Download Linking Asteroids and Meteorites through Reflectance Spectroscopy

Astronomy 101
The Solar System
Tuesday, Thursday
Tom Burbine
[email protected]
Course
• Course Website:
– http://blogs.umass.edu/astron101-tburbine/
• Textbook:
– Pathways to Astronomy (2nd Edition) by Stephen Schneider
and Thomas Arny.
• You also will need a calculator.
• There is an Astronomy Help Desk that is open
Monday-Thursday evenings from 7-9 pm in Hasbrouck
205.
• There is an open house at the Observatory every
Thursday when it’s clear. Students should check the
observatory website before going since the times may
change as the semester progresses and the telescope
may be down for repairs at times. The website is
http://www.astro.umass.edu/~orchardhill/index.html.
Exam #1
• Average was 85
HW #6
• Due by Feb. 23rd at 1 pm
In the News: Meteorite
• Fell in a doctor’s office in Lorton, Virginia
In the News: Asteroid Collision
http://www.csmonitor.com/Science/Discoveries/2010/0202/Has-the-Hubble-Space-Telescope-spied-asteroid-on-asteroid-collision-debris
Energy
• Energy is the ability to generate motion
Conservation of Energy
• Energy is neither created or destroyed – it just
changes forms
• Conservation of Energy
– The energy in a closed system may change form, but
the total amount of energy does not change as a result
of any process.
Energy units
• In English Units, we use calories to measure
energy
• In science (and in this class), we will use joules to
measure energy
• 1 Joule = 1 kg*m2/s2
Joule
• One joule is defined as the amount of work done
by a force of one Newton moving an object
through a distance of one meter
• Work is the change in enerrgy
• Work = Force * distance
3 basic categories of energy
• Kinetic energy – energy of motion
• Potential energy – energy being stored for
possible conversion into kinetic energy
• Radiative energy – energy carried by light
Kinetic energy
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Kinetic energy = ½ mv2
m is mass in kg
v is velocity in meters/s
Remember: a joule has units of kg*m2/s2
• How much kinetic energy does a 2 kg rock have if
it is thrown at 20 m/s?
• Kinetic energy = ½ mv2
• A) 200 J
• B) 400 J
• C) 40 J
• D) 800 J
Answer
• KE = ½ * 2 * (20) *(20) = 400 joules
Thermal energy
(kind of kinetic energy)
• Temperature is a measure of the average kinetic
energy of the particles
• Higher temperature – more kinetic energy,
particles moving faster
• For examples, air molecules around you are
moving at ~600 m/s
http://eo.ucar.edu/webweather/molecules.html
Temperature scales
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In America, we use Fahrenheit
Water freezes at 32 degrees F
Water boils at 212 degrees F
Everywhere else, they use Celsius
Water freezes at 0 degrees C
Water boils at 100 degrees C
In Science
• Temperature is measured in Kelvin
• Zero Kelvin is absolute zero – nothing moves
• Add 273.15 to the Celsius temperature to get the
Kelvin temperature
• 273.15 Kelvin = 0 degrees Celsius
Gravitational Potential Energy
• Gravitational Potential Energy released as an
object falls depends on its mass, the strength of
gravity, and the distance it falls
• For example, your gravitational potential energy
increases as you go farther up in the air
• This is because you hit the ground at a faster
speed if you jump from a higher distance
• KE + PE = 0
• As kinetic energy increases, potential energy
decreases
Converting Mass to Energy
• What is the most famous formula in the world?
E = mc2
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m is mass in kilograms
c is speed of light in meters/s (3 x 108 m/s)
So E is in joules
very small amounts of mass may be converted
into a very large amount of energy and
Who came up with it?
• How much energy can be produced if you can
convert 10 kg of material totally into energy?
• E = mc2
• A) 3.0 x 108 J
• B) 3.0 x 1016 J
• C) 9.0 x 1017 J
• D) 9.0 x 1010 J
Answer
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E = 10 kg * (3 x 108 m/s) * (3 x 108 m/s)
E = 10* (9 x 1016) J
E = 90 x 1016 J
E = 9.0 x 1017 J
Mass-Energy
• E=mc2
• So Mass is a form of potential energy
• Where is one place where you see mass converted
into energy?
Light
• Light is a form of energy
Light
• These are all forms of light
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Gamma rays
X-rays
Ultraviolet light
Visible light
Infrared light
Radio waves
Light
• Can act as a particle
• Can also act as a wave
Particle aspect
• Particles called photons stream from the Sun and
can be blocked by your body
Photons
• Light is quantized
• Comes in discrete packets called photons
Wave aspect
Thomas Young Experiment
• http://micro.magnet.fsu.edu/primer/java/interference/dou
bleslit/
Characteristics of waves
• velocity = wavelength x frequency
• Wavelength = distance
• Frequency = cycles per second = hertz
For light
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c = wavelength x frequency
In vacuum, speed of light stays the same
So if wavelength goes up
Frequency does down
f = frequency
λ = wavelength
c=λxf
Calculations
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c=λxf
So if the wavelength is 1 x 10-12 m
3 x 108 m/s = 1 x 10-12 m * f
f = 3 x 108 m/s/1 x 10-12 m
f = 3 x 1020 s-1 = 3 x 1020 Hz
Calculations
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c=λxf
So if the frequency is 1 x 1015 Hz
3 x 108 m/s = λ * 1 x 1015 Hz
λ = 3 x 108 m/s/1 x 1015 Hz
λ = 3 x 10-7 m
Energy of light
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Energy is directly proportional to the frequency
E=h*f
h = Planck’s constant = 6.626 x 10-34 J*s
since f = c/λ
Energy is inversely proportional to the wavelength
E = hc/λ
VIBGYOR
violet
red
Higher the frequency, Higher the energy of the photon
Higher the wavelength, Lower the energy of the photon
ROYGBIV
• ROYGBIV
• Red – long wavelength
• Violet – short wavelength
http://www.arpansa.gov.au/images/basics/emr.jpg
Calculations
• What is the energy of a radio wave with a
frequency of 1 x 107 Hz?
• E=h*f
• h = Planck’s constant = 6.626 x 10-34 J*s
• E = 6.626 x 10-34 J*s * 1 x 107
• E = 6.626 x 10-27 J
Calculations
• What is the energy of a gamma ray photon with
wavelength of 1 x 10-15 m
• E = hc/λ
• h = Planck’s constant = 6.626 x 10-34 J*s
• E = 6.626 x 10-34 J*s * 3 x 108 m/s / 1 x 10-15 m
• E = 1.99 x 10-10 J
So why are some types of radiation
dangerous?
• Higher the energy, the farther the photons can
penetrate
• So gamma and X-rays can pass much more easily
into your the body
• These high-energy photons can ionize atoms in
cells
• Ionization means removes electrons from an atom
More dangerous
When you measure an astronomical body
• You measure intensity
• Intensity – amount of radiation
Matter
• Matter is material
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
• http://www.periodictable.com/
Elements
• Different elements have different numbers of
protons
• The properties of an atom are a function of the
electrical charge of its nucleus
Charge
• If an atom has the same number of electrons and
protons, it has a neutral charge
• More electrons than protons, negatively charged
• More protons than electrons, positive charged
• Neutrons have neutral charge so don’t affect the
charge of an atom
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
Molecules
• an electrically neutral group of at least two atoms
in a definite arrangement held together by very
strong chemical bonds
• H2O
• CO2
• http://www.hulu.com/watch/63320/cosmos-thelives-of-the-stars
Any Questions?