Astronomy 101 The Solar System Tuesday, Thursday Tom Burbine

Course Course Website: – 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

Exam #1 Average was 85

HW #6 Due by Feb. 23 rd at 1 pm

In the News: Meteorite Fell in a doctor’s office in Lorton, Virginia

In the News: Asteroid Collision

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 * m 2 /s 2

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 Kinetic energy = ½ mv 2 m is mass in kg v is velocity in meters/s Remember: a joule has units of kg * m 2 /s 2

How much kinetic energy does a 2 kg rock have if it is thrown at 20 m/s? Kinetic energy = ½ mv 2 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

Temperature scales 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 to the Celsius temperature to get the Kelvin temperature 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 = mc 2 m is mass in kilograms c is speed of light in meters/s (3 x 10 8 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 = mc 2 A) 3.0 x 10 8 J B) 3.0 x J C) 9.0 x J D) 9.0 x J

Answer E = 10 kg * (3 x 10 8 m/s) * (3 x 10 8 m/s) E = 10* (9 x ) J E = 90 x J E = 9.0 x J

Mass-Energy E=mc 2 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 –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 bleslit/ bleslit/

Characteristics of waves velocity = wavelength x frequency Wavelength = distance Frequency = cycles per second = hertz

For light 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 = λ x f

Calculations c = λ x f So if the wavelength is 1 x m 3 x 10 8 m/s = 1 x m * f f = 3 x 10 8 m/s/1 x m f = 3 x s -1 = 3 x Hz

Calculations c = λ x f So if the frequency is 1 x Hz 3 x 10 8 m/s = λ * 1 x Hz λ = 3 x 10 8 m/s/1 x Hz λ = 3 x m

Energy of light Energy is directly proportional to the frequency E = h * f h = Planck’s constant = x J*s since f = c/λ Energy is inversely proportional to the wavelength E = hc/λ

Higher the frequency, Higher the energy of the photon Higher the wavelength, Lower the energy of the photon redviolet VIBGYOR

ROYGBIV Red – long wavelength Violet – short wavelength

Calculations What is the energy of a radio wave with a frequency of 1 x 10 7 Hz? E = h * f h = Planck’s constant = x J*s E = x J*s * 1 x 10 7 E = x J

Calculations What is the energy of a gamma ray photon with wavelength of 1 x m E = hc/λ h = Planck’s constant = x J*s E = x J*s * 3 x 10 8 m/s / 1 x m E = 1.99 x 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 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

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 U 235 – 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 H 2 O CO 2

lives-of-the-starshttp:// lives-of-the-stars

Any Questions?