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ASTR 1023 Exam 2
Terms in this set (64)
A scientific instrument designed to "break" light from a star into its component
colors is called a
The _____ force of nature is important because it can hold two protons in a nucleus
together despite the incredible repulsive effect of their positive charges.
radially away from us
The reddish emission line of hydrogen, H-alpha, has a "true" wavelength of 656.3
nm. If the H-alpha line in a gaseous supernova remnant's spectrum appears at a measured wavelength of 657.0 nm, that would suggest that the remnant is moving
causes the Sun to gradually lose mass
What effect do solar winds have on the sun?
The parallax p of a star in arcseconds and its distance d in parsecs are related by the simple equation p = 1 / d. Therefore, a star that is 20 pc away will display a parallax of
A Watt is a unit of power often used by engineers and electricians. It is also often used by astronomers as a unit of stellar ________ because a Watt has dimensions of
Two stars known to be equally distant from Earth have the same color. However,
one of them is fainter than the other. This means that the brighter star is _____ than the
Most generally, two stars whose orbital motions around each other are readily
discernable in a series of images are called _______ binaries.
B, A, K
You have observed the spectra of three main-sequence stars, and found them to be
of spectral types A, B and K. Arrange these stars in order of increasing mass (from
lowest to highest).
This instrument measures brightness and can be used with color filters.
This instrument produces an object's light spectrum.
This instrument is used to view long wavelengths (1-10cm), cold gas clouds, and synchrotron radiation. Penetrates space dust well.
Reflector dish, antenna, amplifier, signal recorder
Components of a radio telescope (4)
The diameter of the dish
What does the resolution of radio telescopes depend on?
System of multiple telescopes.
The distance between the two furthest dishes.
What does the resolution of radio interferometers depend on?
A theoretically perfect radiator (stars, space dust)
What unit is used to measure the total light emitted from a blackbody spectra measured?
Absorption Line Spectra
The spectrum formed by electromagnetic radiation that has passed through a medium in which radiation of certain frequencies is absorbed.
Emission Line Spectra
The spectrum formed by electromagnetic radiations emitted by a given source, characteristic of the source and the type of excitation inducing the radiations.
To determine the chemical composition, temperature, speed, and pressure of objects.
What are line spectra's used for? (4)
If the emission line wavelength of an object is increasing (400 to 750) the color becomes more ___ and we can tell that the object is ___.
If the emission line wavelength of an object is decreasing (750 to 400) the color becomes more ___ and we can tell that the object is ___.
The continuous flow of charged particles from the sun that permeates the solar system.
Solar Wind is gas that escapes from the sun's ___.
1 Gauss (2x Earth's)
What is the strength of the sun's magnetic field?
Internal Electric Ring Currents
Where is the sun's magnetic field developed?
How long polarity cycle of the sun's magnetic field?
Sunspots, Prominences, and Flares
The sun's polarity cycle and differential rotation combine to produce...
Cooler areas in the photosphere of the sun due to links in magnetic field that inhibit heat flow fields 1000x stronger than in surroundings.
Huge areas of gas tha connect sunspot pairs and last for months.
Huge, magnetically powered explosions near sunspots that last for hours and produce coronal mass ejections.
How is the distance to stars calculated? What is it generally measured in?
1 pc = 3.26 ly
1 Parsec = X lightyears
At what velocity in km/s do the galaxies stars orbit its center?
Radial Velocity (Vrad)
The speed of a space object toward or away from us along the line of sight.
Tangential Velocity (Vtan)
The speed of a a space object moving perpendicular to (or across) the line of sight.
The gradual rate of change of a star's angular position due to it's Vtan.
The rate at which a star emits light from its entire surface.
How is luminosity generally measured? (equal to 1 Joule/Second)
Formula for the surface area of a sphere.
Observed Brightness (B)
The rate at which a star's light is received at earth by a surface whose area is 1m^2.
B = L/(4πd^2)
Inverse Square Law. Formula that can be used to measure observed brightness, luminosity, and distance, if two of the three are given.
What is the sun's observed brightness (B)?
Apparent Magnitude (m)
Numbers that are used to rank stars according to their observed brightness based on the bright star Vega.
m = +6
The faintest apparent magnitude visible to the naked eye.
m = -27
The sun's apparent magnitude.
For each step of 1 on the magnitude scale there is a x factor change in B (B*x). What is x?
Absolute Magnitude (M)
The apparent magnitude stars would have if all stars were a standard distance of 10pc from Earth.
1) Compute Δm, ((distance in pc)/10pc)^2, if stars distance is not 10pc.
How to compute M
Relative strength and sharpness of absorption lines
Stellar Spectra are sorted on the basis of...
Relative Strength of Absorption Lines
Stellar Spectra classification that depends on surface temperature (in K).
Sharpness of Absorption Lines
Stellar Spectra classification that depends on gas density (or pressure).
Scale used for the Relative Strength of Absorption Lines.
Scale used for the Sharpness of Absorption Lines.
The sun's stellar spectra classification.
The Hertzsprung-Russell (H-R) Diagram
On what diagram do stars form distinct groups including: Main sequence stars, giants, super giants, and white dwarfs.
Luminosity correlates with what?
A binary in which both stars can be seen.
What fraction of all "stars" are actually multiple stars?
Apparent Relative Orbit
Relating to binary stars, this is the observed path of the dimmer (secondary) star, relative to the brighter (primary) star.
Obtained by correcting the apparent relative obit for the orientation of the angle between them.
How is the True Relative Orbit of binary stars obtained?
Use (m1+m2)p^2 = (A1+A2)^3, (m=mass, P=orbital period in years, A=semi-major axis in AU).
1) Find m1 and m2 by using A1/A2=m2/m1.
2) Then use basic algebra to plug and chug that shit.
Method for calculating stellar mass. (First describe Newton's equation)
I = super giants
II = bright giants
III = giants
IV = subgiants
V = main sequence or dwarf stars
Correlation between sharpness and size.
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