stars and galaxies exam 1

sumerias

originated 7-day week

babylonians

continued the sumerians calendar system and developed algebra

egyptians

used 10-day week and developed geometry

thales

introduced concept of “objective reality”

anaximander

the first to imagine an infinite universe

democritus & leucippus

developed the atomic theory and concept of vacuum

pythagoreans

-separated science from philosophy

-proposed that the earth rotates on its axis and might not be the center of the universe

plato

profound thinker who founded the first “university” and focused on empirical philosophy

aristotle

founded current scientific disciplines, made significant contributions to biology, argued for spherical earth, and argued against a heliocentric theory due to the lack of observable stellar parallax

eudoxus

contemporary of plato and aristotle who made early developments in “mechanics”

aristarchus

first major proponent of the heliocentric theory

hipparchus

considered greatest observational astronomer of antiquity. developed the stellar magnitude scale, created a star catalog, measured distances to the sun and moon, discovered 26,000 year precession of earths axis

ptolemy

preserved much of the knowledge from earlier greek astronomers and established principles of celestial navigations and astrology

copernicus

re-introduced the heliocentric theory and correctly described the solar systems side real periods

tycho brahe

compiled vast amounts of precise observational data

johannes kepler

used tychos data to formulate his 3 laws.

1. planetary orbits are ellipses with the sun at one focus

2. a plant sweeps out equal areas in equal times

3. the square of the period is proportional to the cube of the semi-major axis

galileo galilei

known as the father of modern science

• used the telescope to discover jupiters four brightest moons, the phase of views and faint stars

• discovered the law of intertia and introduced the scientific method

isaac newton

the father of modern physics

three laws of motion

1. law of inertia: an object in motion stays in motion

2. F=ma

3. conservation of momentum: action-reaction

electric fields

sources: electric charges (q/r²) and changing magnetic fields

effects: exerts a force on other charges in the direction of the field

magnetic fields

sources: moving charges and changing electric fields

effects: exerts a force on moving charges that is perpendicular to both the field and the charges motion

electromagnetic waves

• created by accelerating charges

• travel at the speed of light in a vacuum

• light itself is an electromagnetic wave

atomic structure

a nucleus w/protons and neutrons is orbited by electrons

the number of protons determines the element

the number of neutrons determines the isotope

electrons and protons

-electrons exist in specific energy levels

-when an electron drops to a lower energy level, it emits a photon

-an electron can absorb a photon to jump to a higher energy level

types of spectra

• continous: all wavelengths are present, like from a hot solid object (black body radiation)

absorptions

light passes through a diffuse gas, which absorbs specific wavelengths, leaving dark lines in the spectrum

emission

a diffuse gas emits light only at specific wavelengths, creating bright lines

spectral lines

• position of lines identifies the chemical composition of the source

• line positions can be shifted by the “doppler effect”, indication motion toward or away from the observer

• line widths can be broadened by thermal motion, collisions, rotations, and magnetic fields

stellar magnitude

• smaller magnitude value means a brighter star

• a difference of 5 magnitudes equals a factor of 100 in brightness

• apparent magnitude: how bright a star appears from earth

• absolute magnitude: how bright a star would appear if it were 10 parasecs away.

temperature

surface brightness varies as T^4

surface area

luminosity is proportioanl R²

distance

apparent brightness is proportional to 1/d²

spectral type

OBAFGKM

sun is a G2 star

binary stars

stellar masses can be determines by observing binary systems using keplers and newtons laws

types of binary systems

visual: both stars can be seen directly

astrometric: only one star is seen, but its motion shows its orbiting a companion

spectroscopic

the stars orbital motion its detected by the doppler shifts of their spectral lines

eclipsing

the systems light dims periodically as one star passes in front of the other

scientific notation

10^n x 10^m = 10^n+m

metric prefixes

kilo )k, 10³

keplers/newtons law for binaries

(m1+M2)p²=a³

doppler shift

an approaching source has its light shifted to a shorter wavelength

wien’s law

the peak wavelength of emission is inversely proportional to L’d²

luminosity vs. brightness

luminosity is proportional to R²T^4, apparent brightness is proportional to L/d²

telescope resolution

the minimum angle that can be resolved

universal gravitation

the force of gravity is proportional to m/r². density is proportional to m/r³