ASTRONOMY FINAL!!!

What is the Maximum number of planets visible to the naked eye on a given night?

5

Planets…

move SLOWLY relative to the stars

The motion of the Earth around the sun is called…

Revolution

The number of seconds in a day is closest to

90,000

The celestial coordinate corresponding to latitude on Earth is called…

Declination

If Sirius the brightest star in the sky, rises at 10pm one night, the following night it will rise at…

9:56pm

Planet X has its rotation axis perpendicular to its orbital plane. Its seasons would be…

constant

At the Vernal equinox, an observer on the Equator will observe the sun to be ___ degrees above the horizon at noon.

90

Ptolemy…

wrote books summarizing astronomical knowledge of earlier cultures

True of False…An observer at a latitude of +27 degrees will have the Sun at its Zenith at least twice each year

False

Which of the following was NOT an important contribution of Brahe

discovery of the rings of Saturn

From his analysis of the motion of Mars, Kepler was able to conclude that…

the planets moves with varying orbital speed

You can tell that Jupiter is at opposition by noting that

it crosses the north-south line passing straight overhead at midnight

The latitude of Washington D.C. is 38 degrees. If the President were to look at Polaris one night, she would find that its altitude is…

38 degrees

Which planet below can never be seen at Midnight?

Venus, because it’s an inferior planet

Newtons law of gravity is…

F = GMm/r²

What force holds the planets in their orbits around the Sun?

Gravitational

The law of inertia states…

objects remain at rest or move in straight lines at constant velocity a net force acts on them.

The ability of a rocket to move through the vacuum of space by firing its engine demonstrates

Newton’s law that every action has an equal and opposite reaction.

Halley’s comet orbits the Sun with a period of 75 years. Write the letter of the equation below that would be used to calculate the the size (semi-major axis) of the orbit of that comet.

P² = a³

Rotation

turning a body about an axis running through it. Ex: Earth completes a ROTATION every 24 hours

Revolution

Motion about an external axis. Ex: Earth completes a REVOLUTION around the Sun once every 365 days

The Meridians

A series of lines passing through theNorth and South poles, that intersect the equator at a 90 degree angle. They specify the East West location of a coordinate.

The Latitude

The angle of a place measured along the Meridian from the equator to the place. Goes from 0 degrees to 90 degrees North or 0 degrees to 90 degrees South.

The Celestial Sphere

an imaginary sphere that astronomers use to describe the positions of celestial objects

Pythagorus (~500BC)

Observed that the moon is spherical and therefore theorized that the Earth must also be spherical

Aristotle (~350 BC)

Observed Lunar eclipses. Earths shadow is always round which meant Earth MUST be a Spherical

Eratosthenes (~200 BC)

made quantitative measurement of the size of the Earth using a stick and it’s shadow.

Motion of the Earth

Corresponds to the Celestial Sphere

Time

The measurement of this is based on the rotation of Earth. Earth’s is based off a Solar day which is why we have time zones.

Solar Day

Based off the Sun. About 1 degree longer meaning it’s 4 minutes longer than it’s counterpart.

Side real Day

Based off a Star. About 1 degree shorter and therefore 4 minutes shorter than it’s counterpart.

Claudius Ptolemy (~140 AD)

Gave a very mathematical description of the Earth centered universe. Predicted Planetary positions with great accuracy relative to his time period.

Earth’s orbit is NOT Circular it’s…

Elliptical

Elliptical (term)

oval shaped

Heliocentric Theory

Heliocentric Theory

the astronomical model that places the sun at the center of the solar system. It states that the Earth and other planets orbit around the sun.

Copernicus

The First Great Astronomer of the Renaissance

Tycho Brahe

Danish Nobleman & Astronomer. Constructed an Astronomical observatory, invented numerous devices for Astronomical measurement with the naked eye (before the telescope). For 20 years recored with great accuracy planetary postions (especially Mars. He also sought help from Kepler.

Johannes Kepler

Brilliant German Mathematician. Worked with Brahe. Established 3 laws for Planetary motion.

Keplers 1st Law

planets move in ellipses, with the sun at one focus

Keplers 2nd Law

The radius vector (the line joining the planet with the sun) sweeps out equal area in equal time.

Keplers 3rd Law

The square of the time revolution of each planet is proportional to the cube of the semi-major axis of its orbit. (T² = Ka³)

Ellipse

a well known geometric shape conic section.

Eccentricity

E = f/m

Galiteo

Helped secure the acceptance of Heliocentric theory as with a telescope he discovered:

1. The moon has craters - not a perfect crystalline sphere

2. Sun spots

3. The phases of Venus, orbiting the Sun not the Earth

4. Saw the moons of Jupiter, another celestial

Sir Issac Newton

Established 3 laws of motion

Newtons 1st Law

A body at rest will stay at rest unless acted upon by an outside force

Newtons 2nd Law

Force = Mass x Acceleration

Newtons 3rd Law

For every action there is an equal and opposite reaction.

Contact Force

A force thats touching. Ex: push or pull

Field Forces

Forces not directly touching. Ex: Gravity, electric, magnetic

Orbits & Center of Mass

Objects (planets) orbit around a point between them called the Center Mass called the Fulcrum. The center of mass is always closer to the bigger object.

Tides

They depend on the difference in gravitational attraction between different locations i.e. where the Moon is located.

Mass of the Moon

~1/80 Mass of Earth

Density of the Moon

~7/10 Earth’s Density

Diameter of the Moon

3500 km

Moon’s Diameter

~ ¼ Earth’s Diameter

Distance from Earth to Moon

~240,000 miles

Why do we always see the same side of the Moon?

Because the Rotation (on it’s axis) and revolution around the Earth periods are the same

Moon’s Sidereal rotation period

27 days

Moon’s Synode period

29.5 days

Why can we see the Moon at night?

Because the sunlight reflects off the Moon

How much of the Sun’s life light is reflected off the Moon?

7% of the incident sunlight

What is the Moon’s FIRST phase? What time of day is it at it’s highest point in the sky?

New Moon. 12 pm

What is the Moon’s SECOND phase? What time of day is it at it’s highest point in the sky?

Waxing Crescent. 3pm

What is the Moon’s THIRD phase? What time of day is it at it’s highest point in the sky?

First Quarter. 6pm

What is the Moon’s FOURTH phase? What time of day is it at it’s highest point in the sky?

Waxing Gibbous. 9pm

What is the Moon’s FIFTH phase? What time of day is it at it’s highest point in the sky?

Full Moon. 12am

What is the Moon’s SIXTH phase? What time of day is it at it’s highest point in the sky?

Waning Gibbous. 3am

What is the Moon’s SEVENTH phase? What time of day is it at it’s highest point in the sky?

Third Quarter. 6am

What is the Moon’s EIGHTH phase? What time of day is it at it’s highest point in the sky?

Waning Crescent. 9am

What is this?

The phases of the moon.

How much later does the Moon rise then the previous day?

50 minutes

Lunar Eclipse

The Moon passes through the Earth's umbra, causing it to appear reddish or dim.

Solar Eclipse

The umbra of the Moon casts a path of totality where the Sun is completely blocked

Umbra

The region of total shadow, where a light source is completely blocked.

Prenumbra

The region of partial shadow, where the light source is only partially blocked.

“Fission” Hypothesis

The Moon was flung away from the Equator of a very rapidly rotating

Proto-Earth.

Problem: The Moon is NOT in the Earth’s equatorial plane + there’s a difference in the chemical composition of the Earth’s crust & Moon’s crust.

“Capture” Hypothesis

Moon was formed elsewhere in the Solar system, ventured close to the Earth and was gravitationally captured

Problem: From a Sun centered orbit to an Earth centered orbit, the moon would have to lose a great deal of kinetic energy - highly improbable

Kinetic Energy of Motion Equation

½ Mass x Velocity²

“Co-Creation” Hypothesis

Earth & Moon were formed side by side at their present distance from the Sun

Problem: Very different chemical composition of high density (Fe) Earth, and Low Density

“Great Impact” Theory

the Moon formed from debris ejected into space after a Mars-sized object, named Theia, collided with the early Earth, which then coalesced to form our lunar companion

Current Favored explanation of the Moon

“Nebular” Hypothesis

Solar system began as Giant cloud of mostly Hydrogen and Helium and i-27 heavier elements

Fragment of solid material begin to form from collision of molecules and atoms

When too massive to be carried by the gas these fragments fall toward the central plane of the cloud where the density is the highest and gravitational anthem is the greatest.

Momentum Equation

Mass x Velocity

Angular Momentum

Mass x Velocity x Radius

Moment of Inertia

I = Σ (miri²)

How many planets are in our Solar System?

8 planets

What is the farthest Planet from the Sun?

Neptune as it’s 30 AU away.

What is the Closest Planet to the Sun?

Mercury as it’s 2/5 AU away

Total Mass of the Planets

~1/1000 Mass of Sun

What is the order of the Solar System?

Mercury, Venus, Earth, Mars, Astroid Belt, Jupiter, Saturn, Uranus, Neptune

Terrestrial Planets

Mercury, Venus, Earth, Mars

Jovian Planets

Jupiter, Saturn, Uranus, Neptune

Terrestrial Characteristics

• 4 closest planets to the sun

• Composed mostly of Rocky Material + Fe

• “Small in size”

• Relatively dense

• Short Revolution period

• Slow Rotations on it’s Axis

• High Surface Temperature

• Few Satellites

Jovian (Gas Giants) Characteristics

• Distant planets from the Sun

• Mostly Hydrogen + Helium

• Much Larger Diameter, much more massive

• Much lower density (Saturn could float)

• Long periods of Revolution

• Rapid rotations on it’s axis (avg = 12hrs)

• Low Surface Temperature

• Many Moons

Astroids

Relics of rocky planetesimals that formed between Mars and Jupiter orbit

• 30,000 Astroids

• Can have very Regular shapes

• A day on an Astroid is only 9 hours long

• More a tumble than a Spin

• We measure rotation periods by watching changes in brightness

• Main Astroid belt is between Mars and Jupiter

Comet

Icy Small bodies that orbit the sun, often leaving a visible tail of gas and dust as they approach the Sun

Come from:

• Kuiper Belt - Flat disk shaped region begins beyond the orbit of Neptune extend s out several thousands Au’s tens of thousands of Icy planetesimals - too far from the Sun to be active

• Oort Cloud - spherical distribution - 50,000 AU ~1/5 of way to the nearest star weakly held by the sun

Like Charges…

Repel

Unlike Charges…

Attract