Earth Science CET (Stars)

A vast cloud of gas and dust in space where star formation

begins.

Consists of hydrogen, helium, and trace amounts of heavier

elements.

Gravitational forces cause parts of the nebula (a cloud of

gas and dust in outer space) to collapse, leading to the

formation of clumps of material.

As the clumps contract, the temperature and pressure

increase, eventually leading to the formation of a protostar.

Stellar Nebula

The early stage of a star’s life where a dense core forms.

protostar forms when the temperature and pressure in the

core are high enough to start nuclear fusion.

The protostar continues to gather material from the

surrounding nebula.

Protostar

The longest stage in a star’s life cycle, where the star is

stable.

Hydrogen atoms fuse to form helium in the star’s core,

producing energy and balancing gravitational collapse.

This stage can last for billions of years, depending on the

star’s mass.

Main Sequence Star

The phase where the star expands and cools, becoming

much larger and redder.

Red Giant / Supergiant

In low and medium-mass stars,

the core contracts, and hydrogen fusion occurs in a shell

around the core.

Hydrogen Shell Burning

These stars enter the supergiant phase,

where the core temperature rises enough for helium and

heavier elements to fuse.

High-Mass Stars

The end stages of a star’s life depend on its mass:

Stellar Death

Types of Low-Mass Stars:

1. Planetary Nebula

2. White Dwarf

The outer layers are ejected into

space, forming a colorful shell of gas.

Planetary Nebula (Low Mass)

The remaining core is hot and dense,

eventually cooling and fading over time.

White Dwarf (Low Mass)

1.5 to ~8 Solar Masses

Medium-Mass Stars

Types of Medium-Mass Stars

1. Planetary Nebula

2. White Dwarf

> ~8 Solar Masses

High-Mass Stars

Types of High-Mass Stars

1. Supernova

2. Neutron Star/Black Hole

A massive explosion occurs, dispersing the

star’s outer layers into space.

Supernova

The core remains as a

neutron star or collapses into a black hole.

Neutron Star / Black Hole

A small, dense, and hot remnant of a star’s

core after shedding its outer layers.

White Dwarf

An extremely dense remnant made mostly of

neutrons; it can be observed as a pulsar if it emits beams of

radiation.

Neutron Star

A region of space with gravitational pull so

strong that not even light can escape, formed from the

collapse of a massive star’s core.

Black Hole

A G-type main-sequence star, is the central and

most massive object in our solar system.

Sun

Age of Sun:

About 4.6 billion years old

Size of Sun:

Diameter of approximately 1.39 million km (864,000

miles), about 109 times that of Earth.

Mass of Sun:

Approximately 1.989 × 10^30 kg, about 330,000

times the mass of Earth.

Temperature of the Sun:

Surface temperature (photosphere) is about

5,500°C (9,932°F), while the core temperature reaches

around 15 million°C (27 million°F).

Types of Solar Phenomena:

1. Sunspots

2. Solar Flares

3. Prominences

4. Solar Wind

5. Coronal Mass Ejections

Dark spots on the photosphere caused by strong magnetic

fields.

Sunspots follow an 11-year cycle of increasing and

decreasing activity known as the solar cycle.

They are associated with solar flares and coronal mass

ejections.

Cool regions on the surface.

Sunspots

Sudden, intense bursts of radiation from the Sun’s surface.

Occur near sunspots due to the release of magnetic energy.

Can disrupt space weather and affect communication and

navigation systems on Earth.

Solar Flares

Large, bright features extending from the photosphere into

the corona.

Formed from plasma trapped in magnetic loops.

Prominences

Description: A continuous flow of charged particles from the

Sun.

Affects Earth’s magnetosphere, leading to phenomena like

auroras and geomagnetic storms.

Solar Wind

Massive bursts of solar wind and magnetic fields rising

above the solar corona.

Can cause significant space weather events and impact

satellite operations and power grids on Earth.

Coronal Mass Ejections (CMEs)

Layers of the Sun:

1. Inner Core

2. Radiative Zone

3. Convection Zone

4. Photosphere

5. Chromosphere

6. Corona

Inner Core

Radiative Zone

Convective Zone

Photosphere

Chromosphere

Corona

The point in a planet’s orbit where it is the farthest from the

Sun.

The distance between the planet and the Sun is

at its maximum.

When a planet is at aphelion, it receives less solar energy

compared to perihelion. However, this distance does not

have a significant impact on Earth’s seasons compared to

the axial tilt.

Earth’s aphelion occurs around July 4th, when Earth is

about 152 million kilometers (94.5 million miles) from the

Sun.

Aphelion

The point in a planet’s orbit where it is closest to the Sun.

At perihelion, the distance between the planet and the Sun

is at its minimum.

When a planet is at perihelion, it receives more solar energy

compared to aphelion.

Earth’s perihelion occurs around January 3rd, when Earth is

about 147 million kilometers (91 million miles) from the Sun.

Perihelion

It is a hypothesis for the ultimate fate of the

universe. According to this theory, the universe will one day

stop expanding and begin to contract, falling inward until it has

collapsed back into a super-hot, super-dense singularity. This

event will ultimately cause the cosmic scale factor to reach

zero, potentially followed by a reformation of the universe

starting with another Big Bang.

The Big Crunch i

Initially, it expands due to the force of the? However, if the density of matter throughout the universe is

sufficiently high, gravity could eventually overcome

expansion.

Big Bang

If gravity wins, the expansion stops, and contraction begins.

As time passes, the universe accelerates toward a

gravitational collapse, akin to turning the entire cosmos into a?

Colossal Black Hole

The universe would heat up

significantly. Stars would collide, creating intense radiation.

Ultimately, the universe would become a blazing fireball

with infinite temperature, and at the very end, neither time

nor space would remain.

Big Crunch

It is a natural process that warms the

Earth's surface. It occurs when certain gases in the Earth's

atmosphere trap heat. These gases allow sunlight to enter the

atmosphere freely, but they prevent some of the heat that the

sunlight brings from leaving the atmosphere.

Greenhouse effect

Key Greenhouse Gases:

1. Carbon Dioxide (CO2)

2. Methane (CH4)

3. Nitrous Oxide (N2O)

4. Chlorofluorocarbons (CFCs)

Emitted through burning fossil fuels,

deforestation, and other industrial processes.

Carbon Dioxide (CO2)

Released during the production and

transport of coal, oil, and natural gas, as well as from

livestock and other agricultural practices.

Methane (CH4)

Emitted from agricultural and industrial

activities, as well as during combustion of fossil fuels and

solid waste.

Nitrous Oxide (N2O)

Synthetic compounds used in

various industrial applications, now largely regulated due to

their role in ozone depletion.

Chlorofluorocarbons (CFCs)

Threats to Biodiversity:

1. Habitat Destruction and Degradation

2. Invaside Species

3. Pollution

4. Human Population

5. Overexploitation

Clearing forests for agriculture, logging, and

urban development.

Deforestation

Breaking up of habitats into smaller, isolated

patches.

Fragmentation

Expansion of cities and infrastructure

development.

Urbanization

Conversion of natural habitats to

farmland.

Agricultural Expansion

Non-native species introduced to new environments, either

intentionally or accidentally. These species often

outcompete, prey on, or bring diseases to native species.

Invasive Species

Pesticides, heavy metals, and other

toxins entering ecosystems.

Chemical Pollution

Emissions from industrial activities

and vehicles affecting air and water quality.

Air and Water Pollution

Accumulation of plastic waste in oceans

and other habitats.

Plastic Pollution

Increasing human population leading to

greater demand for resources.

Population Growth

Overconsumption of natural

resources, leading to habitat destruction and pollution.

Resource Consumption

Depleting fish populations faster than they can

reproduce.

Overfishing

Illegal hunting for trade, bushmeat,

and other purposes.

Hunting and Poaching

Unsustainable logging practices leading to loss of

forests and biodiversity.

Logging

It refers to the increasing concentration of toxic substances

within organisms as you move up the food chain.

Biological magnification

Process of Biological Magnification:

1. Introduction of Toxins

2. Absorption by Producers

3. Consumption by Herbivores

4. Predation

5. Top Predators

Pollutants such as pesticides (e.g.,

DDT), heavy metals (e.g., mercury), and other chemicals

enter the environment.

Introduction of Toxins

Primary producers (e.g., plants,

algae) absorb these toxins.

Absorption by Producers

Herbivores eat the

contaminated plants, accumulating higher toxin levels in

their bodies.

Consumption by Herbivores

Carnivores and higher trophic levels eat the

herbivores, further concentrating the toxins.

Predation

The highest levels of toxins are found in top

predators (e.g., eagles, sharks) due to the accumulation at

each trophic level.

Top Predators