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Final for StarsAGalaxies
Terms in this set (115)
What types of stars are found in the outer part of the halo?
Jupiter sized objects, brown/white dwarfs, neutron stars, and WIMPS
What is an island universe?
Galaxy that lies outside of the milky way
What is a standard candle?
Object of known luminosity
Dark matter in the MWG is in the form of _______.
Collapsed stellar remnant that can be detected as a gravitational lens
Cepheid variables can be used as _____ to determine _____ and _____.
Standard candles, distances to galaxies, luminosity
How did Hubble resolve the debate about the nature of the nebulae?
Using a 100 inch telescope to study Andromeda Nebula. Measured periods, luminosity and distance. Found that the nebula was beyond the limit of the milky way and therefore it is its own galaxy.
Hubble's basic types of galaxies:
Elliptical, lenticular, normal spiral, barred spiral, irregular
- Elli lent norman, barrys illy
Characteristics of elliptical galaxies
Old stars, with little to no dust or gas and have a substantial spheroidal component.
Characteristics of lenticular galaxies
Have disks with no spiral pattern, little gas or dust, and have a substantial spheroidal component.
Characteristics of Normal Spiral galaxies
Have disks with spiral patterns, have gas and dust.
Characteristics of barred spiral galaxies
A spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in approximately two-thirds of all spiral galaxies.
Characteristics of irregular galaxies
Have a wide variety of shapes and characteristics. They are frequently the result of collisions between galaxies or gravitational interactions between galaxies.
Local Group of Galaxies
There are 40 in total and are dominated by MWG and M31
MWG and M31 are falling towards each other causing them to eventually merge into an _____.
Elliptical galaxy in 5x10^9 years
Characteristics of clusters of galaxies
About 10^6 to 10^7 lightyears across and contain tens to thousands of galaxies
Do stars and gas clouds collide when their parent galaxies collide?
Stars do not because they are too far apart, but clouds do because they are so large
Low speed collisions result in _____.
Mergers that cause gas clouds to collide and form stars
High speed collisions result in _____.
No mergers and gas and dust is swept out of the galaxy
What is the dark matter problem for clusters of galaxies?
The mass needed to hold the cluster together was determined to only be 15%. Therefore 85% is still unidentified.
Groups of clusters caused by gravitational attraction
String like structures in the distribution of galaxies
Regions in space where no galaxies are found
What are the sheets of galaxies in space at the edges of the voids?
Velocity = (Hubble Constant) X (Distance to Galaxy)
Megaparsec (Mpc) equals _____.
3.3 x 10^6 lightyears
Velocity wobble method
In ordbit, planets will cause a wobble in the position of a star. Works best for planets with Jupiter-like masses.
Planets will block light from stars causing dips in brightness. Works best for large and small planets.
What Spacecraft telescope has been detecting planets orbiting stars using the transit method?
Results of the Kelper Mission
Discovered 4700 candidate planets
What is an organic molecule?
A molecule involving carbon
Two sites where complex organic molecules are found:
In the interstellar medium and in newly fallen meteorites
What did the Miller-Urey experiment demonstrate?
Simulated primordial conditions on earth by sealing gases in a container and using an electric arc for lightning
Results of the MU experiment:
Amino acids were formed in the container showing that complex organic compounds are easily made, but life itself was not created in a test tube
Dry river channels on Mars indicate that _____.
Mars may have supported life in the past
What shows that Jupiter's moon may support life?
Pattern on ice resembles the arctic sheets on earth, internal heat may keep oceans warm enough for life
What is the Drake equation used for?
Estimating the number of intelligent civilizations in our galaxy but is very uncertain
What method is used to search for extraterrestrial civilizations?
Radio-telescope are used to search for messages broadcasted by other civilizations.
Why are radio waves the best option to search for other civilizations?
They travel far though the disk without being absorbed or scattered
What is the physical interpretation of the Hubble Law?
The further away a galaxy is, the faster it is receding. All galaxies are moving away from each other showing that the universe is expanding.
What gets larger as the universe expands?
The distance between widely separated galaxies
Is there a center to the expanding universe?
Is there an edge to the expanding universe?
The explosive event that caused the expansion of the universe to begin
As the universe expands the photons are stretched and are redshifted. (More distant objects have greater redshifts)
Importance of the cosmic microwave background radiation
Believed to be the remnant of the fireball that caused expansion. Microwaves used to be gamma rays in the past. Direct evidence that the universe passed through a hot, dense phase predicted the Big Bang.
What is WMAP?
Probe that amped cosmic microwave background radiation
Goal of WMAP?
To measure the fluctuations in the CMB at a micro-kelvin level
Results of the WMAP
The age of the universe is 13.7 x 10^9. The universe is flat and there is dark matter and dark energy
The expansion of the universe is _____ as a result of it being filled with _____.
Speeding, dark matter that pushes matter apart
Occurs when mass is added to a white dwarf in a close binary system and reaches the Chandra Mass limit causing a supernova explosion
Type La Supernova
Astronomers use La Supernovas as a _____.
Standard candle to determine the expansion rate (using distance and speeds)
100 km =
Astronomical unit is a unit of _____.
length equal to the average distance between the sun and the Earth
Diameter of the sun is ____ times the diameter of the earth
Volume of the sun is ____ times the volume of the Earth
Earth rotates on its axis from
west to east
How long does the sun spend in each zodiacal constellation?
About 1 month
Radio photons have _____ energy, ____ frequency, and _____ wavelength when compared to infrared photons
lower, lower, longer
An electromagnetic wave is an example of a _____ wave.
Hotter objects emit _____ radiation than cooler objects of the same size.
The hotter the object, the _____ energetic the typical photon emitted. The color of a hot object shifts from _____ to _____ as it gets hotter.
More, red to blue
On the Celsius scale, water freezes at _____ and boils at _____
In black bodies, max wavelength _____ as temperature increases at any wavelength.
A hotter black body has a _____ intensity
Low density, cooler gas produces _____ when viewed in front of a hotter continuous source.
An absorption line spectrum
In the class demonstration of spectra, the tube containing NEON showed _____.
A spectrum with many emission lines
When a light source approaches someone, they see that the wave crests are _____ than they would be if the source were at rest. The observed wavelengths of spectral lines from the source are _____ which is known as _____
Closer together, shortened, blue shift
_____ is closest to the average density of the sun.
The density of water
_____ in the sun is the outward gas pressure force balancing the inward force of gravity.
The energy lost at the photosphere of the sun must be replaced by an internal energy source for the sun to remain in balance. This is an example of ____.
The mass of a normal helium nucleus is ____ times the mass of a normal hydrogen nucleus
Slightly less than 4
Minimum temp required for nuclear fusion of hydrogen
____ dominates in the outer envelope of the sun
Most of the visible radiation from the sun comes from the ____.
The gas motions within granules on the solar surface are ____ in the bright cell centers and ____ around the dark edges
From the bottom to the top of the transition zone the temperature _____.
Rises to above 10^6k
The wavelength of peak emission form a sunspot is ____ than that for the surrounding region.
Aurorae occur near ____ due to the capture of ____.
Magnetic poles, charged particles
When a solar storm occurs, ____ is first observed from the SOHO
Stellar parallax occurs because the earth orbits the ____
Apparent brightness of a star is ____ its distance
Inversely proportional to the square of (1 over distance squared)
Star with a surface temperature of 3000k appears ____.
Spectral classification is based on
What star can have a surface temperature higher than the sun but a luminosity lower?
Energy lost from the photosphere of a protostar is replaced by energy release from ____
Minimum possible mass of a main sequence star is ____.
When a star becomes a red giant gravity causes the core to ____ and the outer region to ____.
Contract and heat, expand and cool
Nuclear fusion in stars produces
____ keeps a white dwarf from contracting further
Chandra demonstrated that there is a ____ possible mass for a white dwarf.
The main sequence turnoff is the location where stars are becoming ____. The older the cluster, the ____ the mass.
Red giants, lower
Right before the supernova explosion the core of a massive star is composed of ____ and ____ undergo nuclear fusion
iron, does not
Electrons and protons combine to form ____ in the cores of a collapsing star
Elements heavier than hydrogen and helium were produced in stars that ____
The gas in supernova remnant like Cas A is ____ and ____.
Expanding and hot
The flash of radiation observed from pulsars are a result of ____.
The rapid rotation of the pulsar
In the collapse of the core of a massive star, the spin rate _____ due to the ____.
Increases, conservation of angular momentum
The point of infinite density is:
In the disk, young stars have ____ metal content than old ones
In the disk, infrared radiation emitted by stars has ____ wavelength than dust because stars are ____ than dust
Orbits of halo stars are similar to
The outer halo of the MWG is composed of ____
When a MACHO passes between a star and us, the distant star:
Rises and then drops in brightness
Most dark matter in the halo of the MWG is in the form of:
Close encounters between pairs of stars in a globular cluster cause some stars to be ____
Kicked into the core and into the halo
The best explanation of the blue straggler stars is that they recently formed from ____ of ____ mass stars in the cluster
For Cepheid variables, the time interval between peaks of brightness is the ____. The quantity directly determines the ____ which taken with ____ drives us the distance.
Period, luminosity, apparent brightness
Elliptical galaxies contain ____ gas and dust and ____ stars
Little, only old
Speeds of galaxies are measured using ____
The doppler shift
According to the Hubble Law the recession velocity of a galaxy is ____ to the distance of the galaxy.
The Hubble Law constant is ____ km/s per Mpc
____ mass planets, close to their ____ is most easily detected by velocity wobble method .
High, parent star
Kepler mission detects planes orbiting stars other than the earth by using the ____ method
Which part of the electro magnetic spectrum has primarily been used to search for extraterrestrial life?
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