Astronomy 1020Spring_2015

Day-6Stellar Astronomy

Course Announcements• Smartworks Chapter 2: Start on –

Grades will be downloaded sometime this coming weekend … hop to it.

• 1st set of Dark Sky observing nights: • Wed. Feb. 11 & Tues. Feb. 17

Celestial Sphere

Celestial Sphere Rotation

Celestial Sphere Rotation

Celestial Sphere

Star A

Star B

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Figure 2

Horizon

Tutorial: Position – p.1Work with a partnerRead the instructions and questions carefullyTalk to each other and discuss your answers

with each anotherCome to a consensus answer you both agree

onIf you get stuck or are not sure of your

answer ask another groupIf you get really stuck or don’t understand

what the Lecture Tutorial is asking as one of us for help

Imagine that from your current location you observe a star rising directly in the east. When this star reaches its highest position above the horizon, where will it be?

A. high in the northern sky

B. high in the southern sky

C. high in the western sky

D. directly overhead

Concept Quiz

Where would the observer look to see the star indicated by the arrow?

A. High in the Northeast

B. High in the Southeast

C. High in the Northwest

D. High in the Southwest

Celestial Sphere

Celestial Sphere Rotation

Celestial Sphere

Star A

Star B

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1

3

2

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4

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3 Horizon

How long did it How long did it take to get this take to get this picture?picture?

Earth’s rotation causes the Sun, Planets, Moon and stars to appear to move when viewed from Earth

Photo: Dr. Spencer Buckner

Celestial Sphere Rotation

Celestial Sphere Rotation

North Star

Star A

Star B

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Earth’s Equator

Figure 1

Celestial Sphere

Celestial Sphere Rotation

Celestial Sphere Rotation

Star A

Star B

1

1

3

2

2

4

4

3

Figure 2

Horizon

Why does the sky change with your location?

As you move away from the pole your horizon moves with you but the locations of the celestial poles and celestial equator remains the same

Time SystemsWe live on Solar Time (time kept by the Sun)Our watches keep Mean Solar Time (24

hours/day)The stars keep Sidereal Time (~23h 56m per day)

The 4 minute difference is due to the Earth’s orbital motion around the Sun.

We reference Greenwich Mean Time (GMT, UT, TAI1)

Clarksville is GMT-6 (5 during daylight savings time)

Why does the sky change over the course of a year?

As we orbit the sun the direction opposite the sun changes and we only see the stars when the sun is not up