STARS There are billions of stars in our galaxy and each one is a little different than the others! This unit teaches us the physical properties of stars. When you’re done, you should be able to describe the properties of the sun and compare it to other known stars in the galaxy.

A star is a sphere of ionized gas. Stars are held together by gravity There are 4 main classifications of stars: dwarf, giant, super giant, and main sequence. They emit heat and light. Powered by nuclear fusion. Composed mainly of hydrogen (H) and helium (He).

Brightness Absolute Magnitude Apparent Magnitude Refers to how bright a star actually is Also known as luminosity Apparent Magnitude Refers to how bright a star appears from Earth

Physical Properties of Stars Color and Temperature Star color is determined by the star’s surface temperature. Mass Least massive are the red dwarf stars. Most massive are the hypergiants. Bigger stars “burn” brighter and “die” faster than smaller stars. Hottest Blue Blue-White White Yellow-White Yellow Orange Coolest Red

Classification of Stars Dwarf Small, faint, and dim Stars are at the end of their “life cycle” Main Sequence Where stars spend most of their “lives” Nuclear reactions are stable Most stars Giant Large and bright Sun-sized stars can become giant stars as they begin to “die” Super Giant Huge stars Stars larger than our sun can become super giants as they begin to “die” Can become black holes

The Sun’s Atmosphere Corona Chromosphere Photosphere Superheated outer layer of the Sun’s atmosphere that emits x-rays Chromosphere Middle layer of the atmosphere that emits ultraviolet (UV) rays Photosphere Visible surface of the Sun that emits visible light

The Sun’s Interior Convective Zone Radiative Zone Core Energy travels from the radiative zone to the photosphere as gases rise and fall Radiative Zone Energy is transferred away from the Sun’s core Core Hottest part of the sun Produces energy through nuclear fusion

solar flare corona chromosphere photosphere convective zone sunspot core radiative zone prominence

Solar Activity Sunspots Solar Flares Prominences Energy travels from the radiative zone to the photosphere as gases rise and fall Solar Flares Energy is transferred away from the Sun’s core Prominences Huge loops of relatively cool gases

Nuclear Fusion High temperatures cause hydrogen nuclei to fuse forming helium nuclei and releasing energy. Energy travels from the core to the Sun’s surface. CONVECTIVE ZONE RADIATIVE ZONE PHOTOSPHERE CORE

Effect on Earth List the effects that the Sun has on Earth. Try to come up with three different things.