Astronomy 311 Professor Menningen January 2, Syllabus overview books & supplies course goals assignments & grading About the professor

Transcription

1 1 Astronomy 311 Professor Menningen January 2, 2014 Syllabus overview books & supplies course goals assignments & grading About the professor

2 2 How to Learn Astronomy Stay curious Interact with the same material several times Work together with someone Try extra homework questions

3 3 How to Succeed in College Set a GPA goal Treat college like an 8 to 5 job Attend class Keep up Relate to your professors Be a "well-rounded square"

4 4 Lecture 1 Introduction & The Night Sky January 2a, 2013

5 5 What is Astronomy? Study of all things outside of the atmosphere of the Earth. Planets Stars Galaxies Structure and Evolution of the Universe (Cosmology)

6 6 The Constellations Groupings of prominent stars which appear nearby in the sky Includes the whole area in the sky- not just the stars 88 constellations

7 7 Constellation of Orion

8 8 Stars are at different distances

9 9 Units of Measure We ll use mainly the metric system, based on the meter, kilogram, and second We ll often use scientific notation: 1 light-year 9, 461, 000, 000, 000, 000 m The speed of light is m 8 c 299, 792, 458 m/s m/s You should know the metric prefixes and scientific notation

10 10 Using your calculator Many times we ll be using very large or very small numbers. We ll write them in scientific notation, such as: J instead of J Use the EXP or EE key on your calculator to save time and avoid errors: or 1. 6 EE ( ) EXP 1 9

11 11 Converting Units Use conversion factors Convert meters to parsecs 1.0 ly 1.0 pc m 6.00 pc m 3.26 ly Move decimel point (requires practice, and good familiarity with metric prefixes)

12 12 If 1.0 AU = m, what is a speed of m/s in units of AU/hr? A AU/hr B. 500 AU/hr C. 7.2 AU/hr D AU/hr 0% 0% 0% 0% 0 of AU/hr 500 AU/hr 7.2 AU/hr 0.12 AU/hr 120

13 13 If 1.0 AU = m, what is a speed of m/s in units of AU/hr? A AU/hr B. 500 AU/hr C. 7.2 AU/hr D AU/hr m 1.0 AU 3600 s 11 s m h 7.2 AU/hr

14 14 Measuring Angles Apparent distances in the sky are determined by measuring the angle between two objects. There are 360 degrees in a circle. Astronomers measure angles in degrees and arc minutes (60 per degree) and arc seconds (60 per arc minute or 3600 per degree)

15 15 Angular Size q As distance increases, angular size decreases q

16 16 Angular Size The size of an object is related to its distance from Earth and its observed angular diameter: physical diameter distance angular diameter 180 D r q r q exact: D rtanq q r D

17 17 Linear Size from Angular Size r D q 180

18 18 If the distance between Earth and Jupiter is cut to a third (due to their orbital motions) the angular size of Jupiter as seen from Earth is. A. cut to a ninth B. cut to a third C. tripled D. nine times larger 0% 0% 0% 0% 0 of 5 cut to a ninth cut to a third tripled nine times larger 120

19 19 If the distance between Earth and Jupiter is cut to a third (due to their orbital motions) the angular size of Jupiter as seen from Earth is. A. cut to a ninth B. cut to a third C. tripled q q D. nine times larger q q new new new old old new old r r old D D old old because new new r old 3 q new r r r D D old 3q old

20 20 On a day when Jupiter is km away from the Earth, the Great Red Spot has an angular diameter of 7.9 arc seconds. What is the diameter of the Great Red Spot in km? A. 24,000 km B km C. 500 km D. 1,250 km 0% 0% 0% 0% 24,000 km km 500 km 1,250 km of 5

21 21 On a day when Jupiter is km away from the Earth, the Great Red Spot has an angular diameter of 7.9 arc seconds. What is the diameter of the Great Red Spot in km? 1.0 q 7.9 arcsec arcsec D km rq ,000 km

22 22 Estimating Angles

23 23 Viewing the Sky Meridian: Line running North- South. Sun and stars reach their highest point in the sky when they cross the meridian each day. Zenith: point directly overhead E S N W

24 24 Positions in the Sky Altitude = the angular distance of an object above the horizon. Azimuth = the angle measured eastward along the horizon from North to the point directly below the object.

25 25 The Celestial Sphere Need a coordinate system in the sky (like latitude and longitude). Locations of the stars, Sun and planets can be specified on the celestial sphere. Stars appear fixed on the celestial sphere. Sun and planets move on the sphere throughout the year.

26 26 The Celestial Sphere Polaris, the North Star North Celestial Pole Equator North Pole Celestial Equator South Pole South Celestial Pole

27 27 Our View of The Celestial Sphere Equator is 90 latitude above S horizon Celestial pole (Polaris) Pole is same angle above N horizon as your latitude on Earth

28 28 Daily Motions The Earth spins on its axis one time every day. Causes day and night. The Sun, Moon, and stars all move from east to west across the sky during the course of a day. The North Star, Polaris, does not move. Its angle above the northern horizon is equal to the observer s latitude on the Earth s surface. The stars that we can see depend on our latitude on Earth.

29 29 View from North Pole Observers can only see stars that are North of the Celestial Equator. The North Star is directly overhead Celestial Equator and Observer s horizon Stars will never rise or set (the stars are circumpolar). They appear to circle the North Star.

30 30 View from the Equator Observers can see all of the stars during the course of a year. The North and South Celestial Poles are on the horizon. Observer s horizon All stars appear to rise and set straight up from the horizon. None are circumpolar.

31 31 View from Northern Hemisphere We cannot see the most southern stars on the Celestial Sphere. Circumpolar star North Star Observer s horizon Some stars will rise and set. The most northern stars will never set (they are circumpolar).

32 32 Star trails in the Northern Hemisphere Motions of stars for part of a night. Center star is Polaris, the North Star. Computer Animation