Unit 4: Space Exploration 11.1 Stars

The Birth of Stars A star is a massive sphere made up of dust and gases. Stars form from the dust and gases (mostly hydrogen gas) found in a nebula, when enough gravity causes all the molecules in the dust and gas to collapse together.

Fusion If enough matter gathers, the gravity becomes so massive that hydrogen atoms (making up hydrogen gas in nebula) join to form helium atoms.

Fusion When hydrogen atoms join to form helium atoms, this produces huge amounts of energy through the process of fusion. The energy given off by fusion causes stars to glow.

The Life of Stars The life cycle of a star depends on its mass. There are low, intermediate and high mass stars. Each of these three has a different life cycle.

Low Mass Stars Spend most of their lives as red dwarfs. Use up their hydrogen slowly. End their lives as small, dim white dwarf stars.

Intermediate Mass Stars Use up their hydrogen more quickly than low mass stars. When the hydrogen is used up, the core contracts and the stars become red giants. Next, they become small and dim white dwarfs. Eventually, they become even cooler and darker black dwarfs.

High Mass Stars 12 or more times more massive than the sun. Use up their hydrogen more quickly than intermediate stars. When nearing the end of life, the core collapses in a powerful explosion called a supernova. After going supernova, these stars become either black holes or neutron stars. hM&list=TLJ6EWeFWcEmM&index=7 hM&list=TLJ6EWeFWcEmM&index=7

High Mass Stars times more massive than sun End their lives as neutron stars. Neutron stars are superheated, super massive dead stars 25 times more massive than sun Become black holes instead of neutron stars. e.com/watch?v=Om gwkq8r9- Q&list=TLJ6EWeFWc EmM e.com/watch?v=Om gwkq8r9- Q&list=TLJ6EWeFWc EmM

The Hertzsprung-Russell Diagram The Hertzsprung-Russell diagram was developed to show the different stages of a star’s life. This diagram shows the relationship between a star’s luminosity, or brightness, and its temperature. Luminosity is the amount of energy it releases.

Star Color The colour of a star reveals its temperature and composition to astronomers. Red stars = cool = 3000 ºC Yellow stars = hot = 6000 ºC Blue stars = hottest = ºC ºC

Star Color Using a spectroscope, the light emitting from a star reveals spectral bands that show certain gases in the star.

Star Movement Along with indicating which gasses are present in a star, spectral lines are used to identify the movement of a star (by analyzing red-shift). Red-shift is an example of the Doppler effect.

The Doppler Effect The Doppler effect refers to the way waves either compress (become shorter) as their source gets closer, or lengthen as their source gets farther away.

References Crab Nebula (Image 1): Formation of a star (Image 2): g g Fusion (Image 3 and 4): 53abfe40b6e01f22c4b5d69e37ebbf916719cbe363c7af25/star- nueclear-fusion.jpg 53abfe40b6e01f22c4b5d69e37ebbf916719cbe363c7af25/star- nueclear-fusion.jpg BC Science 9 (Images 5-9, 10): Red shift (Image 8): dshift_blueshift.svg/2000px-Redshift_blueshift.svg.png