Warm Up/Do Now: 1) When was the universe created Warm Up/Do Now: 1) When was the universe created? 2) How does heat (energy) travel from the sun to the Earth? 3) What do plants do with the energy from the sun?

Star Formation and Life Cycle

What Are Stars? Star - large ball of gases producing heat, light and radiation by the process of nuclear fusion Stars produce energy as long as they have hydrogen Nuclear Fusion -produces energy by fusing (combining) 2 hydrogen atoms to form helium Nuclear fusion is the energy source in the sun and nuclear bombs Stars do it naturally, humans attempt to create a similar effect unnaturally

Atomic Bomb (Nagasaki-1945)

Properties of Stars (how they are classified): Size Determined by using binary star systems The relative sizes of the individual stars can be determined by observing how quickly the brightness changes as the disc of the near star slides over the disc of the distant star

Properties of Stars continued… Temperature- measured in Kelvins, not degrees like Celsius or Fahrenheit Color- related to temperature HOTCOOL Blue-white-yellow-orange-red Very hot stars emit lots of energy in short wavelengths and thus appear blue Stars with temperatures between 5,000 and 6000 K appear yellow, like our sun

Electromagnetic Spectrum

Very hot white dwarfs are the faintest seen in the picture below

Stellar Evolution Star Birth: Stars form in dark, cool clouds called interstellar clouds or nebulae (nebula) Something happens to make these clouds contract and spin (perhaps a shock wave from an explosion of a nearby star) Gravity pulls all of the pieces close to the center and squeezes them creating immense pressure. This contraction could last over a million years.

Interstellar cloud

Interstellar Cloud

Protostar stage (in the womb): Protostar- a collapsing cloud of gas and dust destined to become a star—a developing star not yet hot enough to engage in nuclear fusion The temperature of this gaseous body continues to rise until it starts emitting red light, like the burner of the stove.

Stars that are red have the lowest surface temperature and the longest wavelength. The inside of the protostar continues to increase in temperature - When it reaches about 10 million K (or 17999540.33 degrees Fahrenheit), pressure within is so great that nuclear fusion of hydrogen begins, and a star is born!

Nebula, Birthplace of Stars Makes no sense without caption in book

Main-Sequence Stage (growing up): ***Stars spend 90% of their lives in this stage*** Stars have an enormous amount of pressure inside of them that pushes them outward. Gravity holds this pressure back and keeps the star together. It is this struggle between pressure and gravity that forms a main sequence star.

Different stars age at different rates. Large, hot stars produce a large amount of short wavelength, high energy blue light. These stars burn up their fuel very quickly and burn out within a few million years. A yellow star like our Sun, burns its fuel much slower and lasts about 10 billion years - Small, red stars that burn slowly and produce long wavelength, low energy red light can last for hundreds of billions of years

Red-Giant Stage: As a star gets older, the star grow 100’s or 1000’s of times its normal size. Eventually, the giant uses all of its hydrogen and helium fuel and shrinks under the force of gravity.

Burnout and Death: There are many ways that a star can die. The way in which this happens depends on the size of the star. All stars, regardless of size, eventually run out of fuel and collapse!

Our Sun’s Life Cycle 1. Protostar 2. Main-Sequence Star 3. Red Giant Initially, a cloud of dust and gas (nebula) must exist then: 1. Protostar 2. Main-Sequence Star 3. Red Giant 4. Planetary Nebula 5. White dwarf Eventually, heat and light will no longer be present and it can be termed a black dwarf

Stellar Evolution- page 710 Makes no sense without caption in book

Supernova Explosion Simulation

Classwork 1)Grab a textbook and read page 710 and page 711 (Death of low-mass stars, death of medium stars, and death of massive stars) 2) Create a foldable for the life cycle of each size star (use the chart on page 710) Use pictures and label each stage (birth to death) for all 3 star sizes.