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Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens...

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Star Properties studied so far… • Period • Mass • Eccentricity • Red shift • Velocity • Temperature (Wiens Law) • Composition – which elements and how much of each • Color • Age
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Page 1: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

Star Properties studied so far…• Period• Mass• Eccentricity• Red shift• Velocity• Temperature (Wiens Law)• Composition

– which elements and how much of each• Color• Age

Page 2: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

A star with a continuous spectrum shines through a cool interstellar cloud composed primarily of hydrogen. The cloud is falling inward toward the star (and away from Earth). Which best describes the spectrum seen by an Earthbound observer?1) blue-shifted hydrogen emission lines

2) a red-shifted hydrogen continuum3) red-shifted hydrogen emission lines4) red-shifted hydrogen absorption lines

Page 3: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

Velocity = distance / time

Page 4: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

How do we measure the velocity of a star?

Page 5: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

z = red shift =

How do we measure the velocity of a star?

l0

l

Page 6: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

z = or

Velocity = c × z

How do we measure the velocity of a star?

Page 7: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

What do you get if your l0 Ca line at 393.3 nm in the lab appears at 401.8 nm in the sky?

red shift = = 0.0216Velocity = cz

and the speed of light is 3 x 105 km/s So the star is receding at a speed of

V = (3 x 105 km/s) x 0.0216 = 6,480 km/s!

How do we measure the velocity of a star?

Page 8: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

What do you get if your l0 Ca line in the lab at 393.3 nm appears at 786.6 nm in the sky?

red shift = ____Velocity = c x z,

and the speed of light is 3 x 105 km/s So the star is receding at a speed of:

V = (3 x 105 km/s) x __ = ______ km/s

How do we measure the velocity of a star?

Page 9: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

What do you get if your l0 Ca line at 393.3 nm in the lab appears at 786.6 nm in the sky?

red shift = = 1Velocity = cz

and the speed of light is 3 x 105 km/s So the star is receding at a speed of

V = (3 x 105 km/s) x 1 = 300,000 km/s

How do we measure the velocity of a star?

Page 10: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

We can measure velocityWe can measure distance

red shift = = 1Velocity = cz

and the speed of light is 3 x 105 km/s So the star is receding at a speed of

V = (3 x 105 km/s) x 1 = 300,000 km/s

How do we measure the age of the universe?

Page 11: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

Star Properties studied so far…

• Period• Mass• Eccentricity• Red shift• Velocity• Distance• Temperature (Wiens Law)• Composition

– which elements and how much of each• Color

Page 12: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

How do you measure the distance to a star?

Use 2 measurements of a star’s exact position in the sky, taken exactly 6 months apart.

Page 13: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

Hubble found the relationship between a galaxy's velocity (the radial component, in a straight line) away from us (v) and its distance from us (d) approaches a fairly linear one, which is known as Hubble's Law:

v = H0 x dSo H0 is the slope of that line, which he found to be 73.3 km/s/Mpc

Or about 3.26 million light years

Page 14: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

velocitycedis

timetan

yearsbillionyears

Mpckm

syear

kmsMpc

T

4.131034.1

11009.3

10156.31

731

10

19

70

So time = 1/H. Use this graph to tell us the age of the universe? Because we know that the slope of the line in the plot is 73 km/s/Mpc, we can simply write:

Page 15: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.
Page 16: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.
Page 17: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

Life Cyclye of a Star

Page 18: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.
Page 19: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

http://aspire.cosmic-ray.org/labs/star_life/hr_interactive.html

Page 20: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

We can detect the velocity of a star through the Doppler effect by 1) measuring the shift in distance of the star. 2) taking photographs six months apart. 3) applying the inverse square law of brightness. 4) measuring the shift in wavelength of a spectral line.

Page 21: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

The light from the east limb (edge) of the Sun is blue-shifted and the light from the west limb is red-shifted. This is because 1) different kinds of atoms emit light at the opposite edges. 2) the Sun is rotating. 3) the distance from the Sun to the Earth changes. 4) the two sides of the Sun are at different temperatures.

Page 22: Star Properties studied so far… Period Mass Eccentricity Red shift Velocity Temperature (Wiens Law) Composition – which elements and how much of each Color.

Most of the brightest stars in the sky are 1) relatively hot main-sequence stars that are relatively close to the Sun.

2) relatively cool main-sequence stars that are relatively far from the Sun. 3) relatively cool main-sequence stars that are relatively close to the Sun. 4) giant stars and relatively hot main sequence stars.


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