Reminders Reflective Essay due Friday 4/26 – 5 points for each day late Final Project Thursday 5/16 Final Exam Tuesday 5/21 Observations No Later Than 5/23 – Any star, any constellation- big dipper, summer triangle – Leo (backward question mark), summer triangle

10 Astronomy Things to Remember for 50 Years

Reason for the Seasons Cold winter and warm summer is not because the earth is closer to the sun in summer. Seasons are caused by the tilt of the earth relative to the sun. The north pole of the earth always points toward the same position in the sky As the earth orbits the sun’s light falls more directly on the northern or southern hemisphere during different times of the year.

Draw and label this diagram or the next.

Solar System Terrestrial Planets (earth like rocky) – Mercury – Venus – Earth – Mars Asteroid Belt Gas Giants – Jupiter – Saturn – Uranus – Neptune Dwarf Planets – Pluto

Star Process Stars emit energy produced by the fusion of light nuclei to produce heavier nuclei energy. For much of their life, stars fuse hydrogen into helium. 4 H +  He +4 + energy Later in life some stars are massive enough to generate enough heat to fuse helium into carbon or oxygen. Very massive stars may sustain fusion of even heavier elements up to but not including iron. Elements heavier than iron are produced during the explosion of stars not during life of stars.

Locate a constellation Pick a favorite constellation (asterism) Tell the best time of the year to see the constellation. At that time of year where in the sky would you look for the constellation. Sketch the asterism.

Astronomy versus astrology Astronomy is the branch of science dealing with objects and phenomena that lie beyond the Earth’s atmosphere. Astrology is art or practice that seeks to foresee and foretell future events by the position of the stars and planets.

Gravity The force that ‘won” the universe. Common Sense versus Science – Objects fall “down” when not supported Aristotle- why do things fall? – The natural place for heavy objects is the center of the earth Galileo – How not why do things fall – Objects of different weights fall the same speed – Falling objects move more and more quickly – Distance fallen is proportional to the square of the time lapsed.

Gravity Newton – How but not why? – Why does the moon not fall into the earth? – It is falling but keeps missing the earth. – Moon and objects on the earth experience the force of gravity (unified terrestrial and ethereal laws) – F= G m 1 m 2 /r 2 Einstein – Why? – Presence of matter bends spacetime causing the path of a moving object to appear to be change by a force.

10 things to remember 1.Reason for the seasons (not Christmas season) 2.Solar System- names, order, classification 3.Star process- nuclear fusion 4.Location of a constellation 5.Difference between astronomy and astrology 6.Gravity – Newton and Einstein’s contributions 7.Light, EM spectrum, Doppler effect 8.Phases of Moon 9.Difference between Comets and Meteors 10.Light year – how to calculate

All we know about the Universe Everything that astronomers know about the universe is carried on waves of electromagnetic energy (light) Light is produced when an electron in an atom moves from a higher energy level to a lower energy When an electron in an atom absorbs a photon of electromagnetic energy the electron moves from a lower to a higher energy level. The wavelength of the photon can vary from very short for Gamma rays to very long for radio waves depending on the energy level jumps.

Light Elements can be identified by the wavelength of EM energy emitted or absorbed. Spectral analysis Doppler Effect is the change in wavelength of light energy when the source is moving toward or away from the observer. The wavelength of photons produced in atoms moving away from us are lengthened (red shift) while photons produced by atoms moving toward us are shortened (blue shift)

Electromagnetic Spectrum What we refer to as light is but the small segment of the electromagnetic spectrum which human eyes can detect. The Electromagnetic spectrum is the full range of wavelengths and frequencies of electromagnetic waves extending from long radio waves to short gamma rays.

Light (continued) The wavelength of EM (light) emitted by a star depends on the temperature of the star. Light becomes the cosmic thermometer. The bending of light by mirrors and lenses is used to produce telescopes which perform the following tasks: – Gather light - brighten (light bucket) – magnify – resolve

Light Speed d = s * t c= 186,000 miles/second = 3X10 5 km/s Time in seconds 1 minute = 60 seconds 1 hour = 60 minutes 1 day = 24 hours 1 week = 7 days 1 month = 30 days 1 year = 365 days (ok )

Distance for any period Light hour = Light day = Light week = Light month = – Which month? Light fortnight =

Light Year = distance unit Speed of light is the cosmic speed limit c= 3 X 10 8 m/s = 3 X 10 5 km/s = 186,000 mi/s seconds per year = 365 dys/yr X 24hrs/day X 60 min/hr X 60sec/min = X 10 7 sec/year Distance light travels in a year = (3 X 10 5 km/s ) X ( X 10 7 sec/yr) = 9.46 X km/yr or 5.87 X miles/year

Moon Phases As Moon orbits Earth the half of the moon illuminated by sun light changes position relative to Earth. This results in different amounts of illuminated lunar surface facing Earth at different times during the monthly orbit of the moon.

Comets and Meteors Comet – a small body of ice and dust in orbit about the Sun Asteroid- a larger rock in space Meteoroid- a small rock in space Meteor- The streak of light seen when any space debris vaporizes in Earth’s atmosphere Meteorite – A fragment of space debris which survives passage through the atmosphere and comes to rest on Earth.