What is the approximate rotation period of the sun? - ANSWER 25 days (equator)
36 days (poles)
What is the approximate mean density of the Sun? - ANSWER 1410 kg/m3
What is the approximate surface temperature of the Sun? - ANSWER 5780 K
How do we determine the luminosity of the Sun? - ANS...
what is the approximate rotation period of the sun
what is the approximate mean density of the sun
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AST1002 Final Exam Review UF
Question and Answers
What is the approximate rotation period of the sun? - ANSWER 25 days (equator)
36 days (poles)
What is the approximate mean density of the Sun? - ANSWER 1410 kg/m3
What is the approximate surface temperature of the Sun? - ANSWER 5780 K
How do we determine the luminosity of the Sun? - ANSWER L=Flux* 4 π R²
What is the temperature of the core of the Sun? - ANSWER 15 million K
What mechanism produces the energy in the core of the Sun? - ANSWER In the core,
energy is produced by hydrogen atoms being converted into molecules of helium.
What is the minimum temperature needed to start fusing H into He? - ANSWER The
temperature of the core must be least 10 million K in order to be able to convert H into
He.
What type of spectrum does the Sun emit? - ANSWER The photosphere of the sun
forms the continuous spectrum
How can we see the solar corona? - ANSWER The solar coronal plasma has enough
temperature (kinetic energy) to escape the Sun's gravity
How long does it take for the electromagnetic radiation to reach the Earth? - ANSWER
The radiation emitted by the Sun travel at the speed of light and take about 8 minutes to
reach Earth.
How long does it take for the solar wind and particles ejected from the Sun to reach the
Earth? - ANSWER The radiation emitted by the Sun travel at the speed of light and take
about 8 minutes to reach Earth.
What do we need to know to determine the distance to a star using the stellar parallax?
- ANSWER Knowing the value of the AU in km, we use the stellar parallax, to find
distances to "nearby" stars
How can we determine the radial motion of a star? - ANSWER "line of sight" or radial
motion is measured through Doppler shift of emission/absorption lines
How can we determine the transverse motion of a star? - ANSWER "transverse" motion
is perpendicular to the line of sight
What are the two axes of the HR diagram? - ANSWER Luminosity and temperature
, AST1002 Final Exam Review UF
Question and Answers
Where are the low and high temperature stars located in the HR diagram? - ANSWER
Low-temperature stars are located to the right and high-temperature stars are located to
the left.
Where is a large radius and small radius star located in the HR diagram? - ANSWER
small radius stars are located on the bottom left and large radius stars are located on
the top right.
What is the spectroscopic parallax? - ANSWER The spectral analysis provides
information to determine the temperature of the star or the spectral classification. If we
know the
temperature for a main sequence star then we can deduce the luminosity
Steps to determine the distance d using spectroscopic parallax: - ANSWER Measure
the flux, determine the surface
temperature (or spectral classification), use the HR diagram to determine the luminosity,
use the equation: Flux = Luminosity/ 4^d 2
How can you determine the luminosity L of a star (in solar units) respect to the Sun? -
ANSWER Lstar= (Rstar/Rsun)^2 * (Tstar/Tsun)^4 * Lsun
What parameters does mass of a star determine? - ANSWER Luminosity, radius,
surface temperature, lifetime, evolutionary phases.
A star of smaller mass lives a shorter or a longer life respect to a large mass star? -
ANSWER A star with a smaller mass lives a longer lifetime.
How long will take for the Sun to convert all the H into He until all the H is used up? -
ANSWER In the Sun's core, the conversion of
H to He will take about 10 billion years.
What is the temperature necessary to fuse He? - ANSWER Helium begins to fuse into
Carbon at >108 K (100 million K).
Temperature necessary to fuse Carbon? - ANSWER It will need to
reach a temperature of 600 million K to ignite
carbon
How long will the Sun stay in the main sequence? - ANSWER 10 billion years
At what point in the star evolution it will move off the main sequence? - ANSWER When
the core hydrogen is used up and it begins to fuse helium.
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