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You measure the parallax angle for a star to be 0.5 arcseconds. The distance to this star is
100 parsecs away.
Approximately what core temperature is required beforehydrogen fusion can begin in a star?
The core shrinkswhile the rest of the star expands.
become a white dwarfthat will slowly cool with time
Approximately how long did the nucleosynthesis era last?
What are the two key observational facts that led to widespread acceptance of the Big Bang model?
the cosmic background radiation and the high helium content of the universe
Astronomical Unit (AU)
Light Year (Lyr) (distance NOT time!)
Since it takes time for light to travel to us,
Reads: 35 degrees, 27 arcminutes,15 arcseconds
1 degree = 60 arc minutes
1 arcminute=60 arcseconds
How bright a star appears (brightness) depends on
both distance and luminosity
What is Luminosity?
Amount of power a star radiates
(Measured in Watts = energy per second)
is the apparent shift in position of a nearby object against a background of more distant objects.
Apparent positions of the nearest stars shift by about
Magnitude of Vega is set at 0
Scale is backwards!
Large number = fainter object!
Properties of Thermal Radiation
1. Hotter objects emit more light per unit area at all frequencies.
2. Hotter objects emit photons with a higher average energy.
Absorption lines in a star’s spectrum
gravity and Kepler’s Third Law
Types of Binary Star Systems
• Visual binary
• Eclipsing binary
• Spectroscopic binary
About half of all stars are in binary systems.
We need two out of three observables to measure mass
Orbital period (p)
Average Orbital separation (a)
Orbital velocity (v) -- Doppler!
How do we measure stellar temperatures?
Spectral lines from ionization O B A F G K M (from hot to cold)
Star classifications include spectral type and luminosity class:
I — supergiant
II — bright giant
III — giant
IV — subgiant
V — main sequence
1. Open cluster: A few thousand loosely packed stars
2. Globular cluster: Up to a million or more stars in a dense ball bound together by gravity
How do we measure the age of a star cluster?
Massive blue stars die first, followed by white, yellow, orange, and red stars.
The gas between the stars is called the
a star became REALLY massive
So massive that light could not escape
stars more massive than 300 Msun
Stars less massive than 0.08 Msun
What is the General Theory of Relativity?
The theory that says matter and energy cause space-time to curve which tells matter and energy how to move.
As a space ship with yellow headlights approached the event horizon of a Black Hole, which color would you expect to see?
You synchronize your watch with a friend and then they fly a ship near the event horizon of a Black Hole, if your watch reads 3pm what time would you expect to “see” on their watch?
Gas from dying stars mixes new elements into the interstellar medium, which slowly cools, making the molecular clouds where stars form.
Those stars will eventually return much of their matter to interstellar space.
Active star-forming regions contain molecular
clouds, hot stars, and ionization nebulae.
Much of the star formation in our galaxy happens in the spiral arms.
As your friend approaches the black hole, which best describes what YOU would see?
Converting light-years to meters
(decimal of km/s moved to the left 2 places) x 10e5
What can we use “Standard Candles” for?
To find distances of galaxies further away.
Out of the 3 galactic distance units. which one is better to measure distances between galaxies (and larger), and is referred to as cosmologist units?
The relationship between apparent brightness and luminosity depends on _____.
What gives us the distance of nearby stars, letting us establish their luminosity?
What is useful about using “Main-Sequence Fitting”?
What is difficult about using “Main-Sequence Fitting”?
It is difficult to see clusters outside our galaxy, so it is not well for measuring distances to other galaxies.
Cepheid variable stars (Cepheids)
Through the Hubble Space Telescope using standard candles.
When did the universe’s distance=0?
About 14 billion years ago, when the universe began.
What did the universe do as it expanded?
Copernicus first stated and showed how the Earth is a planet orbiting the sun rather than the center of the universe
As the universe ____, light no longer interacted with matter giving us the __________.
Cooled, Cosmic Microwave Background.
The remnant radiation (“afterglow”) from the Big Bang, which we can detect using radio telescopes sensitive to microwaves (which are short-wavelength radio waves).
We learn from CMB observations that the ingredients of the universe at 380,000 years (13.7 billion ya) were what 4 things? (*Don’t need to know percentages, just what it was mostly made up of*)
What are three hints for dark matter inside galaxies?
All three methods of measuring cluster mass indicate what?
Similar amounts of dark matter.
Dark matter really exists, and we are observing the effects of its gravitational attraction.
Something is wrong with our understanding of gravity, causing us to mistakenly infer the existence of dark matter.
Dark matter interacts with gravity through gravitational lensing. It is weak for particles, which is less mass, and strong for planets, which has more mass.
Suggests possible candidates for the dark matter. Treats matter and force identically to get the same result. Suggests there is a “cousin” particle for every particle we’ve ever observed for matter, but we just can’t fully identify them. The particles are weakly interacting massive particles (WIMPS).
What do we mean when we say that particles such as WIMPs are weakly interacting?
They respond to the weak force (and gravity) but not to the electromagnetic force, which means they cannot emit light.
What are the 3 ways we currently use to look for dark matter WIMPs?
Particle colliders, Direction detection of dark matter, and Indirect detection of dark matter.
By colliding known particles to produce new ones (dark matter).
What does the CMB “Picture” teach us and let us do?
It teaches us about the composition of the universe at that time. It lets us compare the universe then, to the universe now,
Besides the 3 hints for dark matter, what is another evidence for dark matter?
There is evidence of dark matter from the universe expanding (as we try out CMB ingredients).
Can we see the whole universe? Explain.
No, there is a limit on how much we can see. There is this “visible universe” and then there is the “entire universe."
The redshift we see from distant galaxies, caused by the fact that expansion of the universe stretches all the photons within it to longer, redder wavelengths (closer together its blue). (The color of light waves).
Direct Detection looks for dark matter particles as they do what?
Slam into heavy known elements.
How does indirect detection experiments look for dark matter?
By detecting particles and light that result from its annihilation.
Hubble helped settle the debate about Spiral Nebulae, demonstrating they were _____
True or False: At 400,000 years after the Big Bang, the universe was primarily made of Dark Energy.
Supersymmetry is one example of a theory that predicts the existence of WIMPS.
The temperature at which the CMB stopped interacting with atoms was about ____.
What is dark energy?
An unknown form of energy that seems to be the source of repulsive force causing the expansion of the universe to accelerate
*What could Dark Energy be made of (or it may not)?
Which statement about the Big Bang does NOT agree with current observations?
Time and space began at the Big Bang
X-ray emission of hot gas
Kepler’s Law and the motion of galaxies in the cluster
WIMP stands for Weakly Interacting Massive Particle
Indirect detection experiments look for evidence of dark matter by searching for Standard model particles resulting from dark matter annihilation.
We search for dark matter at particle colliders by colliding Standard Model particles (known) to produce dark matter (unknown).
Why is the night sky dark?
Hubble’s law tells us that the further away a galaxy is the....
How did Hubble determine the motion of galaxies?
Main Sequence Fitting is best used to determine distances where?
What is the best way to describe the composition of the universe today?
Mostly Dark energy, some dark matter, and a little bit of atoms and light
Which of the following about the CMB is NOT true?
The horizon defines the visible universe (the most distant light we can see), whereas the entire universe is actually much larger.
The CMB stopped interacting with matter at about _____
True or False: Although right after the Big Bang we could not see the entire universe, today there has been enough time so that we can.
Which are the ways to determining if Dark matter is a particle?
Particle Colliders, Direct Detection, AND Indirect Detection
The Copernican Principle states that...
We do not occupy a special place in the universe, there is no center to the expansion
How much time has passed since the Big Bang (what is the age of the universe)?
What best describes how standard candles are used to determine distance?
Because a standard candle’s luminosity is known, we can determine the object’s distance from observations of its apparent brightnes
Which is NOT evidence for dark matter inside galaxies?
The Bullet Cluster
True or False: CMB stands for the Cosmic Microwave Background
Observations help us estimate the age of the universe through which physical law?
§ Limited Gag order
§ Change of venue- move trial out of district to another place into the state
§ Jury Sequestration- cutting the jury of from the public put up in a hotel room, cut off from world
1. Charge bargaining – bargaining for alesser charge (manslaughter instead of murder)
2. Count bargaining – plea to one or twocounts so the rest of the accounts are dismissed
3. Sentence bargain –
Bargain the sentence time (the range and determinate vs. indeterminate sentencing)
Determinate sentencing: fixed sentencing. doing the full time with no option for parole
Indeterminate sentencing: fixed # with an extension on the end. Serving the minimum with option for parole (parole may be denied)
They act as standard candles. These exploding stars have a well understood pattern of light emission and we compare the luminosity to the observed brightness to learn about the cosmic expansion.
What are two things dark energy are not parts of?
Dark energy is neither an atom nor part of the “Standard Model.”
No, particles pop in and out of existence that we can see below 10 to the negative 10th Meters.
Higgs, it helps explain the origin of mass.
Where do particle masses come from?
Einstein’s cosmological constant and so this term must be small.
*What may be the physical meaning of the cosmological constant?
*What is the early acceleration of the universe?
Through the cosmological constant and the vacuum energy today.
Maybe yes and maybe no because Dark Energy may be vacuum energy, or it could be made of something else.
Small quantum jitters
String theory and we can probe this using inflation.
1. If you increase the mass of a black hoe, this will increase the Schwarzschild radius and the event horizon
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