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Stars & Galaxies Unit 3
Terms in this set (30)
Extrinsic Variable Stars demonstrate ________ .
a variation in flux but not a variation in luminosity of the stars involved
A variable star is a star that over some time period ________ .
has an observed change in flux
RR Lyrae type of variable stars operate by the same mechanism as delta Cepheid stars, but differ in ________ .
the period of their variability; they are small stars that vary in a day or less
What characteristic of Helium makes it a major constituent of the pulsating star mechanism?
Doubly ionized Helium (He III) is opaque and traps EM radiation.
Eclipsing Binary stars, because they vary their flux but not their luminosity, are classed as ________ .
an Extrinsic Variable star
On the HR Diagram, variable stars are found ________ .
in different regions on the HR Diagram depending on the mechanism of variation
The "greying" of light as compared to the "reddening" of light can tell us ________ the intervening ISM.
the dominant dust particle size in
The emission from emission nebulae is caused by ________ .
hot stars nearby that excite the dust and gas causing emission
A Giant Molecular Cloud will develop HII regions when ________ .
hot young massive stars ionize the region of their function
In order to observe the Hot ISM, we must observe at ________ wavelengths.
The interstellar medium has the property of making background stars appear ________ than they really are from their known distance and spectral type.
less luminous and cooler
Dust (non-Hydrogen non-Helium) makes up ______ of the interstellar medium.
about 1 percent
By analyzing the HR Diagrams of clusters of different ages we have been able to discern ________ .
how stars evolve
Determining the age of the stars in a cluster using the HR Diagram makes the assumption that ________ .
both answer a and answer b
Unlike OB Associations, T Associations typically do not form within ________ .
Giant Molecular Clouds
The stellar characteristic that makes it possible to age star clusters is ________ .
that stars leave the Main Sequence in descending mass order
The number of visible Globular Clusters associated with the Milky Way Galaxy is about ________ .
We know that Globular Clusters are very old because ________.
there are no Sun-like mass or more massive stars in the clusters
Harlow Shapley used the asymmetric distribution of Globular Clusters around the Sun to ________
calculate the direction of the center of mass of the Galaxy
If the luminous matter in the Galaxy, alone, was responsible for rotational velocities, ________ .
the Galaxy would rotate more slowly, especially farther out from the center
The Disk component of the Galaxy is actually made up of ________ .
a 1 kilo-parsec "Thin" disk enclosed in a 3 kilo-parsec "Thick" disk
Why is the HI emission line deep in the radio portion of the spectrum?
The energy delta is very small yielding very long wavelengths.
In an attempt to measure the rotation rate of the Galaxy, ________found that there was a great deal of non-luminous matter associated with the Galaxy.
We cannot directly view the central nucleus of our galaxy in visible wavelength light because ________ .
the light is obscured by dust and gas
What is Sagittarius A*?
The source of bright radio emission in the constellation of Sagittarius.
Population I stars, though few in number, can be found in the halo, but ________ .
they formed in the Disk and were ejected into the Halo
Stars orbiting within the disk of the Milky Way have orbits ________ .
have circular orbits that waver up and down through the disk
Using the age of stars and orbital motions around the Galaxy, we can deduce that ________ .
the halo was forming stars before the disk was forming stars
Unless otherwise perturbed, Population I stars tend to have orbits that are ________ .
basically circular and remain within the Disk of the Galaxy
The "bottom up" theory of Galaxy formation, forms the Galaxy from ________ .
the merger of smaller sub-galaxy sized collections of gas and stars
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