Earth Sun Star & Universe Intro to Astronomy

Earth Sun Star & Universe Intro to Astronomy

This Chapter covers Earth Sun Star & Universe Intro to Astronomy


Field View

the visible area in an image, usually given as the diameter or a region


Astronomy is sometimes known as?

the science of big numbers


scientific notion

a way to write big or small numbers without using lots of zeros


solar system

consists of the sun, family of planets, asteroids, moons and comets


planets

small spherical nonluminous bodies that orbit a star and shine by reflected light


Venus is the size of?

earth


how big is mercury?

just over 1/3 of the earths diameter


the sun is a?

star


describe the sun

star
self luminous
ball of hot gas
generates own energy


astronomical unit (AU)

average distance from the earth to the sun = to
1.5 x 10(8)


what is the average (AU) from Venus to the sun

about 0.72 (AU)


what is the average (AU) from mercury to the sun

about 0.39 (AU)


why are distances averages?

because the orbits of the planets are not perfect circles


how long does it take light from the sun to reach earth?

Eight minutes


how long does it take light from the sun to reach neptune?

Four hours


what star is the only visible one?

the sun


how many stars are there?

billions


light year (ly)

the distance that light travels in one year
roughly 10(3) km or 63,000 (AU)
light year is a distance not a time


what is the closest star to the sun?

Alpha Centauri


how many (ly) is Alpha Centauri from earth?

4.2 (ly)


galaxy

great cloud of stars, gas and dust held together by the combined gravity of all of its matter
contains our solar system, billions of stars, planets that orbit them, billions of planetary system


how many stars does a galaxy contain?

some over 100 billion


what is the (ly) diameter of galaxies?

1500 to over 300,000 (ly) in diameter


milky way

hazy band of light that circles the sky, produced by the combined light of billions of stars in our milky way galaxy


milky way galaxy

the spiral galaxy containing the sun; visible at night as the milky way


spiral arms

long, spiral patterns of bright stars, star clusters, gas and dust that extends from the center to the edge of the disk of spiral galaxies


universe

includes all galaxies, stars, planets, our own galaxy and our solar system


how old is the universe?

Fourteen billion years old


when was there light?

Four hundred million years ago, when gravity pulled some of the gases together and formed the first stars


why study astronomy?

to answer:
what are we?
how do we know?


what do we live on?

a planet


why do scientists use the metric system?

simplifies calculations


how long does it take earth to orbit the sun?

one year


how big is the moon compared to earth?

1/4 the diameter of earth


how big is the sun compared to earth?

one hunderd & nine times larger than earth


what is the (AU) from mars to the sun?

1.5 (AU)


how many (ly) in diameter is our galaxy?

Eighty thousand (ly)


Name the event that caused our universe to begin about 14 billion years ago

big bang theory


Big Bang Theory

Four hundred million years after the big bang universe filled with hot gas
cooled & galaxies began to form
stars began to shine


when did the sun and planets of our solar system form?

4.6 billion years ago


where did life begin?

on the ocean floor after the earth formed but did not emerge onto land until 400 million years ago


when did dinosaurs evolve?

Four hunderd million years ago & went extinct 65 million years ago


when did humanlike creatures develop on earth?

Four millions years ago


when did human civilization develop?

about 10,000 years ago


why are light years more convenient than miles, kilometers or astronomical units for measuring certain distance?

because the distance is to large to express


why is it difficult to detect planets orbiting other stars?

because they are to small, to faint and to close to the glare of their star to be easily visible


what does the size of the star image in a photograph tell you?

the stars brightness not its actual size


what is the difference between the milky way and the milky way galaxy?

the milky way galaxy is our galaxy and the milky way is the combined light of billions of stars in our milky way galaxy


how does astronomy help answer the question “what are we”?

it helps us to learn how we fit into the history of the universe


how does the scientific method give scientists a way to know about nature?

it is a general way of testing and refining ideas to better describe how nature works


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