A105 Stars and Galaxies :A105 Stars and Galaxies News quiz today Moon worksheet due Thursday Finish units 5, 6, 10 in text Office hour/Solar Lab at Kirkwood Obs. TODAY, 11:00 – noon Today’s APOD


The Sun Today :The Sun Today Solar Orbiting Heliospheric Observatory (SOHO) Orbits between the Sun and Earth, about a million miles away – a constant view of the Sun


First News Quiz :First News Quiz Put your USERNAME on the scantron form You may consult with your neighbors No books, notes, papers 2 minutes per question


Modern science relies on observations and experiments! :Modern science relies on observations and experiments!


Understanding Science :Understanding Science Purpose – to understand the universe well enough to figure out the basic relationships that govern it A process for understanding and predicting will it rain tomorrow? what will be on the quiz? what will happen if…? What about facts? new discoveries better data new theories facts change!


An Ongoing Process :An Ongoing Process The process of science has been so successful because results are widely shared and evaluated experiments are reproduced and checked value of ideas based on observation and usefulness, not authority


Debating Scientific Issues :Debating Scientific Issues How do we tell who is correct? Majority vs. minority opinions Majority isn’t always right Debate is a poor technique for deciding EVIDENCE and DATA How was the experiment done? Was it repeated by others Is a new theory TESTABLE?


Warning Signs of Bad Science :Warning Signs of Bad Science How is it announced? Is the source reliable? How good is the evidence? is it anecdotal? does it appeal to authority? does it fit what you already know? does it violate widely-accepted laws or theories? is contrary evidence ignored? What kind of reasoning is used? Can the claim be tested? The Baloney Detection Collection Phil Plait's Bad Astronomy: Home Page


Slide 9:Sound travels at a speed of 300 meters per second. In analogy to the light-year, what does 1 sound-minute equal? a) The time sound takes to travel 300 meters. b) The time delay of a sound heard 300 meters away. c) The distance traveled by sound in 1 minute. d) The speed of sound 1 minute later. A Little Review….


The Sky! :The Sky! From wunderground.com The brightness of a star is shown by the size of its dot


Getting Started :Getting Started Which way is north? To find Polaris: find the Big Dipper follow to Polaris


Orion rising :Orion rising The night sky is familiar, but few people look closely at (or think about) the complex phenomena we observe in sky.


Patterns in the Sky :Patterns in the Sky What does the universe look like from Earth? Why do stars rise and set? Why do the constellations we see depend on latitude and time of year? What causes the seasons?


What does the universe look like from Earth? :What does the universe look like from Earth? With the naked eye, we can see more than 2,000 stars, as well as the Milky Way The Milky Way is band of light making a circle around the celestial sphere. What is it? Our view into the plane of our galaxy.


The Celestial Sphere :The Celestial Sphere The stars all appear to lie on a large sphere surrounding the Earth (the celestial sphere) Really, the stars are all at different distances


The Celestial Sphere :The Celestial Sphere The 88 official (defined by the International Astronomical Union) constellations cover the celestial sphere.


Constellations :Constellations A constellation is a region of the sky. The regions of the constellations are irregular in shape


Investigating a Constellation :Investigating a Constellation The stars in a constellation are not all at the same distance from the Sun. They do not form a real group in space.


The Big Dipper is part of the constellation Ursa Major :The Big Dipper is part of the constellation Ursa Major The stars of the Big Dipper are not all at the same distance from the Sun


Review: Coordinates on the Earth :Review: Coordinates on the Earth Latitude: position north or south of equator Longitude: position east or west of prime meridian (runs through Greenwich, England)


Angular Measurements :Angular Measurements Full circle = 360º 1º = 60 (arcminutes) 1 = 60 (arcseconds)


Slide 22:We measure the sky using angles


Angular Size :Angular Size An object’s angular size appears smaller if it is farther away


The Local Sky :The Local Sky An object’s altitude (above horizon) and direction (along horizon) gives its location in your local sky Explore_Celestial_Sphere.swf


Definitions:The Local Sky :Definitions:The Local Sky Zenith: The point directly overhead Horizon: All points 90° away from zenith Meridian: Line passing through zenith and connecting N and S points on horizon


Why do stars rise and set? :Why do stars rise and set? Earth rotates east to west, so stars appear to circle from west to east.


Our view from Earth: :Our view from Earth: Stars near the north celestial pole are circumpolar and never set. All other stars (and Sun, Moon, planets) rise in east and set in west. Celestial Equator Your Horizon A circumpolar star never sets This star never rises in Indiana


The Earth spins under Polaris :The Earth spins under Polaris (Polaris is NOT the brightest star in the sky!)


Altitude of the celestial pole = your latitude :Altitude of the celestial pole = your latitude


The North Star (Polaris) is 50° above your horizon, due north. Where are you? :The North Star (Polaris) is 50° above your horizon, due north. Where are you? You are on the equator. You are at the North Pole. You are at latitude 50°N. You are at longitude 50°E. You are at latitude 50°N and longitude 50°E.


The sky changes as Earth orbits the Sun :The sky changes as Earth orbits the Sun As the Earth orbits the Sun, the Sun appears to move eastward along the ecliptic At midnight, the stars on our meridian are opposite the Sun in the sky


Slide 32:Where on the Earth is it possible to see the most stars through the year? a) From the north pole b) From latitude 23.5 degrees c) From the equator d) anywhere, since latitude makes no difference.


Why do the constellations we see depend on latitude and time of year? :Why do the constellations we see depend on latitude and time of year? They depend on latitude because your position on Earth determines which constellations remain below the horizon. They depend on time of year because Earth’s orbit changes the apparent location of the Sun among the stars.


Precession! :Precession! Over time, the direction of the Earth’s rotation axis drifts around a circle. At different times, different stars (other than Polaris) are close to the pole


Vocabulary Review :Vocabulary Review Constellation Ecliptic Equator Celestial sphere Latitude Longitude Meridian Zenith Horizon Altitude North and south celestial poles


Slide 36:Moon worksheet due Thursday Finish units 5, 6, 10 News Quiz on Tues., Sept. 12 For Thursday...