Mid Term Flashcards
Celestial Sphere
an imaginary sphere of which the observer is the center and on which all celestial objects are considered to lie
-Naked-eye observations treat all stars at the same distance
Models and Science
The celestial sphere is a model and It provides a means to enhance our understanding of nature
Constellation
Fixed arrangement of stars that can resemble, animals, objects and mythological figures
-as months proceed they move positions
Daily Motion
This can be explained by the rotation of the celestial sphere
Examples
– Sun, Moon, planets, and
stars rise in the east and
set in the west
– Due to the Earth’s
rotation
Annual Motion
A given star rises 3 minutes 56 seconds earlier each night and is caused by the Earth’s motion around the Sun, the result of the projection
-Yearly Motion”
– Due to the Earth’s
revolution
The Ecliptic
The path of the Sun through the stars on the celestial sphere
The Zodiac
The belt shaped region of the sky surrounding the ecliptic passes primarily through twelve constellations
What causes seasons
Not caused by the sun’s proximity, but caused by the tilt of the earth’s axial tilt at 23.5 degrees
The Ecliptic’s Tilt
The tilt of the earth’s rotation axis causes the ecliptic not be aligned with the celestial equator
Solstices and Equinoxes
Points on horizons where the sun rises and sets change throughout the year
Solstices (about June 21 and December 21) are when the sun rises at the most extreme north and south points
Equinoxes (equal day and night about March 21 and September 23) are when the sun rises directly east
The Sun’s Changing Position
Sun moves north and south of the celestial equator during the year, causing the sun to not rise due east or west on most day
-The shift of the Sun’s position is particularly obvious near the equinoxes, when the Sun’s position on the horizon shifts by almost its own diameter
each day
Path of Sun Changes with Latitude
-The path the Sun follows each day can be quite different at different latitudes
The Moon
Rises east and sets west
Phases of the Moon
Span of 30 days
Phases: New -> Waxing Crescent
First quarter -> Waxing Gibbous
Full -> Waning Gibbous
Third Quater -> Waning Crescent
Eclipses
Occurs when the sun, earth, and moon are directly in line
Solar Eclipse
Occurs when the moon passes between the sun and earth, the moon casts it shadow on the earth
Solar Eclipse from Space
Casts a umbra and a penumbra
-Umbra the dark center
-Penumbra the outer
Lunar Eclipse
Occurs when the earth passes between the sun and moon, giving the moon a red color
What causes a red moon
The earth’s atmosphere bends some sunlight into the shadow and the interactions with particles in the air remove the blue light
Rarity of Eclipses
Twice a year the moon’s orbit will pass through the sun called eclipse seasons
Eclipse Periods
Do not occur every 30 days since the moon’s orbit is tipped relative to the earth’s orbit
The Scientific Method
A process that describes how scientist go about observing, experimenting, explaining and predicting
1: Make observations
2: Analyze Results
3: Choose simplest theory or develop new theory
4: Propose higher-precision experiment or make predictions
5: Prepare test of new theory
6: back to step one
Ptolemy and Retrograde motion
Used to explained the retrograde motion of the planets using epicycles and dererents
Nicolaus Copernicus
Published De revolutionibus orbium coelestium, which his theory of planets had circular orbits around the sun was flawed and corrected by Johannes Kepler
Tycho Brahe
Created a theory called Tychonic system, where the Earth is stationary, with the sun and moon revolving around, while other planets revolve around the sun
Johannes Kepler
Tried to mathematically predict the planetary orbits and was wrong.
-He deduced his three laws of planetary motion based on Tycho’s observations
Galileo Galilei
Formulated his law of falling bodies, which all objects fall at the same rate
-created the first telescope and made discoveries that contradicted Aristotle and the Roman Catholic Church
Isaac Newton
Created a reflecting telescope and discovered white light is a mixture of all colors
-Calc dude
Average Distance of the Planets From the Sun
Measurement au: modern
Mercury: 0.39
Venus: 0.72
Earth: 1
Mars: 1.52
Jupiter: 5.2
Saturn: 9.54
Uranus: 19.19
Neptune: 30.06
Parallax
Nearby objects are viewed at different angles, from different places and used by astronomers, surveyors and sailors to determine distance
Ellipses
-Oval shaped
The sum of the distances to the foci is a constant
Can have different eccentricities between the range 0 to 1
Kepler’s First Law - The Law of Ellipses
The path of the planets about the sun is elliptical in shape, with the center of the sun being located at one focus.
Kepler’s Second Law - The Law of Equal Areas
An imaginary line drawn from the center of the sun to the center of the planet will sweep out equal areas in equal intervals of time
Kepler’s Third Law - The Law of Harmonies
the ratio of the squares of the periods to the cubes of their average distances from the sun is the same for every one of the planets
Units of Astronomical Distance
(au) astronomical unit is the average distance between earth and the sun
(ly) light-year distance that light travels in a year through a vacuum
(pc) parsec is the distance at which two objects separated by 1 au make an angle of 1 arcsec
Newton’s First Law - The law of Inertia
The law of Inertia
-An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force
Newton’s Second Law - The Force law
The Force law
-the acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object
Newtons Third Law - The Law of Action and Reaction
- every interaction, there is a pair of forces acting on the two interacting objects
Velocity
Speed and direction of motion of an object
Acceleration
the rate at which velocity changes with time
Kinetic Energy
is associated with the object’s motion
Potential Energy
The energy available to an object
Linear Momentum
Indicates how much energy is available to an object because of its motion in a straight line
Conservation of Linear momentum
A body maintains its linear momentum unless acted upon by a net external force
Angular Momentum
A measure of how much energy is stored in an object due to its rotation and revolution
Conservation of Angular Momentum
A body maintains its angular momentum unless acted upon by a new external torque
Newton’s Law of Universal Gravitation
-ALL objects attract each other with a force of gravitational attraction
-G is the universal constant of gravitation, 6.67 x 10^-11
Motion of Earth-Moon System
Paths follow and elliptical orbit around the sun
Conic Sections
A family of curves obtained by slicing a cone with a plane
-Circle - least
-Ellipse - second least
-Parabola - second most
-Hyperbola - most
Prisms and a Spectrum
-When a beam of white light passes through a glass prism, the light is separated into a rainbow-colored band called a spectrum
-1 nanometer = 10^-9m
Properties of Light
-Radiant energy that doesn’t require a medium to travel
-Travels at 299,782.485 km/s
Types of Waves
Pulse
-a disturbance of a short duration and a quick flick of a hand on a taut string generates it
Continuous
-Continuous series of pulses and continuously flipping one end of a taut string
S-wave
-Like light
P-wave
-Like sound wave
S-wave
-On surface of water
Properties of Waves
Amplitude
-Height of wave crest (intensity, brightness, volume)
Wavelength (L or λ)
-Distance between adjacent crests (colour)
Frequency (f)
- # of wavelengths leaving source each second (1 Hz = 1 wavelength/sec) (sound pitch)
Wave speed (v)
-travelling speed of disturbance
v=λf
Electromagnetic Radiation
-radiation including visible light, radio waves, gamma rays, and X-rays
-Travels as a pair of oscillating fields and it oriented at right angles to the magnetic field oscillation
The Nature of Light
-Visible light or any type of EM radiation is electrically charged
-Refraction or bending of light dependent on wavelength (shorter = more light refracted)
-The constant speed of light in a vacuum (a region that contains no matter) is 3.0 × 105 km/s
Electromagnetic Spectrum
400nm to 700nm, is visible to humans (10^-9m)
Refracting Telescope
use one or more lenses to collect and focus the light from objects in space, forming an image.
- Large mirror called primary mirror
Reflection
-The angle at which a beam of light strikes a mirror (angle of incidence) is always equal to the reflected beam
-Curved mirror create a focal point and the distance between the mirror and focal point is called focal length
Parallel Light Rays
-Rays that enter our telescopes are traveling in the same direction and considered parallel
Three Main Purposes of Telescopes
-Light collection
-Higher resolution
-Magnification
Light-Gathering Power
-Larger telescopes produce brighter images, but everything else is the same
A = pi (D/2)2
Resolution
-Measures clarity of images
-A telescope with a bigger primary mirror will see more detail compared to a smaller one
Magnification
-Depends on the focal length
-M = Fo/Fe
focal lengths of:
the primary mirror/lens (Fo)
the eyepiece (Fe):
Chromatic Aberration
Have different focal lengths for light of different colors passing through them
Achromatic Lens
-Using two different shaped lenses, light of different wavelengths can be brought into focus at the same focal length
The Hubble Space Telescope
-Has studied the heavens at infrared, visible light, and ultraviolet wavelengths
Radio Telescope
-detect and amplify radio waves from space
Spitzer Space Telescope
-First telescope to detect light from an exoplanet
-infrared
Nonvisible and Visible Radiation
-McMath-Pierce Solar Telescope (MMPST) at Kitt Peak was used to capture nonvisible and visible radiation
Cosmic Ray Shower
-Primary cosmic rays slam into particles in the atmosphere, breaking them and sending them to Earth, which are called secondary cosmic rays .
Neutrino Observations
-Are subatomic particles
-low mass
-no electric charge
-barely interact with other particles
-three flavors
-electrons
-muon
-tau
Gravitational Wave Observatories
-Large energetic events like black holes mergers in space can cause the fabric of space to distort
Blackbody
-Ideal absorbs all the em radiation that strikes it
-As an object heats up it gets brighter
-The brightest color of the emitted radiation changes with temperature
Wein’s Law
-determines at what wavelength the intensity of radiation emitted from a blackbody reaches its maximum point
λmax = 2.9x10^-3/T
Stefan-Boltzmann Law
-describes the intensity of the thermal radiation emitted
-An object emits energy per unit area
-F= (5.67×10^-8)T^4
Luminosity
-Total energy emitted by a spherical object each second
-L = F x 4pi r^2
Early Spectroscope
-A chemical substance is heated and vaporized, which results a series or bright spectral lines
Kirchhoff’s Laws
Law 1
-A solid, liquid or dense gas produces a continuous spectrum
Law 2
-A rarefield (opposite of dense) gas produces an emission line spectrum
Law 3
-The light from an object with continuous spectrum that passes through a cool gas produces an absorption line spectrum
Atoms
Smallest particle of a chemical element
-Nucleus contains protons and neutrons and is surrounded by electrons
-isotopes are different combination of protons and neutrons
-Electrons and protons have electric charge
Rutherford Scattering Experiment
some helium nuclei scatter backwards as entering a thin foil
The Doppler Shift
-The wave are compressed in front of the source but stretched out behind it
- wavelengths appear shorter and lengthened
Radial and Transverse Velocities of a Star
Velocity of star can be separated into radial and transverse
Radial
-speed of the star towards or away from earth in km/h
Transverse
-The speed in km/h perpendicular to the radial velocity
Exoplanets
-a planet that orbits a star outside the solar system
-Evidence exists for planets around other nearby stars
-New planets are not observed directly, but rather by their gravitational effects on their parent stars
Direct Imaging
-Taking pictures
Radial Velocity
-Watching for wobbles
Transit Method
-Searching for shadows
Gravitational Lensing
-Light in a Gravity Lens
Astrometry
-Minuscule Movements
Pulsar timing method
-Can be detected by the changes in the timing of its pulses
Distorted protoplanetary disks
- If one or more planets orbit in a protoplanetary disk (a rotating circumstellar disk of dense gas surrounding a young newly formed star), their gravitational pull will cause the disk to clump/war/to be off-center from the star
How stars lose mass
-Strong winds
-Shedding outer layers
-Shed mass
Celestial poles
North and South celestial poles are located directly above Earth’s north and south poles
Celestial equator
Lies directly above the Earth’s equator
The Phase Cycle
Origin of the month as a time period
Lunar rise and Set times
The moon rises around 50 minutes later each day
Sidereal Month
New moon is aligned with both the sun and a star
After 27.3 days the moon aligns with the star as a waning crescent
After 29.5 days the moon aligns with the sun
Star Transformation Matter
-Only the lightest elements, hydrogen, helium and a tiny amount of lithium were created in the Big Bang
