ASTRONOMY

TERMSThe Universe: Everything in existence. Created around 15 billion years ago due to the Big Bang. Approximately 30 billion light years in diameter and expanding at the speed of light. Contains possibly 200 billion galaxies.

A Cluster: A grouping of millions of galaxies

A Galaxy: A grouping of around 500 billion solar systems. Many galaxies revolve around black holes.

A Light Year: The distance that light travels in one year; 5,878,625,373,183.61mi

Light Speed: approximately 300,000 km per second

TERMS CONTINUEDThe Milky Way: Our galaxy containing up to 400 billion solar systems. Earth is located on one spiral arm.

A Solar System: One star and any planets, dwarf planets, moons, asteroids, meteors, and comets that revolve around it.

CELESTIAL BODIES

Stars: A massive, luminous ball of plasma (ionized gas) that releases energy due to thermonuclear fusion.

The Sun

CELESTIAL BODIES CONTINUEDConstellations: Man-made groupings of stars usually with mythological associations, created to provide an explanation concerning how they got there; used in the past for navigation and astrology.

Polaris: The North Star which can be found by drawing a line through the 2 pointer stars in the big dipper. (angle in the sky = observer’s latitude)

CELESTIAL BODIES CONTINUED

Planets: A body that orbits the sun, is massive enough to be rounded by its own gravity, and has cleared its neighboring region of planetesimals.

Moons: A celestial body that orbits a planet, or dwarf planet. 240 in solar system.

THE PLANETS

Mercury: Closest to sun, 2nd hottest, smallest, looks like moon, many caters, no atmosphere, visible from Earth.

Terrestrial Planets: Solid inner planets w/ high density: Mer., Ven., Ear., Mars.

TERRESTRIAL PLANETS CONTINUED

Venus: 2nd closest, hottest, extremely thick atmosphere of carbon dioxide, volcanic activity, lightning and acid rain possible, visible from Earth

TERRESTRIAL PLANETS CONTINUEDEarth: Life, water, atmosphere of Nitrogen and oxygen, volcanic activity 1 moon.

TERRESTRIAL PLANETS CONTINUEDMars: 4th planet, red in color, thin atmosphere, 2 small irregular shaped moons, possibly had/has water.

PLANETS CONTINUED

Jovian Planets: Outer, gas-giant planets; Jupiter Saturn, Uranus, Neptune

Jupiter: 5th planet, largest by far, mostly hydrogen some helium, huge storms at least 63 moons, (ref. tables says 16), faint rings Jupiter storms Storms 2

JOVIAN PLANETS CONTINUEDSaturn: 2nd biggest, 93% hydrogen, less dense than water, visible rings of ice rock and dust, around 60 moons, (tables say 18) small rocky core. Hexagonal storm

JOVIAN PLANETS CONTINUEDUranus: Hydrogen, helium and frozen ice, methane and ammonia atmosphere, faint rings, rotates on its side, small rocky core, large icy mantle, 27 moons (tables say 21)

JOVIAN PLANETS CONTINUEDNeptune: Furthest planet, hydrogen, helium, and methane, strongest winds at 1,300 mph, faint rings, 13 moons (tables say 8)

DARK SPOT

To Scale

CELESTIAL BODIES CONTINUEDAsteroids: Solar system bodies that are smaller than planets but larger than meteoroids. (at least larger than 10 meters in diameter) Most can be found in a belt between Mars and Jupiter.

50 km acrossCeres 952 km

253 Mathilde

Meteorites/ Meteoroids + Meteors: Small sand to boulder sized debris in the solar system. (ite=on the surface, oid= in space, or = coming through atmosphere) (Shooting stars)

CELESTIAL BODIES CONTINUED

Comets: Bodies that orbit the sun with an extremely elliptical orbit and exhibit a mini atmosphere or tail due to effects of solar radiation on its nucleus. (rock, dust, water, ice, frozen gases) Comet

West Hale-Bopp

Hyakutake

OTHER CELESTIAL BODIESNeutron stars: The fast-rotating, collapsed remnant of a massive star after a smaller super-nova. Extremely dense, yet very small (10km) with an incredible gravitational force.

OTHER CELESTIAL BODIESPulsars: Highly magnetized, rotating, neutron stars which emit a beam of detectable electromagnetic radiation in the form of radio waves that can only be detected when it points toward Earth.

OTHER CELESTIAL BODIESQuasars: An extremely bright and distant, active galactic nucleus or a compact halo of matter surrounding the central super-massive black hole of a young galaxy.

Black Hole: a region of space in which the gravitational field is so powerful that nothing, not even light, can escape its pull after having fallen past its event horizon. Only around 4 times the size of the sun. Black Hole

OTHER CELESTIAL BODIES

THE BEGINNING?Steady State Theory and Cyclic Universe Theory: Postulate that the universe always existed and never had a “beginning”; matter is created over time.

Big Bang Theory: An explosion (expansion of space-time) occurred roughly 15 billion years ago from an infinitely dense point, the size of ½ an atom, which expanded into (and is still expanding) today’s universe. Accepted by vast majority of today’s scientists. Introduction to the Big Bang Theory

BIG BANG EVIDENCE1) Doppler Effect: Light appears different depending on the motion of the object that is projecting it. Doppler Effect Shifts Video Video 2

Red Shift: If a galaxy is moving away from Earth, the light received from it will be shifted toward the right or red end of the electromagnetic spectrum. (all galaxies show this shift)

Blue (Violet) Shift: If a galaxy is moving closer to us, the light received will shift closer to the left or violet end of the spectrum. (none of the galaxies show this shift)

2) Background Microwave Radiation: Remnants from the Big-Bang has been found showing energy that was produced. microwaves

ELECTROMAGNETIC SPECTRUM

Electromagnetic Spectrum: Chart that shows the varying types of light radiation broken down according to frequency. Only a very small portion is visible with the naked eye.

ENERGY TRANSFER

Radiation: Energy transfer through open space.

Conduction: Energy transfer through solid objects.

Convection: Energy transfer through liquids and gases.

Insolation: Solar energy that is absorbed by the Earth’s surface. June 21st is the date with the greatest potential insolation in the northern hemisphere since the sun is out the longest. Noon is always the time of day when insolation is the greatest since the sun is nearest to perpendicular to the surface. Dark and dull objects will absorb the most solar energy.

SOLAR SYSTEM MODELS

Geocentric Model: The earliest model of the solar system which put the Earth at the center.

Heliocentric Model: The 2nd model showing the sun directly in the center of the planets’ circular orbits.

SOLAR SYSTEM MODELS CONTINUED

The Variable Speed Model: The true model of the solar system which shows the Sun at one focus and the planets orbiting the star in elliptical orbits.

ELLIPTICAL ORBITSEllipse: The shape of the planets’ orbits which is an elongated circle with 2 foci.

Focus: One of 2 central points in an ellipse.

Perihelion: The closest position between a planet and the Sun. The Sun’s gravitational pull is the strongest and the planet’s orbital velocity is the greatest here.(sun looks big)

Aphelion: Where a planet is furthest away from the sun. Planet’s velocity is slowest and Sun’s gravitational force is the least. (sun appears smaller) (nothing to do with seasons)

(Apogee and Perogee refer to Earth/Moon points)

ELLIPTICAL ORBITS CONTINUED

Kepler’s 2nd Law: The line joining the sun and Earth sweep out equal areas in equal times due to change in gravitational attraction.

ECCENTRICITY

Eccentricity: Measures the amount that a planet’s orbit deviates from a perfect circle. The higher the value, the more linear the orbital path. (0= circle, 1= line) NO UNITS!!

Major Axis: The distance between the Aphelion and Perihelion.

E = Distance between the foci Length of the Major Axis

CELESTIAL MOTIONSRotation: When an object spins on its axis. It takes the Earth roughly 24 hours to make one complete rotation on its tilted axis which we call 1 day. (rotates counter-clockwise from north-polar view at 15°/ hour. hence the time-zones)

Revolution: The length of time it takes for one object to make a complete trip around another. Earth’s revolution takes 365.26 days around the sun which we label as one year. (leap year occurs every 4 years to account for the extra .26)

Foucault Pendulum: The instrument that assisted in proving that the Earth rotates.

SOLAR SYSTEM DATA pg. 15

THE SEASONS

Seasons: Man-made groupings of time within a year that vary in temperature and are created due to the revolution of the Earth around the sun and the 23.5° tilt of the Earth’s axis. Seasons Seasons 2

IMPORTANT DATES

June 20th-23rd: Summer Solstice; first day of summer, longest day of the year for locations north of the Tropic of Cancer (approx. 15 hours of daylight for NY), sun appears to be located directly overhead of the Tropic of Cancer at 23.5° N latitude.

September 20th-23rd: Autumnal Equinox; first day of Fall, 12 hours of light and dark, sun appears to be over the equator.

December 20th-23rd: Winter Solstice; first day of Winter, shortest day of the year for locations north of the Tropic of Cancer ( approx. 9 hours of daylight for NY), sun appears directly overhead of the Tropic of Capricorn at 23.5° S latitude.

March 20th-23rd Vernal Equinox; first day of Spring, 12 hours of light and dark, sun appears to be over the equator.

THE SUN’S APPARENT PATH

Arc: The apparent motion of the sun throughout a given day. It rises in the east and sets in the west. (only due east and west during the equinoxes and never at the zenith for NY)

Zenith: Position directly 90° above an observer.

Altitude: The angle of an object in the sky.

SHADOW LENGTH

Note: On a given day, shadows will be longest at sunrise and sunset and smallest at noon. In NY, the noon-time shadow is smallest on June 21st and largest December 21st.

H + R DIAGRAMHertzsprung Russell Diagram: Shows the luminosity, color, temperature and magnitude of star groups as compared to the Sun.

Luminosity: A star’s brightness as compared to the Sun, determined by its magnitude

LIFE CYCLE OF A STAR

The stages in a star’s existence depends on its initial mass: Life Cycle of a Star 4 min vid

THE MOON

Tides: The increase and decrease in sea level due to the gravitational pull of the Moon and, to a lesser extent, the Sun. Tides will switch from high to low or low to high gradually every 6 hours.

Spring Tides: The extremely high high-tides and low low-tides produced twice a month during new and full moon phases due to the Sun, Moon, and Earth being lined up.

Neap Tides: The tides with the least variation between high and low tides. Occurs twice a month at first and last quarter moon phases when the Sun, Moon, and Earth are at right angles.

TIDES CONTINUED

SPRING AND NEAP TIDES

MOON PHASESPhases: At all times (other than lunar eclipse) ½ of the moon is lit. However, due to the position of the moon in its orbit around the Earth, we will see different portions of the lit moon. Each different fraction that we see is called a phase.

MOON INFO. CONTINUED

Lunar Month: The amount of time it takes for the moon to go from full moon to the next full moon. 29 ½ days This is over 2 days more than a Sidereal month to account for Earth’s new position in its orbit around the sun.

Sidereal Month: The amount it takes for the Moon to complete one full revolution around the Earth. 27 1/3 days

Lunar Eclipse: The irregular occurrence of the moon revolving into the Earth’s shadow. Occurs during a full-moon phase and complete darkness lasts for approximately 30 minutes to 1 hour. (Earth is between Sun and Moon)

Lunar Eclipse Animation Lunar video

Solar Eclipse: The irregular occurrence of the moon revolving directly between the Sun and Earth and thus blocking out the light for a very small portion of the planet. Occurs during a New-moon phase and lasts for about 10 minutes. Solar Eclipse Animation Solar Video

ECLIPSES CONTINUED

Why don’t solar and lunar eclipses happen during every new and full moon phase?: The moon’s orbital plane is tilted at 5° relative to Earth’s.

Umbra: The total, dark shadow of an eclipse.

Penumbra: Partial, dim shadow of an eclipse.

KUIPER BELTKuiper Belt: An asteroid belt beyond Neptune that contains the dwarf planet Pluto and is 20 times as wide and 200 times as massive as the belt between Mars and Jupiter. Objects are mostly frozen volatiles such as ammonia, water and methane.

OORT CLOUDOort Cloud: A spherical collection of billions of comets roughly one light year from the Sun, the extent of which defines the outer boundary of our solar system.