Astronomy Final Exam (ch. 10-14)

A, F stars

-1-2 Gyr lifetimes -microbial life may develop

Chapter 11 Concept Summary

-11.1: major diff among stars are result of diff masses -11.2: we can look for planet's gravitational effect on its star thru astrometric method or Doppler Method -11.3: extrasolar planets have wider range of properties than planets in our s.s. -current evidence suggest most stars have planets, and at least some are Earth-sized and in star's h.z. -11.4: surface habitability seems possible for planets or moons sim in size and compo. to Earth and located w/in h.z. -future telescopes should allow us to obtain crude images or spectra of planets w/in stellar h.z. (u.k. if Earth-like planets are common or rare) -11.5: advent of spectroscopy allowed astronomers to study stars by categorizing them according to their spectra -HR diagram plots stars according to spectral type or surface temp on horizontal axis and luminosity on vertical axis

Chapter 12 Summary

-12.1: The Drake equation says that the number of civilizations with which we could potentially communicate is N = NHP ×flife ×fciv ×fnow. -12.2: We don't know whether intelligence is common. The eventuality of technology is ambiguous. -12.3: Today, SETI is conducted primarily by searching for radio or optical signals transmitted by distant civilizations. An important part of SETI is thinking about the ramifications of a successful search. -12.4: Sometimes, people see things in the sky that can't be identified or explained, but no convincing evidence has been found pointing toward an alien origin. However, absence of evidence is not evidence of absence.

Classifying Stars

-1870s, Harvard College Observatory attempts fo classify stars via their spectra -Enormous undertaking in imaging and analyzing the spectra of thousand of stars -tedious work was shunned by men, women referred to as "computers" took up job in rare chance of furthering their educations -initial scheme for Pickering classifies stars from A to O based on strength of Hydrogen lines in stellar spectra, strong to faint -Annie Jump Cannon begins to analyze over 400,000 spectra -she concluded the sequence is OBAFGKM and can be subdivided into spectral classes: B8,B9,A0,A1, etc -Cecilia Payne-Gaposchkin made sense of OBAFGKM pattern -she realized it was a temp scale, hottest stars being O and coolest M

Search for Intelligence

-1924 Army listening for Martian radio signals -listen to 1420 MHz (freq) = 21cm (neutral H gas produces natural radio static) -1st SETI exp. project OZMA 1960, Frank Drake, 26 m disk, listened 4 signals from solar-type stars, didnt detect anything -birth of radios give rise to ability to communicate btwn worlds

Our Broadcast to the Space

-1974, 3 min Arecibo broadcast -M13:25,000 light yrs away -Allen Telescope array, SETI, California

Consequences of Climate Change (rise in greenhouse gas concentrations)

-3-5 C warmer temps in 100 years -changes in local weather patterns, rainfall, hurricanes, ocean currents

The Drake Equation

-R*= stellar birthrate (10/yr for MilkyWay) -fp = fraction of stars with planets (guess: 100% chance) -ne = number of Earth-like (habitable) planets per system (guess: 10% chance) -flife = fraction with life (guess: 100% chance) -fintell = fraction with intelligence (guess: 100% chance) -fciv = fraction with a civilization capable of broadcast (guess: 100% chance) -L = lifetime over which they are "on the air" -Optimistic estimate: N= 10*1*0.1*1*1*1* L or simply N = L -appx L civilizations per year, if we assume 60 yrs of broadcast, we can expect to find 60 civilizations -if we can survive for 10,000 years, then L=N=10,000 -there maybe 10,000 civs that we can receive signals from, avg dist btwn these civs would be abt 1000 light yrs -1 light yr is abt 63,000 AU, Voyager 1 + 2 travelled 100-120 AU in past 35 years

Astrometry

-center of mass -Jupiter orbits center of mass every 12 years but appears to orbit Sun bc center of mass so close to Sun -Sun also orbits center of mass every 12 years -Gaia will obtain precise astronomy for over 1 billion stars

Habitability of Extrasolar Planets

-considering surface hab of any world, to have life world would have to have mostly circular orbit to allow gentle seasonal variations -need to be large enough to retain internal heat for billions of years, driving motions of living world -smaller and larger terrestrial-type worlds called subterrains and super-Earths quite common, orbiting 10-20% of stars -large-scale moons are super-Earths and jovian-type worlds could also provide necessary requirements for surface hab. -higher gravity of super-Earths also allow for more exotic and greenhouse gas driven atmospheres (poss. extending theoretical habitable zones)

Are Planetary Systems like Earth Common?

-current known evidence point to fact s.s. are common, 70% of stars have atleast 1 planet -evidence show smaller worlds outnumbering large worlds (sim. to case for stars) -current data bias due to limitations in detection techniques -in time earth-sized worlds in stellar habitable zones will become more routine detections, increasing our knowledge of habitable worlds in milky way -seems to be many earth-like planets

To be habitable planet:

-distance -planet needs to be large enough to retain internal heat and have plate tectonics -atmosphere so liquid water is present on planet's surface (Mars lost most of it due to small size and loss of magnetic field)

Simplified Drake Equation

-drake equation says the number of civs w which we could potentially communicate is N= N(HP)xf(life)xf(civ)xf(now) -N(HP): number of hab. worlds in galaxy, of 400 billion stars only 10% fall in galactic h.z. leaving 40 bill stars -current estimate put # of stars w planets at roughly 70%; roughly 30 bill stars have planets -how many life-bearing, Earth-like worlds do these stars harbor? estimate put this at 1 in 5 or 6 bill worlds -f(life): fraction of hab planets actually containing life -while no evidence to give reasonable choice, evidence from Earth might point to value of close to 1 -life seems to have been inevitable and robust on Earth, forming quickly and surviving for billions of yrs -f(civ): fraction of life-bearing planets which resulted in technological civilizations at any point in time -little hard evidence, while life on Earth took 4 b.y. to create human level intelligence, numerous stars older than Sun -Intelligence may be inevitable consequence of evolution of life -f(now): fraction of possible civs that exist; ratio of length of time of avg civ to age of possible civs in milky way -latter component is abt 10 Gyr; 13Gyr less 3 Gyr for intelligence to first arise -endurance of an intelligent civ is another unknown; radio sigs are only broadcast for 100s of years, will be few civs at any time -civs that live for thousand of years or longer would vastly increase number of intelligent civs thruout galaxy

Many known exoplanets are massive planets like Jupiter, Why?

-easier to find larger planets (ex w Transit Method) -planets exist at v close and v far separations (easier to find closest ones since orbit their stars quickly)

Are Earth-like worlds common?

-evidence points to earth-life worlds being relative. common in Milky Way, leading to rare poss. of a rare Earth hypothesis: 1. unlikely life can form either too close or too from from center of galaxy, radiation from central stars could sterilize worlds -distant Suns potentially lack sufficient heavy elements 2. Jupiter needed to both instigate and regulate planetary impacts -for Earth to exist, Jupiter must be right size and in right place 3. Earth requires both Moon and plate tectonics for climate regulation -currently, commonality of these features unknown -"luck" of Earth unkown, but due mostly to lack of evidence

What would happen if Earth moved 1 mile closer to or away form sun?

-exit habitable zone and can be dangerous to live on

The Challenge of Interstellar Travel

-exs: Pioneer 10 + 11, Voyagers 1 + 22, New Horizons -Pioneer 10: 2 million years to reach nearest star -our other 4 missions not fare signfic better over same period of time -we have left messages in form of plaques and records as proof

Modern SETI

-fall into 3 categories: 1. local communications, earth-based TV + radio sigs 2. interplanetary or intersellar sigs, communicating over long distances 3. Signal beacons, broadcasting signals specifically broadly to attract attention -both for listening to sigs from ET or for ET to listen to our sigs

Direct Imaging

-gemini planet imager will directly image exoplanets

What would happen if Earth moved to Venus distance?

-global avg temp would rise from 59ºF to 113ºF -water vapor in atmosphere would grad. be broken apart by UV light and lost -Earth would turn into another venus -more intense sunlight would raise surface temp by abt 30C -higher temp increases evaporation and warmer air holds more water vapor -water vapor further strengthens greenhouse effect -results: ocean evaporate + carbonate rocks decompose, releasing CO2 further strengthening greenhouse effect -this make Earth hotter than Venus

Kepler Mission

-greatly increased number of known exoplanets

Artifacts and Interstellar Craft

-if another civ alr visited our s.s. they mightve left an artifact waiting for us to retrieve when our tech is capable of understanding -while Moon and other planets might be prime locations to leave an artifact, L4 and L5 Lagrange points of Earth-Moon system also good -regions where gravity of both worlds effectively "cancel out" and objects placed here are likely to remain in stable orbit -detect alien spacecraft; energy required to traverse galaxy is so massive it may leave telltale signs we havent looked for

Alternate Propulsion Sources

-ion drives -solar sails

Climate Change

-last decade has been hottest on record -satellite imagery show breakup of Antartica Larsen B ice shelf in 2002, melting and fragmenting of lice as large as Rhode island and 200 meters thick -Greenland has had lot of surface melting between 1979 and 2007 and keeps expanding -period of higher CO2 concentration coincide w times of higher global average temp -humans use of fossil fuels raised CO2 levels above all peaks occurring in past 400,000 years -observation show clear rise in avg temp including , human increase of greenhouse gases does explain warming

Pioneer 10

-launched in early 1970s -reached jupiter in 21 months -if headed to closest star near sun (alpha centauri at 4.4 light years), take 115,000 years -cosmic speed limit=speed of light

O , B Stars

-lifetime too short -also produce supernovae explosions

Stellar factor

-luminosity of a star determines how clsoe or far planet can be and still be w/in its habitable zone

Interstellar Arks

-might place crew into suspended hibernation for decades/centuries, awakening crew when reaches destination (beyond current sci means) -generation ship (mult gen of humans born and die on long voyage to new home) -generation ships pose problem that human voyages consisting of confided space and long hauls freq lead to stress, fracturing crew, deteriorating morale

The Question of Intelligence

-modeling rise of intelligence on life-bearing world poses challenges: -is intelligent life the result of chance events guiding evolution? -or is intelligent life the natural result of evolutionary pressure?

Could we survive Sun's death?

-move to other star systems -longest lived stars will run out of hydrogen fusion w/in few 100 billion years

What Happens if SETI Succeeds?

-no confirmed SETI-type signal detected -increases in listening capability and estimates from Drake Eq point to possible success -astronomers will alert other scientists immed to verify signal, while simult. informing media/world governments -any response crafted from ALL humans not just a group

Interstellar Energy Concerns

-nuclear fusion would prove limited in achieving new light speed -100% energy efficiency could b achieve by matter-antimatter annihilation (matter and anti matter collide converting mass to energy E=mc^2) -scientists barely produce any antimatter at all, making such engines devices of future -interstellar ramjet (moon sized ship uses free H in space for fuel, scooping in front and ejecting at high speed from back of thrust) -enormous size needed to scoop up sufficient fuel -problem: at near light speed, any slow-moving particle in space become high speed particle travelers and quite lethal

Spacecraft for Interstellar Travel

-nuclear rockets (powered by nuclear fission) -larger parent atom, often uranium or plutonium split into smaller daughter nuclei -mass of parent nuclei slightly higher than that of daughters w missing mass turned into energy -fission energy roughly 0.07% , higher chemical efficiency -nuclear fusion 100x more efficient; roughly 0.7%; fusion powers solar core and open doors seemingly limitless energy for humans -Project rover: nuclear engine capable of producing signif thrust

Encephalization quotients (EQ)

-offer simple but robust metric to measure intelligence -EQ of an animal is ratio of brain to body mass -Avg EQ of intelligent life is represented as value normalized to 1, species above this value consider more intelligent than most -Human EQ at 7, highest on Earth far above chimps (2.5) and dolphins (4-5)

Idunn Mons Volcano

-on Venus -lava flows w/in 250,000 years -Venus has few impact craters (erased by geo activity)

Why doesnt Earth lose water like Venus?

-on earth water vapor condensed into rain, forming oceans before UV light could break it apart -UV light doesn't penetrate far into atmosphere

Planetary Migration

-orbiting planets nudge particles in disk causing material to bunch up -these dense regions in turn tug on planet causing it to migrate forward

Physical Properties of Exoplanets

-planets exist around v low-mass to abt 2-3 solar mass stars (harder to find planets around more massive stars *PLANETS EVERYWHERE* -stars w lots of metals seem to be better at producing planets (more metals for building planets) -universe didnt have metals at beginning, metal-rich stars came later on thru enrichment from earliest gen. of stars -more massive stars also have more massive planets -many known exoplanets massive planets like Jupiter since easier to find them

Subsurface Life and life on Rogue Planets

-planets like mars and moons like Europa and Ganymede represent locations where sub-surface life might thrive -super-Earths could have deep underground oceans heated by their large cores which provide new places for life to emerge and evolve -another possibility of life on orphan planets (rogue planets) -these worlds eject from their forming solar systems and could have enough internal heat coupled w thick atmosphere laden w greenhouse gases to insulate and heat water, giving life a niche for form

The HR Diagram

-plots the color (temp) of a star vs its luminosity -when done, simple pattern emerges called main sequence (swatch of stars cutting across plot that contains 90% of all stars) -at top right of chart are giants, stars which has run out of hydrogen fuel and evolved off of main sequence -bottom left are hot, dim white dwarfs: final state of stars like your own, 20x hotter than Sun and roughly size of Earth

Limitations of Rockets

-prime limiting factor is mass ratio (ratio of mass of rocket before and after fuel burned) -reaching escape velocity require mass ratio of 39 -single-stage rockets impractical for reaching Earth's escape quality, so use Multi-Staged Rockets -as these stages are used they can be discarded, reducing overall rocket weight -energy released by rocket fuel is high in power and low in efficiency -high power allows for rapid acceleration to escape velocity, low efficiency mean little energy per unit of fuel -to reach faster speeds more efficient and energetic fuels needed

Nuclear Rockets

-project Orion aimed to use conventional nuclear tech to detonate small H bombs against rear pusher plate of spacecraft -large scale craft w suff bombs could reach high speed and be first starship designed by humans -tech exist to build Orion but no construction took place -Project Daedalus: uses fusion reactor to propel space craft (technical working beyond known science)

Ion Drives

-represent low-power, high-efficiency option to chemical rockets -while insuff of producing enough thrust to leave Earth, low-power thrust in space over time can produce high velocities, up to few percent of speed of light -dawn spacecraft is only mission to orbit 2 separate objects and powered by this

Von Neumann Machines

-represent mechanism to side-step relativity using cheap, current tech to colonize universe -such probes could travel to star, land on suitable world, extract resources and use techniques like 3D printing to produce copies of itself -new probes travel to next star systems, replicate, and carry on -such probes would be able to use limited tech to explore galaxy w/out worrying abt time dilation

"evidence" for ET from Ancient Aliens show on history channel

-sky people: ancient stone figure found at Mayan ruins that resemble modern day astronaut -Statue of Akhenaten: pharaoh of 18th dynasty, elongated skull ET heritage -Dendera Wall Carving: lotus flower suggest ancient Egyptians used electric lighting to illuminate their tombs -Great Pyramid of Giza: visitors from other planet helped humans build this -Teotihuacan: knowledge of astronomy -Puma Punku -ancient alien theorist believe Nazca lines of Peru clear evidence of aliens have been visiting for long time

Intelligence on Earth

-study of cetacean species show trend of increasing intelligence, correlated to rise of echo-location as part of body plans -bc large brains r metabolically expensive, evolution of large energy hungry brain must be response to evolutionary pressure -survivors from 1 gen to next r based on intelligent life choices -intelligence on Earth seems to be evolutionarily advantageous trait, via convergent evolution

Surface Habitability Factors

-studying the contrasting natures of Venus, Earth, and Mars we can build picture of factors necessary for habitability -stellar factor -planetary factor -atmospheric factor

Why is Venus so hot?

-surface temp. 470ºC -Idunn Mons volcano -Venus atmosphere has 200,000x more CO2 and no water -30% closer to sun -UV light from sun break apart water molecules

Hot Jupiters

-surprised everybody -large jovian-type worlds

The Search for Intelligent Life

-there are ~4500 stars w/in 60 light yrs of us -probability of success is difficult to estimate, but if we never search the chance of success is 0

Space Time (Sidestepping Relativity)

-time dilation provides a Catch-22: u can travel any distance u like at high enough velocity but time outside your ship races by -proposed by Einstein's gen theory of relativity, 4D fabric of universe -follows diff rules than mass as explained by special theory of relativity -bc spacetime stretched and deformed infinitely, such as black hole it allows for wormholes (shortcut thru curved spacetime) -such shortcut reduce any dist trip to 0 -warp drive deforms local spacetime into wave -as water wave is curvature of water, such gravitational wave is curvature of spacetime (steeper curvature produces more motion)

Relativity in Interstellar Travel

-time dilation: natural consequence of travel close to speed of light -closer speed of light, clocks seem to move more slowly for person moving at high velocity, twin paradox -phenomenon has unusual side effect of allowing humans to travel across any distance w in their lifetime -ship continually accelerates at 1g (Earth surface grav acc), further ship goes the closer it moves to speed of light -cross milky way could be done in 22 years and journey to Andromeda galaxy in 29 yrs -andromeda and back could be achieved in just under 60 yrs, 5 million years will passed on Earth

Modern Radio SETI

-to find signal need to scan sky using radio telescopes -done via targeted search, looking to nearby stars -alt, telescopes can survey the sky looking everywhere for signals

Project orion

-toss small nuclear fusion bombs out rear and let the explosion push craft forward -could take us to Alpha Centauri in 100 years

When Sun-like Stars die

-turn into Red Giant -then planetary nebulae -then to white dwarfs

UFOs and Aliens on Earth

-unidentified flying objects, happen all time but likely not visitors from other worlds -first modern UFO June 1947 by Kenneth Arnold, led to pop cult obsess of flying saucers -US military took interest in investigating UFO claims thru 50s and 60s, most not true, small minority of events couldnt be explain -reported UFO encounter yet t be substantiated

Detectable Properties of Exoplanets

-using combo of Doppler, astrometric, transit, or direct detection methods -the period, distance, eccentricity, and inclination of planet's orbit can be calculated -mass, radius, density, + atmospheric composition/temp can be calc.

CO2 Venus vs. Earth

-venus has 200,000 x more CO2 -all of Venus CO2 is in atmosphere -Earth surface water leads CO2 cycle, most in carbonate rocks

Transiting Planets

-venus transiting in front of Sun

Super Novae

-when massive stars die -they produce supernovae explosions w a neutron star or blackhole left behind

Detecting Life on Exoplanets

-while no current working mechanism to directly detect, indirect methods may give hints -exoplanetary spectra hint at atmospheric temp and composition (poss. to detect gasses like Oxygen, indicative of biological respiratory processes on Earth)

Methods to identify Extra-Solar Planets

1. Astronomy 2. Doppler Shift Method 3. Transiting Planets 4. Direct Imaging -861 known since march 2013 but many more now

The Nature of Extrasolar Planets

1. Many exoplanets orbit signif. closer to host stars than Mercury does the Sun -few worlds are known to exist beyond distance of Jupiter 2. Many worlds close to their stars are large jovian-type worlds called "hot Jupiters" 3. unlike our s.s., many worlds seem to have fairly eccentric orbits -diff from mostly circular orbits or our s.s.

Challenges of listening on ET signals

1. Radio stations broadcast over a particular band of radio spectrum, to listen to ET life need to know what station to tune 2. Once have freq, need to know right bandwidth or range of signals to listen to

Question 3: Jupiter orbits the center of mass of the Solar system in about 12 years. The Sun also orbits the center of mass every 12 years. If aliens are looking down on our solar system and measuring the position of the Sun on the sky, they can detect the presence of Jupiter. What is the name of this method? a. astrometry b. Doppler shift c. radial velocity d. transits e. direct imaging

A. astronomy and E. direct imaging

Correlation or causation? Studies find that many lung cancer patients are smokers. A. Correlation B. Causation

A. is answer

When objects travel close to the speed of light a. time goes slower, distances shrink b. time goes slower, distances get longer c. time goes faster, distances shrink d. time goes faster, distances get longer e. time stops

A. time goes slower, distances shrink

Evolution of Sun

will become: -relative size of red giant star -1000x luminous as the Sun -Earth's surface temp will be 700ºC

Boundaries of Sun's Habitable zone today

-Optimistic inner boundary 0.84 AU (runaway greenhouse) -Conservative inner boundary 0.95 AU (moist greenhouse, water vapor in upper atmosphere and lost) -conservative outer boundary 1.4 AU (atmosphere too cold, CO2 snow) -Optimistic outer boundary 1.7 AU (w greenhouse warming)

Which propulsion method is most energy efficient -A: Nuclear Fusion -B: Rocket with Chemical Fuel -C: matter anti-matter annihilation -D: Solar Sail

-C. matter anti-matter annihilation

Which of the following statements are true? I. Many of the known exoplanets are giants like Jupiter since it is easier to find bigger planets. II. Planets exist at very close and far separations. III. More massive stars have more massive planets IV. Stars with lots of metals are better at forming planets a. I and II b. I and III c. II and III d. I, II, and III e. I, II, III, and IV

-E is correct

Habitable Zone

-Earth has water and Mars had water -planet w abundant liquid water can exist only w/in range of distances from a star -evolves with time -being in this zone not enough for planet to be habitable -might find subsurface life on Mars, Europa, Titan but can't look for subsurface life on planets around other stars yet (can search for hab. zone exoplanets)

Sun's habitable zone through time:

-Earth in HZ for another 1 (or sev.) Gyr -in 1 Gyr, moist greenhouse effect may cause oceans to evaporate -in 3-4 Gyr: runaway greenhouse effect will take place -ideas: build a giant sun-shade, move earth to larger distances, etc.

White Dwarfs

-Earth-sized stars -typically w 60% of mass of Sun -don't produce nuclear energy anymore hence they just cool down with time

Types of Stars in Habitable Zone

-Luminous Stars (stars die quickly) -Sunlike Stars (10% of stars are Sun-like) -Less luminous stars (most stars are fainter) -distance from Star matters: runaway greenhouse effect -luminosity (brightness) of Star matters -small star's habitable zone extends from 0.1 to 0.2 AU -luminous star's habitable zone extends from 1 AU to 2 AU

Let's send the space shuttle to the nearest star, with a speed of 10% of the speed of light.

-Mass of the shuttle: ~100 tons -Velocity = 30,000 km/s -Energy required: 4.5 x 1019 Joules -10% of the World's current annual energy use.

Astro-Engineering

-Type 2 civs might harness power of their local star by building giant Dyson Sphere surrounding their stars + collecting all energy -astronomers might be able to detect object visible in infrared but giving off no vis light -type 3 civ might be galaxy bright in infrared and dim in all other freq

How does Venus lose H2O?

-UV light from sun break apart water molecules -H atoms escape -O react w surface and is lost to stripping by solar winds in upper atmosphere -Venus rotates slowly hence no magnetic field to protect against solar winds

Colonization of Galaxy

-Von Neumann machines -Coral Model -reaching neighbor star in 50 yrs traveling at 10% speed of light, spend 150 yrs to regroup, then send new colonist to neighboring stars -this way colony expands at 2.5% of speed of light -galaxy is abt 100,000 light yrs wide and entire can be colonized in 4 million years

Planetary factor

-a world must be large enough to retain internal heat and have plate tectonics for climate regulation -minimum size unknown (but larger than Mars)

Atmospheric Factor

-a world must have an atmosphere to retain liquid surface water -this might require global magnetic field to mitigate stellar wind stripping

G,K,M stars

-abt 1 solar mass to 0.2 solar mass -provide best chance for habitable planets and life as we know it -97% of stars in Galaxy are these -K star 0.7 solar mass -M star 0.04-0.1 AU, 0.2 solar mass

Doppler Shift Method

-allows us to detect slight motion of a star caused by an orbiting planet -train stationary we whistle sound same no matter where we stand near it -if train moving to right the sound you hear depends if goes toward or away from you (behind train low frequency and pitch but in front higher freq. and pitch) -light source moving to right we have same effect (if moving away light appears redder [longer wavelength] but toward bluer [shorter wavelength]) -radial velocity measurements of stars with planets

Convergent Evolution

-argues for widespread intelligence -tendency of organisms w vastly diff backgrounds to evolve similar advantageous body plans -ex: sharks and dolphins -eyesight being widespread is another ex, came from no accident

The Fermi Paradox

-asks why we have not met older civs -evidence that alien life should emerge elsewhere, develop radio and spaceflight to colonize galaxy -such civ could colonize gal in short time and we have no evidence of their existence, presents paradox -our own galaxy is reasonable to consider another civ w up to 5 Gyr head start on humans -colonizing Milky Way at even slow, sublight speeds would take signif less time (10-100 mill yrs) -modest values of Drake eq, 100,000 civs may have arisen before ours, making human civ young

Kardashev Scale

-attempts to classify diff ranking of civs based upon technological capacity to harness and utilize energy sources -Planetary(Type 1): civs are capable of using resources of their home world -Stellar (Type 2): civs are capable of using rsrces of home star(s) -Galactic (Type 3): civs capable of using rescrce of their home galaxy -Humans ranked around 0.72 , crossing into Type 1 by year 2100

Why do stars have different colors?

-bc they have different temps -more massive star burn hotter (look blue) but die quickly -take million of years for rocky inner planets to form by accretion -life around A + F type stars (prob microbial)

Chemical Rockets

-burn chemical fuel, oxygen and kerosene -combustion product, water vapor expelled at bottom at 3 km/s -Saturn V consisted 3 stages -rocket w 100 stages would be 33x faster or 0.1% of speed of light

Interstellar Rocket Travel

-came with Newton's Principia -late 19th century rocket eq developed -Rockets achieve forward thrust by expelling mass at high velocity in opposing direction (Newton's 3rd Law) -developed rapidly during WW2, launch Sputnik 1 in 1957 -60 yrs l8er rocket tech remain mostly unchanged, igniting mix of chem propellants and expelling at high velocity

Solar Sails

-catching solar wind for thrust represent low power but abundant energy source, slowly accelerating high speed -sails could be artificially powered via terrestrial laster, replacing Sun

Which of the following is NOT AS ESSENTIAL for habitability of a planet? a. its distance from the star b. its size c. having a large moon like the Earth's moon d. an atmosphere e. the atmospheric pressure

C. having a large moon like Earth's

Terraforming Mars is consider which type? A: Type I B: Type II C: Type III

B. Type II

What type of stars live long enough to have microbial life but probably no complex organisms? a. O-B type b. O-A type c. A-F type d. F-K type e. K-M type

C. A-F type

If there are 10,000 civilizations in our Galaxy, what is the average distance (in light-years) between them? a. 1 b. 10 c. 100 d. 1,000 e. 10,000

D. 1,000

Assuming that our Galaxy contains 100 times more smaller stars than larger stars, should we look for habitable planets around small stars or large stars? a) Small stars b) Large stars c) Neither d) Both

D. both

If the humanity can survive for at least 10,000 years with the current technology, this implies that there may be at least N civilizations that we can get in touch with. What is N? a. there is no way to estimate N b. 0 c. 1 d. 1000 e. 10,000

E. 10,000

How likely is it that you will find a habitable planet around the small star compared to the luminous star? a) The same likelihood b) 10 times more likely c) 10 times less likely d) 100 times more likely e) 100 times less likely

E. 100 times less likely

What is the best evidence that extraterrestrials have visited us? a. UFOs b. historical paintings and carvings of important leaders with elongated skulls c. Egyptian and Mayan pyramids d. crop circles e. there is no real evidence

E. no real evidence

The Drake Equation tells us a. the number of planets that are habitable b. the number of planets that host life c. the number of planets that host intelligent life d. the number of planets that host intelligent life and a civilization e. the number of planets that host civilizations from which we could get a signal

E. number of planets that host civilizations from which we could get a signal