Stars And Galaxy Exam

Front 1

Scientific notation

Back 1

Metric system used by scientist and scientific notation for very large or very small numbers

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Solar system

Back 2

Sun is center, all major planets plus their moons, asteroids, comets and dwarf planets bound to sun by its gravity.

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Astronomical unit

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Average distance from Earth to sun. Equal to 1.5 x 10^8

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Star

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Self luminous ball of hot gas, ex. The sun

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Planet

Back 5

Spherical, non luminous bodies that orbit a star and shine by reflected light. Extra solar planets are small, faint and difficult to see because they r too close to parent stars

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Light year

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Distance light can travel in one year. Ex. Nearest star is 4.2 ly from the sun.

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Milky way

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Hazy band of light/stars That encircles the sky. Milky way galaxy is our home galaxy.

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Galaxies

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Cloud of stars, gas and dust held together by combined gravity of all its matter ex. Milky way galaxy- about 80,000 light year is diameter and contains more than 1 billion stars

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Galaxy spiral arms

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Arms winding outward from galaxy, including ours. Places where stars are formed.

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Big bang

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How universe began 14 billion years ago. Filled universe with hot gas. Stars cooled and first galaxies were formed

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Scientific method

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Method used by scientists to test hypotheses against evidence from experiments and observations

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International astronomical union

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Astronomers divided sky into 88 constellations.

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Magnitude scale

Back 13

System used to describe brightness of a star. First magnitude brighter than second and so forth. The larger the magnitude number the fainter the star.

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Apparent visual magnitude

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Describe how stars look to human eyes from Earth.

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Flux

Back 15

Measure of light energy striking one one square meter per second. Magnitude related directly to Flux of light received on earth by that star

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Celestial sphere

Back 16

Scientific model of the sky. Earth Rotates eastward while celestial sphere rotates westward on its axis

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North/south celestial poles.

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Pivots defining four cardinal directions around horizon (north, South, east, West points). Put

Point directly overhead is zenith and below is nadir.

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Celestial equator

Back 18

Imaginary line around sky and above earth's equator. Divides sky into northern and southern hemisphere.

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Angular distance

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Angle between two lines extending from your eye to the two objects. Measured in degrees, arc minutes and arc seconds. Angular diameter is angular distance from one edge to another.

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Earth rotation

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Turning of body on its axis. Earth's rotation produces cycle of day and night

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Revolution

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Motion of body around a point outside the body. Earth revolving around sun produces annual cycle of seasons.

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Ecliptic

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Path of sun around the sky. Also called projection (shadow) of earth's orbit on the sky. Planets move eastward along ecliptic.

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Earth's seasons

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Dates sun crosses these points.

Vernal equinox- March 20- spring begins.

Summer solstice- June 22- summer begins.

Autumnal equinox- September 22- autumn begins.

Winter solstice- December 21- winter begins.

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Milankovitch hypothesis

Back 24

Changes in shape of earth's orbit, angle of axis tilt and axis orientation can alter planets heat balance and cause cycle of ice advances/retreats during ice age.

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Moon orbital motion

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Moon path is always close to ecliptic. It revolves counterclockwise around earth (from direction of North celestial pole)

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Waxing phaser of moon

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Moon "waxes" (illuminated portion increases) from new moon to first quarter.

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Waning phase of moon

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Moon wanes from full moon to third quarter back to new moon (illuminated part becomes smaller)

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Synodic period

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Complete cycle of lunar phase. Takes 29.5 days

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Waxing phase of moon

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Begins from new moon at waxing crescent to first quarter, then full moon at waxing gibbous. (Illuminated side gets smaller)

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Lunar phase

Back 30

Changing appearance of moon as it revolves around earth. We always see same side of the moon. Sunlight illuminates different amounts of this side, signaling the phases

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Sidereal period

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Moon orbits eastward around earth in 27.3 days. It is how long money takes to circle the sky once and return to same position relative to stars.

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Lunar eclipse

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Occurs only at full moon. If moon passes through earth's shadow, sunlight is blocked and moon darkens.

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Umbra

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Region of total shadow

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Penumbra

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Region of partial shadow.

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Total lunar eclipse

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Occurs once or twice a yr. When moon is completely within earth's umbra.

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Partial lunar eclipse

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When moon only grazes umbra

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Penumbral lunar eclipse

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Moon only passes through penumbra and doesn't reach umbra. Moon only partially dimmed

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Totality

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Eclipsed moon looks copper red. Sunlight refracts through earth's atmosphere and bounces off moon on night side of earth

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Small angle formula

Back 39

Used to calculate objects angular diameter. Uses linear diameter and distance of an object. Constant 2.06 x 10^5 is number of arc seconds in one radian

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Solar eclipse/total solar eclipse/partial solar eclipse

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When moon moves between earth and the sun. Total is when moon covers disk of sun completely. Partial is when moon covers only part of the sun

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Perigee

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When moon is at closest point to earth. Angular diameter 5.5 percent larger than average.

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Apogee

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When moon is at farthest point from Earth. Angular diameter 5.5 percent smaller than average

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Annular eclipse

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When moon crosses in front of sun when moons disk is smaller in angular diameter than suns.

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Saros cycle

Back 44

Pattern of eclipses.

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Archaeastronomy

Back 45

Study of astronomy of ancient peoples. Combo of archaeology and astronomy. structures like Stonehenge, newgrange, and other human made phenomena involve astronomical alignments

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Geocentric universe/heliocentric universe

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Geo is Belief that earth was center of universe. Helio is belief that sun is at center

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Uniform circular motion- Plato

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Plato argued most perfect geometrical form is sphere, so, heavens made up of spheres rotating at constant rates carrying objects around in circles.

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Retrograde motion

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Occasional westward, backward motion of the planets

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Hipparchus/ eccentrics

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Motion of sun moon, and planets follows circular path with earth near, but not at its center

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Aristotle/first principles

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Believed universe divided into two parts. Earth is imperfect and changeable while heavens is prefect and unchanging. Reasoned with first principles- something held to be obviously true and needs no further explanation

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Ptolemy

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Preserved principles of geocentrism and uniform circular motion. Added equant, epicycles and deferents. His model was not accurate and had to be revised numerous times

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Coepernican revolution

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Devised heliocentric universe. Preserved principle of uniform circular motion. Argued earth rotates on axis and revolves around sun once a yr.

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Scientific revolution/paradigm

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Shift from geocentric to heliocentric belief. Change that occurs in science.

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Tycho/kepler

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Tycho compiles detailed, precise observations of the positions of the sun, moon, and planets over period of 20 yrs. Observations later used by kepler

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Kepler laws of planetary motion (1st law)

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Orbits of planets are ellipses wroth the sun at one focus

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Kepler second law

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Line from planet to the sun sweeps over equal areas in equal intervals of time.

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Kepler third law

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Planets orbital period squared is proportional to its average distance from the sun cubed

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Galileo

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Helped establish modern science. Used telescope to discover moon had features like earth (mountain and valleys). Phases of Venus and existence of 4 moons circling Jupiter (galilean moons).

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Acceleration of gravity

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Falling object falls at rate of 9.8m/s^2 every second

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Inertia

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Once begun, motion continues until something changes it.

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Newton's first law

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A body continues at rest or in uniform motion in a straight line unless acted on by an external force

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Newton's second law of motion

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Cause and effect. Acceleration of an object is dependent on the net force acting upon that object and the mass of the object. F=ma

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Newton's third law

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To every action there is an equal opposite reaction

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Momentum

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Continued motion of an object

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Acceleration

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Change in velocity

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Velocity

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Speed with a specific direction

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Inverse square law

Back 67

Rule that the strength of an effect (gravity) decreases in proportion as the distance squared decreases. Force of gravity inversely proportional to square of the distance between two masses.

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Universal mutual gravitation

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Earth's bigger size allows its gravitational force to accelerate the moon towards earth.

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Field

Back 69

Earth's mass produces gravitational field throughout space that is directed earth's center

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Geosynchronous satellite

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Orbits eastward with rotation of earth and remains above fixed spot on the equator

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Circular velocity

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Sideways velocity an object must have to remain in circular orbit

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Escape velocity

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Velocity required to escape an astronomical body

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Newton's version of keplers law

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Balance force necessary to keep an object in circular motion with the gravitational force. Equivalent to keplers third law

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Postulates of relativity (Einstein)

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(Relative principle) observers can never detect their uniform motion except relative to other objects

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2nd postulate

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Speed of light is constant and will be same for all observers independent of their motion endive to light source

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3rd postulate (general theory)

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Observers cannot distinguish between inertial forces due to acceleration and uniform gravitational forces.

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Electromagnetic radiation

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Light made up of both electric and magnetic disturbance that transports energy at the speed of light.

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Wavelength

Back 78

Distance between peaks of wave, measured in nanometers or angstroms. Wavelength band of visual light is from 400 nm to 700 nm

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Frequency

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Correlates with wavelength. Number of waves that pass a stationary point in 1 sec.

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Photon

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Packet of light waves that can act as particle or wave. Energy proportional to frequency and inversely proportional to its wavelength.

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Spectrum

Back 81

Array of electromagnetic radiation displayed in order of wavelength. Contains gamma rays, x-rays, ultraviolet, radiation, visible light, infrared, microwaves, and radio waves

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Wavelength/frequency

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The shorter the wavelength, the higher the frequency. The longer the wavelength, the lower of frequency.

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Refracting telescopes

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Uses lens to gather and focus light (primary lens)

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Reflecting telescope

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Uses concave mirror to focus light on focal plane. Secondary mirror redirects light path towards back or side.

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Eyepiece

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Lens used to magnify image and make it convenient to view

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Chromatic aberration

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Different wavelengths are focused at different focal lengths (prism effect)

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Limits of telescope- light gathering power

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Ability of telescope to collect light. Depends on surface area of primary lens or mirror

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Limits of telescope- resolving power

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Ability to reveal fine detail

Front 89

Magnifying power

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Ability of telescope to make an object look bigger. Depends on ratio of length of primary mirror or lens and the eyepiece.

Front 90

Radio astronomy

Back 90

Radio waves can be observed from the ground.

Front 91

Types of telescopes

Back 91

Telescopes observing high frequency lights ex. Gamma rays, x-rays, ultraviolet must be located high in earth's atmosphere or in space.