Earth and Space Science Midterm '26

What is a galaxy?

A collection of billions of stars, held together by gravity.

Definition of Solar System

A star and the system of celestial objects that go around it.

What is the theory of how the Universe began

Big Bang Theory

When did the Big Bang occur?

13.8 billion years ago

Proof of the Big Bang?

Red shift in most galaxies, background radiation, similar spectral lines in all stars, composition of matter in the Universe. (further explanation coming)

What instrument is used to see spectral lines?

Spectroscope

What are spectral lines?

A pattern of lines that are given off by certain elements. Each element gives off a different pattern.

Star composition supports the Big Bang Theory because they are all made of

Hydrogen (so they were created from the same event).

Which elements are in the sample?

B and C

What is the Doppler effect?

sound or light waves get smaller as they come toward you and bigger as they move away from you.

Red shift is when something (like a star or galaxy) is moving ___ and wavelengths are ___

moving away from us (Earth), wavelengths are longer

Blue shift is when something (like a star or galaxy) is moving ___ and wavelengths appear ___

moving toward Earth, and wavelengths appear shorter.

Most stars we view are ___ shifted

RED, which shows that the universe is expanding because most stars and galaxies are moving away.

In spectral lines, the farther to the red side the lines are, the farther the star is. (This is not a question)

What is cosmic expansion?

Galaxies are moving away from each other as space time expands.

Hubble Constant

Galaxies are moving away from each other and the farthest ones appear to be moving the fastest.

Dark Energy

The mysterious force pulling the universe apart.

Dark Matter

The unseen matter around galaxies that gives them their shapes.

Is there more of Dark energy or dark matter in the universe?

Dark ENERGY

What percent of the Universe is visible?

5%

What percent of the universe is dark matter?

27%

What percent of the universe is dark energy?

68%

Which elements were made during Big Bang Nucleosynthesis?

Hydrogen, Helium, Deuterium

What is Nucleosynthesis?

the formation of atomic nuclei; how elements are made

Nucleosynthesis occurs (mainly) when

lighter elements combine (fusion) or heavier elements break apart (fission and radioactive decay)

**We haven’t discussed this so don’t worry about it too much, I included it just because it is in the notes.

What percent of all of the elements in the universe does helium make up?

25%

The amount of helium proves Big Bang theory how?

Though helium is made in stars during nuclear fusion, it makes up too much of the universe for it to only be from stars. This means that the rest of the helium was created during the Big Bang.

Epoch of Recombination

Period of time where elements formed during cooler temperatures - elements had to wait for the universe to cool from the Big Bang in order to form.

Cosmic Microwave Background Radiation

Leftover radiation from the Big Bang

What is it called when stars make elements?

Stellarnucleosynthesis

Theory of Special Relativity (by Einstein)

E=mc² [ Energy = mass x speed of light (constant)² ] - (basically) states that energy can become matter (such as during the Big Bang) and matter can become energy (such as during nuclear fusion).

Nuclear fusion

The process that makes energy in stars - 2 lighter elements FUSE to form a larger, heavier element. ex: 2 hydrogens fuse to make 1 helium in a proton-proton chain reaction.

Where does nuclear fusion occur and under what conditions?

Core of a star, high temperature and high pressure

Larger stars can fuse

heavier elements (than smaller stars)

Elements heavier than Iron are formed through

Supernovas (explosion of supergiant star)

Hottest stars are what color?

Blue

Coolest stars are what color?

Red

All stars begin as a

Nebula (cloud of gas and dust)

Protostars become stars when they

get hot enough and begin nuclear fusion.

90% of stars are what type?

Main sequence (sun-like)

Stars stay in the main sequence for?

10 billion years

Life cycle of small - medium sized stars

1. Nebula

2. Protostar

3. Main Sequence

4. Red Giant

5. Planetary Nebula

6. White Dwarf

The sun is not liquid, solid, or gas; it is

plasma

Energy is carried to the sun’s surface through

convection currents

The sun rotates faster at its

equator

Supergiant stars die in a

Supernova explosion, and leave behind a neutron star (8-40 solar masses) or a black hole (+40 solar masses)

Sunspots

cooler magnetic storms - birthplace of solar flares and cme’s

Coronal Mass Ejections

eruptions of plasma sent into space off of the sun - *cause space weather, which disrupts satellite function and creates auroras.

Solar maximum

times of increased sunspot activity

Insolation =

sunlight

What types of surfaces absorb heat

dark and rough

What types of surfaces reflect heat

white and smooth

Steps in the formation of the solar system

1. Molecular cloud

2. Solar nebula

3. Nuclear fusion

4. Accretion

Molecular cloud

shockwaves from a supernova hit the cloud of dust and elements and collapses due to gravity. Once it flattens and spins it becomes a Solar Nebula.

Solar nebula

spinning disk of gas (hydrogen and helium) that becomes a star once it begins fusion (next step)

Accretion

when cooler, outer areas of rock fuse together to form planets

When did the solar system form

4.6 billion years ago

How did the moon form?

A collision with a Mars-sized object

When did the moon form

during Late Heavy Bombardment (4 billion years ago)

What dwarf planet is the largest

Eris

Formula for eccentricity

distance between foci divided by length of major axis = a # between 0-1**

What rate do things move across the sky?

15 degrees / hour

Why do things “move” across the sky (Apparent motion)?

Earth’s rotation from West to East

Anything that orbits something else in Space is considered a

Satellite

An object being orbited (like the sun) is called the

Primary/Central body

Which forces keep an object in motion?

Gravity and inertia

Kepler’s 1st law

Law of Orbits - States that planets orbit the sun on elliptical paths with the sun on one or focus points.

Kepler’s 2nd Law

Law of areas - States that the planet will cover the same area in space in the same time frame as other areas in its orbit.

Basically, area when faster and closer to the sun = area when slower and farther from the sun, during the same amount of time

Kepler’s 3rd Law

Law of Periods - states that the farther a planet is from the sun, the longer its period of Revolution

Law of Universal Gravitation

Anything with mass attracts anything else with mass - Isaac Newton

What 2 factors affect gravity

mass and distance

Earth’s tilt

23 ½ degrees

Parallelism of Earth’s axis

Earth stays tilted the same way throughout its whole revolution.

Rocky Terrestrial Planets

Mercury, Venus, Earth, Mars.

Gas Giants

Jupiter, Saturn

Ice Giants,

Uranus, Neptune

Which planet is the least dense?

Saturn

Convection currents occur in the

Asthenosphere

Which layer of the Earth is fully liquid

Outer core

The core of the Earth is made of

iron and nickel

Everything in our sky (apparently) moves

East → West

The Sun is directly over the equator on the

Equinoxes (3/21, 6/21)

The sun is directly over 23 ½ degrees North on

6/21 (summer solstice)

The sun is directly over 23 ½ degrees South on

12/21 (winter solstice)

How many days does it take for the moon to go around the Earth

27.3

How many days does it take for the moon to go from new moon to new moon

29.5 - because the Earth is also moving around the sun so the moon has to travel just slightly farther to get back between the sun and earth.

Annular solar eclipse

the moon is farther from the sun and does not cover all of it - leaves a ring of light around it

Umbra

inner, darkest part of a shadow

Penumbra

an outer, lighter, partial shadow

Why don’t we always have lunar/solar eclipses when the moon gets to the full/new moon phases?

The moon’s orbit is inclined, so it doesn’t always line up that way.

How much is the moon’s orbit inclined

5 degrees

Spring tides

highest high tides and lowest low tides, happen when sun, moon, and earth line up (syzygy)

High tides occur where?

On the side of Earth that the moon is on and the opposite side.

Neap tides

regular high tides that happen when the sun, moon, and earth form a 90 degree angle (moon at its quarter phases)

ceres and Pallas are located

in the asteroid belt

dwarf planets in our solar system

ceres, Pluto, and eris

differentiation

when the earth’s layers were separated - dense materials sank (iron and nickel)

Earth was dated to be 4.6 billion years old by

Radioactive dating of rocks