The Universe

Question 1

Define and describe the Sun

Answer 1

The Sun is a yellow dwarf star at the center of our solar system. It provides light and energy and is orbited by planets, moons, asteroids, and other objects.

Question 2

Define and describe the Planets

Answer 2

Planets are large celestial bodies that orbit a star (in our case, the Sun), are mostly round, and have cleared their orbital path of similar-sized objects. There are 8 planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Question 3

Define and describe Orbits

Answer 3

An orbit is the curved path that a celestial body follows around a larger body due to gravitational attraction. Planets orbit the Sun, and moons orbit planets.

Question 4

Define and describe Solar System

Answer 4

A solar system is a collection of celestial bodies, including a star and all objects bound to it by gravity. Our solar system consists of the Sun (our central star) and everything that orbits it, including the 8 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune), 5 recognized dwarf planets (such as Pluto), moons, asteroids, comets, and space debris. The solar system is heliocentric, meaning the Sun is at the center, with all other objects orbiting around it.

Question 5

Define and describe Galaxy

Answer 5

A galaxy is a massive collection of stars, gas, dust, and dark matter held together by gravity. Galaxies come in various shapes, including elliptical, spiral, and irregular. Our galaxy, the Milky Way, is a spiral galaxy.

Question 6

Define and describe Moons

Answer 6

Moons, or natural satellites, are objects that orbit planets rather than stars. Our solar system has approximately 300 moons, including Earth’s Moon, Luna, which is the largest for any rocky planet.

Question 7

Define and describe stars

Answer 7

Stars are massive, luminous spheres of plasma held together by gravity. They produce light and heat through nuclear fusion. The Sun is a star.

Question 8

Define and describe black hole

Answer 8

A black hole is a region of space with such strong gravitational pull that nothing, not even light, can escape from it. They are often found at the center of galaxies, including our own.

Question 9

Describe the structure of the universe and its component

Answer 9

The universe encompasses everything: all of space, matter, energy, and even time. It includes galaxies, stars, planets, and all other celestial objects, with our solar system being just one part of this vast expanse.

Question 10

Describe Star formation

Answer 10

Stars form from dense clouds of gas and dust in space that collapse under the force of gravity. As this material compresses, it forms visible globules, which continue to collapse, creating a protostar. Initially, the temperature of a protostar is not sufficient for nuclear reactions, but as the pressure increases during the collapse, the temperature rises. Once it reaches a critical point, nuclear fusion begins, marking the birth of a new star.

Question 11

Describe Star Brightness

Answer 11

The brightness of a star, or its luminosity, depends on its size and temperature. Larger, hotter stars are generally brighter than smaller, cooler ones.

Question 12

Describe life cycle of stars

Answer 12

Stars form from gas and dust, then go through stages based on their mass. Low-mass stars expand into red giants and end as white dwarfs, while high-mass stars may become supernovae, possibly leaving behind neutron stars or black holes.

Question 13

How do you calculate distances in lightyears

Answer 13

To calculate distances in light-years, astronomers measure the distance that light travels in one year, which is about 9.46 trillion kilometers (9.46 x 10^12). They use parallax, redshift, and other methods to determine how far away celestial objects are from Earth.

Question 14

Compare big bang theory to steady state theory

Answer 14

The Big Bang Theory states that the universe started from a singular, extremely hot and dense point and has been expanding ever since. In contrast, the Steady State Theory suggests that the universe has always existed in the same form, with continuous creation of matter to account for its expansion, maintaining a constant density.

Question 15

Explain how cosmic microwave radiations support the big bang theory

Answer 15

Cosmic Microwave Background (CMB) radiation is residual thermal radiation from the Big Bang, filling the universe almost uniformly. This faint glow is evidence of the early hot, dense state of the universe, cooling as it expanded, which aligns with predictions made by the Big Bang Theory.

Question 16

Explain how redshift support the big bang theory

Answer 16

Redshift occurs when light from distant galaxies shifts towards the red end of the spectrum as they move away from us. This phenomenon, observed in almost all galaxies, indicates that the universe is expanding, supporting the Big Bang Theory.

Question 17

Explain how blueshift support the big bang theory

Answer 17

Blueshift is observed when an object in space is moving towards us, causing light to shift towards the blue end of the spectrum. Although most galaxies show redshift, observing blueshift in certain galaxies or stars within our galaxy helps scientists study movement and validate expansion patterns predicted by the Big Bang Theory.

Question 18

Explain how hubble’s law support the big bang theory

Answer 18

Hubble’s Law states that galaxies are moving away from us at speeds proportional to their distance. This observation supports the Big Bang Theory by showing that the universe is expanding, which implies it was once condensed into a single point.

Question 19

Explain how proportion of matter support the big bang theory

Answer 19

The observed proportions of hydrogen, helium, and other light elements match predictions made by the Big Bang Theory. These elements were formed in the early moments of the universe, supporting the idea of a hot, dense origin.

Question 20

Describe the timeline of major changes in the universe from the Big Bang through to the formation of
stars and galaxies

Answer 20

1. The Big Bang — Singularity forms
2. Time and space form; space expands rapidly
3. Universe cools; reaches size of the solar system
4. Universe has cooled to 10^10 degrees celcius
5. Light matter forms — electrons, positrons
6. Heavier matter forms — protons, neutrons
7. Atomic nuclei form
8. Universe has cooled to 3000 °C; first atoms form
9. First stars appear
10. Galaxies begin to form

Question 21

Describe First Nation Australians’ knowledge of celestial bodies and explanation of the origin of the universe

Answer 21

First Nations Australians believe in the Dreamtime, where ancestral spirits created the land, people, and celestial bodies. These spirits shaped the natural landscape and taught people how to live. Their stories, passed down through generations, explain the origin and connection between life, the land, and the cosmos.

Question 22

What is a nebula

Answer 22

A giant cloud of dust and gas in space, often the birthplace of stars.

Question 23

how does color of a star affect it’s temperature

Answer 23

Temperature: The color of a star indicates its surface temperature.
Blue Stars: Hottest, surface temperatures above 10,000 K.
White/Yellow Stars: Medium temperature, like our Sun (~5,500 K).
Red Stars: Coolest, below 3,500 K.

Question 24

What are the Types of Stars?

Answer 24

Main Sequence Stars
Red Giants
White Dwarfs
Supergiants
Neutron Stars
Protostars

Question 25

Main Sequence Stars

Answer 25

Color: Range from blue (hot) to red (cool).
Temperature: 2,000 - 50,000 K.
Location on H-R Diagram: Diagonal band from the upper left (hot, bright) to lower right (cool, dim).
Key Fact: Once nuclear fusion ignites in the core, the star enters a stable phase. For a star similar in size to our Sun (referred to here as “a star the size as Sol”), this stage can last billions of years as the star converts hydrogen into helium. Most stars, including the Sun, are on the main sequence, fusing hydrogen into helium.

Question 26

Red Giants

Answer 26

Color: Red or orange, due to their cooler surface temperatures.
Temperature: ~2,000 - 5,000 K.
Location on H-R Diagram: Upper right corner, bright but cooler than main sequence stars.
Key Fact: After exhausting the hydrogen in its core, a star of average mass expands and cools, forming a red giant. The core contracts while the outer layers expand.

Question 27

White Dwarfs

Answer 27

Color: White or blue-white, reflecting high temperatures.
Temperature: 8,000 - 40,000 K.
Location on H-R Diagram: Lower left corner, hot but dim due to small size.
Key Fact: They’re the remnants of low- or medium-mass stars, no longer undergoing fusion.

Question 28

Supergiants

Answer 28

Color: Can be red or blue, depending on temperature.
Temperature: Red supergiants are cooler (3,000 - 4,500 K), while blue supergiants are hotter (10,000 - 50,000 K).
Location on H-R Diagram: Top center or top right, extremely bright.
Key Fact: These massive stars end their lives in supernovae.

Question 29

Neutron Stars

Answer 29

Color: Invisible to the naked eye (often observed as pulsars emitting X-rays/gamma rays).
Temperature: Extremely hot initially, but cools over time.
Location on H-R Diagram: Not typically plotted due to their faintness and small size.
Key Fact: Remnants of massive stars after a supernova; extremely dense and small.

Question 30

Protostars

Answer 30

Color: Typically red or orange, as they’re cooler than main sequence stars.
Temperature: Less than 2,000 K, though temperature rises as they evolve.
Location on H-R Diagram: Not on the main sequence; appear in the “pre-main sequence” region below the main sequence.
Key Fact: Early stage of star formation; evolves into a main sequence star once fusion begins.

Question 31

What is nuclear fusion and how does it work

Answer 31

Nuclear fusion is where 2 isotopes of hydrogen (deuterium and tritium) combine to form Helium, along with the release of a neutron and energy (in the form of immense amounts of heat and light)

Question 32

Hierarchy of universe

Answer 32

Universe –> Galaxy –> Solar System –> Planets –> Dwarf Planets –> Moons –> Asteroids –> Meteors –> Space debris

Question 33

What are the parts of a black hole

Answer 33

Singularity
Event Horizon
Photon Sphere
Relativistic Jets
Innermost Stable Orbit
Accreditation Disc

Question 34

Singularity

Answer 34

This is the core of the black hole, where all the matter has collapsed into a point of infinite density and zero volume. At the singularity, the laws of physics as we know them break down, and general relativity cannot describe what happens there.

Question 35

Event Horizon

Answer 35

Often called the “point of no return,” the event horizon is the boundary surrounding the black hole. Once something crosses this boundary, it can no longer escape the black hole’s gravitational pull. This is the outermost layer of what is visually recognized as the black hole.

Question 36

Photon Sphere

Answer 36

Just outside the event horizon, this is a region where gravity is strong enough to make photons (light particles) travel in circular orbits around the black hole. It creates a bright ring due to the bending of light, adding to the black hole’s “shadow.”

Question 37

Relativistic Jets

Answer 37

These are jets of particles that shoot out from the black hole’s poles at near the speed of light. When the black hole consumes material, the energy released sometimes escapes as these powerful jets, which can extend thousands of light-years into space.

Question 38

Innermost Stable Orbit

Answer 38

This is the closest distance from the black hole where material can orbit stably without being pulled into the event horizon. Anything closer than this point would spiral inwards and eventually fall into the black hole.

Question 39

Accreditation Disc

Answer 39

Surrounding the black hole is a disc of stellar debris, gas and dust that is gradually drawn toward the event horizon. As this material gets closer to the black hole, it heats up and emits intense radiation, often in the form of X-rays, due to the immense gravitational energy being released.

Question 40

Life cycle of average sized star

Answer 40

Stellar Nebula, Stable Stage, Red Giant, Planetary Nebula, White Dwarf, Black Dwarf

Question 41

Life cycle of massive sized star

Answer 41

Stellar Nebula, Massive star, Red Giant, Supernova, Neutron star or Black Hole

Question 42

Black Dwarf

Answer 42

Over billions of years, the white dwarf cools and fades into a black dwarf, an inactive remnant with no light or heat (the final, theoretical stage).

Question 43

What is the doppler effect

Answer 43

The Doppler effect is the change in frequency that you hear when a source and an observer are moving with respect to each other.

Question 44

Big Freeze

Answer 44

The Big Freeze is a theoretical end scenario of the universe where it continues to expand forever. As a result, galaxies move farther apart, stars burn out, and temperatures drop. Eventually, the universe becomes cold, dark, and lifeless, with no usable energy left for sustaining processes like star formation.

Question 45

Big Rip

Answer 45

Expansion accelerates to the point where all structures, even atoms, are torn apart.

Question 46

Big Crunch

Answer 46

Expansion halts, reverses, and the universe collapses back to a single point.

Question 47

Explain how the map of the early universe that shows the universe was not evenly distributed supports the big bang theory

Answer 47

The early universe map, showing slight temperature and density fluctuations in the Cosmic Microwave Background (CMB), supports the Big Bang theory by indicating that the universe began in a hot, dense state that wasn’t perfectly uniform. These fluctuations allowed gravity to gradually pull matter into clumps, forming galaxies and stars over billions of years, consistent with Big Bang predictions.

Question 48

How old is the universe

Answer 48

13.7 billion years ago

Question 49

Life cycle of high mass stars

Answer 49

Stellar Nebula (Birth): Like smaller stars, high-mass stars form from a nebula, but they burn hotter and brighter due to their greater mass.

Main Sequence: High-mass stars quickly go through their fuel, fusing heavier elements than hydrogen in later stages of their main-sequence life.

Red Supergiant: When hydrogen runs low, high-mass stars expand into red supergiants. They continue fusing elements in layers around the core, from helium up to iron.

Supernova: Once the core is mostly iron, it can no longer sustain fusion. The star’s core collapses under gravity, triggering a supernova explosion that blasts its outer layers into space, forming elements heavier than iron.

Neutron Star or Black Hole: The remaining core’s fate depends on its mass:

Neutron Star: If the core is about 1.4 to 3 times the mass of the Sun, it becomes a neutron star, incredibly dense and compact.
Black Hole: If the core is more than about 3 times the Sun’s mass, it collapses into a black hole, a point in space with gravity so strong that not even light can escape.

Question 50

Life cycle of low mass stars

Answer 50

Stellar Nebula (Birth): Stars begin in a stellar nebula, a cloud of gas and dust. Gravity pulls particles together until pressure and temperature ignite nuclear fusion, forming a new star.

Main Sequence: The star spends most of its life here, fusing hydrogen into helium in its core. It shines steadily for billions of years, depending on its size.

Red Giant Phase: When the hydrogen in the core runs low, fusion slows, and the core contracts. Outer layers expand, turning the star into a red giant, which shines brightly but is cooler on its surface.

Planetary Nebula: Eventually, the red giant sheds its outer layers into space, creating a colorful shell of gas known as a planetary nebula.

White Dwarf: What remains is the hot core, now a white dwarf. It’s dense, about the size of Earth, and slowly cools over billions of years. It will eventually fade to become a black dwarf, though this final stage hasn’t yet occurred for any known stars since it takes longer than the current age of the universe.

Question 51

What does a planet need to be classified as a planet

Answer 51

it must orbit a star, it must be big enough to have enough gravity to force a spherical shape, and it must be big enough that its gravity cleared away any objects of a similar size near its orbit.

Question 52

What does a moon need to have

Answer 52

is an object that orbits a planet or something else that is not a star

Question 53

What a moon’s sometimes callled?

Answer 53

Natural satellites

Question 54

According to the big bang theory all that existed before the universe was

Answer 54

Energy

Question 55

The apparent slow motion of the stars that is observed during the night is due to:

Answer 55

The rotation of the Earth The apparent slow motion of the fixed pattern of stars at night is due to the rotation of the Earth. The apparent change in position of the constellations is due to the Earth’s orbit around the sun. Parallax is the apparent movement of close stars against the background of distant stars when viewed from different positions around the Earth’s orbit.

Question 56

What is a parsec

Answer 56

a unit of distance used in astronomy, equal to about 3.26 light years (3.086 × 1013 kilometres). One parsec corresponds to the distance at which the mean radius of the earth’s orbit subtends an angle of one second of arc. It is the distance to an object whose parallax angle is one arcsecond (1/3600 of a degree)

Question 57

What is the parallax effect astronomy

Answer 57

Definition: The apparent shift in the position of a nearby star against distant stars due to Earth’s movement around the Sun.
Key Concept: Measured from two points in Earth’s orbit (6 months apart).
Unit: 1 parsec = 3.26 light-years.
Limit: Effective for measuring distances to nearby stars (up to a few thousand light-years).

Question 58

How does the scale for absolute magnitude and apparent magnitude indicate a star’s brightness?

Answer 58

The lower or more negative the magnitude value, the brighter the star is. For both absolute and apparent magnitude, a difference of 1 magnitude equals a 2.512 times difference in brightness.

Question 59

How do astronomers know what elements are present in a star that is millions of kilometres away?

Answer 59

By analysing the spectrum of light emitted by the star and comparing it with known spectra on Earth.

Astronomers can determine what elements are present in a star by analysing the spectrum of light emitted by the star and comparing it with known spectra on Earth. When the spectrum of the light from a star is analysed, some dark lines are observed. These correspond to colours of light that have been absorbed by substances in the star. Different substances absorb different colours of light. By identifying the wavelengths of the colours missing from the spectrum, astronomers can find out which elements are present in the star.

Question 60

At what time would you use the AU, lightyear and parsec

Answer 60

Unit Typical Use Example Distances
AU Within our solar system Earth to Sun: 1 AU, Jupiter to Sun: 5.2 AU
Light-Year Distances to nearby stars and galaxies Alpha Centauri: 4.37 light-years
Parsec Used to measure the large distances to astronomical objects outside the Solar System Proxima Centauri: 1.3 parsecs, Milky Way diameter: 30 kpc

Question 61

according to the big bang theory, the universe is

Answer 61

getting cooler. According to the Big Bang theory, the universe is cooling. According to the big chill theory, the universe will end when the expansion of the universe continues and stars use up their fuel and burn out, causing planets to freeze. The universe would then consist of scattered particles that never meet again.

Question 62

How much is an astronomical unit?

Answer 62

the average distance between Earth and the Sun, 150 millon kilometers

Question 63

What is different between meteor and asteroid

Answer 63

An asteroid is a large rocky object orbiting the Sun, while a meteor is the bright streak of light caused by a meteoroid burning up as it enters Earth’s atmosphere.

Question 64

explain when galaxies begin to form

Answer 64

Galaxies began to form about 13.2 billion years ago, roughly 500 million years after the Big Bang, when gravity caused small, dense regions of dark matter and gas in the early universe to collapse and merge. These regions accumulated hydrogen and helium, forming the first stars, which grouped together into proto-galaxies. Over time, through collisions and mergers, these structures evolved into the diverse galaxies we see today.

Question 65

Explain the link between Einsteins famous equation e = MC^2 and the big bang theory

Answer 65

Einstein’s equation explains how energy in the Big Bang transformed into the matter that makes up the universe today, showing that mass and energy are interchangeable, which was critical for the formation of particles, atoms, and eventually galaxies.

Question 66

what evidence puts an end to the steady state theory

Answer 66

Cosmic Microwave Background Radiation (CMBR)
Hubble’s Law and Expanding Universe
Abundance of Light Elements

Question 67

What evidence supports big bang theory

Answer 67

The Big Bang theory is supported by:

The redshift (via the Doppler effect) showing galaxies are moving away.
Hubble’s Law, indicating the universe is expanding.
The abundance of light elements, which aligns with Big Bang predictions.
The Cosmic Microwave Background Radiation (CMBR), which is considered the “fossil” radiation from the early universe.

Question 68

What is dark matter

Answer 68

Dark matter is an invisible substance that makes up about 27% of the universe and is detected through its gravitational effects on visible matter, yet its exact composition remains unknown.

Question 69

what size as a x is black holes it greater than our sun

Answer 69

Black holes are formed when a star with a mass greater than approximately 20 times that of the Sun collapses under its own gravity after a supernova explosion. If the core’s mass is high enough, it continues to collapse into an infinitely dense point known as a singularity, surrounded by an event horizon, beyond which nothing, not even light, can escape. Black holes can range in size from a few times the mass of the Sun to millions or even billions of solar masses, typically found at the centers of galaxies.

Question 70

What do the black lines in a spectrum represent?

Answer 70

Spectral lines are specific wavelengths of light absorbed or emitted by atoms or molecules; the black lines in a spectrum represent absorption lines, where light is absorbed by elements in a gas or star’s atmosphere.

Question 71

what is a planetary nebula

Answer 71

A planetary nebula is a glowing shell of ionized gas that forms when a dying star sheds its outer layers.

Question 72

What is a neutron star

Answer 72

A neutron star is the dense, collapsed core of a massive star that remains after the star has undergone a supernova explosion.

Question 73

Q: How long does hydrogen fusion last in small to medium-sized stars?

Answer 73

A: Hydrogen fusion (main sequence) lasts about 10 billion years for a star like the Sun.

Question 74

Q: What happens after hydrogen fusion in small to medium stars?

Answer 74

A: The star fuses helium into carbon and oxygen during the red giant phase, lasting a few hundred million years.

Question 75

Q: Can small to medium stars fuse elements heavier than carbon and oxygen?

Answer 75

A: No, they lack the core temperature to fuse heavier elements. Fusion stops after carbon and oxygen.

Question 76

Q: What happens to small to medium stars after fusion ends?

Answer 76

A: They shed their outer layers, forming a planetary nebula, and leave behind a white dwarf composed of carbon and oxygen.