Astronomy Exam 3
What is the range in diameters of stars? Where does the Sun fit in to this range?
0.1 x suns diameter to 1000x suns diameter
What percent of the basic nuclear reaction in the Sun is converted to energy?
0.71%
What is one second in the Cosmic Calendar equal to in real time? What about one month, one day?
1 second = 437 years, 1 day = 38 million years, 1 month = 1.14 billion years
Describe the Orion Nebula.
1,350 light years away,
If a proplyd in the Orion Nebula was a nickel - how far away would that nickel be to appear as a proplyd appears in our telescopes?
10 miles away
How long does the radiation take to go from a) the Sun's core to its surface, b) from that surface to your house? How far are both distances traveled in the above question? Compare this to our galaxy.
100,000-200,000 years, 9 minutes to get to your house, 100,000-200,000 light years which is greater than the milky way's width
Describe the three additional steps in the proton-proton chain.
2. one of the p+ converts to a neutron through the weak nuclear force by emitting a positron (anti-matter electron) and a neutrino 3. Deuterium nucleus meets another p+ and fuses to form a He nucleus, releases gamma ray in process 4. 2 He nuclei slam together releasing 2 p+ and leaving He-4 (2 p+, 2 neutrons)
How often does this occur in the Sun? How many tonnes is this? How many H-bombs per second is this?
3.7 x 10^38 times per second, 600 million tonnes, 100 billion - a trillion H bombs per second
What is the basic formula for the fusion reaction in the core of the Sun?
4 H (protons) = He + gamma rays + 2 neutrinos
How old is the Sun and how much longer will it last?
4.5 billion years, it will last another 5 billion years
What is the range in temperature of the stars? Where does the Sun fit in?
5000 F to 50,000 F, sun is 10,000 F
What is temperature?
A measure of heat, therefore a measure of the speed of particles
What is the "Cosmic Calendar"? What is its scale?
A way to represent all the time that has elapsed since the big bang. January 1st at midnight= Big Bang, December 31st right before midnight = right now
When did the Big Bang occur in the Cosmic Calendar and real time?
Cosmic calendar: January 1 at midnight, real time: 13.8 billion years ago
When did the first stars form in the Cosmic Calendar and in real time?
Cosmic calendar: January 21 real time: 800 million years after Big Bang
What was "first light" of the Universe, and when did it occur in our Cosmic Calendar and in real time? Why can't we see anything earlier than this event?
Cosmic microwave background radiation, cosmic calendar: 14 minutes and 24 s after midnight on Jan 1 real time: 380,000 years after Big Bang
What is the name of our species and when did it first appear on the Cosmic Calendar and in real time? Where on Earth did we first evolve?
Homo sapiens, first evolved in Africa, first appeared: cosmic calendar: 16 minutes before midnight on New Year's Eve real time: about 400,000 years ago
What lives longer - the most or the least massive stars? Give the range in years.
Least massive stars live longer. a few million years (most massive stars) to a few trillion years (lease massive stars)
What are gravitational waves? How are they produced? What theory predicts them?
Predicted by Einstein's theory of general relativity. they are waves produced when something w mass is accelerated -> travels through space-time and causes space to oscillate
What kind of life existed on Earth for the vast majority of its history? How long did this period last in real time and in the Cosmic Calendar?
Single-cellular organisms, this period lasted from: cosmic calendar: October 1 to December 3, real time: 2.5 billion years
What star has the brightest apparent magnitude in our night sky? How much brighter is the Sun's apparent magnitude compared to this star?
Sirius is the brightest star in night sky, Sun is 10 billion x brighter
How far away are Sirius and Rigel?
Sirius: 9 light years away, Rigel: 900 light years away
which of the four fundamental forces a) keeps the nucleus together, b) causes the extreme temperatures and pressures in the Sun?
Strong nuclear force, gravity?
Compare the luminosity of Proxima Centauri, the Sun and Rigel.
Sun = 1, Proxima Centauri = 0.0001, Rigel = 100,000
Compare Rigel and Sirius and the Sun's luminosity.
Sun is 20x dimmer than Sirius, Rigel is 6,000x brighter than Sirius
What is the apparent magnitude of the Sun, Sirius, Polaris, the dimmest star visible to the unaided eye?
Sun: -26.8, Sirius: -1.7, polaris: 2.0, dimmest visible star: 6.5
What is the temperature, pressure, and density in the core of the Sun?
Temp: 27 million degrees F, pressure: 265 billion times sea level air, density = 13x denser than lead
What is hydrostatic equilibrium? How is it maintained in a normal star?
The balance between collapsing inwards and exploding outwards, as fuel is burned it produces radiation pressure which acts against gravity -> star expands and temperature decreases and so does thermonuclear fusion -> radiation pressure decreases and process starts over
What is the Coulomb Repulsive Force?
The repulsion between like charges
What is the Solar System, and when did it form on the Cosmic Calendar and in real time?
The sun and the planets Cosmic calendar: September 3, real time: 4.5 billion years ago
Why is gravity so different than the rest of the forces and why can it become the strongest force in the Universe
a lot weaker than the rest of the forces but the force travels forever so force on mass adds up quickly
What is mass?
a measure of the quantity of matter
What is HL Tauri? How old is it? What is this compared to our Sun's age?
a proplyd that is 100,000 years old in real time sun is 4.5 billion years old -> middle aged man compared to HL tauri which would be an infant
How does color relate to temperature?
as stars get hotter, the light gets bluer, cool stars are red
What is a molecule? How many different kinds have been discovered in GMC's? Name a few of these molecules. What is the largest so far discovered?
atoms that around bond together, 200 been found in GMCs, CO, H20, and CH3OH. The largest is fullerene (70 carbons)
Why is figuring out the diameter of stars so difficult?
because there are only a few stars close/ bright enough to appear on telescopes
What is hotter a blue-white star or a reddish star?
blue-white
What is an "organic molecule"? Give an example or two.
carbon containing molecules, ex: carbon dioxide, sodium cyanide, ethyl formate
Describe the "classical" (and wrong) proton versus the quantum proton.
classical: protons were solid balls of charge, quantum proton: protons exist as clouds of probability as to where the proton actually exists (bc it is always moving)
When did the dinosaurs rule the Earth in real time and on the Cosmic Calendar? When did they go extinct? What is the most likely reason for their extinction?
cosmic calendar: 4:00 pm Christmas Day to 7:00 pm on December 29 real time: 200 million years ago to 66 million years ago most likely went extinct from impact by comet or asteroid
When did the Milky Way form in the Cosmic Calendar and in real time?
cosmic calendar: march 10, real time: 10 billion years ago
What happened in the Universe after this "first light"?
cosmic dark age -> no galaxies, no stars, no planets, just expanding space filled with cooling gas and dark matter
How can astronomers make a comparison of the luminosity of the stars? What method is used to make this comparison (See Sept. 11 notes).
determine distance to the stars using stellar parallax, then they compare them all at the same distance -> true measurement of brightness
Name the four fundamental forces, describe each force
electromagnetic force: visible light, microwaves, electricity, magnets, -> can travel though space forever but gets weaker and weaker Weak nuclear force: a weak attractive force that acts over a small distance Strong nuclear force: strongest of the forces, holds nucleus of atoms together, acts over small distance, only attractive, Gravity: weakest force, attractive force, travels forever
How do astronomers figure out the mass of the stars?
figure out mass of stars by looking at multiple stars orbiting each other -> the more massive, the more gravity, and the faster other stars will orbit it
What kind of electromagnetic radiation is emitted from the core of the Sun? Describe the "scattering" of this radiation.
gamma radiation, gamma rays released from core and travel minimal distance before being reflected off a particle (e-)
How do the protons overcome the Coulomb Repulsive Force and fuse? How long would you have to wait to see this?
if protons are smacked together enough times it is inevitable that the two protons will appear on the inside of the strong and nuclear force, 9 billion years
Describe the interstellar medium. What is a GMC?
interstellar medium: large clouds of gas and dust GMC = giant molecular cloud
Why can't you quantum tunnel through a wall
laws of quantum physics only work on microscopic level, beyond that the same principles don't apply
What is the range of masses of the stars? Why are the most massive stars the most problematic to figure out? Where does the Sun fit in to this range?
least massive: 0.08, most massive as large as 200 but this is rare, some believe the limit is 40-60 or 100 -> debate, sun is equal to 1
What is the first fossil evidence of life on Earth? When did life first appear on Earth in real time and on the Cosmic Calendar?
microfossil evidence of archaea bacteria from Australia, Cosmic calendar: October 1 real time: 3.5 billion years ago
What are the most and least common stars?
most common: red dwarfs (70%), least common: blue giant
What is the difference between nuclear fission and nuclear fusion?Which one of these reactions occurs in the Sun and all stars?
nuclear fission = splitting of nuclei nuclear fusion = joining of nuclei nuclear fusion occurs in sun
What is a brown dwarf
objects without enough mass/ gravity to produce conditions for proton-proton fusion
What star has the brightest apparent magnitude in our sky?
our sun
Describe a proplyd
proto-planetary disc: a disk shaped cloud of dust and gas with a young "proto" star in center
How is probability used to describe the quantum proton?
proton most likely to be in center, least likely to be at outer edge
In the early days of nuclear physics what was the problem that appeared to prevent this reaction from happening in the Sun?
protons are positively charged so they repel each other so you wouldn't expect them to join together
What are the two basic forces in a star?
radiation pressure produced by fusion and gravity
What is the unit used to describe stellar luminosity?
solar luminosities
Describe the difference between the population of the stars we see with the naked eye and the true population of the stars? Why is the sky a lie?
stars seen with the naked eye are the most massive and brightest stars, red dwarfs are 70% of all stars and the closest one we need a telescope to see
Describe the birth of the Milky Way.
started as a bunch of irregular galaxies that merged and became gravitationally organized into spiral over the next few billion years
What is the difference between stellar luminosity and apparent stellar magnitude? Use light bulbs as a comparison.
stellar luminosity: absolute brightness of a star, apparent stellar magnitude: how bright it appears in our sky to our eyes
Describe is the scale of apparent magnitude? What is the mathematical definition?
the magnitude scale: the brighter the star, the lower the magnitude number, stars that are 100x different in brightness have an apparent magnitude difference of 5.
Describe the most common source of gravitational waves observed at LIGO and VIRGO.
the merging of two black holes that are orbiting each other
What is antimatter and what is the unexplained problem with it and the Big Bang?
the opposite of matter, when matter and antimatter react they explode and emit gamma rays, prob w Big Bang is that it didn't make equal amts of anti-matter and matter bc the universe didn't annihilate itself
What is the evidence in our own Solar System of how stars form?
the organization of the planets around the stars -> planets orbit in same direction on same plane, moons orbit same direction on same plane, sun rotates in same direction and plane as planets, planets rotate in same direction as they orbit and along same plane
What is the name of the visible "surface" of the Sun?
the photosphere
What is a "drunkard's walk"?
the ricocheting of gamma rays between electrons
How does the density of gases relate to the temperature of gases? Describe the rave analogy.
thermonuclear fusion decreases so the temperature of the gases goes down, pressure of gas also goes down and therefore the outward force is not as strong and gravity wins -> star collapses rave analogy: ppl in rave, as you make rave building smaller there are more collisions and energy increases, if the building is made larger there are less collisions and energy decreases
How do astronomers figure out the diameter of stars
they time the eclipses of eclipsing binaries and use that to calculate diameter -> extrapolate to other stars
Describe LIGO and VIRGO.
two flat mirrors placed inside a L-shaped vacuum, laser bounces back and forth b/w 2 and the laser light is used to measure the distance b/w the two mirrors. when a gravitational wave passes through earth the distance between the two mirrors shifts.
What are solar masses?
unit used to measure astronomical masses, equal to mass of sun
What kind of radiation eventually emerges from the Sun? Why is it different than the radiation that is emitted from the core of the sun?
visible light, energy is released as the gamma rays collide w electrons
Describe the three triggers of star formation. Why do we need a trigger? (i.e. why don't the clouds collapse into stars on their own?)
we need a trigger bc atoms and molecules are too far apart and move too fast for gravity to cause collapse supernovae: explosion of a supermassive star-> can cause birth of other stars, shockwave from explosion compresses gas and gravity takes over to form stars density waves in spiral galaxies: "traffic jams" of orbiting stars and gas -> gas compresses and decompresses -> gravity causes the gases clouds to collapse -> stars formed galaxy collisions: when galaxies collide, gas collides and gas cloud compresses -> millions of stars born all at once
What is the definition of "civilization"? When did it start on the Cosmic Calendar and in real time?
when Homo sapiens transitioned from hunter-gathering to farming towns/villages, cosmic calendar: 27 seconds before new years real time: 12,000 years ago
What about your life? When did it start on the Cosmic Calendar?
~0.05 seconds before midnight
