Space Science Part 2: The Universe

Space Science Part 2: Stars & Galaxies

​Lesson Objectives

• Describe the relationship between star temperature and brightness

  • Interpret an H-R Diagram

• Describe how a star changes over time

• Distinguish between types of Galaxies

• Describe the Events of the Big Bang

The Night Sky

• Watching the stars was easier before modern cities

  • Lights and pollution make it hard to see​

• Throughout History, people built structures to help follow the movement of the sun and the moon

  • Stonehenge in England

• Every star generates its owns light which is reflected through the atmosphere

  • Stars seen outside of the atmosphere don't "twinkle" the way they do on Earth​

Measuring distance in space

• Unit of astronomical distance is the light-year (ly)

  • The distance light travels in one year

  • 9.5 × 10¹² km​

Origin of Stars

• Stars come from nebulae, swirling clouds of hydrogen

  • Nebulae have very little mass and don't exert much gravity

• As atoms in the nebula move, they are slowly brought closer and closer together and form a protostar

  • Still smaller than a star,

• Protostars tend to shrink and pull matter closer together, raising the pressure and temperature to the point that eventually nuclear reactions take place, making it a full-grown star

  • Radiation forces cause the star to expand, and gravity causes the star to contract​

Hertzsprung-Russell Diagrams

• There are patterns between the luminosity and temperature of stars

• Two Astronomers, Ejnar Hertzsprung and Henry Noris Russel, mapped out this relationship in a chart called a Hertzsprung-Russell Diagram

  • Divides stars into distinct regions

  • Shows that the hotter stars are, the brighter they tend to burn

    • Blue stars burn hotter because they have more energy

Multiple Choice

In the H-R diagram, what happens as we move to the left?

• Stars Get Larger
• Stars get Colder
• Stars get hotter

Multiple Choice

Use the Hertzsprung-Russell Diagram to answer the following question.  Betelgeuse is a _____

• Hot and Bright Star
• Cool and Bright Star
• Hot and Dim Star
• Cool and Dim Star

Multiple Choice

Analyze the HR Diagram. Which group of stars is considered to have lower than average luminosity as well as a higher than average temperature?

• Giants
• Main Sequence
• White Dwarfs
• Super Giants

Multiple Choice

On the H-R diagram, the Sun is a _____.

• Main Sequence star
• Red Giant
• White Dwarf
• Blue Giant

Evolution and Death of Stars

• All Stars "burn" nuclear fuel

  • When that fire burns out, the star dies

• Stars go through several stages before their death that depend on the mass of the star

Medium Sized Star Death

• In Medium-sized stars, As helium contracts, the core heats up and expands to become a Red Giant​

  • Our sun will do this in about 5 billion years

Smaller Sized Star Death

• In Smaller-sized stars, the masses are not hot enough to fuse carbon, so they shrink

• While shrinking, they lose particles and leave behind the core, which is called a White Dwarf

  • will eventually burn out and change into a stellar remnant and change colors from white to yellow to red to black

Binary Stars

• Binary Stars: Some white dwarf stars "pair up" and exert a pull on each other

  • One star may pull hydrogen from the other and ignite fusion

    • Nova: the thermonuclear explosion of a star

Supernovae

• Larger stars don't go through the different dwarf stages

  • As larger stars contract, heat is generated, allowing carbon nuclei to fuse in the core and release heavier elements until iron is formed

    • Contraction pauses until all carbon is fused, then continues

• Fusing elements beyond iron requires more energy than the star can release, causing the star to collapse into a Black hole

  • Gravity in a black hole is so strong that nothing can escape it

Multiple Choice

What determines if a star becomes a white dwarf, neutron star, or black whole?

• Size

• Shape

• Types of Elements in the star

• The age of the star

Multiple Choice

Gases in a nebula come together to form what?

• red dwarfs

• protostars

• black holes

• white dwarfs

Multiple Choice

Smaller stars turn in to these as they age

• nova

• supernova

• black holes

• white dwarfs

Galaxies

• A Galaxy is a large group of stars, planetary nebulae, and interstellar gas/dust held together by gravity

  • We exist in the Milky Way Galaxy​

    • In good conditions, we can see the outline of the Milky Way with our eyes

• Galaxies come in three main shapes

Elliptical Galaxies

• The most Common type of galaxy in the universe

  • Sphere shaped, with most stars crowded towards the center​

  • Contain little gas or dust

  • Are see through, and usually yellow

    • primarily older stars

  • Smaller than other types of Galaxies

Spiral Galaxies

• Have different arrangements of stars

  • Have some sort of hub with in them

  • Most have a black hole in the center​

Irregular Galaxies

• Irregular Galaxies have no clear shape

• As galaxies move in space, they may collide with each other and distort each other into unusual shapes

The Big Bang

• Until the 1920's, scientists thought the Milky way the entire Universe

• 1924: Edwin Hubble used a powerful telescope to see the Andromeda galaxy

• 1931: Fr. Georges Lemaitre proposed the Big Bang theory

  • At one point, the universe exploded into being and began to grow, and it continues to do so

    • A cosmic egg

  • His idea was originally rejected as being too extreme, but was proven correct and accepted

Understanding The Big Bang

• A major implication of the Big Bang is that the universe continues to expand

  • Space itself moves farther apart

    • Example: Think of a collection of ants on a balloon. As the balloon expands, the ants move farther apart, each compared to others

• Hubble's Law: A relationship between the distance of galaxies and the speed they appear to move from Earth

  • The farther away a galaxy is, the faster it appears to move

Multiple Choice

What is the name of the gas/dust clouds where all stars form?

• Nebulas
• Protostars 
• Supernova
• Neutron Star

Multiple Choice

What type of galaxy is this?

• Spiral
• Elliptical
• Irregular 
• Irrational

Multiple Choice

The life cycles of stars are determined by their:

• mass (size)
• color
• distance from Earth
• luminosity

Multiple Choice

What type of galaxy is this?

• Spiral
• Elliptical
• Irregular
• Irrational

Multiple Choice

What is the name of the explosion at the death of a massive star?

• Supergiant
• Supernova
• Black Hole
• Nebula

Multiple Choice

What type of galaxy is this?

• Spiral
• Elliptical
• Irregular
• Irrational

Multiple Choice

What does the Big Bang theory suggest?

• The universe is just there

• The Milky Way is the only solar system
• The universe is continually expanding
• The universe is collapsing in toward a single point