Open up your laptops, go to MrHyatt.rocks, and do today’s bellwork Scale Scale Description 4 Through independent work beyond what was taught in class, you could: investigate the location of seasonal constellations in the local sky. predict location of constellations at future times. determine the celestial equator, latitude and position of the Pole Star for a given position on the Earth. determine the distances of stars in a given constellation to each other and to Earth. 3 You will be able to: describe and apply the coordinate system used to locate objects in the sky. distinguish the various methods of measuring astronomical distances and apply each in appropriate situations. 2 determine the meaning of symbols, key terms, and other astronomy specific words and phrases as they are used in context to relevant topics label diagrams with degree measurements describe how or why different units of measurement are needed for distances in space 1 You will be able to list the different units of measurement needed to measure distances in space

If you were gone Friday, you need to make one of these If you were gone Friday, you need to make one of these. See me after class

The Celestial Sphere Today’s question: How can we measure distances and direction in the sky?

Celestial Sphere Celestial Sphere definition: The huge imaginary sphere on which all the objects in the sky were once considered attached. (was also thought to be centered on earth) Though it’s not actually the case, it’s convenient for describing locations of objects in the sky. (paraphrase this) Similar to an upside-down bowl covering the earth

1.3 The “Obvious” View The celestial sphere: Stars seem to be on the inner surface of a sphere surrounding the Earth They aren’t, but we can use two-dimensional spherical coordinates (similar to latitude and longitude) to locate sky objects Figure 1-11. Caption: Celestial Sphere. Planet Earth sits fixed at the hub of the celestial sphere, which contains all the stars. This is one of the simplest possible models of the universe, but it doesn’t agree with all the facts that astronomers now know about the universe.

Horizon Coordinate System Based on the point of view of the observer It works if you are near somebody Altitude – measurement of height in the sky 0-90◦ Azimuth – measurement around the horizon 0-360◦

This is not a globe, this is you standing on the surface of a planet with certain lines drawn around you.

Pointing Game What object do you find at 30ᵒ alt and 150ᵒ az. Azimuth Altitude Everybody point to 0ᵒ 90ᵒ 180ᵒ 190ᵒ 360ᵒ 270ᵒ 300ᵒ Everybody point to 0ᵒ 45ᵒ 90ᵒ 25ᵒ Zenith Horizon Nadir 28.1ᵒ What object do you find at 30ᵒ alt and 150ᵒ az.

What would the coordinates of the star be that the girl is pointing to?

Example - Sun 60 66 47 134 202 246 11am 1pm 3pm Altitude of Sun Azimuth of Sun 134 202 246 time 11am 1pm 3pm

Remember: Altitude – degrees - height Azimuth – degrees - compass direction

1 Altitude 50ᵒ-60ᵒ and Azimuth 15ᵒ-20ᵒ

2 Altitude 10ᵒ-20ᵒ and Azimuth 245ᵒ-255ᵒ

3 Altitude 75ᵒ-85ᵒ and Azimuth 165ᵒ-175ᵒ

What would the altitude be for the flag?

What would the azimuth be for the flag?

What about the altitude for Violet?

What about the azimuth for Violet?

What would the azimuth and altitude be for the projector mounted on the ceiling? This is why it works great for people near each other, but not so much for people far away from each other (opposite sides of the earth)

Exit Ticket Think of your answer to the last question (the altitude and azimuth of the projector), and then think of the answer of somebody on the other side of the room. Would those answers be the same? Why or why not? What does this mean for those using the “Horizon System?“