February 4

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Transcript February 4

Survey of the Universe
Tom Burbine
[email protected]
Chemistry
• The science of matter and the changes it
undergoes.
Atoms
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Atoms are made up of 3 types of particles
Protons – positive charge (+1)
Electrons – negative charge (-1)
Neutrons – neutral charge (no charge)
Protons and Neutrons are found in the nucleus
Elements
• Different elements have different numbers of
protons
• The properties of an atom are a function of the
electrical charge of its nucleus
Definitions
• Atomic Number – Number of protons
• Atomic Mass – Number of protons and neutrons
• U235 – atomic mass
92- atomic number
• Isotopes – Same number of protons but different
numbers of neutrons
Periodic Table
• A chart in which all known elements are listed in
order of atomic number
• Period – Horizontal row
• Across any period, the properties of elements
change
• Group – Vertical column
• Down any group, the properties of elements are
very similar
Radioactivity
• Radioactivity – decay of an atomic nucleus
• All elements with an atomic number greater than
82 (lead) are radioactive
Bohr’s Planetary Model
• Electrons orbit the nucleus in specific energy levels
• Level n=1 is closest to nucleus
• Level n=2 is second closest
Shell Model
• Electrons behave as they are arranged in a series of
concentric shells around the nucleus
• Innermost shell can contain 2 electrons
• The second and third shells can contain 8 electrons each
• The fourth and fifth shells can contain
18 electrons each
Ion
• Ion – an electrically charged particle created
when an atom either loses or gains one or more
electrons
4 Forces that operate in the universe
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Gravity
Electromagnetism
Strong Force
Weak Force
Examples of elementary particles
• Quarks – make up protons and neutrons
• Electrons
• Neutrino – almost massless particle with no
charge that travels almost at the speed of light
• Photons – particles of light
Celestial Sphere
• an imaginary sphere of infinite extent on which
all celestial objects appear to lie
Celestial Sphere
Terminology for looking at the sky
What is a constellation?
Constellations
• People refer to constellations as a pattern of stars
• Astronomers refer to constellations as specific
regions of the sky
• In 1928, the IAU (International Astronomical
Union) decided there were 88 constellations
• Many of the constellation names go back
thousands of years
Constellations
• The constellations are totally imaginary things
that poets, farmers and astronomers have made up
over the past 6,000 years (and probably even
more!).
• The real purpose for the constellations is to help
us tell which stars are which, nothing more.
What is this
constellation?
Orion
Bigger the star, the brighter it is
Orion was the son of the god of
the sea, Poseidon and a great hunter.
One story is that he made an enemy of
Hera who sent a scorpion to sting him.
Orion was restored to health by
Ophiuchus, the first doctor of medicine.
Another story is that Artemis was
Tricked by Apollo to shoot an arrow
at Orion. When he died, Poseidon
asked Zeus to put him among the stars.
Ursa Major
• Ursa Major, the Great Bear, was identified with a
bear by native American Indians of the
Northeastern United States and the ancient
Greeks.
• The name common in Britain, the Plough, seems
to have a medieval origin,
• Another common name among northern European
cultures is the Wain, a shortened form of wagon
What are the constellations named after
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14 men and women
9 birds
2 insects
19 land animals
10 water creatures
2 centaurs
one head of hair
a serpent
a dragon
a flying horse
a river
29 inanimate objects
Why don’t all the constellations have
ancient names?
• Ancient cultures such as the Greeks and
Egyptians could not see the constellations in the
Southern Hemisphere
Polaris
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Polaris is called the North Star
Brightest star in the constellation Ursa Minor
Does not appear to move in the night sky
It is very close to the north celestial pole, making
it the current northern pole star.
• 48th brightest star in the night sky
Any Questions?