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What are Main Sequence Stars?
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Any star fusing H to He in its core
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What is the composition of a star?
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Our sun is 99.8% H & He; and 0.2% "metals"
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What are the conditions for fusion?
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Extremely high temperature and extremely high pressure
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What allows for extremely high temperature?
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protons move fast enough to overcome repulsion & collide
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What allows for extremely high pressure?
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Protons are VERY crowded together which increase the chance of many, many collisions which maintains a lot of energy
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What does the mass of a main sequence star effect? Name 6
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1. Stellar Radius
2. Core Temp., core pressure
3. Star's luminosity
4. Surface Temp.
5. Stellar lifetime
6. End state of a star
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What defines the size of a low mass star?
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less than 8 solar masses
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Wha is the evolution of a low mass star? 4 steps
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1. Stable fusion of H to He
2. Fuel runs out in its core
3. Outer Atm. expands and cools -> red giant
4. outer layers escape
-> hot,dead solar core
-> white dwarf
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What is the evolution of a high mass star? 5 Steps
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1. MS phase
2. Red Giant
3. Huge temperature in core
-> He fusion -> carbon
Carbon + He -> oxygen
Oxygen + He -> Mg
4. Multiple layers of fusion with many elements & core of iron
5. Core collapses, entire star collapses -> supernova! (star then explodes)
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What is the importance of a supernova?
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1. Creation of lots of metals
2. Dispersal of metals throughout the region
3. Metals -> planets, moons, asteroids, comets
4. Metals -> Life!
5. Shockwave from a supernova -> creates new stars & solar systems
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What is the metals vs. time?
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-Big Bang -> only H/He lots of energy
-Originally no planets/no life possible
-Every SN generation -> more metals
-metal content of universe increases over time
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What is the age constraint of very old stars?
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formed when galaxy was very metal poor -> no planets & few organics
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What is the age constraint of very young stars?
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not enough time to form planets/life/intelligence
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What is the mass constraints for too massive stars?
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-very short lifetime
-too luminous (HZ must be further)
-Lots of UV
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What is the mass constraints for too low mass stars?
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-Very low TOTAL energy emitted -> HZ must be VERY close
-Peak radiation is in IR -> weak energy
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What are the 3 types of solar systems?
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1. single star
2. binary stars
3. star cluster
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What are the characteristics of a single star solar system?
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one energy source & one source of gravity
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What are the characteristics of a binary star solar system?
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-2 energy sources (too much energy for temp. stability)
-2 sources of gravity (danger of unstable orbit, ability to even form the planet)
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What are the characteristics of a star cluster solar system?
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-many energy sources
-many gravity sources
-can planets even form?
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What are the 4 constraints of location in the galaxy?
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galactic center, Halo, edge of galactic disc, and glactic disk/spiral arms
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What are the characteristics of the galactic center?
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-stellar density is way too high
-too many enemy/gravity sources
-huge amounts of x Rays and gamma rays
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What are the characteristics of the halo?
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-globular clusters
-too many energy/gravity sources
-very old stars-> poor metal content
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What are the characteristics of the edge of galactic disc?
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very metal poor
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What are the characteristics of the galactic disk/spiral arms?
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- lots of single stars
- lots of young stars
->good metal content
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Sum up the 4 Key Stellar constraints
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Age, Mass, Types of solar systems, and location in galaxy
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What is the importance of atmosphere?
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-Protection from UV/X rays/ Gamma rays
-Greenhouse effect (holds in heat)
-> creates small day/night temp. differences
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What are the negative effects of a low mass terrestrial?
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-low gravity->weak to hold atm.
-cool interior- no molten core & no magnetosphere & no geology
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What are the negative effects of a high mass terrestrial?
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-Stronger gravity ->atm. becomes too thick
-Strong gravity -> higher chance of collision by comet/asteroid
-Interior is "too hot"
-> too much geology - too much source of CO2 -> atm. too thick
-Strong gravity -> planet can retain Hydrogen which leads to potential production of NH3 & CH4 ->these chemicals may be posionous to life
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What is the range of mass for a habitable terrestrial?
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.93 Earth Masses < MC 1.33 Earth Masses
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How does the HZ relate to the habitbaility of a terrestrial?
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the HZ is a region in the vicinity of a star where temp. are such that H2O, if it exists, will be in liquid form
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How does the HZ relate to a more luminous star?
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HZ is further away
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How does the HZ relate to a less luminous star?
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HZ is closer
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How does slow rotation speed effect a planets habitability?
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Weak magnetic field & large day/night temp. differences
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What are the consequences of a very close HZ?
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-if star/planet are very close & with large gravity/tides, planets rotation is slowed to "synchronous rotation"
-day side is always day -> too hot
night side always night -> too cold
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What is the effect of a large Jovian (jupiter)?
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-sweeps up lots planetary debris -> fewer impacts on Earth
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What is the effect of our moon?
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-some objects hit moon, not us
-moons gravity stabilizes Earth's tilt at 23.5 degrees
-> maintains seasons as pretty constant
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Sum up the 6 major Terrestrial Habitability charcteristics
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Atmosphere, mass, HZ, Rotation speed, large jovian,
moon
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What are the 3 categories for planet forming materials?
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1. Gases
2. Ices/Volatiles
3. Rocks/Metals
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What are the characteristics for gases?
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Like H/He they are very abundant and are never solid
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What are the characteristics for ices/volatiles?
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Like H20/CO2/NH3/CH4 they are somewhat abundant and are only solic at low temps
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What are the characteristics for Rocks/Metals?
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Like iron/Si/Al they are not abundant and are always solid unless the temp. is VERY high
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What are the characteristics of the Extreme inner solar system?
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1. few tenths of an AU from the Sun
2. Temp is > 2000K
3. H/He; Ices/Volatiles; & Rocks/Minerals are all gaseous
4. Planets cannot form here
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What are the characteristics of the inner solar system?
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1. .35-3 AU
2. temps range from hot->medium->warm
3. gases and ices are still gaseous but rocks/minerals can be solid and can form planets
4. Low abundance: small planets
5. High denstiy b/c they are made of heavy material
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What are the characteristics of the Outer solar system?
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1. 4 AU & beyond
2. very cold
3. Gases are still gaseuous but ices & rocks/minerals are solid
4. Jovian core is made from R/M & lots of ices -> huge cores
5. Huge plantary cores gather huge atm. of h/he -> enormous mass and low density b/c of h/he composition.
6. ices -> moons & comets
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What is the idea of late heavy bombardment?
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3.9 million ys. ago the ISS planets were bombarded by many comets from OSS and these impacts deposited H2O & organic chamicals
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What are the consequences of a large Jovian?
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1. sucks up planetary debris
2. circular orbit: no gravitional influences which could eject another planet into the sun or deep into space
3.Jupiter may have robber Mars of significatn mass during formation
4. Jupiter may have robbed losts os mass from "5th planet" -> asteroid belt!
5. Large jovian -> huge tidal forces ->warm interior of Io/Europa
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Sum up the 6 planetary functions
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1. Planet forming materials
2. EISS
3. ISS
4. Outer SS
5.Late Heavy Bombardment
6. Consequences of a large Jovian
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What are the detection methods of Extra solar planets?
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1. Direct Detection
2. Stellar wobble
3. Doppler Shift
4. Planetary occultation (eclipse)
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What is direct detection?
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to "see" a planet
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How does one "see a planet?"
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Planets shine by reflected sunlight (visible light) and in this light starts outshing planets by a factor of 250M -> 1 billion times
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