STARS

BY SEYMOUR SIMON

Stars are huge balls of hot gases

• Our sun is a star, and it is the star nearest our planets Earth and our solar system

• Other stars are so far away we barely see them, they are just pinpoints of light to us

• Stars have names and groups of stars are called constellations

• Many stars are named for gods, heroes, or animals

• Some examples include Orion, Alpha Centauri, all of which are in a large body of stars called the Milky Way

Light Years

• The distance between the stars is so large that scientists measure it as light years instead of miles

• Light travels at a speed of about 186,000 miles per second, so a light year is the distance that light travels in one year: a bit less than 6 trillion miles

• On a clear night you can see about 2000 stars without a telescope

Galileo invented the telescope

• When Galileo looked up into the sky he saw many 1000’s of stars never seen before

• When you look at a photograph of the Milky Way, you see a cloud like area

• The cloud is really millions of stars – like grains of sand on a beach

Nebulas

• Stars are made from giant clouds of gas of hydrogen and helium and dust called Nebulas

• Over millions of years, gravity pulls the gas and dust together and they heat up

• When the gases get hot enough, they explode and the star is born

• When stars get older they are usually blueish in color

• Older stars are yellow and are 10,000 degrees hot

Old stars

• When stars get really old they run out of hydrogen fuel and act like “popcorn” and explode to a much bigger star, called red giant stars

• They can be so big that it would be the size of our Sun, plus Mercury, Venus, Earth and Mars

• Finally, stars shrink and collapse into small planet like stars, called white dwarf stars

• White dwarf stars burn out into Black dwarf stars and then finally die

Stars can explode

• White dwarfs can explode and become much brighter, becoming a Nova

• A supernova star flares up and gets a million times brighter- this may happen only once in a few hundred years

• The Crab Nebula is what remains of a supernova seen by Chinese astrologists in the year 1054 ( almost 1000 years ago!)

Supernovas & Black Holes

• Supernovas often turn into small tight balls, called a neutron star.

• The neutron star spins rapidly and gives off x-rays, called a pulsar

• When a big star cools and collapses, it gets crushed by gravity and then the star disappears- this is a Black Hole

• Anything that gets too close to a Black hole gets “sucked” into it and can’t escape

Our sun

• Our sun is a loner star, without any others nearby it.

• Most stars are paired with other stars- called binary stars

• Some stars are clustered in groups of 3-8 stars- called star clusters

• A globular cluster contains many thousand stars together

• There is a cluster known as M.13 in the Hercules constellation- it has at least a million stars

Galaxies

• Galaxies are large star systems- our solar system belongs to the Milky Way galaxy

• Our sun is on the edge to the galaxy, and it revolves around in a swirl- it would take 225 million years to get to the same spot it is in today

• There are other planet and suns in our galaxy.• Planets form at the same time and from the

same gases as the sun star

Is there life beyond Earth?

• We don’t know if there is life on any other planets like Earth

• Our scientists use radio telescopes to try to find other life forms

• The Andromeda galaxy is a spiral galaxy with twice as many stars as in the Milky Way

• The scientists estimate there are one hundred billion other galaxies, each with millions of stars

Quasars

• Beyond the galaxies are bright star-like objects called quasars.

• Each quasars give off a 100 times more energy of all the stars in a galaxy put together

• Scientists think that quasars may be the centers of young galaxies

• Powerful telescopes orbiting the Earth may show us the very edges of the universe and the beginning of time itself

Questions?• What are stars?

a) hot gases of hydrogen b) lights in the sky

• What is a galaxy? a) lots of stars together

b) few stars together

• How do scientists listen for life on other planets

a) radio wavesb) light waves

VOCABULARY

SPELLING WORDS