PHYS 005 Final: Session 28 FINAL REVIEW
5 Jul 2018
School
Department
Course
Professor
6/06 REVIEW
Light year- nothing travels faster than speed of light
●Sun- 8 ly away from earth
●Proxima centauri- 4.25 ly from sun
Parsec about 3 light years
Stars turn hydrogen to helium
3 options of supernova
●Black hole
●Magnetar
●Puslar
●One more
Low mass- red dwarf -> white dwarf
Med mass-yellow dwarf, orange dwarf, white star, blue star
Terrestrial & jovian
●Planets go fast enough around Sun to keep them from falling into sun
●Further you are, SLOWER the speed need to be
Fusion- several atoms into a new atom
●4 hydrogens -> 1 Helium
●Energy added up gives stars heat & light
Jupiter’s moon-Europa
●Thick sheet of ice covering subsurface ocean
○Hydrothermal vents on the bottom of ocean
Saturn’s moon-Enceladus
●Subsurface ocean as well
○Diff- spewing water into outer space w. cracks in water
Angular sizes
●Subdivided into subunits
○Divided into 60 arcmin
■1 arcmin- 60 arcseconds
●Their apparent size IN THE SKY
Particles of light-photons
●First experiment-Galileo & Romer
○Galileo tried to measure speed of light with light experiment
○Romer calculated using distance from Jupiter & Sun- 26% undercount
Jupiter, earth, sun
●40 light min. From jupiter -> sun Total, but +/- 8 light minutes depending on where earth is
relative to Sun
Fizeu/ Foucalt- over & underestimation
Light behaves as a WAVE
●Distance btw 2 cusps/valleys- 1 wavelength
○Blue light- shorter wavelengths
■Ultraviolet, gamma, xrays
○Red light-longer wavelengths
■Infrared, radio, microwave red lights- can’t detect w eyes
●Ea chemical element produces distinct color signal called SPECTRA
Doppler Shift
●Moving toward us- higher pitch
●Moving away- lower frequency (pitch)
Photography
●Exposure time
●Distance light travels until becoming focused- f
●Detector has electrons (electrical charge)- CCD (charged coupled detector)
○More electrical charge (increase sensitivity)-more photons you can capture
○More charge- MORE NOISE
●Telescopes have a lot of aperture
○Captures more light/sec
Milky Way
●Herschel
○Same number of stars in every direction
○Trumpler found extinction-attenuation of light of stars due to gas & dust
■However, gas & dust block stars- there should be a lot more stars
○STANDARD CANDLES- star that has the SAME AMT OF BRIGHTNESS @ any distance in
universe
■Found ABOVE & BELOW MW disk
■Brightness is only affected by distance
■Globular clusters-spherical group of stars that orbit galaxies
●CEPHEID STARS-by Harriet Leavitt
○Pulsation period signifies brightness (luminosity)
●Hubble found ^ those stars in Andromeda
■Shapley
●RR Lyrae variables
○Cepheid stars that are common in GLOBULAR CLUSTERS
○Because globular clusters are all diff distances-> earth is
OFFCENTERED
MEASURE SIZE OF MW using detecting stars that emit in infrared/red light @ far side of galaxy
Star classification
Spectral classification
OBAFGKM
●Blue-hot stars
●Red-warmer stars
Age classification
Pop I,II,III
●Pop III formed RIGHT AFTER DARK AGES
●Pop II chemically enriched
○POOR in metal content
■(everything other than H)
●Pop I
○Form closer to present (youngest stars)
○Metal RICH
75% of universe is Hydrogen
●Hydrogen emits in radiowaves
●Metallicity
●Hydrogen is in disk of Mw
○blue/redshifted in the disk- found by DOPPLER SHIFT
■Allows 3d map of hydrogen in MW that shows 4 SPIRAL ARMS
●Also includes carbon monoxide
■Where spirals are, how fast they are moving, partial arms
●PARTS OF MILKY WAY
○Halo KEEPS GALAXY bound together
■Stellar halo
■Dark matter halo
Vera Rubin
●Stars, gas, dust only account for 10% of needed mass to hold stars bounded to EDGE of galaxy
Dark matter halo
●Dark matter 24%
○MACHOS
○WIMPS
○Axions
○Neutrinos
Document Summary
Light year- nothing travels faster than speed of light. Med mass-yellow dwarf, orange dwarf, white star, blue star. Planets go fast enough around sun to keep them from falling into sun. Further you are, slower the speed need to be. Energy added up gives stars heat & light. Thick sheet of ice covering subsurface ocean. Hydrothermal vents on the bottom of ocean. Diff- spewing water into outer space w. cracks in water. Galileo tried to measure speed of light with light experiment. Romer calculated using distance from jupiter & sun- 26% undercount. From jupiter -> sun total, but +/- 8 light minutes depending on where earth is relative to sun. Infrared, radio, microwave red lights- can"t detect w eyes. Ea chemical element produces distinct color signal called spectra. Distance light travels until becoming focused- f. Detector has electrons (electrical charge)- ccd (charged coupled detector) More electrical charge (increase sensitivity)- more photons you can capture.
