How Our Solar System Came to Be – Dust to Planets

The formation of our solar system is a captivating tale that spans billions of years, unfolding through a complex interplay of cosmic forces. From a cosmic cloud of dust and gas, the very building blocks of our celestial neighborhood emerged, eventually giving rise to the diverse array of planets, moons, and other celestial bodies we observe today. This extraordinary journey from dust to planets is a testament to the intricate dance of gravitational forces, collisions, and accretion processes that shaped the solar system into the dynamic and awe-inspiring system we know. In the realm of geography, understanding the origins and composition of our solar system not only unveils the fascinating history of celestial bodies but also sheds light on the profound interconnectedness of Earth with the broader cosmic environment. This exploration of “How Our Solar System Came to Be” serves as a captivating voyage into the realms of space and time, intertwining the disciplines of astronomy and geography to unravel the mysteries of our cosmic home.

Formation of the Solar system

The solar system consists of the sun, the eight planets and their satellites, and thousands of other smaller heavenly bodies such as asteroids, comets and meteors.
The solar system is dominated by the sun. The sun accounts for almost 99.9 percent of the matter in the whole solar system. The sun is also the source of all the energy in the solar system.
The Nebular Theory of Laplace (1796) tried to explain the formation of the solar system. But it had many drawbacks as the theory was based on scientifically erroneous assumptions.
One assumption it got right was that the solar system was born from a giant gas of dust called a Nebula.
The solar nebula theory is currently the most widely accepted explanation for the origin of our solar system, and it is supported by a wide range of observations and evidence from various fields of science, including astronomy, geology, and physics.
The nebula started its collapse and core formation some 5-5.6 billion years ago and the Sun and the planets were formed about 4.6 billion years ago.

Formation of the Sun

The nebula began to collapse (gravitational collapse) in on itself after becoming gravitationally unstable.
This was possible because of a nearby supernova sending shock waves rippling through space.
Gravity then caused dust and gas to coalesce at the center of the nebular cloud.
As more matter got pulled in, the center got denser and hotter, increasing the gravity and pulling even more dust inwards causing a snowball effect.
About 99.9% of the material fell into the center and became the protosun (no sunlight yet).
Once the center of the cloud became hot enough it triggered nuclear fusion, and the Sun was born.

The formation of planets

Planets are solid heavenly bodies that revolve around a star (e.g. the sun) in closed elliptical paths.
The hot, rocky material near the center of the solar system gave rise to terrestrial planets with metal cores (mostly composed of iron and nickel): Mercury, Venus, Earth, and Mars And on the cool edges, the gas and ice giants were born: Saturn, Jupiter, Neptune, and Uranus.
Rocks that escaped the pull of planets were left as asteroids, scattered through the solar system.
Many of these rocks orbit the Sun in an area between Mars and Jupiter known as the asteroid belt.
A planet shines because it reflects the light of the sun. Since the planets are much nearer than the stars, they appear to be big and do not twinkle at night.
The 0.1% of matter that remained orbited around the Sun, caused the randomly shaped gas cloud to form a flat disc shape.
The planets move around the sun from west to east, so the relative positions of the planets keep changing day by day.
The planets are very small compared to the sun or other stars. There are 8 major planets including the earth.

These planets in the order of increasing distances from the sun are given below-

1. Mercury (Budha): it is nearest to the sun.
2. Venus ( Shukra)
3. Earth (Prithvi)
4. Mars (Mangal)
5. Jupiter (Brihaspati): Biggest Planet.
6. Saturn (Shani)
7. Uranus (Arun)
8. Neptune (Varun)

IAU’s new definition of planet

The definition of planet set in 2006 by the International Astronomical Union (IAU) states that, in the Solar System, a planet is a celestial body that: is in orbit around the Sun, has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and Has “cleared the neighborhood” around its orbit. For this, they become the dominant gravitational body in their orbit in the Solar System. Pluto lacks it.
Any object that meets the first two criteria but doesn’t meet the 3rd criterion is considered a dwarf planet. Thus Pluto is a dwarf planet.
The classification of planets into these two groups is useful in understanding their different properties and characteristics, as well as their formation and evolution.

The two groups of planets are:

Terrestrial Planets
Jovian Planets

The four nearest planets to the Sun, Mercury, Venus, Earth, and Mars, are called terrestrial planets because their structure is similar to Earth. The common features of the terrestrial planets are:
They have a thick atmosphere composed mostly of hydrogen and helium.
They have no solid surface and are sometimes referred to as “gas giants”.
They have very strong magnetic fields.
They are much larger in size and mass compared to the terrestrial planets.
The Jovian planets also have unique features, such as Jupiter’s Great Red Spot and its numerous moons, Saturn’s prominent rings, Uranus’ tilted axis and its icy moons, and Neptune’s large moon Triton which orbits in a retrograde direction.
The Jovian planets are Jupiter, Saturn, Uranus, and Neptune.

The common features of the Jovian planets are:

1. They are all gaseous bodies (made of gases)

2. They have a ring system around them.

3. They have a large number of natural satellites (or moons).

Planet	Surface Temp in ֯C	Period of Rotation	Period of Revolution	Distance from Sun (AU)	Diameter (km)	SizeRank	Moons	Density (gm/cm3)	Specific gravity (m/s2)
Mercury	+427	58 days	87 days	0.4	4,878	0.38	8	0	5.4	3.7	0.38
Venus	+480	243 days	224 days	0.7	12,104	0.95	6	0	5.2	8.9	0.9
Earth	+22	23:56 hrs	365 days	1	12,756	1.00	5	1	5.5	9.8	1
Mars	-23	1.025 days	687 days	1.5	6,787	0.53	7	2	3.9	3.7	0.38
Jupiter	-150	9.9 hrs	11.9 years	5.2	1,40,000	11.19	1	79	1.3	24.9	2.53
Saturn	-180	10.7 hrs	29 years	9.6	1,16,000	9.46	2	62	0.7	10.4	1.06
Uranus	-214	17 hrs	84 years	19.2	51,000	4.11	3	27	1.3	8.8	0.9
Neptune	-220	16 hrs	164 years	30.0	48,000	3.88	4	13	1.6	11.1	1.13
Pluto (dwarf)	-223	6.39 days	248 years	39.5	2,377	0.18	9	5	1.9

Moon or Satellites

The term “moon” is commonly used to refer to Earth’s natural satellite, but the term can be used to refer to any natural satellite that orbits a planet or other celestial body
A natural satellite or moon is a celestial body that orbits around a planet or dwarf planet. These moons do not emit their own light but instead reflect the light of the Sun.
The Moon is the Earth’s only natural satellite, and it is the fifth largest moon in the solar system.
The moons of different planets vary greatly in size, composition, and other characteristics. Some are small and irregularly shaped, while others are large and spherical. Some moons have their own atmospheres, and some even have signs of potential habitability.

Earth’s Moon key points:

The moon is a natural satellite of the Earth.
Moon revolves around the earth on a definite, regular path- the moon’s orbit.
Gravitational attraction of the earth holds the moon in its orbits.
The moon is about one-fourth the size of the Earth in diameter and its weight is about one-eighth that of the Earth.
Moon has no air or water. Its surface is covered with hard and loose dirt, craters, and mountains.
On the moon, days are extremely hot and nights are very cold.
Because the moon is nearer to the Earth, it appears to be much bigger than the stars.
The moon has no light of its own, it is light from the sun which is reflected by the moon’s surface.

Origin of Moon

In 1838, Sir George Darwin suggested that initially, the Earth and the moon formed a single rapidly rotating body. The whole mass became a dumbbell-shaped body and eventually, it broke.
It was also suggested that the material forming the moon was separated from what we have at present the depression occupied by the Pacific Ocean.
A body the size of one to three times that of Mars collided with the Earth sometime shortly after the Earth was formed. It blasted a large part of the Earth into space.
This portion of blasted material then continued to orbit the earth and eventually formed the present moon about 4.44 billion years ago.

Size comparison of largest moons in the Solar System

Asteroid

Asteroids are small, rocky, and metallic bodies that orbit the Sun, primarily located between the orbits of Mars and Jupiter in what is known as the asteroid belt. They are remnants from the early solar system and are believed to be leftover materials that never formed into planets due to the gravitational influence of Jupiter.
The largest asteroid in the asteroid belt is Ceres, which is also classified as a dwarf planet. It is approximately 590 miles (940 kilometers) in diameter, making it the largest object in the asteroid belt. However, most asteroids are much smaller, some even as small as pebbles.
The collision of an asteroid with the Earth can cause significant damage to life and property, which is why astronomers carefully monitor the orbits of asteroids that come near Earth. In fact, the extinction of the dinosaurs is believed to have been caused by the impact of a large asteroid or comet.
When an asteroid collides with the Earth, it can create a large crater on the surface of the Earth, which can be hundreds of kilometers wide. Many such craters have been identified around the world, but erosion and other natural processes can cause them to become less visible over time.
The Lonar Lake in Maharashtra, India, is one such example of a crater formed by the impact of an asteroid with the Earth. The lake is believed to have been formed around 50,000 years ago, and it is one of the few impact craters on Earth that has a saltwater lake inside it.

Asteroid belt

Asteroids are remnants of planetary formation that circle the Sun in a zone lying between Mars and Jupiter. The circular chain of asteroids is called the asteroid belt.
The remnants of planetary formation failed to coalesce because of the gravitational interference of Jupiter.
The asteroid belt lies between 2.3 and 3.3 AU from the Sun.
Asteroids (planetoids ― another term for an asteroid) are composed mainly of refractory rocky and metallic minerals, with some ice.
Asteroids range in size from hundreds of kilometers across to microscopic.
All asteroids except the largest, Ceres, are classified as small Solar System bodies.
Fragments of asteroids break off to form meteoroids, which can reach the Earth’s surface.

Theory of Meteor & Meteorite

A meteoroid is any solid debris originating from asteroids, comets or other celestial objects and floats through interplanetary space.
A meteor is the streak of light that appears in the sky when a meteoroid enters the atmosphere (mesosphere) at about 200 km at high speed and burns up because of friction.
A meteor is popularly termed a ‘shooting star’ or ‘falling star’.
In some cases, the meteoroid does not burn up completely and makes its way to the Earth’s surface. The surviving chunk is called a meteorite.
The circular depression created on the earth’s surface after the meteorite’s impact is called a meteorite crater.
Meteorite impacts are common on all planets and moons in the solar system.
The most conspicuous meteorite craters can be found on the surfaces of the Moon and Mercury (because they are geologically inactive due to a negligible atmosphere).
Largest Meteor Crater: A meteor crater in Arizona (USA) is 1,300 m deep and is the largest meteor crater in the world. It was formed over 10,000 years ago.

Chicxulub crater

Chicxulub crater (Mexico’s Yucatan Peninsula) was caused by a meteor impact that is believed to have wiped out the dinosaurs (mass extinction at the end of the Cretaceous 65 million years ago).

Meteorite craters in India

Lonar Lake (1.8 km in diameter) in Buldhana District of Maharashtra
Dhala crater (14 km in diameter) in Shivpuri district, Madhya Pradesh
Ramgarh crater (3.5 km in diameter) is a potential meteorite crater in Kota plateau in Rajasthan.

Theory of Kuiper belt

The Kuiper Belt is a region of the outer solar system that is located beyond the orbit of Neptune and is home to many small, icy objects. It is named after Gerard Kuiper, a Dutch-American astronomer who first proposed the existence of this region in 1951.
This Kuiper Belt object was discovered by the Hubble Space Telescope in 2014.
Officially it is known as 2014 MU69 and is nicknamed Ultima Thule. Thule means the most distant places beyond the known world.
The Kuiper Belt is believed to be the source of many comets that periodically enter the inner solar system, and it is thought to contain billions of objects that are larger than 1 kilometer in diameter.
Some of the most famous objects in the Kuiper Belt include Pluto, Eris, Haumea, and Makemake, which are classified as dwarf planets.
The Kuiper Belt and its objects provide valuable information about the early history and formation of the solar system. With the composition and orbits of these objects, scientists can learn more about the conditions that existed in the early solar system and how it evolved over time.
The Kuiper Belt is a potential target for future space missions, as it could provide valuable resources for human exploration and colonization

Theory of comet & Dwarf planets

Comet

A comet is an icy small Solar System body that, when passing close to the Sun, heats up due to the effects of solar radiation and the solar wind upon the nucleus and begins to outgas, displaying a visible atmosphere or coma, and sometimes also a tail.
Meteors are the heavenly bodies from the sky which we see as a bright streak of light that flashes for a moment across the sky.
When a meteor enters the atmosphere of Earth at high speed, a lot of heat is produced due to the resistance of air.
Comets are small celestial bodies composed of frozen gasses, dust, and rock. Comets typically have a nucleus, which is the solid central part of the comet, and a coma, which is the cloud of gas and dust that surrounds the nucleus. As a comet approaches the Sun, its icy surface begins to vaporize, producing a bright coma and a tail that can extend for millions of kilometers.
Short-period comets– The Kuiper Belt is a region of the Solar System beyond Neptune that is home to short-period comets. Some of these objects have been scattered into eccentric orbits that bring them into the inner Solar System where they become visible as comets.
long-period comets-The Oort Cloud is a much more distant and hypothetical region of the Solar System thought to be home to a vast population of icy objects, including long-period comets.
The Oort Cloud is believed to extend out to a distance of up to 100,000 astronomical units (AU) from the Sun.

Dwarf planets

Dwarf planets are celestial bodies that meet the first two criteria of a planet but have not cleared their orbits of smaller debris, such as asteroids and other objects.
As of 2021, there are five officially recognized dwarf planets in our Solar System: Ceres, Pluto, Haumea, Makemake, and Eris.
Ceres is located in the asteroid belt between Mars and Jupiter, while the other four are located in the Kuiper Belt beyond the orbit of Neptune.
They can provide insight into the formation and evolution of the Solar System.

The International Astronomical Unit defines a planet as something that obeys the following criteria:

To be in orbit around the Sun
Has enough gravity to pull its own mass into a round shape
Has cleared its orbit of smaller objects

Frequently Asked Questions (FAQs)

FAQ: What is the origin of our solar system?

Answer: The most widely accepted theory explaining the origin of our solar system is the nebular hypothesis. According to this theory, our solar system formed from a massive, rotating cloud of gas and dust called a nebula. About 4.6 billion years ago, a nearby supernova explosion or a shockwave from a passing star triggered the collapse of this nebula. As it contracted, the nebula began to spin faster and flatten into a spinning disk. The center of the disk became the Sun, while the material in the disk clumped together to form planets, moons, asteroids, and comets.

FAQ: How did dust particles transform into planets?

Answer: The process of transforming dust particles into planets involves several stages. First, within the rotating disk of the solar nebula, small particles collided and stuck together, forming larger objects called planetesimals. These planetesimals continued to grow through mutual gravitational attraction. Some of them reached sizes where their gravity became strong enough to attract even more material, leading to the formation of protoplanets. Over time, these protoplanets continued to accrete material until they became the planets we know today. The leftover material in the disk formed smaller bodies like moons, asteroids, and comets.

FAQ: How did geography play a role in the formation of the solar system?

Answer: Geography, in the context of the solar system’s formation, refers to the spatial distribution of matter within the solar nebula. As the nebula collapsed, the distribution of material was not uniform. Regions closer to the center of the rotating disk were hotter due to the presence of the young Sun, while regions farther away were colder. This temperature gradient influenced the types of materials that could condense and solidify at different distances from the Sun. As a result, rocky planets like Earth formed closer to the Sun, where it was hotter, while gas giants like Jupiter formed in the colder outer regions. The geography of the solar nebula played a crucial role in shaping the composition and characteristics of the planets in our solar system.

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How Our Solar System Came to Be – Dust to Planets – Geography Notes