Lecture Summary 9

Lecture Summary 9 - Lecture Summary (11/2 & 11/4) The...

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The cause of auroras was explained and the connection to why they are more prominent near the poles was linked to Earth’s magnetic field. Understanding the stars has been greatly augmented with the development of large telescopes and instruments that accurately measure and analyze starlight. In particular, stellar spectra provide useful information. From the spectrum a star’s composition and temperature can be determined. (See the lecture handouts for descriptions of how stellar properties are determined.) Astronomers rely on the magnitude system to measure the brightness of stars. The smaller a magnitude is, the brighter the star. In order to understand the stars, astronomers must determine accurate stellar distances. Stellar (heliocentric) parallax was used for determining distances to stars in Lab # 6. But the heliocentric parallax method breaks down beyond 100 parsecs (300 LY). In space, telescopes have increased our ability to use the stellar parallax method out to nearly 1000 parsecs. The presence of spectral features and dominance of certain lines is closely linked to surface temperature and conditions in the stellar atmosphere. Astronomers have based a classification system for stars based on the spectrum. Spectroscopic parallax using the distance
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Lecture Summary 9 - Lecture Summary (11/2 & 11/4) The...

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