#8 Stars and The Milky Way Galaxy

As a Review: What is a Solar System? - Solar means Sun! So our solar system is made up of the sun, the 8 planets, and everything else that travels around the sun. The sun is the only star in our SOLAR system, but one of billions in our galaxy

Groups of Stars = A Galaxy What is the name of our galaxy? What is the name of our galaxy? Milky Way Galaxy What type of galaxy are we in? What type of galaxy are we in? A spiral galaxy? What are the other two types? What are the other two types? Elliptical and Irregular

Spiral galaxy Elliptical Galaxy Irregular Galaxy

Are we at the center of the Milky Way Galaxy? Sorry, um, NO! Let’s draw a picture

How do we measure stars? Hotness by color Blue → Yellow →Red (least hot) Brightness by Magnitude 1 = brightest (1st place winner=brightest!) 9 = less bright (9th place not as bright as 1st)

What kind of star is ours? The sun is a main sequence star The sun is a main sequence star Average temperature (Yellow star) Average temperature (Yellow star) Average size (medium sized) Average size (medium sized) Neutron stars are size of a city Neutron stars are size of a city Dwarf star size of Earth Dwarf star size of Earth Super giant stars 100x sun Super giant stars 100x sun

Billions of stars out there..... The universe has billions and billions of stars (and countless numbers of galaxies) The universe has billions and billions of stars (and countless numbers of galaxies) In between each star is gas and dust In between each star is gas and dust Gas is mostly H (Hydrogen) and He (Helium) Gas is mostly H (Hydrogen) and He (Helium) Dust & gas clump together in huge interstellar clouds called Nebula. Dust & gas clump together in huge interstellar clouds called Nebula.

VERY far away picture of our Universe with billions and billions of stars Power of 10

Star clouds = Nebulas HUGE (takes light 100’s of years to cross) HUGE (takes light 100’s of years to cross) Gravity pulls matter in the nebula together Gravity pulls matter in the nebula together Pressure from collisions pushes it back apart Pressure from collisions pushes it back apart All balanced until All balanced until A nearby star explosion upsets the balance

Nebula NGC 60 - inside the Triangulum Galaxy -estimated distance 2.4 million light- years away

The "Pillars of Creation" from the Eagle Nebula

The Eagle Nebula in its entirety.

Nebulas collapse..... Gravity causes the nebula to collapse inward - causing more gravity!!! Gravity causes the nebula to collapse inward - causing more gravity!!! (Remember, closer together = stronger gravity!) Begins to rotate and flatten into a disk shape Begins to rotate and flatten into a disk shape Bits of dust stick together when they collide to form planetesimals (tiny pre-planets) Bits of dust stick together when they collide to form planetesimals (tiny pre-planets) These collide, stick together & form planets These collide, stick together & form planets

Nebula gas cloud starts to collapse due to gravity Nebula begins to rotate Flattens into disk shape Planetesimals appear Planets begin to form Our solar system

Planets form.... Inner planets -formed from dense pieces, strongly pulled (due to their mass) by gravity towards the new star center (called a protostar = baby star) Inner planets -formed from dense pieces, strongly pulled (due to their mass) by gravity towards the new star center (called a protostar = baby star) gas giants gas giants -collected large amounts of gas (H & He) & smaller bits of dust in the cooler, outer areas of the spinning nebula -far enough from sun to also collect ice -collected large amounts of gas (H & He) & smaller bits of dust in the cooler, outer areas of the spinning nebula -far enough from sun to also collect ice

Meanwhile Center of the nebula Center of the nebula Gas is super compact and hot 10,000,000 ºC Gas is super compact and hot 10,000,000 ºC H begins to fuse together to form He **called nuclear (or H) fusion H begins to fuse together to form He **called nuclear (or H) fusion ** is the energy of the sun Very Hotty Burny in here! Very Hotty Burny in here!

From birth to death..... All stars burn out (run out of H fuel) All stars burn out (run out of H fuel) A supergiant (100x sun) can explode before it dies. Then it is called a supernova. A supergiant (100x sun) can explode before it dies. Then it is called a supernova. A supernova will become one of two things. - a neutron star or a blackhole. A supernova will become one of two things. - a neutron star or a blackhole. Our Sun will become a red giant. - about 3 billion years from now Our Sun will become a red giant. - about 3 billion years from now

Supernova – Huge star explosiony death