Compare the life cycle of a star with that of a human. 191 192 Characteristics of Stars Characteristics of Stars 2/25/15 2/22-25/2013 2/22-25/2013 2/25/15 Starter: Compare the life cycle of a star with that of a human. Application/Connection: HR Diagram Activity 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! Practice: Notes

1. Starter 2. Notes 3 Activity 4. Exit February 25, 2015 AGENDA Objective 8.8C Describe 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.

Table of Contents Date Lecture/ Activity/ Lab Page 2/20 Formation of the Universe 185-186 2/23 Big Bang Lab 187-188 2/24 Lives of Stars 189-190 2/25 Characteristics of Stars 191-192

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

Size- Neutron Star 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- White Dwarf Our Sun, A Red Giant, and a White Dwarf 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.

Size- Medium (main sequence) 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-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.

Approximate Surface 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 Color Approximate Surface Temperature Examples O Blue over 25,000 K 10 Lacertra B 11,000 - 25,000 K Rigel Spica A 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 K Arcturus, Aldebaran M Red under 3,500 K Betelgeuse, Antares

Elements found in most abundance inside the Stars Mass Star name Elements found in most abundance inside the Stars H He Ca Li Na Mg Fe Ne Sun ☼ Procyon Betelgeuse Sirius Aldebaran 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.

Color Color- 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 (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.

Compare the life cycle of a star with that of a human. 191 192 Characteristics of Stars Characteristics of Stars 2/25/15 2/22-25/2013 2/22-25/2013 2/25/15 Starter: Compare the life cycle of a star with that of a human. Application/Connection: HR Diagram Activity 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! Practice: Notes