Solar Atmospheric Temperature So much energy is flowing through this region and the density is so low that the temperature of these regions is very high. All of this energy causes gas to “boil” off into space, or causes gas to be “pushed” off the surface of the Sun. This gas is called the Solar Wind.

Glass has a higher index of refraction for blue light than for red. Consequentially, blue is refracted more and we see the colors of white visible light dispersed into different directions by a prism. (from wikipedia)

Solar Spectrum in the visible region

Solar Spectrum This absorption spectra tells us what elements are in the Sun’s chromosphere and most likely in the rest of the Sun, except in the core. Likewise, spectra of stars tells us about their contents.

Characterizing Stars

Star Colors vary from red to blue; an example is in Orion.

Many star colors are seen in dense regions near the center of the Milky Way galaxy.

The color of a star is due to its temperature. Blackbody spectra (continuous curve) for some representative objects (brown dwarf, Sun, Rigel) FIGURE 11-4 Temperature and Color (a) This beautiful Hubble Space Telescope image shows the variety of colors of stars. (b) These diagrams show the relationship between the color of a star and its surface temperature. The intensity of light emitted by three stars is plotted against wavelength (compare with Figure 4-2). The range of visible wavelengths is indicated. The location of the peak of a each star’s intensity curve, relative to the visible light band, determines the apparent color of its visible light. The insets show stars of about these surface temperatures. Ultraviolet (uv) extends to 10 nm. See Figure 3-6 for more on wavelengths of the spectrum. (a: Hubble Heritage Team/AURA/STScI/NASA; left inset: Andrea Dupree/Harvard-Smithsonian CFA, Ronald Gilliland/STScI, NASA and ESA; center inset: NSO/AURA/NSF; right inset: Till Credner, Allthesky.com)

Blackbody Curves for some typical star temperatures Only two points are needed to determine the temperature.

Stellar Spectra These are simulated spectra Stellar Spectra These are simulated spectra. Real spectra have lots of fine structure. Simulated elemental spectra: (link)

FIGURE 11-5 The spectra of stars with different surface temperatures. The corresponding spectral types are indicated on the right side of each spectrum. (Note that stars of each spectral type have a range of temperature.) The hydrogen Balmer lines are strongest in stars with surface temperatures of about 10,000 K (called A-type stars). Cooler stars (G- and K-type stars) exhibit numerous atomic lines caused by various elements, indicating temperatures from 4000 to 6000 K. Several of the broad, dark bands in the spectrum of the coolest stars (M-type stars) are caused by titanium oxide (TiO) molecules, which can exist only if the temperature is below about 3500 K. Recall from Section 4-5 that the Roman numeral I after a chemical symbol means that the absorption line is caused by a neutral atom; a numeral II means that the absorption is caused by atoms that have each lost one electron. (R. Bell, University of Maryland, and M. Briley, University of Wisconsin at Oshkosh)