Solar System: Consists of the Sun, and everything bound to it by gravity. This includes the 8 planets and their moons, the asteroids, the dwarf planets, all the Kuiper belt objects, the meteoroids, comets and interplanetary dust. Galaxy: large system of stars held together by mutual gravitation and isolated from similar systems by vast regions of space. The Milky Way measures about 100,000 light-years across, and is thought to contain 200 billion stars. Universe: the totality of known or supposed objects and phenomena throughout space; the cosmos; macrocosm

Origin of Modern Astronomy Who is Stan Hatfield and Ken Pinzke

Early Astronomy Ancient Greeks  Astronomy is the science that studies the universe. It includes the observation and interpretation of celestial bodies and phenomena.  The Greeks used philosophical arguments to explain natural phenomena.  The Greeks also used some observational data.

Early Astronomy Ancient Greeks  Geocentric Model = Ptolemy Greek Astronomer • In the ancient Greeks’ geocentric model, the moon, sun, and the known planets—Mercury, Venus, Mars, and Jupiter—orbit Earth.  Heliocentric Model = Nicolaus Copernicus • In the heliocentric model, Earth and the other planets orbit the sun.

Early Astronomy The Birth of Modern Astronomy  Nicolaus Copernicus • Copernicus concluded that Earth is a planet. He proposed a model of the solar system with the sun at the center. Heliocentric Model This model explained the retrograde motion of planets better than the geocentric model.

Early Astronomy The Birth of Modern Astronomy  Tycho Brahe • Tycho Brahe designed and built instruments to measure the locations of the heavenly bodies. Brahe’s observations, especially of Mars, were far more precise than any made previously.  Johannes Kepler • Kepler discovered three laws of planetary motion: 1. Orbits of the planets are elliptical. 2. Planets revolve around the sun at varying speed. 3. There is a proportional relationship between a planet’s orbital period and its distance to the sun.

Early Astronomy The Birth of Modern Astronomy German astronomer Johannes Kepler (1571-1630) helped establish the era of modern astronomy by deriving three laws of planetary motion.

Early Astronomy  Galileo Galilei Italian scientist Galileo Galilei (1564—1642) used a new invention, the telescope, to observe the Sun, Moon, and planets in more detail than ever before.

Early Astronomy  Sir Isaac Newton English scientist Sir Isaac Newton (1642—1727) explained gravity as the force that holds planets in orbit around the Sun.

Gravity’s Influence on Orbits Makes no sense without caption in book

Newton’s Laws of Motion 1st Law A body at rest, or in uniform motion, will remain so unless acted upon by an unbalanced force. 2nd Law The change in motion (acceleration) is proportional to the unbalanced force 3rd Law For every action there is an equal and opposite reaction

Gravity Gravity is the force that holds us to the Earth causes a rock to fall towards the ground causes the Earth to go around the Sun causes the Sun to be pulled towards the center of the Milky Way galaxy Gravity acts between any two objects even if they are far apart. “action at a distance”

Summary Kepler’s and Galileo’s Laws provided Newton with important clues that helped him formulate his laws of motion Newton arrived at 3 laws that govern the motion of objects The law of inertia The law of force The law of action and reaction Newton also arrived at a law of gravity But it seemed to require action at a distance!

Light and Astronomical Observations Earth Science Light and Astronomical Observations

Important Astronomical Measurements • An ellipse is an oval-shaped path. An astronomical unit (AU) is the average distance between Earth and the sun; it is about 150 million kilometers. Light-year The distance that light travels in one year, about 9.5 trillion kilometers. Parsec: A unit of measurement used to describe distances between celestial objects, equal to 3.258 light-years.

The study of light Electromagnetic radiation Visible light is only one small part of an array of energy Electromagnetic radiation includes Gamma rays X-rays Ultraviolet light Visible light Infrared light Radio waves *Energy radiated in the form of a wave, resulting from the motion of electric charges and the magnetic fields they produce.

The study of light Electromagnetic radiation Wave model All forms of radiation travel at 300,000 kilometers (186,000 miles) per second Light (electromagnetic radiation) can be described in two ways Wave model Wavelengths of radiation vary Radio waves measure up to several kilometers long Gamma ray waves are less than a billionth of a centimeter long White light consists of several wavelengths corresponding to the colors of the rainbow A continuum depicting the range of electromagnetic radiation, with the longest wavelength at one end and the shortest at the other.

Light (electromagnetic radiation) can be described in two ways Particle model Particles called photons Exert a pressure, called radiation pressure, on matter Shorter wavelengths correspond to more energetic photons

The study of light Spectroscopy The study of the properties of light that depend on wavelength The light pattern produced by passing light through a prism, which spreads out the various wavelengths, is called a spectrum (plural: spectra)

The study of light A spectrum is produced when white light passes through a prism

The Doppler effect Originally discovered by the Austrian mathematician and physicist, Christian Doppler (1803-53), this change in pitch results from a shift in the frequency of the sound waves.

The Doppler effect The electromagnetic radiation emitted by a moving object also exhibits the Doppler effect. Redshift, a phenomenon of electromagnetic waves such as light in which spectral lines are shifted to the red end of the spectrum.

The Doppler effect Blueshift: This spectrum shows hydrogen shifted to the blue end of the spectrum. This star is moving toward Earth. The radiation emitted by an object moving toward an observer is squeezed; its frequency appears to increase and is therefore said to be blueshifted. In contrast, the radiation emitted by an object moving away is stretched or redshifted. Blueshifts and redshifts exhibited by stars, galaxies and gas clouds also indicate their motions with respect to the observer. Redshift: This spectrum shows hydrogen shifted to the red end of the spectrum. This star is moving away from Earth.

The Big Bang Theory The theory holding that the universe originated from the instant expansion of an extremely small agglomeration of matter of extremely high density and temperature.

Photons converted into particle-antiparticle pairs and vice-versa E = mc2 Early universe was full of particles and radiation because of its high temperature

The Big Band Theory Evidence for Big Bang This is the theory of the universe’s earliest moments. It presumes that the universe began from a tiny, hot, and dense collection of matter and radiation. It describes how expansion and cooling of particles could have led to the present universe of stars and galaxies. It explains several aspects of today’s universe with a very good accuracy.

Evidence for the Big Bang In 1927, the Belgian priest Georges Lemaître was the first to propose that the universe began with the explosion of a primeval atom.