Unveiling the Secrets of Stars: A Brief Overview

1. Stars A brief overview

2. Stars • Stars are extremely far away. • The nearest star is the ________ • Stars provide energy for surrounding systems • Determining star distance and location is difficult because of the great distance.

3. Star distance and parallax • To determine the distance to a near star, astronomers observe a star two times a year (separated by about 6 months). • This ensures the earth is on opposite sides of its orbit. • Allows us to have a stereoscopic view of the star • Allows us to mathematically determine the distance to the star. See page 323 • Parallax –

4. Distance to distant stars • Compare the brightness of the star to the brightness of a star with a known distance • Then we estimate the ____________ to the distant star. • Most stars are so far away it would take thousands of years to send a spacecraft there to study them. • Our knowledge of stars comes from ___________ ___________ and other indirect study techniques.

5. The use of indirect techniques have allowed us to:

6. General information on stars • A star is a massive ball of gas held together by the gravity of all its gas atoms • A star’s TREMENDOUS gravity creates an immense crushing force. • That force is countered by gas pressure as the atoms smash into each other. • As temperature rises pressure increases and halts the collapse of gas molecules by gravity.

7. At some point gravitational pull and pressure forces balance • As a rule, • Results in the Mass-luminosity law. • See figures OV 5.6 and OV 5.7

8. Stars and Energy loss • If a star lost no energy, gravitational force and pressure would keep it stable forever • However, stars lose energy in the form of _________. We see that heat as light and feel its warmth. • If a star continues to lose heat it will ______________.

9. Stars continue to generate Energy • Most stars replenish their energy by the fusion of _____ into ______. • Most stars have enough H to use as a fuel to last for several billion years. (our Sun is projected to last for another 5 billion years) • When the fuel finally does run out the stars enters another stage in its “development” • After all the H is used up and the star adjusts in size it will use He as a fuel (_________________) • Once the He is all used the star cools forming a ________________

10. “star death” • As the white dwarf loses gases it is called a planetary nebula. It glows because of heat emanating from the stars core some of the gases eventually become new stars. • Large stars cores produce enough heat to fuse atoms together forming ___________, ______________ and even ___________ • Iron core stars which collapse inward are called ______________________. • Supernovas may form “neutron stars” or even a black hole.

11. Use notes or the book to answer the following: • What is parallax? • How do we use parallax? • Using your book, what is the wavelength of light in the following colors: Red, orange, yellow, green, Blue and violet • Which elements gives off the following colors when heated: red, yellow, green blue and purple. • What is the “fuel” for most stars? • What two forces are balanced inside a star?