Chapter 24

1. Chapter 24 Studying the Sun

2. Electromagnetic radiation includes gamma rays, X-rays, ultraviolet light, visible light, infrared radiation, microwaves, and radio waves • Electromagnetic Spectrum – the arrangement of electromagnetic radiation according to wavelength

3. The Light Spectrum

4. Spectroscopy – the study of the properties of light that depend on wavelength

5. When the spectrum of a star is studied, the spectral lines act as “fingerprints” • These lines identify the elements present and thus the star’s chemical composition Solar Spectrum

6. Doppler Effect – the apparent change in frequency of electromagnetic or sound waves caused by the relative motions of the source and the observer

7. Red Shift/Blue Shift In astronomy, the Doppler effect is used to determine whether a star or other body in space is moving away from or toward Earth

8. Refracting Telescope – a telescope that uses a lens to bend and concentrate the light from distant objects

9. Reflecting Telescope – a telescope that concentrates light from distant objects by using a concave mirror • Most large optical telescopes are reflectors; light does not pass through a mirror so the glass for a reflecting telescope does not have to be of optical quality

10. Radio Telescope – a telescope designed to make observations in radio wavelengths • A radio telescope focuses the incoming radio waves on an antenna, which absorbs and transmits these waves to an amplifier, just like a radio antenna

11. Space telescopes orbit above Earth’s atmosphere and thus produce clearer images than Earth-based telescopes Hubble Space Telescope

12. Sun Facts • An “Average” Star • Diameter = 109 x Earth • Volume = 1.25 x Earth • Mass = 332,000 x Earth • Density = ¼ x Earth

13. We can divide the sun into four parts: the solar interior; the visible surface, or photosphere; and two atmospheric layers, the chromosphere and corona

14. Photosphere – radiates most of the light we see and can be thought of as the visible “surface” of the sun

15. Chromosphere – A relatively thin layer of hot gases a few km thick above the photosphere

16. Corona – outer most portion of the solar atmosphere, very weak and is visible only when the photosphere is covered • Solar Wind – Streams of protons and electrons that boil from the corona

17. Sunspots – dark regions on the surface of the photosphere, an individual spot contains a black center rimmed by a lighter region • Sunspots appear dark because of their temperature, about 1500 K less than that of the surrounding solar surface

18. Prominences are ionized gases trapped by magnetic fields that extend from regions of intense solar activity

19. Solar Flares – brief outbursts that normally last about an hour and appear as a sudden brightening of the region above a sunspot cluster • During their existence, solar flares release enormous amounts of energy, much of it in the form of ultraviolet, radio, and x-ray radiation

20. Auroras – following solar flares, Earth’s upper atmosphere near the magnetic poles is set alight; also called the northern and southern lights

21. Nuclear Fusion – The process by which the sun produces energy; this nuclear reaction converts four hydrogen nuclei into the nucleus of a helium atom and tremendous energy is released • It is believed that a star our size can exist in its stable state for ~10 Billion years, making our sun middle-aged at ~4.5 Billion years old