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Properties of Stars

How do we classify them?

Multiple Choice

All stars begin their life in a

• Main Sequence

• Nebula

• Protostar

• Black Dwarf

Multiple Choice

Most stars are made of which elements?

• Hydrogen only

• Hydrogen and Lithium

• Hydrogen and Sodium

• Hydrogen and Helium

Multiple Choice

Which might change, depending on the DISTANCE to a star?

• Absolute Brightness

• Apparent Magnitude

Multiple Choice

If a scientist needs to calculate the luminosity of a star, what information would they need?

• Distance

• Apparent Magnitude

• Temperature

• Distance and Apparent Magnitude

Poll

Two stars are being compared. Star A has a greater luminosity than Star B. Star A and Star B have the same apparent magnitude. WHICH STAR IS MORE DISTANT?

• Star A

• Star B

Let's Think...

• Stars A & B have the same apparent magnitude in the sky.

• Can we assume that they have the same absolute brightness? Why or why not?

• What if, star A is 50 LY away & star B is 10 LY away? Which one has the highest luminosity?

​H-R Diagram

​We classify/organize stars on the Hertzsprung-Russell diagram OR HR Diagram.

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​Astronomers sort stars by their:

​

1. ​Temperature

2. Size or Mass

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​Both temperature and size/mass of a star help us understand the ABSOLUTE BRIGHTNESS or how bright a star actually is.

Multiple Choice

What two quantitative measurements do we use to measure absolute brightness?

• Temperature and Color

• Color and Mass

• Temperature and Mass

Multiple Choice

Which Star is the HOTTEST?

• Blue

• Red

• Orange

• Yellow

Multiple Choice

Which Star is the COOLEST?

• Blue

• Red

• Orange

• Yellow