Astro Midterm 3
thought experiment #5: jackie is moving at 0.9c, which means your light beam is traveling ___ faster than her. Before relativity, jackie would have thought you were moving away from her at 0.9c so the light would be traveling at her at 0.1c, but this is wrong because ______. thus, even though jackie still sees you as moving 0.9 c away from her, she sees the flashlight pointed at her at speed __
0.1c, all observers see the same speed of light, c
Short Bursts: Less than _____: _____ Mergers. Can either be two merging _____ or merging ______. Short cannot be explained by the collapse of a _____
1 second, Catastrophic, neutron stars, black holes, supernova
Milky way dimensions: thickness of disk = ____ ly (___ pc)
1,000, 300
"Classical" (newtonian reality) 5 components
1. Absolute time and space 2. Accurate measurements unproblematic 3. Deterministic causal laws 4. Continuously varying processes 5. A completely objective world, independent of observer
Five key ideas from special theory of relativity
1. No info can travel faster than light and no material object can ever reach the speed of light 2. If you observe someone or something moving close to the speed of light you will conclude that time runs slower for that person or object 3. Simultaneous events are in the eye of the beholder 4. The length of something moving close to the speed of light is shorter than if it were not moving. 5. The mass of something moving close to the speed of light is more than if it were not moving.
four things that make up the Milky Way
1. Stars 2. Interstellar medium 3. Galactic center 4. Dark matter
two key takeaways from special theory of relativity:
1. The laws of nature are the same for everyone (i.e., for all observers). 2. The speed of light is a constant and the same for everyone (all observers).
three other proofs supporting relativity
1. The lifetimes of subatomic particles --At rest, the pi+ meson has a lifetime of 18 nanoseconds. But when accelerated close to the speed of light, it has a much longer lifetime, in exact agreement with the time dilation equation. 2. Masses of particles increase when traveling close to the speed of light. 3. A 1971 experiment re: time dilation using airlines.
star gas cycle 6 steps
1. atomic hydrogen clouds 2. molecular clouds 3. star formation 4. stellar lives: nuclear fusion/heavy element formation 5. returning gas: supernovae and stellar winds 6. hot bubbles
Neutron star makeup: Mass ~ ___ solar masses, ~__ km diameter ____ crust, almost perfectly smooth because of such strong ___, ~_km deep ___ core, mainly ___ in it with other particles
1.5, 20, Solid, gravity, gravity, fluid, neutrinos
total radius of a neutron star
10 km
Thought experiment #2: You throw the ball at 100 km/hr, which means you see it going toward jackie at a speed ____ faster than Jackie's 90 km/hr. Jackie sees the ball moving with the 100 km/hr speed you threw it at her with, minus your ____ speed ___ from her, so she sees the ball coming toward her at ____
10 km/hr, 90 km/hr, away, 10 km/hr
Dark matter has like __ or __ times mass of visible things, like neutrinos, its sub atomic particle that carries ____, unseeable by astronomers
10, 12, mass
Because of relativity, GPS becomes inaccurate by ___ km a day unless you take into account impact of less gravity on their ____
10, clocks
From one end of the milky way to the other end is _____ light years
100,000
Milky way dimensions: Diameter of disk _____ ly (_____ pc)
100,000, 30,000
Mass of galaxy internal to sun is somewhat more than ___ solar masses, ___ billion solar masses. Continued flat rotation curve past the solar circle implies a total mass _______, with no firm cutoff since rotation curve hasn't yet been seen to ___. A flat rotation curve implies mass inside r proportional to _
10^11, 100, several times this, decline, r
Total mass of Milky way galaxy: 1 - 2 x ___ Msun, can be estimated with ______
10^11, Newton's Law of Gravity
Neutron stars have strong magnetic fields - around ___ Gauss (Earth field is __ Gauss; the strongest magnets in the world are about ___ Gauss). Sometimes they can form with even stronger magnetic fields up to ____ Gauss...they then become ____. A lot of this is only visible with ____
10^12, 0.5, 10^6, 10^15, magnetars, X-rays
Around ___, there was a core collapsed massive star known in our galaxy called ____, it was ___ solar masses. There is only ____, _____, ____, ___, etc, no ____ or ____. There is a main shell of remnants and then there are two ____that come off the main shell. When you color code this you see sulfur rich ejecta on either bipolar jet, this is interesting because it would have been ______ than some other elements
1680, Progenitor, 15-20, carbon, oxygen, sulfur, iron, hydrogen, helium, bipolar jets, deeper down in the star
The first recorded extragalactic supernova was seen in August ___ in the central bulge of M31. We think it was a __ luminous Type __ event. Down the center of the SN was noticeably ___ temporarily
1885, sub, Ia, brighter
Total number of stars in MW Galaxy ≈ _ to _ x ____. We're not sure of precise number of stars because of unclear ______, but it's roughly this
2, 4, 10^11, stellar demographics
___ of all stars are in binary systems
2/3
Sun makes one trip around the galactic center in about ___ million years, so it has made about ___ orbits during its MS lifetime
200, 25
Milky way dimensions: number of stars ~ ___ - ___ billion
200, 400
Stars in Milky Way: ___ to ___ billion stars, Age: ~__ billion years to just have formed, Many stars are located in star ____
200, 400, 12, clusters
Sun's orbital period in MW
230 million years
How does GPS work? Its a network of __ satellites in high ___ around the Earth. Each satellite in the GPS constellation orbits at an altitude of about ____ km from the ground, and has an orbital speed of about ___ km/hour (the orbital period is roughly __ hours). The satellite orbits are distributed so that at least _ satellites are always visible from any point on the Earth at any given instant (with up to __ visible at one time). Each satellite carries with it an ____ that "ticks" with an accuracy of _ nanosecond (____th of a second). A GPS receiver determines its current position and heading by comparing the ____ it receives from a number of the GPS satellites. (usually _ to __) and ____ on the known positions of each satellite.
24, orbits, 20,000, 14,000, 12, 4, 12, atomic clock, 1, 1 billion, time signals, 6, 12, triangulating
Our galaxy rotates about ___ km/s at sun's distance from center (about __ kpc)
250, 8
Milky way dimensions: Sun is in disk, _____ ly out from center
28,000
There are ______ ly between our sun and the center of the bulge
28,000
Escape Velocity is given by v^2esc = ___. So as radius decreases (becomes smaller) the escape velocity ____
2GM/R, increases
Neutron stars cannot be above _ solar masses
3
Radius of Black Hole ~ _ x Mass
3
Some X-ray binaries contain compact objects of mass exceeding __ MSun which are likely to be ____
3, black holes
General relativity and black holes: Neutron stars must be less than about _ solar masses, what happens if remnant is heavier? It collapses to a ___ (___ size set by ___ mechanics ___ principle). Neither ___ (nor ____) can ____ from a region around the point - black hole
3, point, tiny, quantum, uncertainty, light, anything else, escape
If remaining mass after a red giant supernova is > __ solar masses or so, you cannot have a ____ neutron star (analogous to the _____ limit). In that case, the star ____ further to make a _____
3, stable, Chandrasekhar, collapses, black hole
RECALL: 1 parsec (pc) = ___ light year (ly)
3.26
Einstein says light will be measured at ____ km/s ____ of how the source or the observer is _____
300,000, regardless, moving
Nothing can travel faster than the speed of light, and light takes ___ years to travel to the closest stars. Could people ever travel to another star in a reasonable amount of time? Consider going to the star Vega, which is 25 light-years away. From earth's reference frame, if you travel at ____, the trip would take about ____ in each direction, for __ total. However, from your reference frame, if you are ____ in your spaceship, earth and vega travel at ___, length contraction reduces the ___ light-year rest length to only _ light-year, which means that for you the trip then only takes _ year in each direction
4.3, 0.999c, 25 years, 50, stationary, 0.999c, 25, 1, 1
GPS systems provide positions accurate to _ or __ meters in real time. The accuracy is only possible if they take account of ______ and ____ theory of ____. We can get it to ___ if we use this and the ____ is behaving
5, 10, Einstein's special, general, relativity, 1 cm, ionosphere
Milky way dimensions: radius of disk = ____ ly (____ pc)
50,000, 15,000
Note: 0.1'' is equivalent to ___ AU, or __ light-days
800, 4.5
very massive stars that you see turn into supernovae are how big? what do they release?
> 8 solar masses, shockwaves
White dwarf supernovae = type __
A1
Newton's implicit theory of measurement: ____ time and space, _____ communication, velocities ___ (via _____), Galileo's 'principle of ____' (same physics in ____ reference frames)
Absolute, instantaneous, add, vector addition, relativity, inertial
__________ is the average work done per nucleon to break up a nucleus into constituent particles. This is a measure of nuclear _____
Binding energy, stability
Imagine squeezing a mass until its escape velocity is the speed of light → a _____.
Black hole
Example black hole = ___
Cygnus X-1
Arthur _____ did a test that proved Einstein's idea of light deflection
Eddington
Spiral structure of galaxies: The ____ disk does not appear ____, it has ____ arms, much like we see in other galaxies like ___. These arms are not fixed ____ of stars which revolve like the ___ of a fan. This spiraling creates a ________ around the spiral arm, "____ wave," moves through the disk making new stars (saturn's rings are also like this)
Galactic, solid, spiral, M51, strings, fins, wave of new stars, density
What creates powerful photons that are distributed across the entire sky? _____. What are these? _____ wavelengths going by you at _____ frequency, ____ size What produces gamma rays? Not _____. Discovered in ____ while looking for nuclear test explosions - a 30+ year old mystery!
Gamma ray bursts, Short, enormous, 10^-12, supernovas, 1967
Einstein called his experiments "thought experiments" or ____ experiments.
Gedanken
General Theory of Relativity: _________
Gravity as a Distortion of Spacetime
____ can cause two space probes moving around Earth to meet. ____ relativity says this happens because spacetime is ____
Gravity, General, curved
Rules of Spherical Geometry: 1. ____ is shortest distance between two points 2. ____ eventually converge 3. Angles of a triangle sum to > ___° 4. Circumference of circle is < ___
Great circle, Parallel lines, 180, 2πr
Type ___: the mechanism by which the explosion proceeds in white dwarfs remains ______. The current thinking is that of a "_____" in which the explosion stars in the core as a type of burning _____, which is followed somehow by a _______ of overlying ____ material, which ____ the white dwarf completely. At one point this will hit ____ speed, which is what causes the ____ wave, rolling through the star
Ia SNe, poorly understood, delayed detonation, deflagration wave, shock detonation wave, unburned, unbinds, supersonic, deflagration
Einstein's equivalence principle states:
In any sufficiently small region of space, the effects of gravity cannot be distinguished by any experiment from that of constant acceleration
Consequences of General Relativity: 1. _____ force law isn't exact; minor corrections to _____ trajectories 2. Mercury's elliptical orbit gradually ____, mostly due to the gravitational pull of ____. But a small part of the precession (__ arc-seconds per century) is due to ____ corrections to Newtonian gravity. 3. Gravitational deflection of light ____ the amount that ____ would have predicted
Inverse-square, solar system, precesses, other planets, 43, relativistic, twice, Newton
using ____ Law, we infer a mass of ____ Msun for Sgr A*
Kepler's, 4 million
___ curves of the two basic supernovae types are slightly different. Massive star supernova does not get as ____ as white dwarf supernova, but they take about ___ days (___ total) longer to decline past a luminosity of ___. Temperature of white dwarf ___ explosion is something to the ___ degrees, massive stars have even higher ___ explosion temp, _____ degrees
Light, luminous, 100, 400, 10^7, core, 10^9, core, 3.4 x 10^9
Two types of gamma ray bursts: Long Bursts: _____ --> a ______, which is a SN of high mass stars. We see ___ and _______ coming out of the center of the _____, the jets hitting other gas are what cause the ______. The end of the life of a star that had 100 times the mass of our Sun, A billion trillion times the power from the Sun
Many seconds, Hypernova, jets, beams of energy, black hole, gamma rays,
There are two basic types of supernovae: 1. ____ that blow up via the collapse of their ___ with outer ____ then undergoing a ____ off a newly formed ____ star. 2. ___/___ rich White Dwarfs that blow up bc they are exceeding the __ Msun limit. They explode via _____
Massive stars, cores, falling layer, core bounce, neutron, carbon, oxygen, 1.4, rapid carbon burning
Making a neutron star 3 steps: 1. _____ star with a ___, hot core 2. Supernova explosion blows off ____ layers; ____ core 3. Supernova remnant expands ____; _____ left at "ground zero"
Massive, dense, outer, implodes, forever, neutron star
James ____ produced the theories of electricity and magnetism that are still current today. He proved that light was a wave traveling at ____ km/s. What is it that light waves _____ in? There was ____ answer so an ancient idea was revived: the ____
Maxwell, 300,000, travel, no logical, aether
pre-Einstein It was observed that ____'s orbit was not quite as it should be. People thought that ____ was tugging at it and causing it to deviate from its predicted (_____) path. This hypothetical planet (originally called ____) was ____ seen. Newton's theories worked with _____ known phenomena so the tiny discrepancy in ____'s orbit was forgotten or ignored.
Mercury, another planet, Newtonian, Vulcan, never, all other, Mercury
experiment that said aether didn't exist was the __________ experiment
Michelson-Morley
In the language of Physics, reference frames are the same if they are ____ moving relative to each other. So...the idea that the laws of nature are the same for everyone (all observers) means that they don't depend on your or someone else's_______.
NOT, reference frame
Black holes definition
Objects so dense that not even light can escape
Disk population --> ___ and ____ stars Contains both ___ and ___ stars Have metal abundances much like the ___
Pop I, Pop II, young, old, sun
Spheroidal Population --> ____ Consists of stars in the ___ and ___ Stars are only ___ and therefore ___ in mass Metal abundances around ___
Pop II, halo, bulge, old, low, 0.02%
What remains of the core of a high mass star at the end of its life? ____ + ____ combine to make ___ + ____ (which leave). ____ remains: central density near ___ gm/cm^3, denser than ___ matter, supported by ____ pressure. Radius is only about __ km, ____ energy about __ of mc^2 (compared to _% for nuclear)
Protons, electrons, neutrons, neutrinos, Neutron star, 10^15, nuclear, neutron degeneracy, 10, Gravitational binding, 1/10, 1
____ mechanics says that electrons must move ____ as they are squeezed into a ____ space. As a white dwarf's mass approaches ___ Msun, its electrons must move at nearly the speed of ____. Because nothing can move faster than ___, a white dwarf cannot be any more massive than ___ Msun, the white dwarf ___ (or _____ limit)
Quantum, faster, very small, 1.4, light, light, 1.4, limit, Chandrasekhar
Status of Physics in 1900: ____ explanation of the lines (Bohr atom), Light as energy packets (____)
Quantum, photons
schwartzchild radius formula:
RS = 3 km × [BH mass in solar masses]
the rotation curve was measured by vera ____. You expect the rotation to come up out of the bulge, into sky, and then ____ and ____. Instead she measures that rotational velocity stays around ___ km/s, rather than _____ like the calculated kind
Rubin, dip down, flatten out, 200, dropping down
____ is always relative to the reference frame!
Simultaneity
Status of Physics in 1900: ____ lines in light, ____ and _____ lines = Fingerprints of chemical elements
Spectral, Emission, absorption
_____ pollute the universe with ___ elements, this is how we get things like ____
Supernovae, heavy, planets
Pulsars: ______________
The radiation beams sweep through space like lighthouse beams as the neutron star rotates
____ forces near the _____ of a _ Msun black hole would be ___ for humans. This would be ___ near a supermassive black hole because its ___ is much bigger
Tidal, event horizon, 3, lethal, gentler, radius
An ordinary "nova" is believed to be a _______ system where the WD's companion star sheds mass some of which forms into an accretion disk around the WD
WD in a binary star
Neutron stars have spin periods ranging up to ____ down to ____ and even shorter. Discovered by Jocelyn ____ and ____ in late 1960s. Older neutron stars spin __, lose radio emission; can be faint ___ or ___ sources
a few seconds, 1/30 sec, Bell-Burnell, Hewish, slower, optical, X-ray
what is a magentar
a neutron star with hella strong magnetic field
hypernova
a supernova of really high mass stars
You cannot measure ___ speed. Speed is ____. Thus, this assumption means that many quantities that we thought of as ____ actually vary for different observers.
absolute, relative, constant
Special relativity showed that space and time are not _____ nor _____. Instead they are inextricably ____ in a _______ combination called: spacetime
absolute, separable, linked, four-dimensional
Effects of gravity are exactly equivalent to those of _____. Time must run more _____ at higher ____ in a gravitational field than at ____ altitudes
acceleration, quickly, altitudes, lower
The WD slowly gains mass from its _____. Eventually the gained ___ gas on the surface of the WD ignites, producing a _____, a new ___ star. ____ gas coming from the bigger star to the accretion disk of the _____ cannot cross _____ lines around the WD, so it gets pushed around
accretion disk, H-rich, flash of fusion energy, temporary, ionized, white dwarf, magnetic field
Matter falling toward a neutron star forms an _____, just as in a ______ binary, Accreting matter adds _____ to a neutron star, increasing its ___. Episodes of ___ on the surface lead to ___ bursts
accretion disk, white dwarf, angular momentum, spin, fusion, X-ray
WD in binary systems often lead to the formation of an _____ disk. Friction between orbiting ____ in the disk transfers ____ momentum outward and causes the disk to ___ and ___. Thus leads to variable ____ emission. Note that there is a gas stream from the _____ star and the "____" on the ____ disk. This might push the WD over the ____ and it may ____
accretion, matter, angular, heat up, glow, X-ray, companion, hot spot, accretion, mass limit, explode
Newton viewed gravity as a mysterious "______." Einstein removed the mystery by showing that what we perceive as ____ arises from the ____ of ____.
action at a distance, gravity, curvature, spacetime
The Michelson-Morley experiment: There was a theory that all of space was filled with a weightless, transparent substance called ____ that was the medium through which _____ waved. As the Earth revolved around the Sun, this ____ blew by the Earth. Michelson and Morley tried to _______. It was postulated to be a medium that ____ the _____ along and had never been ____. If it was made of matter then it would _____ objects like the ____ and cause them to spiral into the Sun. The ____ was thus solid enough to let ____ vibrate in...but light enough to let the Earth travel in space without _____.
aether, light waves, aether, see this aether wind, vibrated, light wave, observed, slow down, Earth, aether, light, hindrance
Imagine you and Jackie are in the opposite ends of a spaceship that is floating in space. Both you and her have watches that flash brightly each second. And both see each other's watches flash at the same rate. Now suppose the spaceship engines fire and it begins to accelerate. Because you are in the front of the spaceship, your frame of reference is carrying you ____ Jackie and the flashes from her watch. Thus, the light flashes from her watch will take _____ to reach you than it would if the spaceship were not _____. So you'll see her watch flashes _____ apart. From Jackie's point of view at the back of the accelerating spaceship, her frame of reference is carrying her ____ and the flashes from your watch. Thus, the light flashes from your watch will take _____ time to reach her, so she sees them ____ than 1 second apart.
away from, a little longer, accelerating, more than 1 second, toward you, a little less, faster
Light moving upward (____ from an object with mass like earth or a star) ____ energy... like a ball thrown upward. Recall : E = ___ so if E decreases its frequency ____, hence a ____ (red = _____ frequency in visible band). Near earth, the shift is very ___ but detectable with precise instruments (1 part in ___ climbing away from Earth). It's much ___ in other contexts. But for massive objects...or very compact ones with a _____, the effect is ____.
away, loses, h x f, decreases, redshift, lower, small, 109, larger, high surface gravity, significant
Prediction: a light beam will be ____ by gravity. This idea is initially weird bc _____. BUT! Why do golf balls and bowling balls fall at the same rate? Because the trajectory is a property of ____ itself, not a property of the ____
bent, photons have no mass, spacetime, object
Einstein's relativity path says light takes the _____ in comparison to newtonian vision or no gravity path. As star is closer to gravity pull, light _____
biggest angle, bends more
One famous X-ray ___ with a likely black hole is in the constellation ___; a binary star with ___ solar masses and an ___ companion. From its binary orbit, the companion mass is at least __ solar masses and likely ~__ Msun. ___ are emitted due to the million degree gas ___ into the black hole
binary, Cygnus, 30, unseen, 7, 15, X-rays, falling
Note how the spiral arms appear ____ compared to the bulge or the gaps between the arms
bluer
Einstein thought that time and space were _____ in this _ dimensional grid that had its own weird ____, things moved across surfaces that are warped like _____. The warping of ____ causes the appearance of ____. Gravity travels at the speed of ___ in ____ waves through space fabric. This is all called _____
bound together, 4, geometry, trampolines, spacetime, gravity, light, curved, general relativity
Because _ is the same everywhere, then the longer distance you saw Jackie's light beam take as she travels away from you means that her clock ____. Because you can see her clock as well as you own, you see her clock running at a ___ rate than yours in order for it to end up reading less ____ for the light beam to complete it round trip ____ inside here spaceship. So - from your point of view - time runs ___ for someone moving at ____. This is called ____, when time ____ in a moving reference frame
c, runs slower than yours, slower, elapsed time, up and down, slower, high speeds, time dilation, expands
Sgr A * = ____ of our galaxy, ____ solar mass black hole. We know there is a black hole bc we can see _______
center, 4 million, matter falling into it
You classify supernovae into groups, but the ____ one is white dwarf being pushed over its ____, puts out amount of light as almost an _____ for _____
classic, mass limit, entire galaxy, a few weeks
Stars are caused by _____ which propagate around the ___ of a galaxy
compression waves, disk
Pulsar at center of ___ nebula pulses __ times a second, but it looks ____, pulses faster than your eye can process, and is __ Msun. It pulses throughout the __ spectrum. Size of a ___ with immense ____ fields
crab, 33, continuous, 1.5, EM, small city, magnetic
The Sun's mass ____ spacetime near its ____. If we could shrink the Sun without changing its mass, curvature of spacetime would become ____ near its ___, as would the strength of ____
curves, surface, greater, surface, gravity
As one considers larger and larger masses the density required to make a black hole _____, because the formula for this is density is proportional to _____
declines, 1/m^2
What density is required to make a black hole? As one considers larger and larger masses the density required to make a black hole ____. With a little over ____ solar masses of ordinary water, one could make a black hole without further _____!
declines, 10^8, compression
space and time look ____ from different perspectives in ____. Observers in relative motion ____ the same definitions of x, y, z, and t, taken individually. However, ___ is the same for everyone
different, spacetime, do not share, spacetime
Stars in the bulge and halo all orbit the Galactic center in ____ directions, at ___ inclinations to the disk, they have ____ velocities, they are not slowed by the ___ as they plunge through it. nearby example: ____ Star
different, various, higher, disk, Barnard's
stars in the ____ orbit in the same direction, while stars in the ___ and ____ orbit in different directions
disk, bulge, halo
Neutron stars in close _____ systems can ____ matter, be strong ____ sources (all that _____ binding energy released in so little space!)
double-star, accrete, X-ray, gravitational
Albert Michelson and Edward Morley set up an experiment to try and measure the ____ of the ___ on the Earth. They measured the speed of a ____ traveling ____ to the direction of the Earth's motion and compared that to a ____ traveling ____ to the Earth's motion. The aether idea predicted that light would have a ______ in the two directions. They would, in fact, be measuring the Earth's ___ against the ____.
drag , aether, light beam, parallel, light beam, perpendicular, slightly different speed, speed, aether
Status of Physics in 1900: Light as an _____, Frequency, wavelength, amplitude, formula: _____
electromagnetic wave, C = f * λ
Imagine squeezing a mass until its ____ is the speed of ___ --> a black hole
escape velocity, light
Nothing can escape from within the ____ of a ____, because nothing can go faster than ___. No escape means there is no more ____ with something that ____. It increases the hole ___, changes the ___ or ___, but otherwise loses its identity.
event horizon, black hole, light, contact, falls in, mass, spin, charge
Dark matter: The total mass of the milky way far ____ the mass with ____ and _____ put together. hidden, invisible or missing component, responsible for Milky way ___ rotation curve
exceeds, stars, interstellar medium, flat
Black holes can ___ & have a ____ point in their interiors.
exist, singularity
Some stars die by actually ___. They can either be ____ stars that simply _____ in their cores, leading to a departure of _____ and hence rapid ____ toward their centers, OR They involve ____ in some sort of ___ system where mass from the ____ star is transferred to the white dwarf, eventually raising its mass past __ solar masses at which point it collapses in a ______ runaway explosion THESE EXPLOSIONS ARE CALLED_____, releases huge amounts of ____
exploding, high mass, run out of fuel, hydrostatic equilibrium, fall of material, white dwarfs, binary, companion, 1/4, thermonuclear, SUPERNOVAE, energy
Gamma ray burst = ________
explosion of stars w/black hole in the center of the galaxy
Oribital velocities in the Disk: Stars in the galactic disk should orbit according to Kepler's laws, HOWEVER: The _____ rotation curve we actually observe for our galaxy implies that 1. Its mass is not concentrated in the ____ 2. Its mass extends ______. BUT we do not "___" this mass We do not detect ____ from most of this mass in the ___ so we refer to it as "____ matter"
flat, center, far out into the halo, see, light, halo, DARK
Geometry of the Universe: 1. The Universe may be either ___, ____, or _____ depending on how much ____ (and ___) it contains. 2. ___ and ____ universe are infinite in extent 3. ___ universe is finite in extent 4. No ___ and no ___ to the universe is necessary in any of these cases
flat, spherical, saddle-shaped, matter, energy, Flat, saddle-shaped, Spherical, center, edge
Light pulses travel more quickly from ___ to ___ of an accelerating spaceship than ______. Everyone on ship agrees that time runs faster in ___ than in ____
front, back, in other direction, front, back
Within a massive, evolved star (a) the onion-layered shells of elements undergo ____, forming an ___ core (b) that reaches ______-mass and starts to collapse. The inner part of the core is compressed into _____ (c), causing infalling material to ____ (d) and form an outward propagating _____ (red). The shock starts to ___ (e) but it is re-invigorated by a process that may include ____ interaction. Surrounded material blasts ___
fusion, iron, Chandrasekhar, neutrons, bounce, shock front, stall, neutrino, away
At the heart of every ___ lies a black hole, millions to billions of times the mass of ____
galaxy, our sun
Gravity is a _____ distortion of spacetime, explains why ______ (m in F = ma) same as ______ (m in F = GmM/r2 ).
geometrical, inertial mass, gravitational mass
How can one detect a black hole? Only through its ______ on other ____! An isolated black hole would be virtually _____ to detect. In a close binary system, a black hole can _______. As the gas spirals ____ it becomes extremely ___ and emits ____. Most famous example: ____. It is a ___ system (8000 ly away) of a _____ star and a compact ___, both ___ solar masses, too massive for a ____ star.
gravitational pull, objects, impossible, suck gas off the companion star, inward, hot, x-rays, Cygnus X-1, binary, blue supergiant, object, 20-30, neutron
Accelerating masses generate _____ waves that propagate at speed of ___.
gravitational, light
Misconceptions: 1. Black Holes "inexorably swallow everything!" but at distance, ___ of BH is ________. 2. Wormholes etc = entirely ____ 3. You can "detect" a BH due to "____ Radiation" from pair production near ____ radius.
gravity, just the same as an ordinary mass, hypothetical, Hawking, Schwarzschild
Really weird that ____ can impact light deflection bc photons have ____, so newtonian physics would suggest that bending of light is ___ of what einstein says it is (which is ___ arcsec)
gravity, no mass, half, 1.7
Einstein's theory of _____ says that masses can _____ the "___" of spacetime, much like ____ on a sheet
gravity, re-shape, fabric, weights,
Geometry on a curved surface: 1. The straightest lines on a sphere are _____ sharing the same ___ as the sphere 2. Great circles ____, unlike parallel lines in flat space 3. Straight lines are _____ between two points in flat space 4. _____ are the shortest paths between two points on a sphere
great circles, center, intersect, shortest paths, Great circles
Matter accreting onto a neutron star can eventually become hot enough for ___ fusion
helium
The ____ the mass, the ____ the white dwarf. In higher mass WDs, the electrons move ____ and ___. The speed limit is of course the speed of ___. That sets the maximum mass of a WD to be ___ solar masses
higher, smaller, faster, faster, light, 1.4
Black holes in brief: A spherical "____" surrounds the region from which ______. The radius of the horizon is _____ to the black hole's mass (surface area is ___). For a solar-mass black hole, the horizon radius is __ km (only a few times smaller than a ___ star). Neutron stars, like _____, ____ with increasing mass; maximum mass is ___ solar masses. So a collapsing stellar core more massive than this should form a ____!
horizon, nothing can escape, proportional, 4πR2, 3, neutron, white dwarfs, shrink, 2-3, black hole
atmosphere of a neutron star is made of ___
hot plasma
Rules of Saddle-Shaped Geometry: 1. Piece of ____ is shortest distance between two points 2. ____ diverge 3. Angles of a triangle sum to < ___° 4. Circumference of circle is > ___
hyperbola, Parallel lines, 180, 2πr
As you approach the speed of light, your effective mass _____, which implies that your kinetic energy ( formula = ____) ____. This fact combined with conservation of energy lead to the conclusion that objects have a '__' mass energy, as the relativistic expression for kinetic energy is ______, hence we say ___
increases, ½ mv^2, increases, rest, KE=mc^2 + ½ mv^2, E=mc^2
An object's number of dimensions is the number of ______ in which _____ is possible within the object. We can move through ___ dimensions in ___ (___). Our motion through __ is in __ direction (_). ____, the combination of space and time, has ___ dimensions (____)
independent directions, movement, three, space, x,y,z, time, one, t, Spacetime, four, x,y,z,t
Thought Experiment: #1 Ordinary Speeds: free-floating frames of reference: "________", that is one that is not accelerating, I see jackie in a space ship and I think she's _____, but she sees me and she thinks I'm _____
inertial reference frames, moving, moving
We measure the orbits of fast-moving stars near the Galactic center. these measurements must be made in the ____
infrared
Einstein discovered that space and time are ______.
interconnected
Most ____ in universe comes from ____ explosions, producing almost a solar mass of it
iron, white dwarf
crust of a neutron star is made up of a ____ of ____, enforced by pressure from _____
lattice, heavy nuclei, degenerate electrons
The fact that time is different in different reference frames (time dilation) means that ___ (and ___) are also strangely affected by motion. Dimensions (lengths) in the direction of motion are ___ while an object's mass ____.
lengths, masses, shrunk, increases
More ____ bursts of gamma rays happen than ____ bursts
long, short
High mass stars can ________ prior to the supernova explosion; the dividing line between stars which end up as ____, and those which will become ___ is not well defined, but is around __ solar masses.
lose large amounts of mass, neutron stars, black holes, 25
Hawking radiation: Black holes emit hawking radiation and ____, how you can make tiny black holes ____
lose mass, disappear
A spinning neutron star can emit radiation off its _____ poles giving it a "____" effect of blinking on and off from our viewpoint.
magnetic N-S, lighthouse
If ___ warps spacetime, then enough ____ packed into a small enough space should create an ____. In other words, it would warp space so much that ______, including ___, creating what would come to be known as a ____.
mass, mass, infinite warp, nothing could escape from it, light, black hole
Accreting (______) neutron stars can be "____" to huge rotation rates (record is ___ pulses per second!); this is called ____ pulsars or "___" pulsars.
mass-gaining, spun up, 642, millisecond, recycled
Thought experiment #3: You throw the ball at 90 km/hr, which means you see it ______ with Jackie, neither ____ her nor _____ her. Jackie sees the ball moving with the 90 km/hr speed you through it at her with, minus your 90 km/hr speed away from her, which means that she sees the ball ______ at the point where you released it
matching speed, catching, falling behind, perfectly stationary
Interstellar Medium is ____ (gas/dust) between the stars _____, _____, and mostly empty space in between . This is also where stars are _____ and where diffuse remnants of ____ are stored
matter, Nebulae, molecular clouds, born from, stars,
In a nutshell: ___ tells spacetime how to curve, _____ tells matter how to move
matter, spacetime
Travelers going in opposite directions in straight lines will eventually ___. Because this happens, the travelers know Earth's surface cannot be ___—it must be ____
meet, flat, curved
Our galaxy is one of _____. Our sun is in the ___, no accident that this is the case bc 1st gen stars had to be in the ____ and blow up and then _____ material would form new 2nd gen stars ______
millions, disk, bulge, metal rich, further out
there are ____ phases of interstellar medium, it ___
multiple, shifts
Why does the apple fall? Aristotle: it's seeking its _____ toward the _____ Newton: the earth ____, pulling the apple _____ Einstein: it's moving along the s______ through _____
natural place, center of the universe, exerts a force, downward, straightest possible path, curved space-time
Michelson and Morley found ____ in the speed of light in two ____ directions. So - ___ doesn't exist. Einstein knew about this result and this led him to consider the speed of light as a ____.
no difference, perpendicular, aether, constant
When you pour more energy in than you're getting out of core reaction, there's _________ so it ____ down
nothing holding the star up anymore, collapses
Can we ever reach the speed of light? Or even go faster?it turns out that ______ can ever ____ the speed of light and certainly never ___ it.
nothing that has mass, reach, exceed
pop II stars
old
Stars in the halo are quite ___. Fraction of ____ elements is much ___ than the Sun. They are Mostly ____, ___ stars. Stars in the halo must have formed ___ in the milky way galaxy's history. they formed at a time when few ____ elements existed. there is essentially no ___ in the halo. star formation ____ long ago in the halo when all the gas flattened into the disk
old, heavy, less, low mass, red, early, heavy, ISM, stopped
Regions of the Milky Way Galaxy: "Halo" contains ___ generation of stars, contains very little ___ or ____, location of the _____ clusters
older, gas, dust, globular
Although observes in different reference frames will measure your speed differently, they will all agree on two points: 1) Your headlight beams are moving _________ 2) The headlight beams are moving at ______
out ahead of you and your spacecraft, a speed exactly equal to c
To a moving observer, ___ clocks seem to take ___. Conversely... To outside observers, ____ clocks seem to run ____.
outside, longer, moving, slower
General relativity: the basic idea is a graph of ____ vs ____, which appears ____ because space-time itself is ____ (distorted by the _____)
position, time, curved, curved, Earth's mass
Additional ___ of elliptical orbits (____'s orbit) is predicted by _____
precession, Mercury, general relativity
If you are moving really fast, very close to the speed of light, and then turn on your headlights, your own light ______ at speed _. you cannot ___ your ____
races ahead of you, outrace, own lights
Is motion no longer relative? Einstein believed all motions should be considered ____...but that was for ______ reference frames! So he came up with his ___/___ equality idea. This also had the effect of explaining Newton's "_____" problem: that is what exactly is gravity? The equivalence principle states that the effects of gravity are exactly _____ to the effects of _____
relative, non-accelerating, gravity, acceleration, action at a distance, equivalent, acceleration
Michelson's great idea was to construct a race for pulses of light like the _____ analogy, with the ____ playing the part of the ___. The scheme of the experiment is as follows: A pulse of light is directed at an angle of ____ at a halfsilvered, half transparent mirror, so that half the pulse goes on through the ___, half is ____. These two ____ are the two swimmers. Now, if there is an aether wind blowing, someone looking through the telescope should see the ___ of the two ____ arrive at _____ times, since one would have gone more upstream and back, one more across stream in general.
river swimmer, aether wind, river, 45 degrees, glass, reflected, , half-pulses, halves, half-pulses, slightly different
Suppose you roll a ball down the aisle of an airplane. The ball rolls slowly in the reference frame of the airplane. Observers on the ground see the ball moving at the___ speed plus the speed of ____, so: Speeds _____. BUT now suppose you turn on a flashlight and measure the emitted light beam. What's its speed now? Einstein's second "absolute" was that light can only move at _____, regardless of the ______.
rolling, the airplane, add up like vectors, c = 300,000 km/sec, frame of reference
Stars in the disk all orbit the Galactic center: in the ___ direction, in the same ____ (like ____ do), they "____" up and down, this is due to ____ pull from the disk, which gives the disk its ____
same, plane, planets, bobble, gravitational, thickness
Thought Experiment: #4 Life at High Speeds, same as thought experiment #1, you see jackie moving at 0.9c and you think _____, whereas jackie sees you moving at 0.9c and she thinks _____.
she is moving, she is stationary
Orbits of masses follow ____ pathways (___) in spacetime.
shortest, geodesics
Time ____ when a clock is in a gravitational field.
slows down
Time ____ in a gravity field: time ___ again
slows down, dilation
A spacetime diagram plots an object's position in ___ at different moments in time. A _____ shows an object's path through spacetime in a spacetime diagram: a vertical means: ____. Diagonal: _______. Curved: _____. These for light go at __° angles in diagrams with ____ on one axis and ___ on the other. These look ____ in different reference frames, But everyone will agree on the "____" between two different events in spacetime
space, worldline, no motion, worldline, constant-velocity motion, accelerating motion, 45, light-seconds, seconds, different, distance
Time dilation makes it possible for people in a fast-moving vehicles (i.e. close to the ____) to travel while ____ little. This is because at great speeds time as measured on the spaceship's clocks ____ relative to that of an observer outside. That is to say, a spaceship's clock (and according to relativity, any human traveling with it) shows _____ than the clocks of observers on earth. At sufficiently high speeds the effect is ____. For example, one year of travel might correspond to ___ at home.
speed of light, aging, slows down, less elapsed time, dramatic, ten years
Young neutron stars ___ rapidly and often have strong _____ not aligned with __ axis; emit ___ waves beamed out ____.Energy source is rotational _____ of all that ___ (like a flywheel). If we happen to be aligned with the _____ (like searchlight) we see a rapidly ______ called a ___ - rotating, magnetized ns.
spin, magnetic fields, spin, radio, magnetic poles, kinetic energy, mass, rotating beam, pulsing radio source, pulsar
Pulsars must be neutron stars because they ___ too fast, anything else would be _____. Circumference of NS = __, (radius) ~ __ km, Spin Rate of Fast Pulsars ~ ____ cycles per second. Surface Rotation Velocity ~ ___ km/s, ~ __% speed of light, ~ ___ velocity from NS
spin, torn to pieces, 2π, 60, 1000, 60,000, 20, escape
Galaxy has these parts: 1. ____, 2. ___, 3. _____ 4. ___ 5. ____
spiral arms, halo, surrounding globular star clusters, disk, bulge
black holes would ____ and ____ humans
squeeze, stretch
inside a train, if you throw a ball up you see it come _____. from a reference frame outside the train you see it ___ with the same speed and also with the ____. the faster the train the ___ this goes
straight down, go up, motion of the train, further
Rules of geometry in flat space: 1. A _____ is shortest distance between two points. 2. ____ lines stay same distance apart 3. Angles of a triangle sum to ___, circumference of circle is ___
straight line, parallel, 180, 2πR
On a flat rubber sheet: Free-falling objects move in _____. Circles all have circumference ___. Mass of Sun ____ spacetime. Free-falling objects near Sun follow ____ paths. Circles near Sun have circumference ____. However, this analogy is limited for two reasons: 1. Masses do not ____ the spacetime like they rest on a rubber sheet 2. Rubber sheet shows only _____ of space
straight lines, 2πr, curves, curved, < 2πr, rest upon, two dimensions
Jackie sees her laser beam go _____ and accurately measures the time of travel from floor to the ceiling and back. On the other and, because you are moving 0.7c toward her, see her approaching you - much like the train moving past an observer on the side of the tracks. So to you, the laser beam moves in a _____ relative to the floor and ceiling. Thus you would say that the light beam traveled a ____ than just going _____. You and Jackie would agree on ______ for the light beam to go up. But here's where the problem comes in... You can't explain the light's ____ by saying that light is moving ___ than if the beam was just going _____. Both you and Jackie have to see the ____ for light. So the only solution - assuming the speed is _ in both cases and the distances are different - is that the ____ must be different! So -- The two clocks must be running at ______
straight up and down, slanted angle, longer path, up and down, the time it took, longer path, faster , straight up/down, same speed, c, elapsed times, different speeds
Galactic center has a _______
supermassive black hole
Crab nebula: remnant of a ____, exploded in 1054 and recorded by the ancient chinese. Supernova 1987A Exploded in ___ in the Large Magellenic Cloud observed with HST
supernova, 1987
The collapse of a super massive star may cause violent expulsion of the outer layers of the star resulting in a ____, or the release of ______ energy may be insufficient and the star may collapse into a _____ or _____ with little radiated energy.
supernova, gravitational potential, black hole, neutron star
Relative motion: if you ran a physics experiment on the ground or in an airplane, the results should be _____
the same
Thought Experiment #9: Length Contraction: Suppose you and Jackie are again in spaceships coming toward one another at speeds close to that of light...so the effect of _____ becomes important to consider. Jackie estimates the length of your spacecraft and she does this by the formula: Length = __ x __. You see her clock running ___, so she arrives at a ___ value than you in the direction of ___.
time dilation, speed, time, slow, shorter, motion
time dilation means
time runs slower for someone moving at high speeds, time is different in different reference frames
if speed of light was not absolute, we would see stars that are in binary in _______.
two different places at the same time
Most common way to blow up a white dwarf is ________, leading to a ______ explosion or a "_____"
two of them merging together, thermonuclear runaway, supernova
Escape Velocity is given by ______. So as Radius decreases the escape velocity _____.
v^2esc = 2GM/R, increases
distance =
velocity x time
A black hole's mass strongly ___ space and time in vicinity of ____; light follows ___ paths. Bending of __ by ___ (gravitational lensing) was predicted by Einstein and observed during a total ___ eclipse in 1919
warps, event horizon, curved, light, gravity, solar
you feel ____ when you are hovering in a gravitational field while Jackie is ____ because she is in free-fall through the gravitational field
weight, weightless
Neutron stars: _______________________
what's left behind in a supernova remnant, cores of exploded stars
Two types of supernovae: Type 1: ____, ___ star system, _____ contributes ____ disk to the growing white dwarf (after it did ______ a while ago), eventually when it hits the ______ it detonates. Type 2: ____ star: ____ does normal star fusion getting through hydrogen, helium, then carbon, then eventually ____ elements, then the _____, pushing out ____, then massive shedding of _____
white dwarf, binary, red giant, accretion, planetary nebula, mass limit, Massive, red giant, heavy, core rebounds, hydrogen, outer layers
The ___ point source in the Cas A supernova remnant could be a ____ with ___ Gauss, or a very slowly rotating ___ with ___ Gauss
x-ray, magnetar, 10^15, neutron star, 10^9
formula for distance between different events in spacetime
x^2 + y^2 + z^2 - (ct)^2
pop I stars
young
Open cluster: ___ and sparse; has ____ stars, found in the ___ and ____ Globular cluster: ___ and dense; has ___ stars, found in _____ or ___.
young, fewer, disk, spiral arms, old, many, Galactic halo, bulge
Regions of the Milky Way Galaxy: "Bulge," contains mixture of both ___ and ___ stars
young, old
Stars in the disk are relatively _____, in the disk there are a fraction of heavy elements same as or greater than the ____. Plenty of ___ and ___ mass stars, ___ and ___
young, sun, high, low, blue, red
Regions of the Milky Way Galaxy: "Disk" contains: ____ generation of stars, contains ___ and ___, location of the ____ clusters, Where ____ arms are located
younger, gas, dust, open, spiral