NATS1745 6.0 History ofAstronomyChapter 9 Exam Review
1. Why did all attempts to detect stellar parallax fail until the 1830s? There were
many failed attempted due to the incorrect assumption that the brightest stars are
the nearest stars.
2. What did Halley announce about stars in the early 1700s? The stars had no
motion of their own. Stars do have motion in space but because they are so
distant, they appear to barely move. He compared his star observations to
Ptolemy’s ancient star catalogues and he found 3 moving stars. The 3 stars were
moving in their own directions. Change in co-ordinates of those stars couldn’t be
due to Earth’s precession. How did this discovery aid the detection of stellar
parallax? This suggested that the stars had their unique motion across the sky. We
can’t perceive it. Bernard’s star had the fastest motion of any star seen from Earth
and that allowed for stellar parallax to be detected.
3. What is our nearest star, and how far away is it (approximately) in light
years? The nearest star isAlpha centauri, has a distance of 270’000AU (4.4 light
years or 1.3 parsec)
4. What is the definition of a light year? The distance light travels in 1 year. What
is the definition of a parsec? The distance of an object with a parallax of 1
arcsecond. (NOTE: the specific values in km aren't necessary here). Which unit
is bigger, and by approximately how much? Parsec is bigger by 2/3
5. According to the wave theory of light, what are all light waves composed of?
Contain charged particles which are moving around and when charged particles
move, they create electric energy fields.
6. Describe how a wave from a bright blue light source is different from a wave
from a faint red light source. The blue light source is hotter as it has shorter
wavelength and is more energetic as compared to red light sources. The red light
source is the coolest because it is longer in wavelength and less energetic than
blue light source.
7. What colour of visible light is shortest in wavelength? BLUE
What colour of visible light is longest in wavelength? RED
What colour of visible light has the lowest frequency? BLUE
What colour of visible light has the most energy? BLUE
What kind of light is longest in wavelength? Radio waves
What kind of light has the most energy? Gamma waves
9. What is a spectroscope?An apparatus that produces a light spectrum that can be
observed through a telescope.
1 10. What is Fraunhofer’s Spectrum a spectrum of? Passing sunlight through glass
and observed the spectru through a telescope. The passed light through the prism
created a rainbrow. Spectrum of Sunlight. What does it contain (ie., continuum
emission, absorption lines, and/or emission lines)? Absorption Lines
11. Describe (briefly) how the chemical composition of a star can be determined.
Each gas contains a unique sequence of bright colored lines.
12. What did Bunsen and Kirchhoff observe in the spectrum of sunlight
combined with a gas flame? The spectrum of each glass contains a unique
sequence of bright colored lines. After the spectrum of sunlight passed through a
gas flame, they found the darkness got thicker. What was their correct
explanation for this, and what did it cause them to predict about the Sun?
Concluded that the Sun’s core, which produces the full spectrum of light, is
surrounded by a gas layer. How was their prediction proven in the 1860s?
During the solar eclipses in the 1860s-70s, the spectrum of the Sun’s atmosphere
was produced, revealing the emission lines predicted by Bunsen and Kirchhoff.
15. What does the spectrum of a star contain (ie., continuum emission,
absorption lines, and/or emission lines)? Star: continuum and absorption line
How about the spectra of a gas cloud, a star cluster, and a gas/star system?
Star cluster – continuum and absorption lines, a gas cloud – emission lines,
gas/star system – continuum, emission line, and absorption line.
16. Why was the element Oxygen originally named "Nebulium"? It contained
undefined emission lines, named “Nebulium” until matched with Oxygen.
17. What does the spectrum of a planetary nebula contain (ie., continuum
emission, absorption lines, and/or emission lines)? Contained undefined
When Huggins discovered this, what did it prove about planetary nebulae
(ie., what are they made of)? Proved they are produced by heated up gas flames.
How does it effect light waves? When source of sound if moving closer to the
listener, the waves stretch into longer wavelength. The larger the wavelength, the
faster the radial velocity.
What is the name of this effect? Doppler Effect – the stretching (or
2 compressing) of a wave due to the approaching and receding motion of the source
of the wave.
19. How does a light source's spectral lines reveal that the spectrum is
redshifted? Stretched waves are red shifted. How about blueshifted? Compressed
waves are blueshifted.
If a spectrum is redshifted, what does this tell us about the motion of the light
source? The source of sound is moving away, the waves stretch into longer
wavelength. Absorption lines shifted slightly to the redder side.
How about if the spectrum is blueshifted? The source of sound is moving
closer, gets compressed into shorter wavelength.Absorption lines shifted slightly
to blue side.
20. What is astrophotography? The production of long exposure sky photos using a
camera attached to a telescope.
Why does it allow us to see deeper into space than wthh the eye and telescope
alone? Acamera len