Unit 1: Space Section 2- Stars
Stars Recall: stars are celestial bodies of hot gas that give off heat and light
Stars The milky way contains hundreds of billions of stars and is only one of hundreds of billions of galaxies
Stars The milky way contains hundreds of billions of stars and is only one of hundreds of billions of galaxies Where do all of these stars come from?
Nebula Stars a cloud of dust and gases in outer space where stars are born (sometimes called Stellar Nurseries )
Stars Forming stars Gravity pulls some of the gas and dust in a nebula together The contracting cloud is called a protostar As the cloud becomes denser, pressure and heat build Continues until it is hot enough for nuclear fusion to begin This is when the protostar becomes a star
Lifecycle of Stars When a protostar begins nuclear fusion it is called a main sequence star This is the main point in the life cycle of the star The mass of the star will determine the rest of its life cycle
Low mass stars Lifecycle of Stars Small dim stars that burn for longest time period (100 bil.yrs)
Low mass stars Lifecycle of Stars Small dim stars that burn for longest time period (100 bil.yrs) Intermediate mass stars Similar mass as the Sun Burns faster (lasts about 10 billion yrs)
Low mass stars Lifecycle of Stars Small dim stars that burn for longest time period (100 bil.yrs) Intermediate mass stars Similar mass as the Sun Burns faster (lasts about 10 billion yrs) High mass stars 12 or more times more massive than the Sun Burn fastest, shortest life (about 7 billion yrs)
Lifecycle of Stars
Lifecycle of Stars Why?
Lifecycle of Stars Why? Burns hotter Fuses elements more quickly Uses up all material more quickly
Lifecycle of Stars How does the stars life end?
Lifecycle of Stars Low mass stars become small, dim white dwarfs and burn out quietly
Lifecycle of Stars Intermediate mass stars expand into Red giants Eventually collapses in on itself Outer layers expand in ring of gas called a Planetary Nebula core becomes a white dwarf
Lifecycle of Stars High mass stars expand into Red supergiants Eventually collapses in on itself Cause massive explosion called Supernova Core becomes a neutron star or black hole
Evolution of Stars
Black hole: a large sphere of tightly packed material with an extraordinary amount of gravitational pull created when a high mass star collapses into itself called black because nothing, not even light, can escape the powerful gravitational field
Neutron star: a very small, very dense celestial object form by the gravitational collapse of a massive star after a supernova explosion
Star life cycle foldable
Quasars Quasars: Regions of extremely intense energy that can surround a supermassive black hole in the center of a galaxy brightest objects we know in the universe
Movement of stars In the northern hemisphere stars appear to rotate counter clockwise around the north pole the north star Polaris lies almost exactly over the north pole
Movement of stars This means that stars appear to rise in the east and set in the west Skecth: Polaris West East
Movement of stars as the earth moves around the sun in a given year, we face different parts of the sky at night and the stars that are visible to us change
Movement of stars At different places on earth, especially the N & S hemispheres, stars appear differently
Movement of stars the apparent motion of the stars and the sun is really due to Earth s rotation and revolution and not due to the movement of the stars themselves
Movement of stars Constellations: groups of stars that can be viewed to create a pattern or image Constellations are often used to locate other objects in the night sky This is Ursa Major or Big Bear
Movement of stars Asterisms: smaller groups of stars found within a constellation The Big Dipper is an asterism within the constellation Ursa Major or Big Bear
Movement of stars Asterisms: smaller groups of stars found within a constellation The Big Dipper is an asterism within the constellation Ursa Major or Big Bear
The Sun The sun is the closest star to us and is the centre of our solar system As discussed, it is an intermediate mass star
The Sun- Facts Millions of km from earth 300,000 times more massive than Earth Estimated to be 5 billions yrs old and have 5 bil yrs remaining
The Sun- Facts The Sun is the main source of energy on Earth The energy comes from thermonuclear reactions in the Sun s core Thermonuclear reaction: atoms combine creating a different, larger atom releases a lot of energy (heat, light and other radiation)
The Sun- Facts Solar radiation: Energy emitted from the sun in the form of electromagnetic radiation Comes from the thermonuclear reaction converting hydrogen to helium
The Sun-Characteristics (p.392) Sun spots: darker patches on the surface of the sun that indicate cooler areas Solar prominences: large loops of super-hot gas that extend out from the Sun s surface
The Sun-Characteristics (p.392) Solar flares: Occasional, extremely violent eruptions of gas ejecting material from the sun s surface out into space Create solar winds
The Sun Solar winds: hot gases around the Sun get ejected in a sudden burst high-energy particles rush past Earth, they create an effect called solar wind Earth s magnetic field deflects most of the solar wind around the planet
The Sun Solar winds: at the N & S Poles, some charged particles from the sun collide with gases in the atmosphere and create light shows in the sky (Auroras) Solar storms can also Cause power outages Disable satellites &GPS systems Expose astronauts to high levels of radiation
The Sun
Stars
Stars Lifecycle of stars video (Institute of Physics) Crash course Stars Asteroids