Stars

1. Stars

2. Nebula – massive cloud of dust and gas in the universe

4. Nebulas are; • Star nurseries • Star graveyards

5. Measurement of distance in space • Light – year – distance that travels in one year • 287,000m/sec – speed of light • 1 ltyr = 6 trillion miles • Proxima Centauri – nearest star other than sun • 4.3 light years

6. Measurement of distance in space • Parallax – the apparent shift in the position of an object when viewed from two different positions • Determined by observing a star at two different points in its orbit around sun. • Star’s position appears to change in relationship to the background star.

7. What are stars ? • Stars – massive balls of gases • Held together by gravity • rotating • Color of stars – • Temperature • Red – coolest • Blue - White – hottest • Composition of stars • Spectrum – • Spectroscope acts as a prism

8. A spectroscope helps us find out what stars are made of. It disperses, or separates, white light from a star into a very wide spectrum of colors — much wider than a normal prism does. When spread very wide, black lines appear in the spectrum.

9. Spectrum – from star tells astronomer: • Temperature • Composition • Show absorbed elements(black lines) • Each element has unique pattern of black lines • Like a fingerprint each pattern denotes elements that compose the star.

10. Luminosity – how much radiation a star is emitting.

11. Absolute magnitude – amt. of light produced by a star Apparent magnitude – measure of amt of light received by the earth affected by: 1. size of star 2. temperature of star 3. distance of star • A first magnitude star is very bright, • a sixth magnitude star is at the limit of normal vision.

12. HR Diagram – relationship between temperature, color and size • Based on this evidence, we conclude • Stars spend most of their lives as main sequence stars. • During its lifetime, the surface temperature and luminosity stays pretty much constant. • The star's mass determines what the temperature and luminosity is during the star's main sequence lifetime. • More mass -> hotter. • More mass -> more luminous. • Also, more mass -> bigger.

13. Which named star on the H-R Chart has the greatest absolute magnitude? • Rigel • What is this star’s temperature? • 15,000 K • Red giants have the same color and temperature as red dwarfs. How do these star types differ from one another? • Red giants more massive than red dwarfs • What is the range of absolute magnitude for yellow giants on the diagram? • -1 to -4

14. Antares is a red giant. Is this star hot or cool? Explain. cool; red shows cooler temps from an expected surface area. What is the absolute magnitude of the sun? +5 What conditions do the H-R chart show between stars? absoulte magnitude, temperature, size

16. Where on the H-R chart do the following stars fall? • Star Absolute mag Temp • A +10 10,000 K • B -2 3,500 K • C +3 7, 000 K • D -9 6,000 K • Which star is a giant? B Which star is a dwarf A Which star is a supergiant? D Which star is like the sun? C

17. Main sequence stars • Everyday ordinary stars • Our sun – Sol • Energy – fuses H into He

18. Red giants • H is depleted • Core contracts and temps rise • Outer atmosphere expands and cools • Core begins to change He into C

19. White dwarf • Uses up H and He • Core implodes on self • Gets very hot and explodes gaseous atmosphere • Core very denseand very hot

20. Neutron star • So dense 1tsp weighs 600 million metric tons • Some become pulsars

21. Black hole A Black Hole is a region of space where the gravitational force is so strong that not even light can escape from it.

23. Sol

24. Sun’s layers

25. Sol our sun • Photosphere – surface of sun • Light given off • Temps. 6.000K • Granulation – due to rising of energy onto surface

26. Chromosphere– sun’s atmosphere

27. Corona – largest layer of sun’s atmosphere - temps 2million K - gives off solar wind

28. Core – interior of sun where fusion takes place • Radiation zone – interior where radiation moves through • Convection zone – energy moves to photosphere in a swirling motion making granules.

29. Surface features of sun • Sunspots – cooler darker areas on sun • Rotate around sun • Equator 25days • Pole 35 days • Occur in pairs of opposite charges • Caused by magnetic forces from sun’s rotation

30. Sunspot cycles – come in cycles of 11 years. • High part of cycle – produces greater solar wind • Interfere with communication satellites and radio transmissions • Cause auroras

32. Prominence • Huge arching columns of gas which shoot out and are drawn back to the sun’s surface.

33. CME – coronal mass ejection

34. Solar wind • The solar wind streams off of the Sun in all directions at speeds of about 1 million miles per hour. • Two to three days to travel. • The source of the solar wind is the Sun's hot corona. • The temperature of the corona is so high that the Sun's gravity cannot hold on to it. • Ions from sun • Interferes with communication satellites.

35. Solar flares – eruptions from sunspots.

36. 4 hydrogen atoms are combined to form one helium atom and energy.