Category: 8. Analyzing Starlight

Learning Objectives By the end of this section, you will be able to: Analyzing the spectrum of a star can teach us all kinds of things in addition to its temperature. We can measure its detailed chemical composition as well as the pressure in its atmosphere. From the pressure, we get clues about its size.…

Learning Objectives By the end of this section, you will be able to: Measuring colors is only one way of analyzing starlight. Another way is to use a spectrograph to spread out the light into a spectrum (see the Radiation and Spectra and the Astronomical Instruments chapters). In 1814, the German physicist Joseph Fraunhofer observed that the spectrum of the Sun…

Learning Objectives By the end of this section, you will be able to: Look at the beautiful picture of the stars in the Sagittarius Star Cloud shown in Figure 17.3. The stars show a multitude of colors, including red, orange, yellow, white, and blue. As we have seen, stars are not all the same color because…

Learning Objectives By the end of this section, you will be able to: Luminosity Perhaps the most important characteristic of a star is its luminosity—the total amount of energy at all wavelengths that it emits per second. Earlier, we saw that the Sun puts out a tremendous amount of energy every second. (And there are…

Everything we know about stars—how they are born, what they are made of, how far away they are, how long they live, and how they will die—we learn by decoding the messages contained in the light and radiation that reaches Earth. What questions should we ask, and how do we find the answers? We can…