Starter:

Compare the life cycle of a star with that of a human.

2/22-25/2013

145 1462/22-25/2013

Exit: If there are more low-mass stars than high-mass stars in the universe, do you think there are more white dwarfs or more black holes? Explain!

Characteristics of Stars

Application/Connection: HR Diagram Activity

1/20/15 1/20/15

Practice: Notes

Characteristics of Stars

January 20, 2015AGENDA

Objective 8.8CDescribe components

of the universe, including stars, nebulae, and

galaxies, and use models such as the Herztsprung-Russell

diagram for classification by

taking notes and a HR diagram graph.

1. Starter2. Notes 3 Activity4. Exit

12/16 Light Years 125-12612/17 Formation of the Universe 127-12812/18 Big Bang 129-13012/19 Early Astronomers and Light year Writing 131-132 1/7 Waves and the EM Spectrum 133-134 1/8 Wavestown 135-1361-9 EM Writing and Quiz 137-1381-14 Galaxies 139-1401-15 Counting Galaxies 141-1421-16 Lives of Stars 143-1441-20 Characteristics of Stars 145-146

Table of Contents

Characteristics of Stars

• To an astronomer stars appear very different in many ways such as their size, temperature, color, brightness, density and mass.

NEUTRON STAR- A very small and dense star made almost completely of neutrons.

Neutron stars have a radius of about 10 kilometers (6.2 mi) and a mass from about 1.4 to 5 times the mass of the Sun. The density is a billion times the density of Earth.

They are usually what is left of supernovas.

Size- Neutron

Star

White Dwarfs are about the same size as the Earth and 200,000 times as dense. (They may weigh the same as the sun.)

White dwarf stars are extremely hot (100,000 Kelvin); so they emit bright white light. Because white dwarfs are extremely small, it takes them a long time to cool down.

A star like our Sun will become a white dwarf when it has run out of fuel. Near the end of its life, it will go through a red giant stage, and then lose most of its gas.

Our Sun, A Red Giant, and a White Dwarf

Size- White Dwarf

Main Sequence or Medium size star are about the size of our Sun which has a diameter of about 1,392,000 km, about 109 times that of Earth, and its density is 330,000 times that of Earth.

Main sequence stars all undergoing fusion of hydrogen into helium within their cores.

Mass is the key factor in determining the lifespan of a main sequence star, its size and its luminosity. Stars on the main sequence also appear to be unchanging for long periods of time.

Size- Medium (main sequence)

Size-Giant star

Giant star-a star with a diameter about 10 to 100 times the size of our sun and has a lower density due to the massive size. Giant stars are swollen in size towards the end of its life, having converted all the hydrogen in its core to helium.

A giant star is brighter, larger, and cooler than a main-sequence star of the same mass. and luminosities from tens to thousands of times the Sun's.

Common types of giants are: blue giant and red giant.

Size-Super Giants

Super giant star- 1000 times the diameter of out sun; dies out quickly and the shortest lived in the universe (only a few million years).

Density is very slight due to super-massive size but the luminosity is nearly 1,000,000 times as great.

The super-giant can explode (at the end of its life cycle) into a supernova.  This explosion is so powerful that for a few weeks, this supernova can outshine an entire galaxy.

Temperature The color of the star determines what the surface temperature is. The hotter the star the brighter the star will be. Temperature is measured in degrees Kelvin.

Star Type ColorApproximate

Surface Temperature

Examples

O Blue over 25,000 K 10 Lacertra

B Blue 11,000 - 25,000 KRigelSpica

A Blue 7,500 - 11,000 K Sirius, Vega

F Blue to White 6,000 - 7,500 K Canopus, Procyon

G White to Yellow 5,000 - 6,000 K Sun, Capella

K Orange to Red 3,500 - 5,000 KArcturus, Aldebaran

M Red under 3,500 KBetelgeuse,

Antares

Mass

Mass- is the composition (hydrogen, helium)of the star

As Hydrogen burns the mass of the star increases due to new elements being fused together.

Star nameElements found in most abundance

inside the Stars

H He Ca Li Na Mg Fe Ne

Sun ☼ ☼ ☼ ☼ ☼ ☼

Procyon ☼ ☼ ☼ ☼ ☼

Betelgeuse ☼ ☼ ☼ ☼ ☼ ☼ ☼ ☼

Sirius ☼ ☼

Aldebaran ☼ ☼ ☼ ☼ ☼ ☼

ColorColor- ranging from blue to red and depending on the elements that are burning.

Most stars are currently classified using the letters:

O stars are called "blue" B "blue-white" A stars "white" F stars "yellow-white" G stars "yellow" K stars "orange" M stars "red"

Brightness (Luminosity)

Brightness is constant amount of light that is emitted by the star.

Brightness depends on the size of the star, its surface temperature, and its distance from the Earth.

Apparent magnitude-the brightness of a star as it appears

Absolute magnitude-the amount of light a star actually gives off

.

Hertsprung-Russell Diagram

Astronomers have discovered that there is a relationship between a star’s surface temperature and its brightness.

Two astronomers named Hertsprung and Russell plotted the data of the stars on a chart according to their surface temperature and brightness.

Grouping Stars on the H-R Diagram

Hertsprung and Russell found the stars fall into one of three groups.

Most stars fall into a narrow band on the chart called the Main Sequence.

A second group appears at the third upper right of the chart called the giants and supergiants.

A third group of stars appears at the very bottom of the chart and are called white dwarfs.

H-R Diagram Main-sequence Stars

Main Sequence stars fall into the an area from the upper left corner to the lower right corner of the H-R diagram

The hottest are blue or blue-white and are in the upper left corner of the diagram

The cool, dim stars are red in the lower right corner.

Starter:

Compare the life cycle of a star with that of a human.

2/22-25/2013

145 1462/22-25/2013

Exit: If there are more low-mass stars than high-mass stars in the universe, do you think there are more white dwarfs or more black holes? Explain!

Characteristics of Stars

Application/Connection: HR Diagram Activity

1/20/15 1/20/15

Practice: Notes

Characteristics of Stars