Astronomy 1020 Final Exam Study Questions and Answers UPDATED 2024
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Course
Astronomy 1020
Institution
Astronomy 1020
What is the difference between brightness and luminosity? - Brightness is how it appears to us, distance is a factor. Luminosity is how much total light a star gives off.
What is parallax? - Over the course of a year, the star's position in the sky appears to shift back and forth, returning to i...
Astronomy 1020 Final Exam Study
Questions and Answers UPDATED 2024
What is the difference between brightness and luminosity? - Brightness is how it
appears to us, distance is a factor. Luminosity is how much total light a star gives off.
What is parallax? - Over the course of a year, the star's position in the sky appears to
shift back and forth, returning to its original position 1 year later. The amount of this
shift— the angle between one extreme in the star's apparent motion and the other— is
equal to twice the parallax. You can use parallax to find the distance of a star from
us.*https://o.quizlet.com/i/9pmp-JIToJDRsrNY3YQ6DA_m.jpg
What is a stars apparent magnitude? - a logarithmic scale dating back to ancient
Greece, where the brightest stars seen by the naked eye are labeled magnitude 1 and
the faintest are magnitude 6
What is a stars absolute magnitude? - the apparent magnitude of an object if it was
exactly 10 parsecs away.
-Absolute magnitudes and luminosity are related the same way apparent magnitudes
and apparent brightness are related
What can we learn from a star's spectrum? - Tell us what stars are made of by
observing spectral lines.
What is the formula for apparent brightness? - Apparent Brightness = Luminosity/
4pi(distance)^2
Astronomy 1020 Final Exam
, Astronomy 1020 Final Exam
Since apparent brightness depends on area, it decreases with the square of the
distance to a star!
What is a parsec? - Distance at which the parallax is one arc second. = 3.26 light years
Formula for parallax and distance? - distance (in parsecs) =1/parallax (in arc seconds)
What is an astronomical unit? - Average distance between the Earth and Sun
What is a light year? - Distance light travels in vacuum in one year
Which is more common, faint or bright stars? - Faint Stars
What is the 0 point of the magnitude scale? - Star Vega
How much change in brightness on each step of the magnitude system? - 2.51 times
brighter
The ratio of the difference in the apparent brightness between two stars is - 2.51^N (n is
the apparent magnitude difference)
The Hubble Space Telescope has a limiting apparent magnitude of about 30. Compared
to the human eye, the HST can see objects that are _________ times fainter. - 2.51
^(30-6)= 4 x 10^9
Because the apparent magnitude of the human eye is a 6.
Color of hot objects? - Blue b/c high energy wavelength
Astronomy 1020 Final Exam
, Astronomy 1020 Final Exam
Wein's Law - For two objects the same size the hotter one will emit more total light at all
wavelengths, emit more total energy per second, emit light at shorter wavelengths.
Formula for Wein's Law - Temperature = 2,900,000 nm K / peak wavelength
What are stars made of? - Hydrogen and Helium
What is the spectral sequence? - Lines in a stars spectrum are used to define its
spectral type. Spectral type depends on the surface temperature. OBAFGKM. Further
split by number. Correlates to the size.
How do we determine the masses of stars? - Studying binary star systems.
What is the HR diagram? - Luminosity vs temperature. Two stars with the same
temperature but different luminosity's must be different sizes.
How do the various observed properties of stars correlate with each other? - more size,
hotter, brighter
Binary Star Orbits - Two orbiting stars always stay on opposite sides of their common
center of mass (also known as the barycenter). Binary systems are helpful when finding
the mass of a star.
Eclipsing Binary - Star system where one star passes directly in front of another star as
they orbit their common center of mass, relative to our line of sight
Formula to find mass of eclipsing binary - (M1 + M2) * p^2 = a^3
p=period of orbit in years
a= semimajor axis
Astronomy 1020 Final Exam
, Astronomy 1020 Final Exam
Spectroscopic Binary Stars - One in which we can observe spectral lines undergoing
redshift and blueshift due to the orbit around the center of mass.
Formula to find mass of spectroscopic binary - M1 * V1 = M2 * V2
v= velocity
What is the main sequence? - Where the vast majority of stars are located. On-going
core fusion.
What are supergiants? - Largest and brightest stars.
What are giants? - Stars larger than the main sequence stars but smaller than the
supergiants
What are white dwarfs? - Lie below the main sequence. Relatively faint but hot.
What are the roman numerals for super giant, giant and main sequence? - I -
Supergiant
III- Giant
V- Main Sequence
Luminosity and size - The larger the size, the more luminous it is because of more
surface area.
Range for star mass? - Between .008 Msun and 150 Msun. Any more massive would
blow apart any less massive can't complete fusion.
Astronomy 1020 Final Exam
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