Name the waves of the electromagnetic spectrum in order from longest to shortest wavelength

Describe our place in the universe:

What is a galaxy?

A vast collection of stars, gas & dust all held together by gravity and orbiting a common center

M31, The Great Galaxy in Andromeda

What is a Light-year?

The distance light can travel in one year (about 10 trillion km or 6 trillion miles).

If we reduce the size of the sun to a large grapefruit (14 cm in diameter) How far away would the nearest star be?

the nearest star (Alpha Cenauri) is 2500 miles away (about as wide as the US).

About how many stars are estimated to be in the Universe?

As many stars as grains of (dry) sand on all Earth’s beaches…

In what way are IR & UV telescopes different from visible light telescopes?

Infrared and ultraviolet-light telescopes operate like visible-light telescopes but need to be above atmosphere to see all IR and UV wavelengths

Describe the movement of the Earth

The Earth - rotates around its axis once every day.Revolves around the sun once every 365 days.

How many stars can we see with the naked eye?

We can see a few thousand (as well as the Milky Way).

How do we mark the progression of the seasons?

summer solsticewinter solsticespring (vernal) equinoxfall (autumnal) equinox

What is a Constellation?

A constellation is a recognized pattern of stars that refers to a region of the sky.

How do we measure the altitude of an object?

An object’s altitude is measured up from the horizon (in degrees).

How many arc-seconds are there in a degree?

1º = 60 (arcminutes) x 60 (arcseconds) = 3600 (arcseconds)

How do we calculate an object’s Angular Size?

distance

sizephysical sec206,265arc = sizeangular

What is a circumpolar star?

Your Horizon

A circumpolar star never sets

How can you determine your latitude using the pole star?

Altitude of the celestial pole = your latitude

What causes seasons?

Seasons depend on how Earth’s axis affects the directness of sunlight

What is timing?

A study that measures how light output varies with time

Why do we see phases of the Moon?

We see a changing combination of the bright and dark areas on the moon as it orbits around the earth

Why do we see only one side of Moon?

Synchronous rotation: the Moon rotates exactly once with each orbit

What causes eclipses? The Earth and Moon cast shadows. When either passes through the other’s

shadow, we have an eclipse.

When can a lunar eclipse occur?

Lunar eclipses can occur only at full moon.

When can a solar eclipse occur?

Solar eclipses can occur only at new moon.

What is apparent retrograde motion? This is when planets appear to go westward

(backwards) relative to the stars. (Planets usually move slightly eastward from night to night relative to the stars).

What causes Apparent Retrograde Motion?

occurs when we “lap” another planet (or when Mercury or Venus laps us)

Gravitational effects of sun & moon reinforce each other

What causes spring tides?

How did astronomical observations benefit ancient societies?

• Keeping track of time and seasons– for practical purposes, including agriculture– for religious and ceremonial purposes–Aid to navigation

What did Copernicus do?

Copernicus (1473-1543):

• Proposed Sun-centered model (published 1543)

How did the Greeks explain planetary motion?

• Geocentric model - Earth at the center of the universe

• Heavens must be “perfect”: Objects moving on perfect spheres or in perfect circles.

What did Johannes Kepler (1571-1630) do?

• determined planets move in elliptical orbits

•Kepler’s Laws

How does gravity cause tides?

Moon’s gravity pulls harder on near side of Earth than on far side

Difference in Moon’s gravitational pull stretches Earth

•Sunspots on Sun (“imperfections”)

•Mountains and valleys on the Moon (proving it is not a perfect sphere)

•moons orbiting Jupiter

• phases of Venus

Using his telescope, Galileo saw what 4 things?

What are the Hallmarks of Science?

1. Seeks explanations for observed phenomena that rely on natural causes.

2. Progresses through the creation and testing of models that explain the observations as simply as possible.

3. Model must make testable predictions that would force us to revise or abandon the model if the predictions do not agree with observations.

What is Newton’s Law of Gravitation?

What is Occam’s Razor?

This is the idea that we prefer the simplest explanation.

Does astrology have any scientific validity? No, scientific tests have shown that

astrological predictions are no more accurate than we should expect from pure chance.

What did Tycho Brahe do?

• Compiled the most accurate (one arcminute) naked eye measurements ever made of planetary positions.

(1546-1601)

Conservation of angular momentum.

Angular momentum depends on mass, velocity and radius. If the momentum is constant, then if the radius decreases the velocity must increase.

m x v x R = m x V x r

Why do objects rotate faster as they shrink in radius?

What does Gravitational Potential Energy depend on?

object’s mass (m)strength of gravity

(g)distance object

could potentially fall

What are particles of light called?

Particles of light are called photons

What does the law of Conservation of Energy say? Energy can be neither created nor

destroyed. It can change form or be exchanged between objects.

Where in their orbits do planets have the most gravitational energy and the least kinetic energy?

More PE;Less KE

Less PE;More KE

Perihelionaphelion

Happens at either new moon or full moon

Spring tides occur during which phase(s) of the moon?

What causes neap tides?

the tidal effects of the Sun and Moon partially cancelled each other

What are the colors of visible light?

ROYGBIV

What is the structure of matter?

AtomNucleus

ElectronCloud

What is the law of reflection?

The angle of incidence equals the angle of reflection

Why is a red chair red?

Pigments in the chair absorb all colors of light except red, which they reflect. So the chair looks red.

What is the range of wavelengths for visible light? (longest to shortest)

700 nm (red) – 400 nm (violet)

Neap tides occur during which phase(s) of the moon?

Happens at either first quarter or third quarter

What information do the atomic number and mass number provide?

Atomic Number = # of protons in nucleus Atomic Mass Number = # of protons + neutrons

What is an isotope? Atoms that have the same # of protons but

different # of neutrons.

What are the phases of matter?

Solid Liquid Gas (vapor)Plasma (ionized gas)

How is energy stored in atoms?

Energy is stored when electrons absorb energy and move up to a higher level

Ground State

Excited States

Why does each element produce a unique spectrum ? Each type of

atom has a unique set of energy levels

Each transition corresponds to a unique photon energy, frequency, and wavelength

How can you identify what distant stars are made of ?

Observing the fingerprints in a spectrum tells us which kinds of atoms are present

Which letter(s) labels the peak (greatest intensity) of infrared light?

A B C D E

E

Name the 3 types of spectra:

ContinuousEmission or Bright LineAbsorption or Dark Line

Describe a continuous spectrum

An unbroken band of colors produced by glowing solids, liquids & high pressure gases.

Describe an emission spectrum

Bright lines produced by hot gases under low pressure.

Describe an absorption spectrum:

Produced when a continuous spectrum of light is passed through a cooler, low pressure gas leaving dark lines.

Which letter(s) labels emission lines?

A B C D E

A

On what property does an object’s thermal radiation spectrum depend?

An object’s thermal radiation spectrum depends on only one property: its temperature

What are the 2 Properties of Thermal Radiation ?

1. Hotter objects emit more light at all frequencies per unit area.

2. Hotter objects emit photons with a higher average energy.

How can you determine a telescope’s light collecting area?

A telescope’s diameter tells us its light-collecting area: Area = π(diameter/2)2

How do we measure the doppler shift with light?

We generally measure the Doppler Effect from shifts in the wavelengths of spectral lines

Stationary

Moving Away

Away Faster

Moving Toward

Toward Faster

If I measure a line in the lab at 500.7 nm and the same line in a star has wavelength 502.8 nm what does that tell me?

The star is moving away from me.

How does light tell us the rotation rate of an object?

Different Doppler shifts from different sides of a rotating object spread out its spectral lines

How does your eye form an image?

Light comes in through the lens which focuses the image on the retina.

What is refraction?

Refraction is the bending of light when it passes from one substance into another

How do digital cameras detect light?

Digital cameras detect light with charge-coupled devices (CCDs)

What are the two most important properties of a telescope?

1. Light-collecting area

2. Angular resolution

What is angular resolution?

• This is the minimum angular separation that the telescope can distinguish.

What are the two basic designs of telescopes?

Refracting telescope: Focuses light with lenses

Reflecting telescope: Focuses light with mirrors

What type of telescope do most modern astronomers use?

Most modern telescopes are reflectors

What spectroscopy?

Spectroscopy: Breaking light into spectra

What is the diffraction limit ?

• The limit on angular resolution caused only by the interference of light waves.

What do astronomers do with telescopes?

ImagingSpectroscopyTiming

How does Earth’s atmosphere affect ground-based observations?

Light pollution Twinkling due to turbulence Only radio & visible light pass through

What is adaptive optics?

Rapidly changing the shape of a telescope’s mirror to compensates for some of the effects of turbulence

Without adaptive optics With adaptive optics

What is a radio telescope?

A radio telescope is like a giant mirror that reflects radio waves to a focus

What is interferometry?

This is a technique for linking two or more telescopes so that they have the angular resolution of a single large one

How do you measure the wavelength of a wave

Measure the distance from crest to crest on a wave.Measure the distance from crest to crest on a wave.

What is the Doppler Effect?

An apparent shift in wavelength caused by motion between the source and the observer.

What is imaging?

Imaging: Taking pictures of the sky

What line in the sky is created by our revolution around the sun?

The Ecliptic

What is a sidereal month?

The amount of time it takes the moon to orbit the earth.

What is a synodic month?

The amount of time it takes for the moon to realign with the sun and the phases to repeat.

Given two stars at the same distance from the earth. Which one has a higher surface temperature, a red one or a blue one? The blue one

What is an astronomical unit?

The average distance between the earth and the sun.

What causes stars to twinkle?

Bending of light rays by turbulence in the atmosphere

What is radiative energy?

the energy carried by light

What is Newton’s 2nd law?

F = ma The force acting on an object is equal

to its mass times its acceleration

Why do visible constellations change throughout the year?

The constellations change because of the earth’s motion around the sun.

What is Newton’s 1st law?

Objects in motion stay in motion, and objects at rest stay at rest unless there’s an external force acting on them.

What is the meridian?

The imaginary line that passes through your zenith and connects your north to your south.

What is the zenith?

the point directly over your head

What is Kepler’s 1st law?

All planets move in elliptical orbits with the sun at one focus.

What is Kepler’s 2nd law?

Planets sweep out equal areas in equal times.

What does Kepler’s 2nd law mean?

Planets travel faster when they are closer to the sun and slower when they are farther away.

What is Kepler’s 3rd law?

p2 = a3

What is an ion?

an atom that has lost or gained an electron.

How old is the universe?

about 14 billion years

What is spectral resolution?

a measure of how close two spectral lines can be distinguished.

What is an opaque material?

opaque materials absorb most of the light.

What is declination?

Declination is a lot like latitude on earth. It is an objects angular distance above or below the celestial equator.

On which two days of the year does the sun cross the celestial equator? the sun crosses

the celestial equator on the equinoxes

vernal

autumnal

What is Right Ascension?

Right ascension is similar to longitude on earth. RA is measured in hours eastward of the vernal equinox.

What is Newton’s 3rd law?

For every action force there’s an equal an opposite reaction force. See the rocket example…