Astronomy Checklist

Question 1

Describe the main features and characteristics of galaxies, stars, planets, nebulae and solar systems

Answer 1

Galaxy: A collection of stars, interstellar dust, dark matter, gas, etc, spanning solar systems
Star: A giant luminous ball of gas, mainly hydrogen and helium, held together by its own gravity
Planet:
1. Orbits the Sun
2. Hydrostatic Equilibrium (a nearly round shape)
3. Cleared the neighbourhood
Nebula: Cloud of gas and dust; birthplace of stars
Solar System: A gravitationally bound system of a central star and the objects that orbit it

Question 2

Identify whether light years are a unit of distance or time

Answer 2

Light years are a unit of distance

Question 3

Explain how stellar parallax is used to calculate distance between Earth and stars

Answer 3

Use 2 points of the Earth’s orbit to form a triangle and apply the formula: d = 1/p

Question 4

Outline the importance of the invention of the telescope in investigating the universe

Answer 4

The invention of the telescope enabled humanity to view distances of up to 100 light years

Question 5

Explain the difference between emission and absorption spectra

Answer 5

The difference between an emission and an absorption spectra is that one depicts the emission of elements while the other depicts the absorption

Question 6

Explain redshift and how it can be used to measure the movement of galaxies

Answer 6

Red shift is a shift towards the ‘red’ in a spectrum, indicating a lower frequency and that the galaxy is moving away

Question 7

Briefly explain the main events of the Big Bang

Answer 7

1. The universe began from a singular point containing large amounts of energy
2. Space and time are created from the big bang
3. The energy was converted into matter - atomic nuclei and clusters of protons and neutrons
4. Within 400 00 years, the universe began to cool until the point where it was possible for electrons to combine with the atomic nuclei to form neutral atoms
5. Electromagnetic radiation and CMBR entropied throughout the universe.
6. The universe was cool enough for gravity to clump matter and form celestial bodies

Question 8

Describe the role of gravity in the formation of the universe

Answer 8

Gravity clumped matter and formed celestial bodies

Question 9

List and briefly explain some of the evidence that supports the Big Bang Theory

Answer 9

CMBR, red shifts of faraway galaxies, radio sources all provide evidence that support the Big Bang Theory. CMBR is the remnant radiation from the early stages of the Universe, the red shifts show that galaxies are moving away at faster velocities, and radio sources show that the Universe changed and adapted

Question 10

Use the Hertzsprung-Russell diagram to describe the life cycle of a star

Answer 10

Nebula –> Protostar –> Main Sequence Star
–> Brown Dwarf (not a star)

Main Sequence Star –> Red Giant
–> Red Super/Hyper Giant

Red Giant –> Planetary Nebula
Red Super/Hyper Giant –> Supernova

Planetary Nebula –> White Dwarf
–> Gas and Dust

Supernova –> Black Hole
–> Neutron Star
–> Gas and Dust

The star goes from the main sequence to a giant (increase in luminosity)

Then the star deflates into a white dwarf

Question 11

Explain how Hubble determined the age of the universe

Answer 11

By precisely determining the expansion rate, called the Hubble constant, the cosmic clock can be rewound and the age of the universe calculated