Descriptive Astronomy Test 1

What are Kepler's Laws?

1. Eliptical Orbits - a planet's orbit around a star is an ellipse and the star is located at one of the focal points of the ellipse 2. Equal Areas in Equal Times - in equal times, a planet sweeps out pie-shaped portions of the ellipse with equal areas 3. Period and Orbital Distance - average orbital distance cubed is proportional to the orbital period squared

How many galaxies are in the known universe?

100 billion

How many stars are in our galaxy?

100 billion

How many constellations are there in the zodiac?

12 sometimes 13 depending on how you count them

What is the age of the universe?

14 billion years old

How many stars can you see without a telescope?

2000

How much is the earth tilted on its axis?

23.5 degrees

How long does it take the sun to go around the galaxy once?

230 million years

How long does it take the axis of the earth to precess?

26 thousand years to go around the circle once

How far is the sun from the center of the galaxy?

27,000 light years

What is the known size of the universe?

28 billion light years across

How far would Alpha Centauri be away from the sun if the galaxy was the size of a football field?

4.5 mm away

How many constellations are there in a standard set?

88

How does the scientific theory work?

A hypothesis that is supported by an enormous amount of data for a long time is called a theory. Theories tend to explain large bodies of facts in very simple ways. You can't prove a theory; you can only disprove it. But if it works over and over again you eventually end up just accepting that it's probably correct. Especially successful theories are called laws.

What is the nearest star to us (except the sun) and how far away would it be on the Washington, D.C. model?

Alpha Centauri. It would be the located in California

What is the name of the nearest large galaxy to us, and how far away is it?

Andromeda and it is about 2.5 million light years away

What are comets made of?

Ice

What are the different types of eclipses?

Lunar - moon falls in the earths shadow Solar - moon gets in the way of the sun

Which planets can you see without a telescope?

Mercury, Venus, mars, Jupiter, and Saturn

What makes stars shine?

Nuclear Reactions

What were the objections to Kepler's model of the solar system and how were they overcome by Galileo?

Objections a. there was doubt that the earth was moving (wouldn't any object fall off if it were?) b. The idea of non-circular orbits was ugly c. If the earth were moving around the sun, then why don't we detect stellar parallax? Galileo Overcomes a. No friction in space b. showed that the moon wasn't perfectly round with the use of a telescope c. Jupiter had moons so not everything had to orbit around the earth

What is the current north star?

Polaris

Constellations

Regions of the sky

What is the Angular size of the moon, sun, etc?

Sun: 1/2 degree Moon: 1/2 degree Distance between Big Dipper Pointer Stars: 5 degrees Southern Cross: 6 degrees fist: 10 degrees finger: 1 degree

Star

a giant, more or less round, ball of gas out in space that glows

Nuclear Fusion

a process where light atoms combine to form heavier ones and release energy

Solar System

a star and all the various objects that orbit it

Name the important events on the calendar where the entire life of the universe is shrunk down to one year.

a. Galaxies would have started to form in mid-February b. Our solar system and our planet would have formed in September c. The dinosaurs would have emerged and disappeared during a few days in late December d. The pyramids would have been built just ten or so seconds before midnight on New Year's Eve e. Columbus would have first visited America about a second before midnight on New Year's Eve f. A person's life span would be just a tiny fraction of a second

What is the difference between Hypothesis, law, and theory?

a. theory - a hypothesis is supported by an enormous amount of data for a long time. they explain large bodies of facts in very simple ways (cannot prove a theory) b. fact - a theory that works over and over that is especially successful. c. hypothesis - a question based on an observation

What are the characteristics of ancient greek science?

a. tried to avoid invoking supernatural explanations for natural phenomena b. thought of the world around them in terms of simple models, often pictorial and mathematical c. understood that an explanation can't be correct if it doesn't explain the facts.

What are the characteristics of science?

a. tries to explain natural phenomena without supernatural intervention b. tries to explain phenomena in very simple ways c must make predictions about phenomena which can be tested

Why did ancient people care about astronomy?

aid to navigation and planting crops

Moons

an object that orbits a planet, just as planets orbit stars

What are arcseconds and arcminutes?

arcminutes - 1 degree broken down into 60 equal parts arcseconds - 1 arcminute broken down into 60 equal parts

Astronomical Unit (AU)

average distance from the earth to the sun (about 93 million miles)

Big Bang

best available theory of the beginning of the Universe. The Universe started out a long time ago squashed down to a single point, exploded, and has been expanding ever since

Galaxies

enormous collections of stars (and star systems) held together by gravity

Universe

everything that ever was

What is the size range for asteroids?

from grains of dust to a few dozen miles across

Galaxy Groups or Clusters

galaxies come in groups that are held together by gravity

What are epicycles and how did the geocentric model work?

geocentric placed the earth at the center of the universe the ptolemaic model had the planets orbit in circles on top of circles on top of circles called epicycles.

What did Tycho Brache do?

he and his assistants determined the position of the planets in the sky for different times of the year to within 1 arcminute. (this took 30 years)

Planets

moderately large objects that orbit the star in a solar system

Are all stars in a constellation the same distance away?

no

Comets

objects in the same size range as asteroids but are made of ice

Local Sky

part of the celestial sphere you can see when you go outside

Apparent Retrograde Motion

periodic movement in the opposite direction of planets

Zenith

point directly above you

Asteroids

relatively small objects made of rock and metal that orbit a star

What are asteroids made of?

rock or metal

What can planets be made of?

rock, metal, ice, and/or gas

Altitude

the angle an object is above the horizon

Stellar Parallax

the apparent motion of nearby stars compared to ones that are very far away

Horizon

the border between the land and the sky

Celestial Sphere

the constellations all appear as though they're painted onto the inner surface of a sphere

Meridian

the curve from the north, through the zenith, to the south

What is the saros cycle?

the cycle of eclipses

A Light Year

the distance that light can travel in one year (about 6 trillion miles)

Correctly explain retrograde motion.

the earth is orbiting faster than the outer planets, so it passes them periodically. When this happens, the planet it is passing appears to move backwards temporarily against the background of stars.

Why do we have seasons?

the earth is tilted with respect to the sun so that for part of the year the northern hemisphere gets more or less direct sunlight, while for the other part of the year the southern hemisphere gets more or less direct sun light.

Why are there phases of the moon?

the phases are due to half the moon always being in shadow. the portion of the part not in shadow changes as the moon orbits the earth

Zodiac

the set of 12 (sometimes 13, depending on how you count them) constellations along the ecliptic

What are the sizes and distances for the earth and sun in the scale model in Washington, D.C.?

the sun would be about the size of a grapefruit, and the earth would be about the size of the tip of a ballpoint pen. The sun would be about 50ft away from the earth

What is the ecliptic plane?

the sun's path through the celestial sphere

What is the center of the universe?

there is none

Orbit (Revolution)

when a planet moves around a star

Rotation

when a planet spins like a top

Lunar Eclipse

when the moon falls in the earth's shadow

Solar Eclipse

when the moon gets in the way of the sun