Exam 2 Flashcards
What is the general result of the proton-proton chain?
4H -> He + energy + other products
The corona of the sun:
is visible during a solar eclipse
In the convective zone of the sun:
columns of hot gas rise, cool, and descend
What part of the sun do we typically see?
Photosphere
In nuclear fusion, energy is produced because…
the mass of the reacting chemicals is larger than that of the products
When using different points in the earths orbit as a baseline for a parallax experiment, it is best to do the observations:
6 months apart
One star is 4 times farther away than another, the parallax angle of the more distant star is
four times smaller than that of the nearest star
Put your thumb at arms length in front of your face. Focus on something in the background and look through one eye at a time. What do you notice about your thumb?
It appears to move more when it’s closer
Star A is 4 times as luminous as star B. Star A is 2 times as far away as star B. which star appears brighter and by how much?
the same: brightness = luminosity/ distance^2
An “onion“ skin burning shell, with elements up to iron being produced, develops in:
A star much more massive than the sun
What is at the center of a planetary nebula?
Both the core of the dying star and something that will eventually become a white dwarf
How do solar-sized and smaller stars die? About how large are their remnants?
They become white dwarfs, about the size of Earth
What does NOT happen when an object approaches a black hole?
It quickly gets sucked in even from a large distance
How can we measure the mass of a black hole?
measure the speed of the orbit of a star in a binary system with the black hole
What is the main requirement for a habitable zone?
Liquid water
A star that is twice the mass of our sun would have a habitable zone that:
Includes Mars but not the Earth
A star that is 3/4 the mass of our sun would have a habitable zone that:
Includes Venus only
What factor is not in the Drake Equation?
Communication lag due to large distances between stars
What does the Drake Equation estimate?
The number of technological civilizations in the Milky Way
If a red giant appears the same brightness as a red main sequence star, which one is farther away?
The Red Giant
The heaviest nuclei of all are formed…
during a supernova explosion
Hydrogen-2 + Proton = ??? + Energy
Helium-3
What are the differences between open star clusters and globular star clusters?
Open clusters are less concentrated, younger, and have fewer stars
Which of the following is false? A) A supernova is an explosion of a high mass star at the end of its life; B) a nova can be caused by a white dwarf gaining material from a nearby companion star C) a type 1a supernova is caused by addition of hydrogen- rich material onto a white dwarf D) a light echo is caused by light from an exploding star that’s gradually reaches different layers of gas around the star E) a nova is more luminous than a supernova
E
What kind of gas cloud can collapse and form stars?
The gas cloud must have a mass that exceeds the Jeans mass so that gravity overcomes the internal pressure in the cloud
What is the mass of the black hole at the center of the Milky Way?
4 million solar masses
How do you measure the mass of the supermassive black hole at the center of the Milky Way?
Look at the orbits of nearby stars and apply Kepler‘s third law
You will see that the universe is almost 14 billion years old. That’s means that we see the most distant galaxies as they were when the universe was:
1-2 billion years old
According to models of galaxy formation, which population of stars formed first?
The spheroidal population
What type of galaxy can result from collisions between galaxies?
Elliptical or irregular
What is a starburst galaxy?
A galaxy with a very high rate of star formation
In what part of the spectrum are starburst galaxies brightest?
Infrared
In the symbol for the hubble type of a galaxy, SBc, the ‘B’ denotes
The presence of a bar
What happens to the planets in a galaxy when that galaxy collides with another galaxy
Nothing, the spaces between stellar systems in a galaxy is much larger than their size
Which properties of spiral galaxies allow us to sub classify them as Sa, Sb, or Sc?
The size of bulge and extent of spiral arms
Compared to spiral galaxies, elliptical galaxies have
Less gas, redder colors, and less new star formation
What is the difference between an E0 and an E7 galaxy?
The E7 has an oval shape and the E0 is circular
What parameters do Hubble‘s law relate to each other?
Galaxy recession velocity and distance
What technique for measuring distance can you use to discover Hubble‘s Law?
Cepheid variables in galaxies and white dwarf supernovae in galaxies
How do you measure the speed of a galaxy relative to you?
Doppler shifts
What is Hubble‘s Law?
The faster a galaxy is moving, the farther away it is
Where is the center of the universe?
There is no center of the universe. Expansion is happening everywhere
How have astronomers interpreted the unexpectedly fast rotation of galaxies?
There must be a lot of dark matter whose gravity can be felt but not seen
Which of the following is not true about dark matter?
Dark matter and dark energy are two aspects of the same phenomenon
Why do we think there is a lot of dark matter in cluster galaxies?
Individual galaxies are moving so fast that they could not be held together by the gravity of visible matter and gravitational lensing lets us measure mass even when we can’t see it
How do we know that the universe‘s expansion is speeding up?
We look at objects from different times in the past to see how expansion changes with time
How could the universe be accelerating, despite the gravitational pull of all matter in it?
There could be a new force or property of space that affects the universe on its largest scales
Which force is responsible for holding the nucleus together via gluons?
strong force
How many types of fundamental particles exist?
30
How many types of quarks are there and how many types of antiquarks?
6 quarks and 6 antiquarks
What kind of particle carries the force?
Boson
Particle formation in chronological order
Quark soup, protons form, nucleosynthesis, atoms form, star formation
What happens because of the formation of atoms?
The cosmic microwave background is produced
What forms in nucleosynthesis?
Most of the Helium-4 in the universe
What is a quasar?
A very luminous source due to a black hole at the center of a galaxy that is quickly growing
How did the conditions differ from the present era when the universe was young?
The universe was hotter, more dense, and smoother
Why does the main sequence part of a star’s life end?
The hydrogen in the core is exhausted
Which of the following will have the shortest lifetime on the main sequence?
Main sequence star with surface temp 20000K
The largest fraction of nearby stars are
red main sequence stars
Which of the following is the sequence of events for a 40-solar mass star
Stellar nursery, protostar, blue main star on sequence, Type II supernova, black hole
What is the name of the slightly cooler layer of the sun just outside the photosphere?
chromosphere
A galaxy has an H-alpha emission line observed at a wavelength 10 percent larger than the rest wavelength of H-alpha. What is the redshift of the galaxy?
0.1
Galaxy A appears twice the angular size of galaxy B. Assuming the two galaxies have the same physical size in kiloparsecs, how far apart is Galaxy B from Galaxy A relative to you?
2 times as far
What fundamental particles make up a Helium-3 atom?
five up quarks, 4 down quarks, 2 electrons
How many times bigger is the local group of galaxies in which the Milky Way resides than the Milky Way itself?
about 100 times bigger
Why can we NOT see back the whole way to the time the Big Bang expansion began?
The radiation scatters off matter frequently so the universe is opaque
What are the “standard candles” that we used to determine the universe is accelerating?
Type Ia supernova
