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97 terms

Astronomy exam 3

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T/F Our Sun lies about 300,000 light years out from the Galactic Center
True
T/F The Earth lies close to the center of the Galaxy
False
the longer the period of pulsation for the Cepheid, the more massive and luminous the variable giant star is
True
True or False William Herschel's original model for our Galaxy was based on counting stars.
True
Herschels original disk model placed use close to the center of the galaxy.
True
The instability strip is above teh main sequence on the H-R diagram
True
William Herschel made the fist map of the Galaxy about 200 years ago
True
True or False RR Lyrae stars pulsate, but with shorter periods and lower luminosiites than cepheids
True
True or False It is harder to map the structure of the Milky Way in visible wavelengths than with radio and infrared waves
True
T/F Shapley found the globulars were strongly concentrated toward Sagittarius
True
Shapley found that globular clusters are only found in the Galactic bulge
come back
Harlow Shapley mapped the Milky Way using the period luminosity relationship for RR Lyrae stars
True
T/F 21-cm radio waves allow us to map the distribution of hydrogen in spiral arms on the opposite side of the Galaxy
True
T/F Halo stars are all Population II objects
True
The orbit of the solar system around the Galaxy is similar to that of a planet, almost circular and in the galactic plane
True
stars with an emission nebula such as m42 are considered
...
The thickness of the Galaxy, near the SUn, is aout 1000 light hers pulsation I stars
...
The globular star clusters are the most obvious examples of population II around us
True
Population I stars came billions of years before population II stars
false
Halo stars are all population II objects
true
the RR lyre stars all have periods of
a few hours
a star in the instability strip of the H-R diagram would
vary in both temperature and raidus
for finding the distances to globular clusters, Harlow Shapley used
RR Lyrae variables
Which is the correct description of the Sun's location within the Milky Way
above the disc and about one-third of the galactic radius from the center
Galactic disks appear blue because
O and B blue giants are much brighter than G, K, or M dwarfs.
The Galactic Year is the time for our solar system to orbit the Galaxy; it is about
225 million years
Detailed measurements of the disk and central bulge region of our Galaxy suggest our Milky Way is a
barred spiral galaxy
Between us and the Galactic Center, the Milky Way has a mass of
100 billion suns
In the formation of our Galaxy, the formed first
globular clusters?
Which sequence of formation is best, oldest to youngest
Globular clusters, open clusters, OB associations
Most of the new star formation in the Galaxy is found in the
spiral arms
Most of the mass of the Milky Way seems to exist in the form of
dark matter out in the Halo
At the center of our Galaxy lies
A black hole of millions of solar masses
The radio source blank is located in a place consistent with the center of our Galaxy
Sgr A*
What are the three main parts of our Galaxy?
Galactic Disk Globular clusters, Halo
Describe our location in the Milky Way
he Milky Way's outer spiral arms, known as the Orion Arm or Local Spur. The Sun lies between 25,000 and 28,000 light years from the Galactic Centre.
What do the orbits of Populations I and II stars tell us about the formation of the Milky Way?
the metallicity of the star
How and when did the Miky Way Galaxy form?
The milky way was formed by stars gases and dust . The milky way also started as a black hole and stars dust and gases gathered around the black hole. When? with our current astronomical knowledge, scientists predict it was approximately 1 billion years after the big bang
T/f Compared to the spirals, elliptical galaxies tend to be more dusty
True
T/f Unlike spirals, elliptical galaxies do not contain a flattened disk.
true
T/f There are more giant elliptical than dwarf galaxies
false
T/f Most galaxies are spirals.
True
T/f Irr II galaxies may be the result of a collision, or close encounter, of two normal galaxies
True
T/f On average, elliptical galaxies are richer star forming regions than spirals.
false
T/f In the Local Group, most members are either dwarf ellipticals or spirals.
True
T/f The closest other galaxy to our solar system is the Sagittarius Dwarf.
true
T/f While our Magellanic Clouds are irregulars, the two companions to Andromeda are both ellipticals.
true
T/f Virtually all galaxies are moving away from the Milky Way.
True
T/f Space itself is expanding.
True
T/f Quasars can emit thousands of times as much energy as normal galaxies.
False
T/f Quasars are the brightest objects in the universe.
True
T/f When observing a quasar, we are probably looking at a stage of evolution in the very early universe.
True
T/f Radio galaxies emit only radio waves, and are not otherwise observable.
True
On average, active galaxies are rare and most are fairly distant from us.
True
There is evidence that a collision between a spiral and an elliptical galaxy has produced a radio galaxy.
?
Synchrotron radiation is the major source of energy for active galaxies.
false
Which property is common to spiral galaxies?
on-going star formation and emission nebula in the arms
The astronomer who originally classified galaxies into S, E, and Irr was
Edwin hubble
Compared to our own Galaxy, elliptical galaxies
have no arms, but a better defined disk
The Milky Way is often considered to be an intermediately wound, barred spiral, which would be type ________ according to Hubble.
SBb
The flattest of all galaxies belong to class
Sc
In shape and component stars, elliptical galaxies are most like our own
Galactic center
What is true of giant and dwarf elliptical galaxies?
?
The greatest variation in size, mass, and luminosity occurs in
elliptic galaxies
What is true of the Local Group?
The milky way and the andromeda galaxy are two of the largest members of the local group.
About how many galaxies are presently known in our Local Group?
54
Why does the Cepheid distance method fail us beyond about 20 Mpc?
Even with the HST, the most luminous Cepheids are too faint to be seen beyond.
What is the nearest huge cluster of thousands of galaxies, to which the Local Group may belong?
Virgo Cluster
What are Type I supernovae used for?
Standard candles for determining distances to other galaxies.
Which statement about the Magellanic Clouds is false?
They are close to the south pole of the sky
Most of the galaxies in the Local Group are
small irregulars like the Magellanic Clouds
According to Hubble's Law, the greater a galaxy's redshift, the
farther it is from us.
A billion-solar-mass black hole would still have a radius of only
20AU
The energy radiated by a typical quasar requires that its black hole accrete about
Ten solar masses a year
Not only does the central engine of active galaxies and quasars require a black hole, but also ________ to provide the radiate energy.
an accretion disk of infalling matter
When mass is accreted into a black hole, how much total mass-energy can be radiated away?
The whole of its gravitational potential energy
Who invented the galaxy classes, and what three major groups did he invent? Which telescope did he use?
Edwin hubble. ellipticals, lentriculars and spirals. Hubble space telescope
To which portion of the Milky Way are the Magellanic Clouds most similar? Why?
the closest similarity would be to the arms of the Milky Way - the Magellanic Clouds themselves are small irregular satellite galaxies of the Milky Way and contain many of the same features found in the spiral arms - nebulae, star clusters, supernova remnants, etc
Why do quasars die out over time?
they get all the gas and then run out and become black holes
Most of the mass in the universe is dark matter.
True
There are large amounts of superhot intergalactic gas/matter
True
As with stars, binary galaxy pairs are useful in finding their total mass
True
For nearby galaxies, determing the rotation curve allows us to calculate the mass
True
The total mass of a galaxy tends to be only slightly larger than the visible mass
false
Head-tail radio galaxies reveal their motion through the intergalactic gas with a tail like structure
True
The Great Wall is a huge sheet of galaxies that stretches for over 100 Mpc
True
Galaxies contain less mass as dark matter than as visible stars
True
The largest known galaxies contain about 10 billion solar masses
True
The Andromeda galaxy will eventually collide with the Milky Way
True
Collisions between galaxies have little effect on the individual stars.
True
Galactic collisions are believed to be commonplace.
True
In the larger clusters, colliding galaxies tend to pass through one another
True
When galaxies collide, the large scale galactic structure if affected, but the individual stars are not
False
Our theories of galaxy formation are just as well developed and tested as are our theories of star and planet formation
True
Most galaxies are isolated in space
False
The pregalactic blobs started with masses comparable to big globular clusters
False
Supermassive galaxies are found at the core of rich galaxy clusters.
True