Main Sequence Stars

• all stars fuse hydrogen into helium

• 90% of all stars, including our Sun, are main sequence stars

• range from high luminosity (brightness) and high surface temperature to low luminosity and low surface temperature

Hertzsprung-Russell Diagram

Classifies stars based on their absolute magnitude and surface temperature.

Absolute magnitude is how bright a star would be if all of the stars were the same distance from Earth.

Surface temperature is related to a star’s color.

Nebulae

• A nebula is a cloud of dust, hydrogen gas and plasma.

• The material clumps together to form larger masses that eventually are big enough to form a protostar.

• This is the first stage in the star life cycle.

• Nebulae often create star-forming regions, such as the Eagle Nebula.

Eagle Nebula – Pillars of Creation

Cat’s Eye Nebula

Ant Nebula

Crab Nebula

Protostar

Brown Dwarf• have a size between that of a giant planet like

Jupiter and that of a small star• any object 15 to 75 times the mass of Jupiter • the object would not have been able to sustain

fusion like a regular star - called "failed stars"• all are parts of a binary system. (two stars orbit

around one another)• possible that brown dwarfs represent a lot of the

mass in the universe

Main Sequence Star (our sun)

Red Giant

• When a middle aged star begins to die, the temperature near the core rises.

• The star expands.• This will happen to

our sun in about 5 billion years.

• Once the red giant runs out of energy, it collapses and becomes a white dwarf, a small and dense star.

• A white dwarf is the core of the original star. It is very hot and cools down over the next billion years.

White Dwarf

- star near the end of its life

- was a red giant star that lost its outer atmosphere

White Dwarves photo taken by the Hubble Space Telescope

BPM 37093 is a huge white dwarf star nicknamed Lucy

• 50 light years from Earth in the constellation Centaurus

• 2500 miles across

• weighs 2.27 thousand trillion trillion tonnes

BPM 37093 = Lucy

•the diamond core is 50% to 90% of its mass (size of our moon!)

• equal to 10 billion trillion trillion carats, which is 1 with 34 zeroes (1 carat = 200 mg)

• will happen to our sun in 7 billion years.

BPM 37093 = Lucy

Named Lucy after The Beatles’ hitLucy in the Sky with Diamonds

Black Dwarf – a white dwarf that has cooled, lost its energy and no longer gives off light. It is a black object in space.

Giant Stars are more luminous than our sun and are 10 to 100 times larger in diameter than our sun.

Supergiant Stars are more luminous than giant stars and more than 100 times the diameter of our sun. They are

relatively cool stars.Betelgeuse is a supergiant star.

Supernova – collapse of the core of a red giant star produces a shock wave that blasts the star’s outer layers into space

Remains from a supernova

Neutron Star – the core left behind after a star’s supernova explosion

Pulsar – a neutron star that spins very fast and emits burst of radio waves

What if the star was SUPER MASSIVE?

• Disclaimer: The following was put together by Mrs. Donahue. Upon discussion, both myself and her head began to hurt. In lieu of our brains exploding, we decided that we will both never fully understand what you are about to observe.

• Here goes nothing….

• Einstein’s mathematical formulas predicted the existence of very dense invisible stars but he did not believe they actually existed. He was wrong!

• As a giant star collapses, its core plunges inward and temperatures reach 100 billion degrees.

• Hunks of iron bigger than Mount Everest are compacted to the size of grains of sand.

• Atoms are shattered into electrons, protons, neutrons and these are pulped into quarks, leptons, and gluons.

• Tinier and tinier, denser and denser…………………………

• Most massive stars become black holes when they die.

• The dividing line between inside and outside a black hole is called the event horizon.

• Quasars are galaxies with black holes at their center. The Milky Way Galaxy has a black hole at its center named Sagittarius A*.

Black Hole

Here is a picture of a black hole.

Black Hole

• To escape Earth’s gravity you need to accelerate at 7 miles per second (12 times faster than a bullet). We have been able to do this with rockets since 1959.

• The gravity of a black hole is so strong that even light can’t escape. The speed of light (186,282 miles per second) is too low!

Time is affected by gravity.• Extremely accurate clocks

placed on the lowest and highest levels of the Empire State Building tick at different rates.

• Clocks on GPS satellites have to be set to tick slightly slower than those on Earth’s surface to make GPS accurate.

• One minute on the Sgr A* event horizon is 1000 years on Earth.

• Therefore, black holes are time machines.

What happens if you cross the event horizon into a black hole?a) You burn up in the fire wall.

b) Nothing. You pass through. You’re fine.

c) Then you get “spaghettified.” a) As you fall, gravity gets stronger so the pull

on your feet is greater than the tug on your head and you get stretched until you are ripped apart.

b) The pieces that reach the bottom encounter a singularity. ???????????????????????

New Thoughts• We are in a multiverse – a collection of

universes, each of which is a separate bubble of reality.

• The Big Bang that created our universe was the result of a singularity “opening.”

• March 10 on the National Geographic channel, series premiere of Cosmos: A Space Time Odyssey.