Studying Space

Space Science Part 3: The Universe

By Abby Fancsali

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​

Fill in the Blanks

The nearest star to the Earth beyond the sun is proxima centauri, located 4.2 light years away. Express this distance in Kilometers

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 stars 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, gravity causes the star to contract​

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

  • Stages depend on the mass of the star

    • 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

Evolution and Death of Stars

• Stars go through several stages before their death

  • Stages depend on the mass of the star

    • Smaller sized stars: 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

Evolution and Death of Stars

• Stars go through several stages before their death

  • Stages depend on the mass of the star

    • 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 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 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

  • spiral

  • irregular​

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

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

Irregular Galaxies

• 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 proposes the Big Bang theory

    • says that at there was one point where 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