Characteristics of Stars Get out a paper and pen/pencil to take notes

Daily Question 12/9/11 1. What are some characteristic of stars you would use to help identify them? - size, color, temperature, composition, brightness

Big Dipper

Constellation Groups of stars in which people at one time thought they saw imaginary figures of animals or people The Queen

dippers

Constellations Are star groups that form patterns Light year – distance light can travel in one year (9.5 million million kilometers) Polaris is 700 light years away

Daily Question 12/13/11 Which star is hotter – a red or blue star? Which star is brighter – a supergiant or our sun? Which tool is used to break light into its characteristic colors? Blue Supergiant prism

The Winter W As seen in Star Lab

Orion

Circumpolar Constellations

Classifying Stars Classification through the physical characteristics Color Temperature Size Composition Brightness

Color and Temperature Hot stars – burn white or blue Rigel (Orion) Cool stars – burn reddish Betelgeuse (Orion)

Size Neutron stars are the smallest stars (20 km in diameter) White dwarfs (size of Earth) Medium-sized stars (Our Sun) Giants and Super Giants are the largest stars comparison

Daily Question 12/12/11 1. List the stars in order of smallest to largest. 2. List the colors of temperature in order of hottest to coolest. 1. Neutron Star, White Dwarf, Medium, Giant, Super Giant 2. Blue, White, Yellow, Red-Orange, Red

Chemical Composition Most stars are 73% Hydrogen (H); 25% Helium (He); 2% other elements Spectroscope is a device that breaks light into colors and produces an image of the resulting spectrum (spectrograph). Each chemical absorbs light at a particular wavelength on the spectrum, each unique. How Spectroscopy Works

Brightness of a Star The brightness of a star depends upon both its size and temperature Brightness is described in two ways Apparent brightness Brightness as seen from Earth Absolute brightness Is the brightness of a star from a standard distance from Earth (its true brightness)

Daily Question 12/15/11 The color of the star can also act as an indicator of what two characteristics? What are the two types of brightness that have been discussed? Name one constellation.

Answers Temperature and Chemical Composition Absolute and Apparent brightness

Measuring Distances to Stars Parallax –used to measure distances to near by stars Apparent change in position of an object when you look at it from different places.

Hertzsprung-Russell Diagram Ejnar Hertzsprung (Denmark) and Henry Norris Russell (USA) plotted absolute brightness of stars and their temperature to show their relationship. Astronomers use H-R diagram to classify stars and understand how stars change over time. 90% of stars are main sequence (found in diagonal area from lower right to upper left) where surface temperature increases as absolute brightness increases.

Constellations

Cass