Earth and Space Year 9 Real

Life cycle of a star

• a star's life cycle depends on its size

• as stars age, they change in size, colour, and energy, ultimately reaching one of several possible endings

First step in the star life cycle

Nebula/e

• stars are formed from massive clouds of dust and gas in space called nebulae which are mostly composed of hydrogen

• as gravity pulls the cloud closer together, it heats up and begins to glow

• eventually, it becomes hot enough for nuclear fusion to begin

• A large collection of gas and dust

The second step of the star life cycle

Proto star

• the larger the star, the shorter the protostar stage

• A young, forming star that's still gathering mass

Third step in cycle

Main sequence star

• nuclear fusion takes place deep in the cores of main-sequence stars, fusing hydrogen into helium

• this releases massive amounts of energy as heat and light

• A star in the most stable and longest phase of its life; nuclear reactions inside the star produce light and heat

life cycle of a star order

Star nebula → proto star

average star/ main sequence star

• Red giant

• plantery nebula

• white dwarf

Massive star

• red supergiant

• supernova

• neutron star/black hole

Next step for average star

red giant

• hydrogen in the star’s core runs out so it begins to use hydrogen further out from its core

• it grows 400 times its original size

• as the star expands it also cools, causing the star to glow red

• nuclear fusion in the core now fuses helium into heavier elements like iron

• Forms after a star has run out of hydrogen fuel for nuclear fusion and has begun the process of dying

• An aging giant star that has used up all its core's supply of hydrogen fuel

Second step in the average star life cycle

Planetary nebula

• when the red giant runs out of fuel for nuclear fusion, it becomes unstable and explodes

• the outer layers of dust and gas are shedded, forming a planetary nebula

• A ring-shaped nebula formed by an expanding shell of gas round an ageing star

Final step in average star life cycle

White dwarf

• the hot, dense solid core that remains after a red giant has shed its outer layers of dust and gas

• very dense

• emit large amounts of heat and light energy

• eventually the amount of energy emitted becomes so low that the star becomes a black dwarf and can no longer be seen

• A stellar core remnant, formed after a star exhausts its nuclear fuel and sheds its outer layers

Next step for a massive star

Red supergiant

• forms when massive stars run out of hydrogen

• helium fuses into heavier and heavier elements until the core consists of iron

Second step massive star cycle

Supernova

• an enormous explosion that forms when a supergiant collapses under its own gravity

• huge amounts of energy are released - bright

• new elements form in the process, like gold, silver, uranium and copper

• some material is expelled outwards, leaving behind a very dense core

• The colossal explosion of a star

Whats one of the things after supernova

Neutron Star

• the collapsed core left behind after a supernova explosion

• very small and dense

• some have been found to rotate several hundred times a second - called pulsars

• A dense, collapsed remnant of a massive star after a supernova explosion

Second thing that could happen after a a super nova

Black Hole

• extremely dense

• gravitational forces are so strong, that nothing, not even light, can escape once it crosses the boundary known as the event horizon

• A region of spacetime with such strong gravity that nothing, not even light, can escape its pull

What is the Hertz-spring russel diagram

a diagram that helps scientists classify stars based on their physical properties and evolutionary stages

What does the H-R diagram do

plots a star’s luminosity (often compared to the Sun) against its surface temperature

stars at different stages in their life cycle are located in different regions of the graph

A scientific diagram that can be used to find the temperature, luminosity, spectral class and absolute magnitude of any star

What is the Big Bang Theory

• the most widely accepted explanation for the origin of the Universe

• according to this theory, the Universe expanded from an extremely small, extremely hot, and extremely dense state around 13.7 billion years ago

• evidence for the origin and evolution of the universe

What happened to the universe after the big bang

the Universe has expanded and become less dense and cooler

Edwin Hubble’s theroy

red shift, blue shift

what is edwins hubbles theory

• galaxies that are far away have greater red shifts

• he realised this by analysing the redshift of light from distance galaxies

• this provides evidence the universe is expanding

What is hubbles law

the farther away a galaxy is from Earth, the greater its velocity

what is red shift

• when light from an object in space moving away from Earth is stretched to longer wavelengths

• this causes spectral lines to shift towards the red end of the electromagnetic spectrum

• provides evidence for the origin and evolution of the universe

Evidence for the big bang

Cosmic microwave background (CMB) radiation

• light from the beginning of the Universe released about 380,000 years after the Big Bang

• at first, CMB was very energetic X-ray light but, over time, it has lost energy and become lower-energy microwaves

• accidentally discovered by Robert Wilson & Arno Penzias, while using a microwave telescope

• scientists consider this 'fossil' radiation to be a 'shockwave' of the Big Bang

How is the universe changing

• the Universe is continuing to expand, with galaxies moving farther apart over time

• star formation and stellar evolution are ongoing, with new stars forming while others age, explode as supernovae, or collapse into neutron stars or black holes

• galaxies are changing shape and size through collisions and mergers

• the Universe is cooling overall as it expands

What is the nebular theory?

The scientific explanation that the Sun and planets formed from a rotating cloud of gas and dust called a nebula.

What is a nebula?

A large cloud of gas and dust in space that can form stars and planetary systems

Why does nebular theory apply beyond Earth?

It explains the formation of the entire solar system and can be applied to other star systems

What force first causes dust particles to stick together?

Electrostatic attraction (“static cling”).

How old is the solar system according to the nebular theory

About 4.6 billion years

How quickly did the solar system form after the supernova?

Within 2–5 million years.

What existed before the solar system?

A massive star that exploded as a supernova.

white dwarf cooling

• phase in between white dwarf and black dwarf

What is the final final step in the stars life cycle

• A white dwarf that has cooled sufficiently to no longer emit significant heat or light

cosmic microwave background radiation

• the faint, nearly uniform, remnant glow or "afterglow" of the Big Bang, representing the earliest light in the universe, released roughly 380,000 years after its origin

• provides evidence for the origin and evolution of the universe

Luminosity

The total amount of energy it radiates per second of time. Hotter stars produce more energy per unit area making them more luminous than cooler stars of the same size. Larger stars have a greater surface area than smalll stars, allowing them to radiate more energy.

Absolute Magnitude

How bright a star would appear if it were located at a standard distance of 10 parsecs (32.6 light years) from Earth. Also the lower the magnitude the brighter the star is

Spectral Class

What category a star is in

Electromagnetic spectrum

Encompasses all types of electromagnetic radiation

Types of electromagnetic radiation (in order of shortest wavelength to longest)

Gamma rays, x-rays, ultraviolet, visible light, infared, microwaves, radio waves