by Paul Nervy
Copyright (c) 2006 by Paul Nervy
Visit www.paulnervy.com.



Space exploration.  
History of astronomy




Astronomy is the study of outer space.


Sub-areas of astronomy



Space is empty.  Except for small amounts of gas and dust.

Space is a vacuum.  Space is not a perfect vacuum, rather a functional vacuum.

Sound does not travel in space.

Light does travel in space.

Space is very cold.

You can't breath in space because there is no oxygen.

Since there is no air in space, there is no air pressure in space.  Humans are adapted to living with air pressure.


Key ideas in astronomy.

The sun is a star.  

Planets, such as earth, orbit stars, such as the sun.

There are billions of stars in each galaxy.

There are billions of galaxies in the universe.

Therefore, there are billions and billions of planets in the universe.

Therefore, life, intelligent life, has to be out there somewhere.



There are nine planets in our solar system.  Some of the planets are small and rocky, other planets are large and gaseous.

The planets in our solar system all have similar orbit, in that they follow the eliptic across sky.

Mercury is one of the small, rocky planets.

Venus is one of the small, rocky planets.

Earth is one of the small, rocky planets.

Mars is one of the small rocky planets.
Water on Mars?  Life on Mars?  Humans visit Mars?  Terra form Mars?

Saturn is a large, gaseous planet.
Rings around Saturn.

Jupiter is a large, gaseous planet.
Big spot on surface of Jupiter is a storm.
Shoemaker-Levy explosions.

Uranus is a large, gaseous planet.

Neptune is a large, gaseous planet.

Pluto is something of an anomalous planet.

Planets outside our solar system.
Dozens found

Planet formation theories.



Night and day.
Night and day are caused by the earth spinning on its axis once every 24 hours, in relation to the sun.

Seasons are caused by the tilt of the earth, as the earth revolving around sun once every 365 days.  When tilted away from the sun, days are longer, nights are shorter.  When tilted toward the sun the days are longer and night is shorter.

The orbit of the earth around the sun is elliptical, not oval, and not a perfect circle.

Vernal (spring) equinox is in spring when night and day are equal lengths.
Autumnal equinox is in fall when night and day are equal length.

Summer solstice is the longest day.  
Winter solstice is the shortest day.


Daylight savings time, spring ahead, lose an hour, lighter in evening.

Daylight savings time, fall back and gain an hour, lighter in morning.

Longest day, June 21.

Shortest day, December 21.

Day and night equal is September.

Day and night equal is March.



Moon's are not planets.  Moons orbit planets.  Planets orbit stars.

Moon.  The Earth's moon.

Moon missions.  Man on the moon.  

Water on the moon.

Phases of the moon are caused by the moon moving around earth.  It takes 30 days for the moon to circle the earth.

Tides are due to the earth rotating and the pull of the moon.

Other moons of other planets.
Moons of Jupiter.


Solar eclipse is when the moon blots out the light of the sun.

Lunar eclipse is when the shadow of the earth blots out the light refected off the moon.


Comets are balls of ice and dirt.  Comets have a tail.

Famous comets
Hale Bopp
Shoemaker Levy

Especially killer asteroids.  How often do they hit earth?  Can we stop them?
The asteroid that killed the dinosaurs.
The search to track asteroids.

An asteroid in our atmosphere.  I.e., a shooting star.  Most burn up in atmosphere.

A meteor that hits earth.

Meteor showers
Named after constellations they eminate from.

Oort cloud - many short-period comets

Kuiper belt - many long-period comets, many asteroids



Types of stars vary by size, color and brightness.

Star size.  

Star color.  

Young,  big, blue.

Old, small, red.


Star brightness.

How is star brightness measured?
	Brightness due to nearness to earth.
	Brightness to to heat of the star.
	Brightness due to size of the star.

The Hertzsprung-Russell diagram charts luminosity and temperature.

objective brightness

What are the methods used to determine the distance from earth of a star?

Life cycle of stars.  
	Star birth
		Gravity pulls materials together
		Nuclear fussion begins
	Star death
		Super novae leads to either black hole or neutron star.
		Planetary nebulae leads to white dwarf.

There are three types of stars and star life cycles.
1. White dwarf stars burn out and end up as black dwarf stars.
2. Main sequence stars turn into red giants and then white dwarfs.
3. Big stars eventually go supernovae and then turn into either neutron stars or black holes.

A quasar is an object very far away, emitting a very strong radio signal.

 A pulsar is a rotating neutron star.

Neutron star
A neutron star is a small, dense star.

Variable stars.
A variable star appears to have changing brightness, due to the orbit of a nearby star.

Double stars
Double stars appear to the naked eye as one star, but a telescope reveals two stars.  The two stars need not be physically near each other, only appear near each other. 

Binary stars
Binary stars are two stars that orbit each other.

Black holes.
Black holes are collapsed stars.

Star maps.  
The northern sky.  The southern sky.  Constellations.


The Sun.  Our star.  

Sunspots are dark areas on the sun.

Solar flares.
The sun emits heat, light, and other forms of radiation.  Solar flares are emissions that can interfere with electromagnetic equipment.




Precession is the movement of the earth over thousands of years causes the constellations to be in different places at different times.

The Zodiac is a line of constellations that runs along the Milky Way galaxy.

Milky Way.  
The Milky Way is a light band across the sky made visible when we see our galaxy from the side.

Local Group.  
The Local Group is our cluster of galaxies.

The closest stars.  Alpha Centauri.
The farthest stars.  Galaxies 14 billion light years away.

Siderial time

Light pollution
The presence of so many nearby lights causes light pollution, which makes it difficult to see the stars at night.

Celestial poles.  Polaris in north.  ? in south.

Celestial equator - between celestial poles.

Equinox.  Path of sun in sky.

Zodiac.  Constellations found along equinox.


Deep space objects.


Clusters are groups of stars.  The clusters that we can see in our sky are within our own galaxy.  There are two types of clusters, open clusters and globular clusters.

Globular clusters 
Globular clusters are dense, with many stars

Open clusters
Open clusters are diffuse, fewer stars


Nebulae are clouds of dust or gas.  Nebulae can have their own light, or reflect light of nearby stars.

Bright nebulae
Bright nebulae can be seen because they are lit up by nearby stars.

Emission nebulae.
Emission nebulae actually emit their own light.

Dark nebulae
Dark nebulae are regions of dust or gas that block the view of the stars behind it.  For example, the Coalsack is a dark nebulae in the southern hemisphere.

Planetary nebula
Planetary nebula are the outer layer of a collapsing star.



Galaxy types by shape.  

Galaxy types
Active - black hole powered
Starburst - making new stars
Dwarf - most common

Milky Way galaxy.  Our galaxy.

Super clusters of galaxies



Age of the universe.
How old is the universe?  About 14 billion years old.

Hubble: proved that universe is expanding.

Birth of the universe.
Big bang.

End of the universe.
	Open universe.  Expansion theory.
	Closed universe.  Contraction theory.
	Flat universe.  Steady state theory.

Death of universe.  Contraction and collapse vs. expansion and cold death.  Or steady state.

Red shift.  Doppler shift.  The universe is currently expanding.

Is the universe...
		steady expansion
		steady contraction

Multiverse theories.
parallels universes.
Sequential universes.
Nested universes.

Size of the universe.
How big is the universe?

Structure of the universe
What is the shape of the universe?
Maps of the universe.

Composition of the universe
Evidence from the WMAP and COBE show
Dark energy 73%
Dark matter 23%
Visible matter 4% (stars, planets, dust, gas)

Dark matter.
Who theorized dark matter?
Who found proof for dark matter?
Dark energy.
Who theorized dark energy?
Who found proof for dark energy?

How many galaxies are there?
How many stars per galaxy on average?
Thus, how many stars in universe?
How many planets per star on average?
Thus, how many planets in universe?

How many planets around the average star?
How many stars in an average galaxy?  100 million?
How many galaxies in universe?  100 million?
So how many planets in universe?  Billions?


Near.  Far.

What is the nearest star to earth?

What is the nearest galaxy to the Milky Way galaxy?

What is the farthest glaxay from earth?

Closest star - Alpha Centauri is several light years away.

Closest galaxy - Andromeda galaxy

Farthest object visible to naked eye - M33 galaxy in Triangulum.

Farthest object visible to any telescope - 14 billion light years away or ago.

Earth to moon.
Earth to sun.
Sun to closest star.
Milky way to closest galaxy.

Astronomical distance units

Astronomical unit (AU).  
An astronomical unit is the distance from the earth to the sun.  About 100,000,000 miles.

Light year.  
A light year is the distance light travels in a year.  Light travels how far in a second?  How far in a year?

A parsec is about three light years.

Speed of light
The speed of light is about 186,000 miles per second.

Methods of measurement of cosmic distances.
Paralax method.
Variable star method.
Quasar method.

Measurement of cosmic speed and acceleration.
Doppler shift method.



Everything is moving.

The earth is moving.
	The earth spins on its axis every 24 hours, causing day and night.
	The earth orbits the sun every 365 days.  The orbit is ellipitical in shape.  The earth is on a tilted axis relative to the sun, causing longer and shorter days, causing hotter and colder seasons.  

The stars are moving relative to each other.  Gravity is a force that .  Stars collide.

The galaxies are moving.  Galaxies collide.

The universe is expanding.

The stars, the constellations, rise in the east and set in the west every night, due to the earth spinning.

The stars, the constellations, change with the seasons as the earth moves around the sun and tilts this way or that.

Precession is another form of movement over thousands of years.

Over millions of years the stars move apart as the universe expands. 

Star movement to human observers.

The stars move throughout the night because the earth is revolving.  The stars rise in the east and set in the west just like the sun does.

The stars move throughout the seasons because the earth is moving around the sun.

The stars one sees from the northern hemisphere of earth differ from the stars one sees from the southern hemisphere of earth.

In reality the stars are moving in galaxies, and galaxies are moving in space, but all too slowly for humans to easily perceive without instruments.

In addition, time space is warped according to Einstein's theory of relativity.


Philosophy of astronomy

Origin of universe.  Big bang.
What came before the big bang?

End of universe.  Expansion or contraction.
What comes after end of universe?

Other universes


Extraterrestrial life

Life beyond earth.  


Drake equation.  

Intelligent life.



Space missions.

Manned space missions.  Humans in space.

Unmanned space missions.

Space probes.  (No humans aboard.)  

Space missions.  (Humans aboard.)
Apollo missions to moon.
Space shuttle.  

Space stations.  (Humans aboard.)  
International space station.

Apollo project, 1969, man on moon.

Pioneer project, 1973-74, Jupiter and Saturn.

Voyager project, 1980-86, 

Hubble telescope, 1990, first space telescope.

Pathfinder, 1997, Mars landing.

Lunar Prospector, 1998, water on moon.

Mars Prospector, 2000, water on mars.



Light telescopes.  
	Refractors use lenses.  
	Reflectors use mirrors.

Infra-red telescopes.  Longer waves than light waves.

Ultra-violet, x-ray, gamma-ray and radio telescopes.  Shorter than light waves.

Spectroscopes.  Determine chemical composition.

Telescope arrays - networked telescopes.

Telescopes movement controlled by computer, and with computer display.



Telescope types
	Schmidt -Cassegrain

Computer guidance systems.  
"Go to" capability.

Aperature = diameter of objective lense in millimeters or inches.

f number =

Focal length = aperture times f number

Magnification = focal length divided by eyepiece magnification.

Focal ratio

Eye pieces for telescopes
A telescope can have multiple eyepieces of different magnification.

Mounts for telescopes

Alti-azimuth mounts can move up or down, left or right.

Equatorial mounts can track stars across the sky.


NASA scopes in orbit

Hubble - visible light

Compton - gamma ray

Chandra - x ray



Famous scopes.  Location.  Date built.

Largest refractor.



Keck.  Hawaii.

Very Long Baseline Array


Magnitude 1 stars are bright.  The sun is one.
Magnitude 5 is  100x less bright.
Magnitude 10 stars are 10,000x less bright.
Magnitude 15 stars are 1,000,000x less bright.

Apparent magnitude.  How bright it seems to humans on earth.
Absolute magnitude.  How bright it actually is.


Star temperatures and color
Blue  hottest.
Red  coolest.


Horizon.  0-360 degrees.
Altitude.  0-90 degrees.


Zenith.  The highest point in the sky.
Zenith.  The highest point in the sky reached by any particular night object on any particular night.


Naked eye astronomy.
Binocular astronomy.
Telescope astronomy.

Get a pair of 10x50 binoculars for $50.  
Wait for a clear night with low humidity and few clouds.  
Drive an hour from the city, and 10 minutes from small towns.  
Point the binoculars at the night sky.  
See a carpet of stars.


Eye.  Magnification 1x.  Maximum magnitude 6.  FOV 180 degrees.

Binoculars.  Magnification 10x.  Magnitude 8.  FOV 10 degrees.

Small telescope (2-5").  Magnification 100 - 200x.  Magnitude 8-9.  FOV 1 degree.

Medium telescope (6-10"). Magnification 300-500x. Magnitude 10-12. FOV .1 degree.

Large telescope (11-20"). Magnification 600-1000x. Magnitude 13-14.  FOV .01 degree.


Lists of cool deep space objects.
Messier list.  110 cool deep space objects.
Caldwell list.  110 cool objects missed by Messier.
NGC list.  New General Catalog.
IC list.  Index Catalog.


The brightest stars (and the constellations they are in).  
The sun.
Sirius (Canis Major) 
Canopus (Carina)
Alpha Centauri (Centaurus)
Arcturus (Bootes)
Vega (Lyra)
Capella (Auriga)
Rigel (Orion).
Procyon (Canis Major)
Achernar (Eridanus)
Betelgeuse (Orion)
Agena (Centaurus)
Altair (Aquilla)
Aldebaran (Taurus)
Spica (Virgo)
Antares (Scorpius)


360 degrees in a circle.
60 minutes in one degree
60 seconds in one minute.


Field of view

10 magnification yields a 10 degree field of view
100 magnification yields a 1 degree field of view
1000 magnification yields a .1 degree field of view.

10 degrees is the distance of one fist at arms length.
2 degrees is the width of one finger at arms length

Most binoculars can see around 6 degree field of view.

Orions belt is about 3 degrees
Bowl of Big Dipper is abotr 10 degrees



Naked eye can see 5-6 mag
10x binoculars can see7-8 magnitude
Small telescopes (2 to 4 inches) can see 100x  to200x, and can see 8-9 magnitude stars.
Medium telescopes (6 to 10 inches) can see 300x to 500x, and can see 10-12 magnitude stars.
Largest amatuer telescopes (12 to 20 inches) can see up to 600x to 1000x, and can see 12-2 magnitude stars
Largest ground scopes like Palomar or Keck ( ? inches) can see up to ?x, and can see 25 magnitude stars.
Space-based telescopes like Hubble sees 30 magnitude

-25     Sun
-1     Sirius
0     Arcturus
5     100 times less bright
10     10,000 times less bright
15     1,000,000 times less bright


Light telescopes.

Relate the variables of aperature size, focal length, focal ratio, field of view, magnification and magnitude.



Larger aperature gathers more light.  More light means seeing fainter stars.

Approximately 25 mm per inch

50mm = 2 inch scope.
50mm = 2 inch scope
75mm = 3 inch scope
100mm = 4 inch socpe
125mm  = 5 inch scope
150mm = 6 inch scope
200mm = 8 inch scope
250mm = 10 inch scope
300mm = 12 inch scope


Focal length
Focal length equals the distance from lense or mirror to eyepiece.
300mm = 1 foot focal length
600mm = 2 foot focal length
900mm = 3 foot focal length
1200mm = 4 foot focal length
1500mm = 5 foot focal length
1800mm = 6 foot focal length
2100mm = 7 foot focal length
2300mm = 8 foot focal length

A longer focal length has what effect?
A shorter focal length has what effect?


Focal ratio
Focal ratio equals the focal length divided by aperature.  

Low focal ratio.  F4.  F6.
High focal ratio.  F8.  F10.

Large aperature with low focal length equals
Narrow aperature with high focal length equals

Deep sky telescopes typically have low f ratios
Planetary telescopes typically have high f ratios.

A larger aperature results in a lower focal ratio.  A smaller aperature results in a higher focal ratio.
A shorter focal length results in a lower focal ratio.  A longer focal length results in a higher focal ratio.



Manification equals focal length of scope divided by focal length of eyepiece.
Working magnification is approximately 50 times the aperature in inches.  Or 2 times the aperature in millimeters.

50mm or 2 inches.  100 magnification.
75mm or 3 inches.  150 magnification.
100mm or  4 inches.  200 magnification.
125mm or 5 inches.  250 magnification.
150mm or 6 inches.  300 magnification.
200mm or 8 inches.  400 magnification.
250mm or 10 inches.  500 magnification.
300mm or 12 inches.  600 magnification.


Field of view
Field of view is how wide an area you can see, measured in degrees.
Its good to have a wide field of view.

Field of view depends on magnification.  
Field of view depends on aperature.  
Field of view depends on focal ratio.  
Field of view depends on eyepiece size.

What field of view at 25 magnification is considered good?
What field of view at 100 magnification is considered good? 
What field of view at 200 magnification is considered good?

(1 degree field of view at 100 magnification is considred wide or narrow?)


Field of view can be increased by lowering magnification or increasing aperature.

AOTBE: all other things being equal.

AOTBE, an increase in magnification results in a narrower field of view. 
AOTBE, a decrease in magnification results in a wider field of view.

AOTBE, as aperature increases, field of view increases, and magnitude of star visible increases.
AOTBE, as aperature decreases, field of view decreases, and magnitude of star visible decreases.

Typical telescope stats
<aperature in mm>50mm
<aperature in inches>2 inches
<approx. magnification>100x
<approx. field of view>
<approx. viewable magnitude>

<aperature in mm>62mm
<aperature in inches>2.5 inches
<approx. magnification>125x
<approx. field of view>
<approx. viewable magnitude>

<aperature in mm>75mm
<aperature in inches>3 inches
<approx. magnification>150x
<approx. field of view>
<approx. viewable magnitude>

<aperature in mm>100mm
<aperature in inches>4 inches
<approx. magnification>200x
<approx. field of view>
<approx. viewable magnitude>

<aperature in mm>125mm
<aperature in inches>5 inches
<approx. magnification>250x
<approx. field of view>
<approx. viewable magnitude>

<aperature in mm>150mm
<aperature in inches>6 inches
<approx. magnification>300x
<approx. field of view>
<approx. viewable magnitude>

<aperature in mm>200mm
<aperature in inches>8 inches
<approx. magnification>400x
<approx. field of view>
<approx. viewable magnitude>

<aperature in mm>250mm
<aperature in inches>10 inches
<approx. magnification>500x
<approx. field of view>
<approx. viewable magnitude>

<aperature in mm>300mm
<aperature in inches>12 inches
<approx. magnification>
<approx. field of view>
<approx. viewable magnitude>

<aperature in mm>
<aperature in inches>14 inches
<approx. magnification>
<approx. field of view>
<approx. viewable magnitude>

<aperature in mm>
<aperature in inches>16 inches
<approx. magnification>
<approx. field of view>
<approx. viewable magnitude>

<aperature in mm>
<aperature in inches>18 inches
<approx. magnification>
<approx. field of view>
<approx. viewable magnitude>

<aperature in mm>
<aperature in inches>20 inches
<approx. magnification>1000x
<approx. field of view>
<approx. viewable magnitude>



Constellations are groups of bright stars that appear to be near to each other.

Constellations are stars that appear near to each other, at least to humans on earth looking at the night sky.  In reality the stars can be very far from each other in space.

From ancient times insomniacs looked at stars and picked out patterns, much like day dreamers look at clouds and pick out patterns.  The patterns of stars are called constellations.  For hundreds of thousands of years people have been looking at constellations.  Astronomers agreed on a formal list of 88 constellations in the 1930's.  Then, with the invention of the chair, people shifted their gaze to television sets.

The constellations divide the sky up into areas and make night objects easier to locate.  There are 54 constellations in the northern hemisphere and 34 constellations in the southern hemisphere.

A sky map makes it easier to spot constellations, stars, planets, etc.  Sky maps can be found in books, magazines, the Internet, etc.

(See the Astronomy database)


HISTORY OF ASTRONOMY (see history database)