Spiral Galaxies Similar to the Milky Way. Edge view. View from above. The Milky Way. The Sun is located on the Orion spiral arm about 30,000 LY from the galactic center. It takes about 230 million years for the sun to complete one orbit around the galactic center.
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Spiral Galaxies Similar to the Milky Way
View from above
The Milky Way
The Sun is located on the Orion spiral arm about 30,000 LY from the galactic center
It takes about 230 million years for the sun to complete one orbit around the galactic center
Other Galaxies in Our Local Group
A Ring Galaxy
The Andromeda Galaxy
2.3 million LY away
Deep field view - about 10 billion LY away
If the Universe was one year old (instead of 15 billion years)
The Cosmic Calendar (Carl Sagan)
1027 meters = 1000 yottameters
100 Billion Light Years
This image represents the size of the known universe -- a sphere with a radius of 13.7 billion light years.
1026 meters = 100 yottameters
Ten Billion Light Years
Light from galaxies on the edge would require 5 billion years to reach the center. Observers at the center are seeing light that was emitted by these galaxies before the solar system formed. The largest scale picture ever taken. Each of the 9325 points is a galaxy like ours. They clump together in 'superclusters' around great voids which can be 150 million light years across.
1025 meters = 10 yottameters
One Billion Light Years
Astronomers have determined that the largest structures within the
visible universe - superclusters, walls, and sheets - are about 200 million
light years on a side.
1024 meters = 1 yottameter
100 Million Light Years
Clusters of Galaxies
1023 meters = 100 zettameters
10 Million Light Years
Within the Virgo Cluster
1022 meters = 10 zettameters
1 Million Light Years
The Local Group - Our galaxy with the Magellanic
Clouds - two companion galaxies on the right.
1021 meters = 1 zettameter
100,000 Light Years
Our galaxy - the Milky Way - looks rather like a whirlpool. It has spiral arms curling outwards from the center and rotates at about 900 kilometres per hour. It contains about 200 billion stars.
1020 meters = 100 exameters
10,000 Light Years
Our Spiral Arm
1019 meters = 10 exameters
1,000 Light Years
The Stars of the Orion Arm
1018 meters = 1 exameter
100 Light Years
Stars within 50 Light Years
1017 meters = 100 petameters
10 Light Years
The Nearest Stars
1016 meters = 10 petameters
1 Light Year
The Oort Cloud
1015 meters = 1 petameter
0.1 Light Year
Sol - our Sun
1014 meters = 100 terameters
Our Sun and a few rocks
1013 meters = 10 terameters
The solar system. Only the orbit of Pluto, the furthest planet from the Sun, is off the picture.
1012 meters = 1 terameter
Within the orbit of Jupiter - the orbits of the inner four planets : Mercury, Venus, Earth and Mars. All four have rocky crusts and metallic cores.
1011 meters = 100 gigameters
Six weeks of the Earth's orbit. The orbits of Venus and Mars are just visible on either side.
1010 meters = 10 gigameters
Four days of the Earth's orbit.
109 meters = 1 gigameter
The moon's orbit around the Earth, the furthest humans have ever traveled.
108 meters = 100 megameters
107 meters = 10 megameters
North and Central America
106 meters = 1 megameter
105 meters = 100 kilometer
The San Francisco Bay Area
104 meters = 10 kilometers
103 meters = 1 kilometer
Golden Gate Park
102 meters = 100 meters
Japanese Tea Garden - one hectare (10,000 m2)
101 meters = 10 meters
A pond with lily pads
100 meters = 1 meter
A one-meter square
10-1 meters = 10 centimeters
A bee on a lily pad flower
10-2 meters = 1 centimeter
A bee's head
10-3 meters = 1 millimeter
A bee's eye
10-4 meters = 100 micrometers
10-5 meters = 10 micrometers
10-6 meters = 1 micrometer
Virus on a bacterium
10-7 meters = 100 nanometers
10-8 meters = 10 nanometers
The structure of DNA
10-9 meters = 1 nanometer
The molecules of DNA
10-10 meters = 100 picometers
Carbon's outer electron shell
10-11 meters = 10 picometers
The inner electron cloud
10-12 meters = 1 picometer
Within the electron cloud
10-13 meters = 100 femtometers
10-14 meters = 10 femtometers
The nucleus of carbon
10-15 meters = 1 femtometer
10-16 meters = 100 attometers
Within the proton
10-17 meters = 10 attometers
Quarks and gluons
We are “Star Stuff”
The Orion Nebula
Located in the sword of the constellation Orion.
Proplyds or Proto Solar Systems in the Orion Nebula
Gaseous Pillars - Stellar Nursery
What is Science?
Why study science?
Why study science? (Continued)
Why are we able to study nature?
Philosophical approach to the study of nature.
Scientific approach to the study of nature
Scientific approach to the study of nature.
– Hypothesis that cannot be tested with reproducible results;
Cold fusion, ufo's, astrology. . .
Scientific approach to the study of nature.
Scientific approach to the study of nature.
The Scientific Method
Hallmarks of Science
The idea that scientists should prefer the simpler of two models that agree equally well with observations - the second hallmark - after medieval scholar William of Occam (1285 - 1349).
For instance, original model of Copernicus (Sun-centered) did not match the data noticeably better than Ptolemy's model (Earth-centered). Thus, a purely data-driven judgment based on the third hallmark might have led scientists to immediately reject the Sun-centered idea. Instead, many scientists found elements of the Copernican model appealing, such as the simplicity of its explanation for apparent retrograde motion. Was kept alive until Kepler found a way to make it work.
The most exciting words in science are
not “Eureka (I found it)” but “Now that’s
1. ROTATION ON ITS AXIS - Day
2. REVOLUTION ABOUT SUN- Year
3. PRECESSION- Wobble of spin axis
Motions of Earth
The Earth rotates about its axis axis once per day - one rotation equals one day. The axis goes through the north and south poles and through the center of the Earth. It rotates counterclockwise when looking down on the north pole which means that the sun rises in the east and sets in the west.
The Rotation of the Earth From Space
Earth’s rotation causes the stars - the celestial sphere - to appear to rotate around the Earth. Viewed from outside, the stars (and the Sun, Moon, and planets) therefore appear to make simple daily circles around us. The red circles represent the apparent daily paths of a few selected stars.
Envisioned by the ancients, the celestial sphere had Earth at the center with the stars emblazoned on the sphere. They thought the stars rose and set because the celestial sphere (the sky) rotated, carrying the stars from east to west. All stars appear to move around two points on the celestial sphere, the north and south celestial poles—projections of earth’s axis of rotation. Earth's equator projected on the celestial sphere becomes the celestial equator.
Our lack of depth perception when we look into space creates the illusion that the Earth is surrounded by a celestial sphere. Thus, stars that appear very close to one another in our sky may actually lie at very different distances from Earth.
Constellations - groupings of stars named after mythical heroes, gods, and mystical beasts
- made up over at least the last 6000 years - maybe more
- used to identify seasons:
- farmers know that for most crops, you plant in the spring and harvest in the fall.
- in some regions, not much differentiation between the seasons.
- different constellations visible at different times of the year - can use them to tell what month it is. For example, Scorpius is only visible in the northern hemisphere's evening sky in the summer.
- many of the myths associated with the constellations thought to have been invented to help the farmers remember them - made up stories about them
Picture at right shows a start chart of the region around the constellation Orion. Picture at the left is an ornate star chart printed in 1835 - shows the great hunter Orion. He is holding a lion's head instead of his traditional bow or shield. He is stalking Taurus, the Bull in the upper right hand corner. Behind him, his faithful dog, Canis Major, is chasing Lepus, the Hare.
Western culture constellations originated in Mesopotamia over 5000 years ago - added to by Babylonian, Egyptian, and Greek astronomers - current list based charts of Roman astronomer, Claudius Ptolemy (~140 AD)
In modern world - constellations redefined so now every star in the sky is in exactly one constellation.
In 1929, the International Astronomical Union (IAU) adopted official constellation boundaries that defined the 88 official constellations that exist today.