SSA Review # 1 - Astronomy

Universe - Space and all of the matter and energy that is in it.

UNIVERSE GALAXY STARS SOLAR SYSTEMS PLANETS

*Galaxy – a massive system of stars (billions), gases, dust, and other matter held together by a central gravitational force

Spiral Elliptical Irregular

*Stars – large spherical(round) bodies composed of gas (H, He) and gives off light The Sun Sirius Betelgeuse Aldebaran Regulus

*Solar System – a central star with planets and other small objects orbiting it

*Planet – a spherical body that orbits a star

Measuring Distances in the Universe

*Astronomical Unit (AU’s) – the distance from Earth to the Sun --used to measure distances in the Solar System

*Light year – the distance light travels through space in 1 year of time (measures distances in the rest of the Universe) From Earth to stars The size of galaxies From galaxy to galaxy

Size of Stars

*The color of a star indicates its temperature Blue (Hottest) Red (Coolest)

*Apparent Magnitude - How bright a star appears to be from Earth The Sun 26.8 Sirius -1.46 Vega +0.03 Betelgeuse +0.5 *The smaller the number (value), the brighter the star appears

*Absolute Magnitude (Luminosity) – How bright a star actually is Apparent Magnitude Absolute Magnitude The Sun 26.8 +4.8 Sirius -1.46 +1.2 Vega +0.03 +0.6 Rigel +0.12 -8.1 Betelgeuse +0.5 -7.2 *The smaller the number (value), the brighter the star actually is

Models of the Solar System

*Geocentric Model – Earth in the center

*Heliocentric Model – Sun in the center

Structure of the Sun Core where energy is produced through the process of fusion

Structure of the Sun Convective Zone – Energy moves to the surface by convection currents

Structure of the Sun the visible surface of the sun Photosphere the visible surface of the sun Structure of the Sun *approx 300 miles thick *takes 8 minutes for light to reach the Earth

The Sun’s Rotation – Differential Rotation *Different parts of the sun rotate at different rates of speed (the sun is a ball of gases , not solid like the Earth

SOLAR ACTIVITY Solar Flare an explosive burst of energy extending out from the sun *appears as very bright spots on the photosphere *Similar to a volcanic eruption on Earth

SOLAR ACTIVITY Prominence huge loops of gases extending out from the sun *many Earths could fit inside one

SOLAR ACTIVITY Sunspots dark areas that form on the sun’s surface *cooler regions of the photosphere caused by a change in the sun’s magnetic field

*How does solar activity affect conditions on Earth? *Solar flares can affect satellites, astronauts, GPS systems, jet airplanes, and electrical systems and devices on Earth.

1 - Inner Planets (Terrestrial) *Small *Rocky *Thin atmospheres *Closer to the Sun

*Fast rotational period 2 - Outer Planets (Gas Giants) *Large *Thick, gaseous atmospheres (hydrogen & helium) with a solid core *Fast rotational period *Many moons and rings *Farther away from the Sun (colder)

1. Dwarf Planet *A round object that orbits the Sun, but has other objects that cross its orbit PLUTO

2. Natural Satellites (Moons) *A round object that orbits a planet *Why does Jupiter and Saturn have so many satellites? *They have a stronger gravitational pull on objects

3. Asteroids *Chunks of rocks & metal orbiting the Sun

5. Comets *An icy body that releases glowing gases as it orbits close to the Sun Coma Tail

What is the universal force that hold galaxies together, caused a nebula to collapse inward and flatten into a disk that eventually formed our solar system, and keeps objects in orbit around other objects? Gravity