Astronomy and the Universe
Charting the Heavens
Solar system = 4.6 billion years old
The universe holds matter, space, time, and energy
Astronomy is the study of the universe
Galileo was the first to use the telescope to observe the sky
Light year = the distance light travels in one year, approximately 6 trillion miles (300,000 km/sec)
Scientific theory = theory, prediction, observation, etc.
1 Astronomical Unit (AU) = The distance from the earth to the sun
Inside the sun is nuclear fusion. Neutrinos are a byproduct, and are part of dark matter.
The spiral arm is 1000 light years thick
Tachyon allows for the violation of the laws of physics for a short time
Kinetic energy = ˝ (mv2)
4 fundamental forces = electromagnetic, weak (radioactivity), strong (binding forces), gravity
The speed of light = c = approx 299,792,458 mtr/sec = 186,322 miles/sec = 671 million miles/hr
Eyes see ten flashes per second
Aristotle found earth was round in 322 BC through lunar eclipse
88 constellations visible from North America
Celestial Sphere = imaginary sphere that surrounds the earth that the stars are attached to.
Earth is at the center
Top is North Celestial Pole (where Polaris, the north star, is)
Bottom is South Celestial Pole
Middle (in line with the earth’s equator) is the celestial equator
Circle has 360 degrees. Each degree has 60 arc minutes (60’). Each arc minute has 60 arc seconds (60”)
Points on celestial sphere are measured like latitude and longitude
Declination measured in degrees/minutes/seconds north or south of the celestial equator
0 to + or – 90 degrees
Right ascension measured in hours/minutes/seconds east of the vernal equinox (0RA)
0 to 24 hours
Sun moves along the celestial sphere along a path called the ecliptic
Ecliptic is off by 23.5 degrees angle from the celestial equator. High on summer solstice, low on winter solstice.
This is due to earth being at a tilt.
More light is spread across a greater area at winter solstice (Dec 21), more concentrated at summer solstice (June 21).
North changes due to earth spinning like a top. Currently, north is Polaris. 14,000 AD it will be Vega.
This change is called Precission, and lasts 26,000 years for one full cycle.
Atmosphere is gas bound by gravity, very thin
To measure cosmic distances, use triangulation and parallactic angles.
Parallax = The apparent displacement of a foreground object relative to the background as the
observer’s location changes. The closer the object to the observer (the further away from the background object), the larger the parallax.
The Copernican Revolution
Geocentric universe = earth is at the center, surrounded by the celestial sphere
Because this is wrong, it caused the plants to appear to loop. The backward (westward) paths are known as retrograde motion
Ptolomaic model is geocentric
Heliocentric universe = sun is at the center
Inferior orbit = between the earth and the sun
Superior orbit = outside the earth
Planet comes from planets, which means wanderer
Johannes Kepler discovered that the planets orbit in an ellipse, not circle
Issac Newton invented calculous
Radar = radio detection and ranging
Newton’s laws
Law 1 – A body at rest tends to stay at rest. A body in motion tends to stay in motion (unless acted upon by another force)
Law 2 – Force = mass times acceleration. F = ma.
Law 3 – To every action there is an equal and opposite reaction
Gravity – any object with mass exerts an attractive gravitational force on all other objects with
Mass. Can be reworded in a formula:
Force = gravitational constant times mass of object 1 times mass of object 2 divided by radius (distance) squared
F = (Gm1m2)/r2
Gravitational constant = 6.67 X 1011 N meter2/kg2 (N·m2/kg2) (can also be expressed as m3/(kg*s2))
When solving for F, use (N·m2/kg2)
When solving for V use m3/(kg*s2)
1 N = 1 (kg·m/s2) = The amount of force required to move one kg at a rate of one meter per second per second
1 kg = 2.2 lbs
1 lbs = 4.45 N
The habitable zone is between Venus and Mars
Gravitational slingshot = closer to the sun, the faster you go. Spot closest is called perihelion, spot farthest is called aphelion
Keppler’s 3rd law: [P (in yrs)] 2= [a (in AU)] 3: Modified is [P (in yrs)] 2= [a (in AU)] 3/[Mtotal (Mo)]
Orbital velocity: Vorb = v((GM)/(r)) M=Mass being orbited, r=radius being orbited
Escape velocity: Vescape = v((2GM)/(r))
When comparing two velocities, put the bigger number on top (ex: earth 25k mi/hr, mars 11k mi/hr, write as 25/11 = 2.3; Earth’s escape velocity is 2.3 times faster than that of Mars)
Speed of sound in air = 770 mph
Speed of sound in water = 3500 mph
Andromeda Galaxy = 2.5 mil lt yrs away, visible w/naked eye
Velocity = wavelength times frequency (freq is in Hz, is = to number of cycles per second: 60Hz = 60/s)
Magnetic field lines dissipate aprox 500k yrs: reverse, polarity changes
Magnetic fields keep out some of the sun’s harmful rays
Wave packets refer to electro magnetic
Radio wavelengths travel at the speed of light
Frequency and wavelength are inverse – as one increases, the other decreases
2 windows in atmosphere to view: radio and optical
Radio is bigger and can be viewed at night
Diffraction: wave ability to bend around corners (you’re in one room and can still hear the tv)
Interference: wave ability to either cancel or reinforce each other
Add the amplitudes – in phase, reinforce; out of phase, cancel
Kelvins used for temperature
1k = degree C + 273
O k = absolute zero, no molecular motion
1F = 1.8C + 32
Planck or blackbody curve
E = Plank’s constant * frequency
higher frequency, higher energy
Planks constant = 6.63 X 1034 Joules * sec
Joule = N * m
Radiation
EM waves curve, interfere with the ionosphere. During the day, more interference due to charged particles. In winter there is less radiation.
Wien’s law = (0.29 cm*K)/(Temperature in Kelvins)
The wavelength is in centemeters, the temperature is in kelvins
The hotter the object, the more blue is the radiation
Eyes tend toward the yellow part of the spectrum
A sunspot cycle is 11 years
F = total energy emitted per square meter per second of an object
Stefan’s Law: F = s *T4
s is Stephan’s constant (5.67 x 108 W/(m2K4))
W = 1 J/second
T is in Kelvins
Energy flux per F
F is approximately 1/distance squared
Doppler effect is the shift of wavelength
Pitch gets higher as it approaches, and lowers as it is leaving.
Spectroscopy
Wave particle duality – is in terms of waves and wave packets
Photons – particles called Bozans of light
Bozans transmit energy – bind particles
All elements have a signature spectrum of absorption and emission lines.
Hydrogen atom is the simplest atom
At the right wavelength, the wave will not pass through the atom. It puts the electron into a higher
orbital for 108 seconds, then goes back to “ground state”
Cool gas absorbs wavelength at some wavelength of the emission spectrum.
Ground state = lowest energy state
Excited state = electron pushed to a higher level
Periodic table is on pg A4
Absorption lines are the dark lines on the spectrum
Ionization – enough energy to knock the electron off of the nucleous
E = hf
H = 6.63 X 1034 J * S
1 J = N * m
Electron volt = 1.6 x 1019 J
Red light photon is approximately ˝ EV
Xray and gama ray = high energy astronomy
Wave particle duality – particle is small scale, water is large scale (deals with light)
It takes 13.6 EV to ionize a hydrogen atom
En = 13.6 (1 – (1/n2)) EV
Telescopes
Reflector telescope – uses mirrors to point light to a focus
Refractor telescope – uses lenses to point light to a focus
Interferometer is an array of telescopes used to get a clearer picture
Seeing – the measurement of the turbulence in the atmosphere that causes the waves of light to be distorted
Hubble Space Telescope is better than ground telescopes because there is no seeing, so don’t have to mess with adaptive optics
Adaptive optics distort the lens of a telescope using computers thousands of time per second to adjust for seeing
