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N
# of civilizations in the Milky Way where communication is possible
R_* term meaning
average rate at which stars are formed in the Milky Way
f_p
fraction of stars with planets
n_e
average number of planets per planet-hosting star that could support life
f_l
what fractionof planets that could support life do go on to develop life
f_i
what fraction of planets that develop life go on to develop intelligent life
f_c
what fraction of planets with intelligent life develop techno-communications
L in the context of the Drake
amount of time in which an intelligent civilization remains communicable
Scope of scientific endeavors of a professional astronomer
Taxonomy and physical characterization, both observationally and theoretically, of all extraterrestrial phenomena and objects
What does “taxonomy of extraterrestrial phenomena” mean
how do we classify the objects in the night and sometimes day sky
Planets
Large, gravitationally bound, sphericla bodies, that cannot support thermonuclear fusion
Types of planets
terrestrial and giant
Terrestrial planets
planets with a solid surface that are comprised mostly of metals and heavy elements
Giant Planets
Planets with a large mas, relative to Earth, have no solid surface, and are comprised of low BP materials
Types of Giant planets
Gas Giants and Ice Giants
Gas Giants
Planets comprised mostly of hydrogen and helium gas
Ice Giants
PLanets comprised mostly of low BP compounds and a Hydrogen and Helium atmosphere
“Normal” Stars
Stars that are normally fusion hydrogen and helium into heavy elements
Giant Stars
Stars undergoing a period of instability as they use up their fuel for nuclear fusion
Stellar Remanants
Objects like white dwards and neutron stars that represent the end-stage of stellar evolution (end product of nova and supernova)
Extended Objects
Celestial objects which appear large and extendedon the sky but originate from a common origin
Nebula
Large luminious regions of gas and dust that are often being illuminated by the birth of young stars
Star Clusters
Large collections of stars that are gravitationally bound that formed at generally the same time
Stellar Explosions
Large expanding regions causeed by the late-stage evolution of a dying star
Galaxies
Gravitationally bound collections of stars, gas, dust, black holes, and dark matter
What governs the dynamics of planetary motion
Gravitational interactions between the planets and the sun are the source
What properties of stars contribute to how bright they appear in the night sky?
For identiical stars, distant stars will be fainter than closer ones, but how bright they appear depends on their temp and radius
What governs how sprial galaxies spin?
Gravity is the governing force but it alone does not account for the motion. Outskirts of galaxies must contain large amounts of non-luminous matter aka dark matter
Why is it that as galaxies get farther away from us, they are also moving faster away from us? Who first observed it?
Hubble first observed it and it can be explained by an expanded universe using Einstein’s Equations
Why should general astronomy research be pursued and why should it be funded by national gov’ts
The pursuit of fundamental knowledge is always useful and curiosity about the workings of the universe is, he feels, an integral part of the human condition
Correlation between Einstein and GPS Satellites
Without his general relativity, GPS satellites would not be terribly useful for day to day navigation
Why were ancient civs interested in understanding astrnomy
Bc there was a religious/spiritual connection between lived experiences on Earth and the movements of the celestial bodies; also, the sky moves with regularity and could be used as a timekeeper or calendar
Who developed sexagesimal numbering system + what is it?
base 60 and Babylonians
Difference in speed (in a vacuum) of microwaves and gamma rays
No difference. All electromagnetic radiation propagates through empty space at a fixed speed
Light can be treated as
discrete packets of energy (quanta) named the photon
Wave-Particle Duality
Light is both a particle and a wave
Can a single source of light emit at multiple frequencies? Give a reason you know this?
Yes, the sun emits light at all wavelengths
Why does the sun emit light at all wavelengths?
It is an example of a non-ideal blackbody radiator
Blackbody radiation
Electromagnetic radiation that occurs at every frequency and the peak emission is set by the tempof the source
Wien’s Law
relates peak wavelength of blackbody radiation with temp of radiation source
What is different across the types of light in the electromagnetic spectrum
The wavelength
Why does the Milky Way look different at different wavelengths?
Diff components of the Milky @Wway shine brighter at different wavelengths
Lyman-Alpha Emission
When hydrogen atom goes from excited to ground state and releases a photon
Star
massive sphere of plasma that produces light and heat through thermonuclear fusion in its core which releases energy that balances the inward pull of gravity
A stars color can tell us about
temperature
A stars absolute magnitude can tell us about
luminosity
Stars fit into three categories
main sequence, giant stars, and compact objects
Main Sequence
Longest phase where star is normal fusing hydrogen into helium (90% of a stars life)
What percent of stars in the sky are observed to be in the main sequence?
90
Are all stars in the main sequence stars with the same properties
no they may have differing properties
Giant Stars are responsible for the
production of a lot fo the heavier elements responsible for life
What percent of observed stellar populations are giant stars
Less than 1%
TF: Giant Stars can only belong to a few spectral classificatinos
F
Giant Stars are characterized by
larger luminosity due to larger radius and cycles of instability and changes in size and luminosity
Compact Objects are called
Final stage of stellar evolution and often called stellar remnants
Compact objects are characterized as
very high density objects including, in word of increasing density, white dwarfs, neutron stars, and black holes
COmpact Obects make up
~10% of all stars
White dwarfs
stars with masses less than 10* Solar mass that become giant stars, go nova have the central regions collapse into a white dwarfs
Do white dwarfs undergo nuclear fusion?
No
What supports white dwarfs?
electron degeneracy pressure
Neutron Stars
Stars with masses between 10x and 25x solar mass that become giant stars, go suprnova and have the central regions collapse into a neutron star
What supports neutron stars
neutron degeneracy pressure
Do neutron stars undergo nuclear fusion?
no
What is special about neutron stars?
When imbedded in a magnetic field, they can product readily seen radio pulsars
Black Holes
When stars with masses greater than 25x solar mass become giant stars, go nova and the central regions collapse into a black hole
All mass of a black hole is concentrated in
a single singularity
Black holes warp space and time so significantly that
there are some distance from the center of the black hole where nothing can escape
Stefan Boltzman Law
relates size and temp of a blackbody emitter to total received luminosity
Molecular clouds
often referred to as stellar nursuries and properties of the clouds are correlated with the types of stars they form
What can cause the formation of stars in molecular clouds
once the clouds become dense enoughm the pressure of the gas can nno longer support the cloud and it collapses in on itself. This can happen naturally or by any manner of collisions
Can multiple stars form at the same time in a molecular cloud
Yes, if the cloud is large enough
What can regulate the collapse of the molecular clouds?
energetic processes from supermassive black holes to magnetic fields
Jeans radius
maximum radius a molecular cloud can have before it collapses dfue to gravity
Explain what happens after the gas in a molecular cloud collapses
the physical conditions become appropriate, mitigating material disperses, fusion can begin and a star is born
The dispersion of mitigating material leads to the formation of
a protoplanetary disk forms which has the protostar at the center
What are the gaps in the disks an indication of
active formation of planets
Young stars emit ____ which can be used to
UV light; estimate recent star formation
How can infrared light be used to extrapolate back to initial star formation?
Intense hot radiation is emitted by young OB stars. this light is absorbed and reemitted by intervening dust, which can be in turn measured again to extrapolate back to star formation
How can radiowaves be used to extrapolate back to initial star formation?
The large mass OB stars recently formed will eventually go supernova and release massive amounts of energetic electrons that inteact with the magnetic firelds of the galaxy and produce radiowaves. Measuring this radio emission can allow you to extrapolate back to initial star formation
Qualifications for a planet to be considered one in the solar system
Must be in orbit around the sun, must be massive enough to be rounded by its own gravity, must have cleared the neighborhood around its orbit
Which planets are the giants in our solar system
Jupiter, Saturn, Uranus, and Neptune
Describe Giant Planets
Radial profile is a seamless transition from gas to liquid to sometimes a solid core; often intense storms and bands of diff atmospheric composition; intense magnetic fields that can create brilliant aurorae
Which are the gas giants?
Jupiter and Saturn
Describe Gas Giants
Abt 90% of mass is H and He even though these exist in diff phases throughout and abt 10% can exist as heavier elements
Which are Ice Giants
Uranus and Neptune
Describe Ice Giants
abt 80% of mass from heavier elements and other 20 is atmospheric envelope of H and He
Why are they called ice giants
an old naming convention abt compounds that exist on them; not actually spheres of ice
Describe Terrestrial planets (surface and composition)
generally smaller than gas giants and contain mostly heavier eleements and metals with rocky hard surfaces
Inside to outside, what is the structure of a terrestrial planet
hot metallic core of mostly iron surrounded by silicate based mantle and crust with atmosphere of heavy gases
Surface attributes of terrestrial planets
volcanoes, canyons, mountains and valleys (stuff from earth). Surface of planets evolve through tectonism which only appears to exist on earth in this solar system
Atmospheric attributes of terrestrial planets
Lost original atmosphere of hydrogen and helium bc they were too. small to hang onto them. They then form atmosphres of heavier elements that evolve as the planet ages
Hot Jupiters
Gas giants found near host stars. Easiest to detect
Super Earths
Terrestrial type planets that have up to 10x the mass of Earth (almost up to size of ice giant) and can exist in many orbital parameters and can have wildly interesting climates
Newton’s FIrst Law
Body at rest will stay at rest unless acted upon by a force
Newton’s second law
net force is equal to body’s acceleeration multiplied by its mass or the rate at which the body’s momentum changes with time
Newton’s third law
if two bodies exert forces on each other, these forces have the same magnitude but opposite directions
Equation given by Newton’s Second Law
F=ma
Gravity is the ______ of space-time
curvature
Kepler’s THree Laws
Planet Orbit is an ellipse with the sun at one of two Foci, Line segment joining a planet and the sun sweeps out equal areas during equal intervals of time, Square of a planet’s orbital priod is proportional to the cube of the lenth of the semi-major axis of its orbit
Ellipse
Plane curve surrounding two focal points such that for all points on the curve, the sum of the two distances to the focal points is constant.
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Flashcard (59)