Astronomy

Gibbous

Like a 3/4 moon.

Crescent

Like a 1/4 moon.

Waxing

The phase where the moon is increasing in illumination (↑).

Waning

The phase where the moon is decreasing in illumination (↓).

Eclipses

A celestial event where a celestial body is covered up.

Lunar Eclipse

An eclipse where the Earth covers the moon.

Solar Eclipse

An eclipse where the moon covers the sun.

Cone-shaped shadow

The shadow cast during a solar eclipse.

Moon's orbit

The path the moon follows around the Earth, which is tilted relative to Earth's orbit.

Zenith

The highest point above you in the sky.

Circumpolar stars

Stars that never set because they are positioned near the poles.

Half stars

Stars located near the equator.

Gigaton

An American billion, equivalent to the weight of the sun (1.9x10^30 kg or 1 solar mass).

Luminosity

The brightness of a star, measured by its energy output.

Celestial sphere

A sphere that encompasses the stars, rotating around the Earth once every 24 hours.

Altitude

The angle above the horizon.

Circumpolar stars

Stars that never set, close to the poles.

Stars in motion

The daily motion of the sky caused by the rotation of the Earth.

Time conversion

1 billion years equals 1 gigayear.

Cosmological positioning

Related questions based on whether one is at the equator, near a pole, or in between.

Celestial sphere

The location of the stars in the sky as it rotates around the earth (24 hrs) w/ the sun. So as sun moves, so do stars (why Gemini is closet to sun at noon and sunset)

Ptolomey

• Almagest - first earth central model

• Collection of math, tables, physics to predict planetary positions

• Made motions (epicycles) of the heavens perfect (circular motion/constant speed)

       *not accurate to actual planetary motion.

• epicycle- a small circle within a larger circular pattern (revolution vs rotation)

Tycho Brahe

• " de nova stella” (on the new star)

• Saw a new star - wrote a book- star goes away (was a supernova- star explosion - bright)

• Convinced dutch king to fund observatory

• Uses Almagest - does not work - uses uraniborg (observatory) to make better system

• Geo-helio system: the sun and moon orbit the earth, all else orbits the sun

Copernicus

• Heliocentric theory - sun is at the center (religiously risky - Catholic backlash)

johannes Kepler

• Orbits of planets are ellipses w/ sun as foci

         - eccentricity - how squished an ellipse is

• As planets move around the sun, sweeps out equal orbits at equal times

        -as you move farther away from what you orbit, you more slower

• Longer it takes a planet to complete its orbit, the further it is from the sun

              equ: p^2=a^3

Where p is planet’s orbit in yrs (time), and a is semi-major axis (distance) (AU) ( mass is negligible)

Galileo Galilei

• Sidereal messenger (book-what do you see in a telescope)

• There are lots of stars in the sky

• Jupiter has moons!!

• Discovers that the sun rotates, sun spots, and sphere

• Moon has mountains/valleys

• Saturn has rings

• Dialogue on the two chief word systems: heliocentric is best

Heliocentric vs geocentric

Sun is at the center of universe is the earth

Solar luminosities

how to measure luminosity

Light wavelength vs frequency vs energy

Short wavelength=high energy/frequency (blue)

long wave Is vice versa (red)

Spectral lines

• different atoms have different  spectral lines (atomic fingerprints)

• Light is energy & conserved

• Energy is passed too/from electrons

•  as electrons ↓, light is released, photons ↑

Issac Newton and gravity

Mathematical proof of kepler’s laws

Cannonball experiment

If an object fall sideways as fast as 8 km/s it will orbit the earths

Escape velocity

Speed needed to break out of earths orbit

Speed of light

3.0×10^8 m/s (as c)

Black hole

An object w/ an escape velocity of greater than speed of light (large mass in tiny space)

Newton and prisms

Shone a white light through one prism and funneled a particular light into another-the color of light remained the same-proved white light is a collection of all colors

How to make light

• Hot and opaque (stars) (blackbody radiation-continous spectrum)

• Clouds of gas/dust (not opaque)(nebula)

Emission vs absorption

Continuous spectra: intensity vary, no gaps. HOT AND OPAQUE

Emission spectra: emissions/lines only @ specific wavelengths

Absorption spectra: continuous light w/ dark lines

Looking @ a graph and relating color and energy

Peak of graph (determined by temp, akin to a certain color)

• Red → blue.   Low → high temp

• Stars are diff colors due to temp!

•  as temp ↑, energy ↑

 

*look at graph x axis to sere color emission amounts 

William Herschel

Infrared light

Fraunhofer

Spectral lines

Kirchoff and Bunsen

Can observe spectral lines as elemental emissions

-elements have certain orbitals that are filled in accordance to the specific permitted energies of each orbital. Thus, each specific element emits different lights w/ diff energies