- Speed of a wave (how fast it travels): wavelength / period = wavelength X frequencyThe speed of light: 300,000 km/second (3E8 m/s). Andromeda galaxy is the nearest galaxy to us. We see galaxies that are billions of light years away, so the light we see from them left billions of years ago. Each little slight of the universe is giving you a different snapshot in time. You can trace the evolution of the universe because light takes TIME to travel, and we can capture the light and study it. Remember, light behaves like a wave! The Ripple Tank Effect is an illusion, where you drop pebble in water, waves emanate from inside out. Property of waves is interferenceof waves, where you see bright dots and dark dots. Waves essentially are emanating from points. Crests are the brighter regions and troughs are the darker regions and when they interfere, you will see brighter points and darker points. Bright and dark bands are unique to waves when they interfere or “run into” each other, which we saw in water in the Ripple Tank Effect. Light has short wavelength, so it’s difficult to see it. You want to capture light using equipment to capture light waves that interfere with each other. Coinciding crests = brighter (constructive interference) Coinciding troughs = darker (constructive interference)Every object we see is made up of positive and negative charged particles. When you increase the T of an object, you are actually increasing the average thermal motion between those particles.Whenever charged particles oscillate (move rapidly) they emit electromagnetic radiation. Temperature: measure of how fast particles are moving in given material being analyzed/ Absolute scale gives more accurate characterization of thermal motion: kelvin scale. At 0 K, all molecular motion stops.A Blackbody is an ideal object that can absorb every light or energy. As it absorbs it, it transforms the energy and thermalizes the energy, and emits it back into space in a particular fashion. Stars are good representations of Black Bodies. Blackbody spectrum is determined ONLY by its TEMPERATURE. Given a certain temperature, a curve (Planck curve) shows how much light that particular object is emitting. Radiation Laws include Wien’s Law and Stefan-Boltzmann Law. Wien’s Law:the higher the temperature, the more to the left the peak will be. More ration of SHORTER wavelengths are being emitted (higher temperature, shorter wavelength). Lambda of max = .29mm/T (in K). Stefan-Boltzmann Law: Tells how much energy is being emitted when increasing Temperature: Curve gets taller and taller as you increase the T. The peak goes to the left (Wien’s) AND the peak gets taller (Stefan-Boltz). F = sigma * T^4 (sigma – constant 5.67E-8 W.m^2 * K^4) F = energy per second per unit area. Two stars with different surface areas and SAME Temp: stars with BIGGER SA will look BRIGHTER.Kirchhoff’sthree laws are important for understanding the composition of a given object through spectroscopy. First law: Hot dense objects emit a continuous spectrum. Light is emitted when an electron jumps down an orbit (shell) and light is absorbed so that an electron can climb up to a higher energy level. Bigger jumps have higher energy associated with the jumps. Blue light emitted for big jumps (UV or X ray emitted from even bigger jumps to higher energy levels). Red light emitted from a smaller jump (jumping to a lower energy level). Planck’s constant: 6.63E-34 joule seconds (J * s); light comes in packets of energy called photons.Second law: A hot transparent gas produces an emission light spectrum; a series of bright spectral lines against a dark background (emissionspectra).Light passing through prism show colors that electrons like to emit; the colors you see are opposite of colors that are absorbedThird law: whenever you have dark lines (corresponding to colors missing) produces absorptionspectra. Absorption spectrum used to identify elements. Sodium emits yellow light (i.e. flame test) so it absorbs all other colors besides the two nanometers of light that are missing). For absorption spectrum of the sun, the dark spots help us identify which elements are present on the sunASTRON 0089 1st EditionExam # 1 Study Guide Lectures: 1 - 11Lecture 1 Notes from this lecture will not be on the exam.Lecture 2 Light year is a unit of distance, NOT a unit of time! “light years away” is the correct way to express this unit “Light years ago” is incorrect, because that would imply a unit of time, which is incorrect. - 1 light year = 9.46E12 km (about 10 trillion km) - 100,000 light years across is how large the Milky Way Galaxy is - Though light year is not a unit of time, light minutes is The time it takes for light to travel from the sun to the Earth is expressed in light minutes, seconds, hours, etc. I.e. Light travels from the Sun to the Earth in 8 minutes, ergo 8 light minutesthe distance between the Earth and the Sun is 1 astronomical unit (AU) - The distance from the Sun to Mercury: .39 AU - The distance from the Sun to Pluto: 40 AU **Note: the lecture provided under January 5th is also part of this lecture on January 6th. Lecture 3 Half of the Earth is ALWAYS lit by the Sun. Earth is not exactly a sphere. There are DIFFERENTparts of Earth are lit by the Sun because the Earth spins. Light always comes from the left. The rising and setting of the stars is the effect of Earth’s rotation. You see different parts of the sky atdifferent times of the year. The Sun appears to move through a fixed set of constellations over a year. The apparent path of the Sun is called the ecliptic. A Zodiac is defined as constellations along the ecliptic. Faint stars together give impression of a band. You can see about 3,000 stars in sky with naked eye. Stars are distributed randomly. Human brain picks up patterns, which is why constellations exist and helps humans locate stars. Stars are at different distances from each other and they are not physically related to eachother! Asterism is a recognizable dot-to-dot pattern of stars, used to navigate through the sky. Constellation is one of 88 sections in the sky (each section is a constellation). Procession is a term used to describe that the Earth spins like a top. The Sun and the Moon influence Earth, so that there is a slight tug on Earth from both entities, causing procession. Similar to a tug of war, except the Earth isn’t being pulled linearly back and forth, but in a circle. There is a