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AST 2002 Exam 3

Terms in this set (35)

Properties of Light and Atoms
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Stellar properties - brightness, mass, temperature, size,
composition.
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Understand how to measure properties of stars and their distances.
- how we use parallax to determine the distances to stars
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Differences between continuous, emission, and
absorption spectra
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How do we determine stars'
- composition
- temperature
- radius
- mass
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What do spectral types represent?
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Measuring the color of a star tells us ______
The surface temperature
The spectrum shifts to _____ at higher temperatures
Shorter
Wien's Law
The higher the object's temperature, the shorter the wavelength (higher the frequency) of the peak for the light emitted by the object
In a binary system the (less massive/more massive) star moves faster on a longer orbit
Less massive
Spectroscopic Binary
Pair of stars that we can detect the spectral lines of one or both stars alternately becoming blueshifted and redshifted as the stars orbit each other
Eclipsing Binary
The total light coming from the star system decreases when one star passes in front of the other; allows us to determine the relative sizes of the stars.
H-R Diagram
Hertzsprung-Russel diagram, a graph that shows the relationship between a star's surface temperature (luminosity) and absolute magnitude (brightness)
Key to unravelling stellar evolution
How stars change with time
Describe the structure of the Sun's interior and atmosphere
Interior:
Density, pressure, and temperature
decrease away from the center of
the Sun.
▪ Energy production peaks in the center
- the core of the Sun.
▪ The size is determined by hydrostatic
equilibrium
Explain how energy is produced and transported by the sun
1. Energy is produced in the core
2. Energy is carried outward first by radiation
3. Then carried out by convection
4. Then energy is carried away from the sun by radiation
Solar activity
Short-lived phenomena on the Sun, including the emergence and disappearance of individual sunspots, prominences, and flares; sometimes called solar weather
How do we track solar activity? Why should we be concerned about solar activity?
Can impact climate on Earth
Sunspot
A dark area of the photosphere of the sun that is cooler than the surrounding areas and that has a strong magnetic field
Understand the role of
stellar mass in the
evolution of a star.
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Explain the future
evolution of the Sun.
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Which stars never start fusion?
Brown dwarfs
Mass of low-mass stars
M < 8 M⦿
What elements do Main Sequence stars burn?
Hydrogen; then H and He shell burning
What are the relationships between temperature, pressure, location in the star, and how much energy is
produced? How do these affect size and luminosity?
A luminous red giant star is enormous relative to the sun (a MS star) but the luminosity comes from hydrogen burning in a thin shell around a tiny degenerate core. More mass= more pressure, more heat, faster nuclear reactions.
How does a Main Sequence star evolve?
1.Main sequence; hydrogen burning in core
2.Red Giant Branch Star; Hydrogen burning envelope with a degenerate He core
3.Helium Flash; Runaway He burning in degenerate core
4. Horizontal Branch Star; Hydrogen burning shell with a Helium burning core
5. Asymptotic Giant Branch Star; Hydrogen burning shell, Helium burning shell, Degenerate Carbon core
6. Planetary nebula ejection
7. White dwarf with degenerate Carbon cinder
Why are stellar clusters useful?
Helps us understand stellar structure and evolution
How do stars evolve in a binary system?
1. More massive star evolves until it overfills its roche lobe, then transfers mass onto the second star
2. Star 2 gains mass, becoming a hot and luminous main sequence star
3. Star 1 becomes a white dwarf
4. Star 2 overfills its roche lobe and transfers mass onto the dwarf
5. Star 1 experiences novae and a possible type 1a supernova. If it does not supernova, it leaves behind two white dwarfs
6.If it does supernova, it leaves star 2 to evolve into a white dwarf
Nova
The temperature in the degenerate hydrogen skni climbs until the hydrogen burns explosively in a nova. This lives a white dwarf and the process may repeat.
Type 1a Supernova
If the white dwarf mass exceeds the Chandrasekhar limit, it begins to collapse, pushing up the temperature until carbon ignites and burns explosively. Type 1a supernova consumes the white dwarf completely.
Variable stars
change brightness, due to the increase and decrease of surface area, classified by the shape and period of their light curves (mira-long period and cepheid- short), NOT main sequence stars.
Cepheid
A slightly unstable star that has a regular variation in brightness and luminosity due to a periodic expansion and contraction in its outer layers.
Standard candle
an astronomical object that has a known luminosity; apparent brightness can then be used to calculate its distance through inverse square law
RR Lyrae Variables
Low mass stars on the horizontal branch
Cepheid variables
High mass stars become supergiants. More luminous stars have longer periods
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