’s orbit can be compared to a “cosmic refugee camp”: the ices,

water, and some of the metals originated in the outer Solar System but

settled in this area, forming the super-Earth Phaeton, while the stony

metals such as iron and nickel originated from the inner Solar System and

settled in the area, forming Phaeton’s planet-sized satellites.

Phaeton and its satellites disastrously became the ancestors of the

modern-day asteroid belt, which we’ll look more at later.

Formation of the Earth: 4 570 000 000 BC

By this time, the Hadean Eon had begun. The proto-Earth’s surface was

red-hot and overall, the planet was violent. Supervolcanoes, magma

fields, and constant asteroid impacts dominated the surface. Life could

not exist in such an environment.

While the Earth had finished its accretion process, it was only half of its

original size. Any water oceans would have been small and contained

gases toxic to life on Earth today, rivaled by the magma oceans. The

Earth’s atmosphere contained no oxygen and would have appeared a dull

orange or red.

The Earth’s molten crust cracked into sections, which eventually became

the tectonic plates, which were driven by the still-molten and cooling

mantle and outer core. The Earth, originally upright, had no magnetic

field due to lacking iron in its original core and as a result was

continually exposed to harmful radiation from the Sun.

By the end of the Hadean, the Earth’s surface had cooled significantly.

Life was still not possible on the infant and heavily cratered planet. But

the largest asteroid impact the world has ever faced started to be nigh.

Formation of the Moon and Oceans: 4 530 000 000 BC

Theia, also named Orpheus, the largest asteroid/dwarf planet in the Solar

System, was straddling along the Earth’s orbit, in one of the planet’s

lagrange points. Rich in water ices and molybdenum from the Kuiper belt,

the Mars-sized body, assisted by the gravitational forces of Jupiter and

Venus, started heading towards Earth.

20 to 30 million years later, the asteroid finally hit the proto-Earth,

travelling faster than a bullet and liquifying the surface of both bodies.

The impact eventually established the Earth’s axial tilt; as a result, the

Earth would now have seasons and a varying axial tilt of roughly 23

degrees, and a slightly tilted equator.

Trillions of tons of silicate material and magma debris were shed from the

Earth’s mantle as a result of the collision. Theia, originally the largest

asteroid, was destroyed, though its molybdenum, water, and ices

survived. The silicates and magma from the Earth’s mantle settled into an

orbit around the planet, forming a ring comparable to that of Saturn.

Theia’s original dense, iron core separated from the rest of the asteroid’s

globe shortly following the impact. Around four hours after the collision,

the Earth suffered another mighty blow - Theia’s independent core had

collided with it, and sunk and fused into the Earth’s original non-iron

core!

Back in space, accretion started to occur within the silicate and magma

ring around the Earth. Small bodies grew by collisions with smaller bodies

until they stuck together to form two large bodies that dominated the

ring. This would have been done in the same period of time as human

gestation (nine months). Furthermore, the water on Theia had safely

arrived on Earth as it cooled following the collision, and began

accumulating until it covered large areas of the planet’s surface. The

Moons and Oceans were born - only through this collision!

These Moons had huge magma oceans with depths from 500 kilometers to

their entire radius! Their cores of iron were very small in relative to

their size. The larger of the Moons was more than 3 400 kilometers in

diameter, while the smaller one was slightly larger than 1 200 km.

The larger of the Moons was heavily cratered throughout its surface; the

smaller Moon was not. Both Moons started to cool and shrink. The larger

Moon’s magma oceans cooled all over its surface, forming solid dark

“seas” called maria.

Only a few million years later, the two Moons collided. The collision was

very slow and the actual process took hours. The smaller Moon’s impact

did not produce a crater - rather, its uncratered contents spilled all over

the larger Moon’s dark side, filling up the seas (maria) on that side. Both

Moons merged to form our current Moon. To this day, all of the maria

(magma seas) are concentrated on the Moon’s side facing the Earth with

there being no maria on the dark side.

This “giant impact hypothesis” is the most widely-accepted hypothesis on

how the Moon was formed. However, it is challenged by the fact that

Venus, which is expected to have also experienced a comparable impact

event, does not host a similar moon.

Late Heavy Bombardment and Growth of the Earth’s

Oceans:

4 100 000 000 - 3 800 000 000 BC

This was the most catastrophic and beneficial string of events in the

history of the Solar System. Almost all of the craters on the inner planets

and the Moon are the result and evidence of this event.

The gravitational forces of Mars and Jupiter caused Planet V, which was

less than a quarter the mass of Mars, to undergo an eccentric orbit. The

new orbit of Planet V caused it to perturb many planetesimals and

residue from the protoplanetary disk, sending them on a collision course

with the inner planets. Ultimately, Planet V crashed into Mars, forming

the Borealis Basin - an impact crater large enough to contain two

Canadas, and the Valles Marineris - an enormous canyon system which

would stretch all the way from Vancouver to Iceland if placed in Canada.

The Martian debris thrown into space formed new asteroids which

collided with the inner planets, and possibly even Phobos and Deimos -

which could have also been captured asteroids from elsewhere.

Many of the iron Martian meteorites formed landed on the Moon’s

surface, disfiguring it so much, and on the Earth, where some remain in

Antarctica.

At the same time, the outer planets began to change orbits. Uranus and

Neptune likely swapped orbits, perturbing the courses of many comets,

throwing them on a collision course with the inner planets, including the

Earth. Around the same time, Planet Nine and Vortex were ejected from

their original orbits between Saturn and Neptune, with Planet Nine

ending further out into the Oort cloud, where it still remains, unseen. The

other ice giant, however, was ejected out of the Solar System forever.

As Planet Nine and the other planet were ejected and Neptune swapped

orbits with Uranus, Neptune captured a planet, which is now its current

largest moon Triton. At this point, Titan, formed from the accretion of

Oort cloud comets, spiraled closer towards the Sun, where it was

eventually captured by Saturn, becoming the planet’s largest moon.

Meanwhile, the perturbed comets contained lots of ices, water, and even

sodium chloride (table salt), just like Theia. When these comets collided

with Earth, the water and salt within them were deposited on Earth,

increasing the amount of water left on the planet’s surface following

the collision with Theia. It wasn’t long before salty water 4 kilometers

deep entirely dominated the surface of the globe - there was no land

visible!

But the Late Heavy Bombardment didn’t stop yet. Caloris, another of the

late planets, collided with Mercury, forming the Caloris basin and blasting

away the majority of Mercury’s mantle, leaving Mercury with an

unusually large and heavy core. Shockwaves generated from the impact

came together on the opposite side of Mercury’s globe, crumpling up the

land and forming a rough terrain. The debris blasted from the collision of

the two planets continued to impact the inner planets. Vulcan, the super-

Earth between the Sun and Mercury that cleared its neighborhood of

debris, was drawn into the Sun by its gravity, eventually crashing into

its surface. Currently, there are no asteroids whose orbits are within

that of Mercury’s.

Over time, the rate of meteors crashing into the water-dominated Earth

slowed over time, and the Late Heavy Bombardment stopped.

Oldest life on Earth: 3 800 000 000 - 2 400 000 000 BC

Life started on Earth in a process called abiogenesis. Basically, life,

including nucleic compounds such as DNA and RNA, evolved from inorganic

(non-living) matter. The first bacteria clustered in and around rock

formations called stromatolites, which are still present in the saline

western coasts of Australia.

At this time, the Earth would have looked very different. More than 95%

of the Earth’s surface was dominated by dark green to black oceans,

filled with primordial cells and bacteria. The skies were cloudy and

looked orange due to the wildly different atmosphere at the time - a

reducing atmosphere in which oxidation is prevented by the removal of

then-very rare oxygen.

Bacteria eventually developed photosynthesis, allowing them to convert

sunlight into energy for food. However, these bacteria excreted oxygen.

Cyanobacteria, before the accumulation, starting adapting to oxygen.

Eventually, oxygen levels began to rise, until it took up 25% of the

Earth’s atmosphere and oceans. Since most life back then did not find

oxygen essential, this resulted in the first and deadliest extinction in the

Earth’s history - the Great Oxidation Event. 99% of Earth’s life back then

perished.

Destruction of Phaeton and the creation of the Asteroid

Belt:

4 000 000 000 - 250 000 000 BC

(as stated earlier, this is rivaled by the more popular theory that the

asteroids never formed a large body and are the remnants of the

protoplanetary disk, due to Jupiter’s large gravity.)

Phaeton, the only super-Earth in the Solar System, was about to meet a

premature demise. The planet’s orbit was unstable and constantly being

perturbed by the Earth, Mars, and Jupiter. Worst of all, the gravities of

the three planets were about to pluck Phaeton’s planet-like moons loose

into unstable orbits around the Sun. Finally, Phaeton’s moons briefly

achieved independence, with unstable orbits crossing each other by

indefinite perturbations from the other planets. As a result, the moons

collided with each other, before spiraling back into Phaeton’s grip and

hitting their parent planet.

Phaeton and all of its moons were shattered in the series of collisions.

Their fragments scattered along Phaeton’s original orbit and formed a

ring around the Sun - the main Asteroid Belt. Phaeton’s moons are the

ancestors of the S-type (silicate-rich) asteroids, while Phaeton itself was

the ancestor of the C-type (carbonaceous) asteroids (including the dwarf

planet Ceres) which originally formed its mantle and crust.

The original asteroid belt was originally much denser and massive than it

is today. All of the missing mass was lost within the time period from the

asteroid belt’s formation to today, through collisions with other planets

and asteroids, the Sun, and ejection from the main Solar System. Today,

only 0.01% of the primordial asteroid belt’s mass remains, which weighs

only 4% of the Moon’s mass, and the average distances between the

asteroids are on the order of millions of kilometers. Meanwhile, Phaeton’s

exposed core cooled down and became the iron asteroid 16 Psyche

(which is not round).

The Great Dying: 250 000 000 BC

The Great Dying, or Permian-Triassic Mass Extinction, was the worst mass

extinction in history (by common convention, not including the Great

Oxidation Event, see above). 97% of Earth’s life perished. The cause of

the extinction has not yet been firmly established, but possible causes

include a giant asteroid impact and the eruption of the Siberian Traps.

However, most scientists believe that the Great Dying was the result of a

chain reaction of events, with this being a possibility:

• An asteroid or comet (likely a fragment of Phaeton or a newly-

made asteroid knocked out of orbit by Phaeton’s exposed core) at

least 50 kilometers wide hit the Earth in either South America,

Africa, Siberia, or Antarctica.

• The Siberian Traps were created at either the impact site or the

impact site’s antipode. The excessive volcanic activity triggered

was enough to cover Canada in 7 meters of magma.

• These in turn triggered underwater eruptions that released

hydrogen sulphide. This hydrogen sulfide began to make the Earth’s

general environment toxic.

• Finally, the fumes and gases produced by the Earth’s oceans, the

impact site, and the supervolcanic eruptions killed off almost all of

the species on the planet.

Scholz’s Star: 70 000 BC

70 000 years ago, two stars briefly joined the Solar System!

Scholz’s Star, a binary consisting of a red dwarf and a brown dwarf,

passed through the Solar System’s Oort cloud. At its closest, the Scholz

system was 52,000 astronomical units away from the Earth.

Despite the comets in the Oort cloud being perturbed by the gravity of

the star, it would take them 2 million years to reach the Earth. At closest

approach, the star’s dim red light would have been visible to the

ancestors of humanity in high latitudes in the northern hemisphere,

mostly in Autumn.

Today: 2019 CE

The real center of the Solar System is not the Sun, but rather the Solar

System barycenter, where the gravity of all solar system objects evens

out. Since the Sun contains more than 99% of the Solar System’s mass,

the Solar System barycenter is always within it. Jupiter is more than

twice as massive as the other planets combined, so it pulls the

barycenter to a point just over the Sun’s surface. To an extraterrestrial

observer on a planet orbiting a nearby star, the Sun would appear to

wobble due to Jupiter’s gravity pulling at it, indirectly informing them

that there is a massive planet orbiting that star. This is how humans

discover other solar systems containing Jupiter-sized exoplanets.

The four closest planets to the Sun are the terrestrial planets. They are

small and made of rocky materials. Mercury is the closest to the Sun and

has a very little Oxygen and Sodium atmosphere. Venus has a dense

Carbon Dioxide atmosphere which makes it the hottest planet in the

Solar System, hotter than Mercury. The size of Earth, it is dominated by

volcanoes such as Ishtar Terra, which is as large as Australia. Earth has

an atmosphere of nitrogen and is orbited by a moon, the largest relative

to the size of its parent planet, and a quasi-satellite called 3753

Cruithne. Mars has a thin Carbon Dioxide atmosphere, half the size of

Earth, dominated by red iron oxide, and is orbited by its two moons

Phobos and Deimos. Further out is the asteroid belt, containing one round

asteroid (1 Ceres) and many others with moons (243 Ida with satellite

Dactyl for example). And of course, there are the comets, which are

masses of frozen ice and dust that sublime to form “tails” as they

approach the Sun. Further away from the asteroid belt is the massive

Jupiter, a giant ball of liquid and gaseous hydrogen and helium orbited

by four planet-sized moons and 77 asteroid-like moons. Next out is

Saturn, also a giant ball of liquid and gaseous hydrogen and helium

orbited by many asteroids which form rings. It has many asteroid-like

moons and a moon (former planet) called Titan. Further out is Uranus,

with is mostly methane and ices and rotates on its side, then Neptune, a

very windy blue planet, and finally Pluto, its moons, and the other dwarf

planets whose orbits are being perturbed by a potential but likely Ninth

Planet and a smaller but closer Tenth Planet’s gravitational forces.

Finally, the two outermost, smallest, and least-known planets are 15760

Albion and 1993 FW.

(Major) Bodies in the Solar System

Bold, ALLCAPS - Star | Bold - Planet | Italic - Dwarf planet/asteroid |

Normal - Satellite

Strikethrough - no longer existed or part of the Solar System (date

stopped existing)

• SUN

o 1566 Icarus

o Caloris (4 100 000 000 - 3 800 000 000 BC)

o Vulcan (~4 000 000 000 BC)

o Mercury

o Venus

o Earth-Moon system

o Earth

o Luna (Moon)

o 2nd Moon (4 530 000 000 BC)

▪ 3753 Cruithne

o Ghost Zone (fictional)

o Mars

• Phobos

• Deimos

o Planet V (~4 000 000 000 BC)

o Phaeton (4 000 000 000 - 250 000 000 BC)? → Asteroid Belt

▪ 1 Ceres

▪ 2 Pallas

▪ 3 Juno

▪ 4 Vesta

▪ 16 Psyche

▪ 243 Ida

• Dactyl

▪ 433 Eros

▪ 951 Gaspra

▪ Comet Encke

▪ 311P/PANSTARRS

▪ C/1907 L2 (Daniel)

o Theia (4 530 000 000 BC)

o Jupiter and ring system

• Io

• Europa

• Ganymede

• Callisto

• Amalthea

• Thebe

• Metis

o Comet Hale-Bopp

o Saturn and ring system

• Titan

• Mimas

• Enceladus

• Dione

• Tethys

• Iapetus

• Janus

• Rhea and ring system

• Hyperion

• Phoebe

• Disasteroid (fictional)

o 2060 Chiron

o Halley’s Comet

o Uranus and ring system

• Titania

• Umbriel

• Ariel

• Umbriel

• Miranda

• Puck

o Gna?

o Vortex (3 800 000 000 BC)

o Neptune and ring system

• Triton

• Proteus

• Nereid

o Pluto-Charon system

• (134340) Pluto

o Nix

o Hydra

o Styx

o Kerberos

• Charon

▪ 15810 Arawn

o 15760 Albion

o 1993 FW

o Ultima Thule

o 2004 XR190

o Orcus-Vanth system

• Orcus

• Vanth

o 50000 Quaoar

• Weywot

o Haumea

• Hi’iaka

• Namaka

o Makemake

• MK2

o Eris/Xena

• Dysnomia/Gabrielle

o Sedna

o Tenth Planet

o Ninth Planet/Tyche/NEMESIS/NIBIRU etc. (pseudoscientific)

• SCHOLZ’S STAR A (70 000 BC)

o SCHOLZ’S STAR B (70 000 BC)

• NEUTRON STAR (4 600 000 000 BC)

• DRAGON’S EGG (fictional)

Bullet List (incl. discoveries & future evolution of the

Solar System) • 10 000 000 000 BC: Orpheus explodes in a supernova, leaving

behind a neutron star.

• 7 000 000 000 BC: The remains of Orpheus’s outer layers become a

nebula.

• 5 000 000 000 BC: The nebula becomes a protostar - Timmy Turner.

• 4 990 000 000 BC: Timmy Turner breaks apart into multiple pre-main

sequence stars due to rotational instability. Two of these become

the Sun and HD 186302.

• 4 950 000 000 BC: The Sun and HD 186302 become T Tauri stars. HD

186302 slowly begins to move away from the Sun.

• 4 940 000 000 BC: The Sun and HD 186302 become main-sequence

yellow dwarfs. The Sun captures Orpheus’s neutron star remnant.

• 4 600 000 000 BC: The Sun’s pulsar companion collides with another

neutron star, resulting in a giant kilonova explosion giving birth to

heavy elements, including gold.

• 4 590 000 000 BC: The remains of Timmy Turner form a

protoplanetary disk around the Sun.

• 4 580 000 000 BC: 21 major planets are successfully formed around

the Sun from the accretion of planetesimals in the protoplanetary

disk. In order, they are:

Caloris, Vulcan, Mercury, Venus, Earth, Mars, Planet V, Phaeton,

Theia, Jupiter, Saturn, the Ninth Planet, Vortex, Gna, Neptune,

Uranus, Triton, Pluto, 15760 Albion, 1993 FW, the Tenth Planet, and

Titan.

• 4 570 000 000 BC: The Hadean Era. Earth is a very violent place

with a molten and volcanic surface.

• 4 530 000 000 BC: Theia starts heading towards Earth.

• 4 529 999 925 BC: Theia hits the Earth. Water is deposited on Earth

as a result.

• 4 529 999 924 BC: Two Moons are formed around the Earth from

the accretion of debris thrown into space from the collision with

Theia. These Moons later merge into one.

• 4 100 000 000 BC: The Late Heavy Bombardment begins. Neptune

and Uranus switch places multiple times. Neptune captures Triton.

Saturn captures Titan. Jupiter and Saturn migrate outward,

resulting in the Ninth Planet being ejected into a much further

orbit and Vortex out of the Solar System altogether.

• 3 900 000 000 BC: Caloris hits Mercury, forming the Caloris Basin.

Vulcan spirals down into the Sun. Planet V hits Mars, forming the

Borealis Basin and possibly Phobos and Deimos.

• 3 800 000 000 BC: The Late Heavy Bombardment stops. Water from

the impacts with Theia and comets dominates the Earth’s surface.

• 3 800 000 000 - 2 400 000 000 BC: First life on Earth.

• 260 000 000 BC: Phaeton’s orbit is unstable due to perturbations

from the Earth, Mars, Jupiter, and Saturn. It is orbited by many

captured planet-sized moons of varying chemical composition.

• 250 000 000 BC: Perturbations from nearby planets cause Phaeton’s

moons to spiral inward and collide with Phaeton, destroying all

bodies. One fragment of Phaeton hits the Earth causing the Great

Dying; 95% of life on Earth is killed. The rest of Phaeton and its

moons’s fragments form the asteroid belt. Phaeton’s core becomes

an independent planet with an eccentric orbit before plunging into

the Sun a few million years later. Earth’s sole continent, Pangaea,

breaks apart due to plate tectonics.

• 66 000 000 BC: A C-type asteroid or comet perturbed by the Ninth

Planet or Jupiter hits the Earth, killing of 75% of life on the planet.

• 70 000 BC: Scholz’s Star, a binary system of two cool and small

stars, temporarily joins the Solar System.

• ~500 BC: Pythagoras of Samos finds that the Morning Star and

Venus (the Evening Star) are actually the same planet, rather than

two separate planets. He also determines that the Earth is a

spherical shape. Mercury and its morning aspect Apollo are also

found to be the same planet.

• ~200 BC: Aristarchus of Samos comes up with a heliocentric model,

where the Sun (only 1.5 times the diameter of Earth) lies in the

center of the universe and that stars are more or less like the Sun.

His accurate guess is unprovable at the time due to then-impossible

stellar parallax. People continue to believe that the Earth is at the

center of the universe and that the other planets, which include

the Sun and Moon, orbit around it, and will have to wait almost

2,000 years to find out what is true.

• 1543 AD: Copernicus publishes his book De revolutionibus orbium

coelestium, reviving the heliocentric Solar System view. Like

Aristarchus, he proposes that the Earth orbits the Sun, which is the

center of the Solar System.

• 1610 AD: The Galilean Satellites of Jupiter are discovered,

delivering a massive blow to the geocentric model - proving that

not everything orbits the Earth and confirming the views of

Aristarchus and Copernicus.

• 1655 AD: Christiaan Huygens discovers Titan, Saturn’s largest moon.

It is classified as a planet at first - before being reclassified as a

moon! It is not yet known that Titan is a captured planet.

• 1749 AD: French mathematician Georges-Louis Leclerc, Comte de

Buffon theorizes that the Solar System was formed after a comet

collided with the Sun, sending matter out to form the planets. His

theory dies an early death as matter ejected in such a collision

would just crash back down into the Sun’s surface.

• 1755 AD: Immanuel Kant puts forward the nebular hypothesis, the

widely-accepted theory on the formation of the Solar System,

developed by other scientists afterwards.

• 1781 AD: Uranus is discovered by William Herschel.

• 1796 AD: Pierre-Simon Laplace develops the nebular hypothesis. The

exact nature of spiral galaxies is not known and at this time it is

still commonly believed that they are nebulae that are contracting

to form stars and solar systems, thus used as evidence of the

Nebular Hypothesis.

• 1801 AD: 1 Ceres is discovered by Giuseppe Piazzi.

• 1802 AD: 2 Pallas is discovered by Heinrich Wilhelm Olbers, and is

found to occupy the same orbital region as 1 Ceres. It is then

realized that the two are likely fragments of a planet which had

been destroyed in the distant past - Phaeton.

• 1846 AD: Neptune is discovered by Johann Galle, John Couch Adams,

and Urbain Le Verrier thanks to their mathematical calculations of

perturbations in the orbit of Uranus less than an hour before.

Partly due to his success in discovering Neptune, Le Verrier

believes that perturbations in Mercury’s orbit are due to an even

closer planet pulling on it. He names this planet Vulcan, but nothing

is found.

• 1917 AD: James Jeans conceives the Encounter Hypothesis, where

the Solar System was born after the gravity of a passing star drew

matter away from the Sun.

• 1920 AD: The Great Debate is held between Harlow Sharpley and

Heber Curtis, concerning whether spiral galaxies are protostars on

the way to becoming solar systems, or independent galaxies

beyond the Milky Way. With the help of Edwin Hubble, it is

discovered that they are independent galaxies - a boost for the

sense of the real scale of the universe but a massive blow for the

Nebular Hypothesis.

• 1930 AD: Pluto is discovered by Clyde William Tombaugh. It is hailed

as the 9th planet but is not the same as Planet X as proposed

earlier by Percival Lowell.

• 1937-1940 AD: Ray Lyttleton suggests that a binary companion to

the Sun collided with another star when the Solar System formed.

Unfortunately, his theory cannot be confirmed until roughly 70

years later, when the origins of gold, etc. are confirmed.

• 1950 AD: Jan Oort proposes the existance of the Oort cloud. Despite

being treated as if it were scientific fact, its existance has not yet

been confirmed.

• 1976 AD: Canadian astronomer A. G. W. Cameron realizes the former

existance of Theia, and that it crashed into the Earth to form the

Moon and oceans.

• 1978 AD: Kant and Laplace’s Nebular Hypothesis (now developed by

others such as Fred Hoyle) again becomes the widely-accepted

theory on the formation of the Solar System when the angular

momentum problem is solved by friction created by dust particles in

the protoplanetary disk, slowing down the rotation at the center.

• 1992-1993 AD: 15760 Albion and 1993 FW, the first trans-Neptunian

planets, are discovered by David C. Jewitt and Jane X. Luu.

• 2003-2005 AD: The dwarf planets Quaoar, Haumea, Makemake,

Sedna, and Eris are discovered by Michael E. “Mike” Brown.

• 2006 AD: Pluto is demoted to dwarf planet status.

• 2014-2015 AD: Dawn passes by Vesta and Ceres. Titan is realized to

be a captured planet originating in the Oort cloud.

• 2015 AD: “Gna”, a possible planet, is first observed. However,

scientists (including Mike Brown) are skeptical of its existance. At

the same time, New Horizons passes by Pluto.

• 2016 AD: Mike Brown, Konstantin Batygin, Sverre Aarseth, and

Carlos and Raúl de la Fuente Marcos realize that the Ninth and

Tenth Planets are responsible for the eccentricity of the orbits of

the trans-Neptunian dwarf planets. The Nice Model on the

formation of the gas giants also explains how the planets ended up

in such far-off orbits, and the existance of Vortex is realized. Also

earlier in the same year, the existance of Vulcan - the super-Earth

closer than Mercury to the Sun that cleared its orbit - is realized.

• 2018 AD: HD 186302 is identified as one of the Sun’s siblings,

having formed from Timmy Turner.

• 2018 AD: Lyttleton’s theory on a companion star to the Sun

colliding with another star is proven true in a new study that

suggests that the Earth’s heavy elements (including gold)

originated in a collision between two neutron stars near the Sun.

• 2019 AD: New Horizons passes by the asteroid Ultima Thule.

• 1 281 000 AD: Gliese 710 temporarily joins the Solar System,

perturbing various comets in the Oort cloud and possibly sending a

few on a collision course with Earth.

• 100 000 000 AD: Saturn’s rings would have entirely dissipated by

this time. Meanwhile on Earth, the Atlantic Ocean begins to close as

the Americas move back towards Europe and Africa. The Philippine

Sea closes as Australia and Antarctica collide with eastern Asia.

• 300 000 000 AD: The Atlantic Ocean completely closes, forming a

new supercontinent - Pangaea Ultima.

• 600 000 000 AD: Tidal acceleration moves the Moon further away

to a point that total solar eclipses are now impossible. The Moon

may now be considered a binary planet with the Earth in its own

right at this time.

• 1 000 000 000 AD: The Sun has fused all the hydrogen in its core. It

will begin swelling to become a red giant.

• 1 100 000 000 AD: The Sun is now brighter, causing Earth’s

temperature to rise to a median 47 degrees Celsius. All plant life is

destroyed and the oceans have evaporated; plate tectonics will

then stop completely.

• 3 000 000 000 AD: By this time, there is a chance that the Earth

may be captured by another passing star. Were this to happen, life

could go on for much longer. Meanwhile, Jupiter would have likely

perturbed Mercury’s orbit to a point that it may be ejected from

the Solar System or collide with the Sun, Venus, or even Earth.

• 3 600 000 000 AD: Triton is shattered due to tidal forces from

Neptune and forms a Saturn-like ring system around Neptune.

• 4 000 000 000 AD: The Andromeda Galaxy collides with the Milky

Way, forming a large reddish elliptical galaxy. Before the merger, it

is likely that the Solar System will be captured by the Andromeda

Galaxy. Collisions with other stars or the black holes of both

galaxies is highly unlikely. By this time, the Moon would have likely

collided back with Earth or have exploded due to tidal forces

forming a ring around the planet.

• 5 000 000 000 AD: The Sun is now a red giant 100 times wider than

its current size. If Mercury survives perturbation, it would have

been swallowed by the dying Sun at this point. Venus may also be

destroyed.

• 5 500 000 000 AD: The Sun shrinks to become a helium-fusing

orange giant only 10 times wider than its current size. If Venus

was destroyed by the Sun’s earlier red giant phase, its core (hotter

than the Sun) may survive.

• 5 800 000 000 AD: The Sun now has fused all of its helium. Now it

has to fuse it into carbon. As its core becomes hotter and smaller,

its outer layers become much cooler and larger. The Sun again

becomes a red giant, but this time it is over 256 times wider than

its current size. It will grow to a size that it will engulf Earth and

Mars, though their hotter cores may survive within the Sun’s cooler

outer layers. Saturn’s moons Titan, Iapetus, and Enceladus, along

with the Pluto-Charon system and other dwarf planets, as well as

the Centaurs, may become habitable.

• 7 000 000 000 AD: The Sun ejects its outer layers, forming a

beautiful planetary nebula. Its core becomes a hot, dense Wolf-

Rayet star. The cores of the Earth and Mars survive and continue to

orbit the dark blue-hot star.

• 10 000 000 000 AD: The Sun becomes a white dwarf. This Earth-

sized white dwarf would be made of diamond (literally) and have

54% of the Sun’s current mass. It would be 100 times more luminous

than the Sun today. Temperatures may drop back to normal and

life, if it still exists, may continue to do so, even if life resides only

on Pluto.

• 1 000 000 000 000 AD: The Sun, though classified a “white dwarf”,

would now be only red-hot with a temperature of around ~3,000

degrees Celsius or Kelvin. All surviving planets will undergo a “big

freeze” as temperatures drop rapidly.

• 10^12 AD: The Sun is now a black dwarf. By this time, the Earth

would have likely merged with the dark Sun. The other surviving

planets of the Solar System would have likely been captured by

passing stars. The Solar System no longer exists.

• 10^1500 AD: If protons do not decay, then by this time quantum

tunnelling would have converted all matter into iron. Thus, the Sun

would become an “iron star”.

• 10^10^76 AD: If protons do not decay and iron stars form, then by

this time the Sun would collapse into a new neutron star or black

hole.

Alternative Hypotheses on the Solar System’s Evolution

Laplace’s widely-accepted Nebular Hypothesis wasn’t the only theory on

the formation of our Solar System - there were many more, some of

which are still accepted by fringe theorists. Other scientists devised their

own versions of the Nebular Hypothesis.

Fred Hoyle’s version of the Nebular Hypothesis Fred Hoyle, in 1944 and 1945, argued that the star (nicknamed Orpheus

in this document) whose supernova birthed the solar nebula was the

Sun’s former binary companion, with the Sun being separate from the

supernova remnant (which it captured) and as old as the star itself

(which, as we now know, is not). The high temperatures of the

supernova allowed more nuclear fusion after the star’s death and the

force of the explosion threw the star’s degenerate out of the Sun’s

gravitational field altogether. The supernova may have also birthed the

Local Bubble, in which the Sun resides, and Geminga may well be the

remnant star.

It is now known that the Sun itself was also birthed from the star’s

supernova remnant and is roughly the same age as the planets that

formed.

W. H. McCrea’s version of the Nebular Hypothesis W. H. McCrea’s version of the nebular hypothesis states that the planets

also contracted from the Solar Nebula by themselves (like sibling stars),

before being individually captured by the Sun. Collapsing segments of gas

formed the Sun and others formed the planets; the ones that formed the

planets underwent fission to form the current planets. The moons of the

gas giants formed from “droplets” in the neck from which they fissioned

off; this is also the origin of the asteroids. Terrestrial planets would

have no major satellites. Mercury and Venus fissioned off from each

other, while the Earth, the Moon, and Mars fissioned off from the same

parent body. In this scheme there are six principal planets: two

terrestrial, Venus and Earth, two major, Jupiter and Saturn, and two

outer, Uranus and Neptune, along with the dwarf planets, which do not

only include Pluto, but also the Moon, Mercury, and Mars.

There are several problems with his version of the Nebular Hypothesis;

for example, all of the planets revolve around the Sun in the same

direction in orbits with relatively low eccentricity, which would be

highly unlikely if they were all individually captured.

Gerald Kuiper and Otto Schmidt’s version of the Nebular

Hypothesis Gerald Kuiper argued that the solar nebula, from which the

protoplanetary disk and thus the planets formed, could either be co-

genetic with the Sun or captured by it. Soviet astronomer Otto Schmidt

was a proponent for the solar nebula originally being a part of the

interstellar medium that the Sun (in its current state) passed through and

captured to form the planets from. Its density distribution at the time

could determine on what may form: either an entire planetary system or

another G-type main-sequence star.

The major problem against the protoplanetary disk originating from the

interstellar medium and being captured by the Sun is that the required

time for planets to condense from the interstellar medium far exceeds

the calculated age of the universe.

Harold Urey’s version of planetary accretion

American chemist Harold Urey put forward his own version for accretion

and collisions between protoplanets in the 1950s where in order to

retain volatile elements, the protoplanets (some of which were pure

carbon, moon-sized, or gas spheres), would have to form within the

protoplanetary disk and dissipate at a later stage, all while being

separated from the Sun by a moderately thick and dusty halo. Pressure

fell as gas was lost and the diamonds became graphite, while the gas

became illuminated by the Sun. Under these conditions ionization would

be present and the gas could be accelerated by magnetic fields, thus the

angular momentum could be transferred from the Sun to the planets.

Finally, the lunar-sized protoplanets would be destroyed by collisions

with each other, with their gases dissipating, with solids being left at

their cores and the smaller fragments escaping into space, while the

larger fragments remained and accreted to form the planets. Urey

suggested that the Moon is nothing more than an exposed planetary

core.

The dust on the Moon’s surface was once estimated to be six billion years

old - older than Earth - however new analysis suggests it is around the

same age as Earth - 4.51 billion years. Planetary cores are made of iron

and nickel due to density and buoyancy. The Moon is made of granite and

silicate rocks - no way it is a planet’s exposed core.

Herndon’s version of planetary accretion

American scientist James Herndon’s model proposes that the inner planets

were originally the cores of former gas giants that formed from

condensation of material within them. Earth was originally the core of a

Neptune-like ice giant originally 300 times more massive than the Earth

today whose mass compressed its core (Earth) to a diameter only two-

thirds of today. These gas giants would not last long because the Sun,

when it was in its T Tauri phase, stripped the gases and ices away from

the planets, leaving behind only their rocky cores. Mercury did not form

fully from its parent gas giant and the Sun’s eruptions stripped part of

its gases away, to the region between Mars and Jupiter. There Mercury’s

gas fused with oxidized condensate from the outer Solar System,

solidifying to form meteorites, the Asteroid Belt, and the iron oxide

coating of Mars. Differences between the inner planets depend on how

much they were compressed when they were formerly gas giant cores.

Encounter hypothesis

The encounter hypothesis states that the Solar System’s planets were

formed when a star passed by the Sun around 5 billion years ago. Hot

gas was stripped off both stars, which cooled and contracted to form the

planets. The other star’s material became Jupiter, Saturn, Uranus, and

Neptune while the material from the Sun became Mercury, Venus, Earth,

and Mars. The earliest hypothesis on how the Solar System was formed, it

has the advantage of explaining why the planets orbit and rotate

(except for Venus) in the same direction, why the Sun has the least

angular momentum in the Solar System, and explains why the terrestrial

planets are denser than the gas and ice giants.

The major problem with this theory the probability of it happening: such

an encounter is very, very, very unlikely (much more than you think) and

it is expected that such an event has never occurred in the universe yet.

Chamberlin-Moulton planetesimal hypothesis This hypothesis proposed in 1905 by Thomas Chamberlin and Forest

Moulton is nothing more than a cross between the accepted Nebular

Hypothesis and the Encounter Hypothesis. Put simply, after the intruding

star’s gravity pulls matter out of the Sun (also with the help of the

mechanism behind solar prominences), the matter begins to flatten into a

rotating disk around the Sun - the protoplanetary disk - from which

planetesimals form, which in turn accrete the remaining material, forming

the planets.

Again, the major problem against this hypothesis is the unlikelihood of

the stellar encounter, although the protoplanetary disk accreting into

planets is still widely accepted.

Lyttleton’s scenario

Ray Lyttleton proposed a scenario in which a companion star to the Sun

collided with a passing star. Henry Russell already rejected such a

scenario (though it may have been more likely considering that the Sun

may have been born in an open star cluster). However, Lyttleton

continued saying that the merged star later split into two because of

rotational instability, forming Jupiter and Saturn, with the filament

forming from the “neck” where the two broke off forming the other

planets. A later model from 1940 involves the Sun in a triple star system,

in which the Sun’s companions merge but later break up due to

rotational instability, with the filament forming from the “neck” between

them being captured by the Sun to form all the planets. The stars (blue

stragglers) then leave the system.

Lyttleton’s idea of a companion star to the Sun colliding with another

star has recently been proven correct with finds of a neutron star

collision near the Sun around the time when the Solar System was born

(see above). The other half on planetary formation has been refuted.

Band structure model In the mid-1900’s, Swedish astrophysicist Hannes Alfven proposed the

band structure model in which he proposed the existance of four

molecular clouds by the Sun:

• The A cloud, which contained mostly helium and iron

• The B cloud, mostly hydrogen

• The C cloud, mostly carbon

• The D cloud, mostly silicon and iron.

The A cloud condenses to form Mars and the Moon, the B cloud condenses

to form Jupiter, Saturn, Uranus, and Neptune, the C cloud condenses to

form Mercury, Venus, and the Earth (or the B cloud forms Mercury, Venus,

and Earth while the C cloud forms the outer planets), while the D cloud

collapses to form Pluto and Triton. Just like how a prevailing theory

states that the Asteroid and Kuiper Belts never formed a large planet in

the first place, in his theory it is probable that the two are the remnants

of the C and D clouds respectively.

Fission theories Greek philosopher Anaxagoras and French mathematician Rene Descartes

believed that various celestial bodies are fissioned off their parent

bodies. This “fissioning off” is due to centrifugal forces results from the

body’s rapid spin. Bulges appear on the equator, which spin off and

become independent.

George Darwin, son of Charles Darwin, advocated that the Moon was

once part of the Earth before the rapidly spinning proto-Earth’s

centrifugal forces spun it off. The Pacific Ocean’s basin is supposedly the

hole left by the Moon’s separation from Earth.

Swiss astronomer Louis Jacot, in the 1900s, jumped on the idea’s

bandwagon, believing that moons are fissioned off their parent planets,

which in turn are fissioned off their parent stars, which in turn are

fissioned off from the centers of their galaxies due to the expanding

universe. He claimed that due to this, the orbits of planets around the

Sun are growing spirals, not circular orbits or ellipses, and that moons

are moving away from their planets (which is true in the Earth’s Moon’s

case). Jacot stated that planets were expelled, one at a time, from the

Sun - the furthest to the Sun currently being the first expelled, with the

closest being the last - and that one of them - Phaeton - shattered in its

expulsion leaving the asteroid belt. Moons start off as centrifugal

expulsions from their parent planets - some shatter of course, leaving

the rings - and Earth is eventually going to expel another moon (which

would be disastrous for life on Earth today).

The differences between the inner and outer planets can be explained

by vortex behavior and expulsion order. Mercury’s relatively eccentric

orbit is explained by its recent expulsion and Venus’s slow and reversed

rotation due to having been expelled second to last.

Fringe astronomer Tom Van Flandern believed that the Sun’s fast rotation

caused it to expel six pairs of twin planets, or twelve planets in all:

• Venus

• Earth

• Maldek

• Planet K

• Planet LHB-A

• Jupiter

• Planet LHB-B

• Saturn

• Uranus

• Neptune

• Planet T

• Planet X

Venus was twinned with Earth, Maldek with Planet K, Planet LHB-A with

Jupiter, Planet LHB-B with Saturn, Uranus with Neptune, and Planet T

with Planet X. Six planets have exploded so far, and these were helium-

dominated or gas giants. Planet T exploded to form the Kuiper Belt and

Planet X exploded to form the Oort cloud and its comets. For the two

pairs of Planet LHB-A and Jupiter and Planet LHB-B and Saturn, the

smaller and inner partner in each pair was subject to enormous tidal

stresses from the Sun and other planets, causing them to blow up before

they could fission off moons. Planets LHB-A and LHB-B exploded, causing

the Late Heavy Bombardment. As they had no moons and were gas giants

they left no trace of themselves. Twins Planet K and Maldek exploded or

collided to form the asteroid belt and short-period comets. Solid planets

fission off only one moon and Mercury was the moon of Venus but drifted

away because of the Sun’s gravity. Mars was the moon of Maldek.

There are many problems with these fission theories. For one, the Moon

(which consists mostly of granite and silicates) is not made of oceanic

crust (which consists mostly of basalt), but rather material from the

proto-Earth’s mantle before Theia’s material “contaminated it”. The

Pacific Ocean’s floor is only 200 million years old, whereas the Moon is

much older. One major argument against exploding planets and moons is

that there would not be an energy source powerful enough to cause

such explosions.

Capture theory

Proposed by Michael Mark Woolfson in 1964, this theory proposes that

the Sun’s gravity and tidal forces completely ripped apart a nearby

forming low-density protostar with a diameter 4,000 times greater than

the Sun today (the size of Pluto’s orbit). Since the Sun is denser than the

protostar and much smaller (more compact), it had a much greater

gravitational pull than the protostar. The Sun’s gravity ripped off the

protostar’s diffuse material, which condensed to form the planets.

Woolfson added the concept of a collision in a later version of the

hypothesis. As the protostar is ripped apart by the Sun, its material

originally forms seven planets, in order:

• “A” (nicknamed “Enyo” after the Greek goddess of war, the sister

of Ares)

• “B” (nicknamed “Bellona” after the Roman equivalent of Enyo;

Mars’s sister)

• Jupiter

• Saturn

• Uranus

• Neptune

The orbits of Enyo and Bellona are eccentric, and as a result, they collide

with a force powerful enough to briefly cause deuterium-deuterium

nuclear reactions. Enyo, with a mass twice that of Neptune, is ejected

out of the Solar System, while Bellona, a third of the mass of Uranus, is

shattered by the nuclear reactions, forming the Earth, Venus, Mercury,

asteroid belt, and comets. Mars, the Moon, Pluto, Haumea, Makemake, Eris,

and V774104 (2015 TH367) are the former satellites of Enyo.

There are a few problems with this theory; for example, it again

suggests that the Sun and the planets are not the same age. However, it

has been accepted that planets like “Enyo” have been ejected from the

Solar System and that Triton was captured by Neptune.

Former Planet Counts

Birth of Solar System (4 580 000 000 - 4 530 000 000 BC):

Caloris Vulcan

Mercury Venus

Earth Mars

Planet V Phaeton

Theia Jupiter

Saturn Ninth Planet

Vortex Neptune

Gna Uranus

Triton Pluto

Albion 1993 FW

Tenth Planet Titan

After the formation of Earth and the LHB

(4 530 000 000 - 250 000 000 BC):

Mercury Venus Earth Mars Phaeton Jupiter Saturn

Uranus Gna Neptune Pluto Albion 1993 FW 10th Planet 9th Planet

Phaeton’s destruction

(250 000 000 BC at latest to a few million years later):

Mercury Venus Earth Mars Jupiter Saturn

Uranus Gna Neptune Pluto Albion 1993 FW 10th Planet 9th Planet

Former 9 planets before the time of Pythagoras:

Moon Apollo Mercury Evening Star Morning Star

Mars Jupiter Saturn

Ptolemy’s 7 planets (100-1543)

Moon Mercury Venus Sun Mars Jupiter Saturn

Renaissance planets (1543-1610, 1680-1781)

Mercury Venus Earth Mars Jupiter Saturn

7 planets (1781-1846)

Mercury Venus Earth Mars 1 Ceres Jupiter Saturn Uranus

16 planets (1846-1931)

Mercury Venus Earth Mars 1 Ceres 2 Pallas 3 Juno 4 Vesta

Astraea 6 Hebe 7 Iris Jupiter Saturn Uranus Neptune Pluto

9 planets (1931-1977)

Mercury Venus Earth

Mars Jupiter Saturn

Uranus Neptune Pluto

10 planets (1977)

Mercury Venus Earth

Mars Jupiter Saturn

Chiron Uranus Neptune Pluto

9 planets (1977-1992)

Mercury Venus Earth

Mars Jupiter Saturn

Uranus Neptune Pluto

11 planets (1992-2006)

Mercury Venus Earth Mars Jupiter Saturn

Uranus Neptune Pluto 15760 Albion 1993 FW

10 planets (2006-2016)

Mercury Venus Earth Mars Jupiter

Saturn Uranus Neptune 15760 Albion 1993 FW

10 planets, 3 possible (2015-)

Mercury Venus Earth Mars Jupiter Saturn

Uranus Gna Neptune Albion 1993 FW 10th Planet 9th Planet

Glossary

• accretion - the name of the process in which an object attracts

more objects to merge into it because of gravity.

• accretion disk - a ring of gas, dust, etc. in a torus shape in orbital

motion around a star, with small particles in it taking shape due to

accretion.

• albedo - how much incident light is reflected by an object. In

simple terms - how “bright” or “reflective” an object is. This is

measured from a scale from 0 (absorbs all light; dark) to 1 (reflects

all light; bright).

• angular momentum - a principle in physics. When the mass of a

large, rotating objects shrinks to a smaller size, the law of

conservation of angular momentum dictates that the object - now

smaller - will spin much faster.

• asteroid or dwarf planet - minor planets that do not meet at least

one of the conditions set by the IAU to be a planet (see below).

• carbonaceous - containing lots of carbon compounds.

• centaur - an asteroid orbiting the Sun between the orbits of the

outer planets. Named after the half-horse, half-human creatures in

Greek mythology.

• centrifugal force - an inertial force causing the matter at the edge

of a spinning object to be held on much weaker to it.

• clearing the neighborhood - the act of a body’s gravity forcing

aside any rubble within its path or accreting it into its mass, so

that its orbit will have little to no rubble. This is necessary for a

body to be considered a planet in its own right.

• comet - these are bodies made of ice and water that usually have

eccentric orbits. When they pass close to the Sun, their volatile

compositions sublimate and evaporate, leaving behind a coma.

• density - how distributed the mass of something is within its

volume. Metals are denser than rocks, rocks are denser than water,

water is denser than gas.

• eccentric - how different a planet’s orbit is from a perfect circle

around its parent body. Very eccentric orbits have orbits

resembling parabolae.

• exoplanet - a planet that orbits another star.

• fringe theories - theories that do not follow or differ from the

majority or mainstream theories and evidence. Those who propose

fringe theories and advocate them are called fringe theorists.

• frost line - the distance from a star within the protoplanetary disk

from which water would be cool enough to remain in liquid or solid

form. Any closer and the water will evaporate and not accrete.

This can be thought of as the “proto-habitable zone”.

• gas giant - a planet with a very thick atmosphere or outer layers

made mostly out of gas or liquid.

• habitable zone or ecosphere - the distance from or region around a

star where water can naturally exist in liquid form.

• hypothetical - theorized in a hypothesis, but not proven to exist

yet.

• ice giant - a planet with a very thick atmosphere or outer layers

made mostly water, methane, and nitrogen gases or liquid. These

are usually the smaller, less massive “failed cores” of gas giants.

• isotopes - variants of an element’s atoms with different neutron

counts. Many with large neutron counts are very unstable and

decay over time. Thus, isotopes can be used to date the ages and

origins of many objects.

• kilonova - the collision between a neutron star and a black hole or

two neutron stars.

• Kuiper Belt - an asteroid belt of Pluto-like objects orbiting the Sun

thirty times further away from the Sun than Earth. Asteroids in this

belt are called Kuiper Belt Objects or KBOs for short.

• meteoroid - a fragment of an asteroid or comet that hits the

Earth’s surface.

• moon or satellite - an object that orbits a planet and is many times

less massive than its parent body so that the barycenter of gravity

between the two is not outside any body. The latter term can be

used for natural bodies, although it has become closely associated

with man-made bodies.

• Nice model - named for the French city of Nice, this is a scientific

model on the formation and subsequent evolution of the outer

Solar System. It suggests that Neptune was originally closer to the

Sun than Uranus, and Jupiter’s migrating outward shoved all the

planets much further out.

• orbit - the path of an object around another object.

• perturbation - when an object’s trajectory, orbit, or path through

space is affected by the gravitational pull of another object.

• planet - a large object that orbits the Sun, has enough mass for its

gravity to pull it into a roughly spherical shape and clear the

neighborhood around it of rubble.

• protostar - a large cloud of gases (especially hydrogen and helium)

that is about to collapse into a through nuclear fusing star (which

it is currently not doing).

• refractory - a substance with a relatively high boiling point, such

as rocks and metals.

• retrograde - orbits a body contrary to the spin of its parent body

or the orbital direction of the majority of other orbiting bodies.

Non-retrograde objects are prograde.

• rocky or terrestrial planet - a smaller, less massive planet made

mostly out of rock or metal.

• semi-major axis - the longest diameter of a circle, oval, or ellipse.

• silicates - minerals consisting of anions of silicate and oxygen.

• solar system - the collection of the Sun and all the objects that

orbit it due to its gravity.

• trojan - a body that shares in the orbit of a major body, usually

orbiting 60 degrees ahead or behind of it. Jupiter has many trojan

asteroids.

volatile - volatiles are substances with low boiling points. Examples

include nitrogen, water, carbon dioxide, ammonia, hydrogen, methane

and sulfur dioxide.