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Introduction

The Celestial Sphere

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Outline

• Lab notes• Review• Observing the Sun• Unit Conversions• RA/Dec• SETI

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Notes

• Homework 1 due on Friday. • Sun lab(s) due in “box”:

• Noontime Sun by next Friday 5:00• Sunset part1 by next Friday 5:00

• Lab Resources Part B next week.• Binocular lab next Mon,Thur (?)

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Observing the Sun

• http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/safety2.html

• http://www.mreclipse.com/Special/filters.html

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Measuring Angles

• A fist at arms length is about 10°• Fingers spread wide are about 15°• Three fingers together are about 5°• One pinky width is about 1°• The full moon is almost exactly 0.5°

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Dimensional Analysis

• Dimensional Analysis is VERY helpful in problem solving.

• Check your equations with specific units.• Velocity example - how do distance (x), time (t),

and Velocity (V) relate?

V = x/t

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Dimensional Analysis Example - Which equation is correct?

A) velocity = distance * time

B) time = velocity * distance

C) time = distance / velocity

D) time = velocity / distance

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Which equation is correct?

A) velocity = distance * time

B) time = velocity * distance

C) time = distance / velocity

D) time = velocity / distance

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Velocity Exercise

• The laser travels 9.6m across the room. How many seconds does it take?

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Light Travel Time Across the Room (9.6 meters)

A) 2.9x106 sec

B) 2.9x10-6 sec

C) 3.2x10-5 sec

D) 3.2x10-8 sec

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Light Travel Time Across the Room (9.6 meters)

A) 2.9x106 sec

B) 2.9x10-6 sec

C) 3.2x10-5 sec

D) 3.2x10-8 sec

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Conversion Factors

• Conversion factors are equivalence statements expressed in the form of ratios

• Example: 1 in = 2.54 cm• Conversion factors let you express a

quantity in terms of other units without changing its physical value.

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Conversion Exercise

• Convert 0.61 m to inches.

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How many inches is 0.61m?

A) 0.24 inches

B) 1.56 inches

C) 24.0 inches

D) 156 inches

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How many inches is 0.61m?

A) 0.24 inches

B) 1.56 inches

C) 24.0 inches

D) 156 inches

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How many light years was that 9.6 m?

A) 9.1x1012 ly

B) 1.0x10-15 ly

C) 2.9x109 ly

D) 1.1x10-14 ly

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How many light years was that 9.6 m?

A) 9.1x1012 ly

B) 1.0x10-15 ly

C) 2.9x109 ly

D) 1.1x10-14 ly

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Significant Figures

• Example• 4.56 has three significant figures.• 4.56x106 also has three significant figures.• .000456 also has three significant figures.

• A calculation output can not have more significant figures than the input.• If an equation has a whole number (for example 2) it is

considered to be 2.00000 etc.• Calculation hint - it is often best to keep all available

figures until the last step, and then round your answer.

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Scientific Notation

• What does 1.0x106 mean?• Positive exponents mean shift the decimal place to the

right (bigger numbers).• Negative exponents mean shift the decimal place to the

left (smaller numbers).• Usually only have one digit to the left of the decimal.• Most calculators have a single key to add the (x10^)

term. (EXP, EE)

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Measurements

Multiple Prefix

109 giga-

106 mega-

103 kilo-

10-2 centi-

10-3 milli-

10-6 micro-

10-9 nano-

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Algebra Hint

• The following relationship will be useful to remember:

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Introduction

The Celestial Sphere

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Oslo, Norway is 60°N latitude. What declination line passes through the zenith in Oslo?

A) 0°

B) 30° N

C) 60° N

D) 90° N

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Oslo, Norway is 60°N latitude. What declination line passes through the zenith in Oslo?

A) 0°

B) 30° N

C) 60° N

D) 90° N

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Astronomy Picture of the Day

http://antwrp.gsfc.nasa.gov/apod/ap080922.html

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The Celestial Sphere

• Locations to note• North celestial pole• Celestial equator

• Declination corresponds to latitude. • Right ascension corresponds to

longitude. • RA and Dec are “fixed” onto the

celestial sphere.

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Figure P.4Right Ascension and Declination

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Declination

• Declination corresponds to latitude. • Units are degrees (and minutes and

seconds). • Durango’s latitude is +37.275° N.

The declination line passing directly overhead is also +37.275° N.

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Oslo, Norway is 60°N latitude. How high does the star Polaris appear?

A) 0°

B) 30° N

C) 60° N

D) 90° N

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Oslo, Norway is 60°N latitude. How high does the star Polaris appear?

A) 0°

B) 30° N

C) 60° N

D) 90° N

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What is the southernmost declination line visible from Oslo (at 60° N)?

A) 60° N

B) 30° N

C) 0°

D) 30° S

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What is the southernmost declination line visible from Oslo (at 60° N)?

A) 60° N

B) 30° N

C) 0°

D) 30° S

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Standing on the equator, you can see…

A) the celestial equator directly overhead

B) entire celestial sphere during a 24 hour day

C) both celestial poles on your horizon

D) all of the above

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Standing on the equator, you can see…

A) the celestial equator directly overhead

B) entire celestial sphere during a 24 hour day

C) both celestial poles on your horizon

D) all of the above

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Durango’s latitude is 37.275° N. What is the southernmost declination line visible?

A) 0°

B) 37.275° S

C) 52.725° S

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Durango’s latitude is 37.275° N. What is the southernmost declination line visible?

A) 0°

B) 37.275° S

C) 52.725° S

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Right Ascension

• Right Ascension corresponds to longitude. • Units are Hours (and minutes and seconds).• The trick (as with longitude) is to decide on

the zero point.• Longitude zero is at the observatory in

Greenwich England.• RA zero is where the sun crosses the

celestial equator going north.• RA is always moving w.r.t. longitude.

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PRS question

• How long is the following exposure?

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Figure P.3The Northern Sky

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How long is the exposure? Enter the correct number of hours.

A) 4

B) 5

C) 6

D) 7

E) 8

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Three Minute Paper

• Write 1-3 sentences.• What was the most important thing

you learned today?• What questions do you still have

about today’s topics?