Astronomy 100. Unit 8 - Differentiating between stars and other key terms. PDF

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Differentiating between stars and other key terms....

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van den Vlekkert 1 Astronomy 100 1. What properties of stars does the spectral type describe? The spectral type of a star determines its color. So, redder main-sequence stars are fainter than bluer main-sequence stars. 2.  What properties of stars are plotted on the H-R diagram? The properties of stars plotted on the H-R diagram show the temperature of stars against their luminosity or the spectral type against their absolute magnitude. 3. Which stars age faster? High mass or low mass? High mass stars age faster than low mass stars. The reason behind this is because high mass stars have a higher temperature and pressure than their low mass counterparts, causing them to run out of fuel faster. 4. What is the difference between luminosity and apparent brightness? Luminosity it’s he rate at which a star radiates energy into space while apparent brightness is the rate at which a star’s radiated energy reaches an observer on Earth. Apparent brightness relies on luminosity and distance. 5. Which luminosity class represents stars that are still fusing hydrogen into helium? Luminosity class V represents main-sequencing stars, which fuse hydrogen into helium in their core. 6. Which star is brighter? Mag +3 or Mag +10? A Mag +3 star is brighter than a Mag +10 star. Although it sounds counterintuitive, when comparing the magnitude of a star, the lower the number, the brighter the object. 7. What are the spectral types in order (from coolest to hottest)? The spectral types go in this order: M, K, G, F, A, B, and O. This goes from red to blue-white.

van den Vlekkert 2 8. What are the three main luminosity classes? The three main luminosity classes are based on Roman numerals ranging from I to V. I - Ib, these represent the super giants. From II to IV, represent giants. While the final one, group V, represents main sequence stars. 9. What are the four main groups on the HR diagram? What is a property of each? The four main groups on the HR diagrams are supergiants, giants, main sequence, and white dwarf. Supergiants have masses from eight to twelve million times that do the Sun upwards and a luminosity from about a thousand to over a million times the Sun. Giant stars have radii between ten and a hundred solar radii and luminosities between ten and thousand times that of the Sun. An interesting property of main sequence stars is that most stars fall in this area and are bigger, hotter, and more luminous than other stars. Finally, white dwarf stars have half the mass of the Sun, yet are only slightly bigger than Earth. 10. Which is the hottest? A.) Star B  B) Star E

C) Star D

11. Which star is larger (C or D)? A.) Star C 12. Star C is _______ star D. B.) the same temperature as 13. Stars C and F share the same B.) Size 14. Which pair of stars have the same luminosity (brightness)? A) C & F 15. Which is brighter?

van den Vlekkert 3 A) B2V 16. Which is brighter? B) G2III 17. Which is larger? B) M3I 18. Define the following terms: Apparent brightness: A measure of the brightness of a star or other astronomical object observed from Earth. Luminosity: An absolute measure of radiated electromagnetic power, the radiant power emitted by a light-emitting object. H-R diagram: A scatter plot of stars showing the relationship between the stars’ absolute magnitudes or luminosities versus their absolute magnitudes or luminosities versus their stellar classifications or effective temperatures. Main sequence: A continuous and distinctive band of stars that appears on plots of stellar color versus brightness. Supergiants: The most massive and luminous stars. Giants: A star with a substantially larger radius and luminosity than a main-sequence star of the same surface temperature. White dwarfs: A stellar core remnant composed mostly of electron-degenerate matter. Black hole: A region of space time where gravity is so strong that nothing, including particles or even electromagnetic radiation, can escape from it. Neutron star: The collapsed core of a massive supergiant, which had a total mass of between ten and twenty five solar masses, possibly more if the star was especially metal-rich.

van den Vlekkert 4 Spectral type: The classification of stars based on their spectral characteristics. Luminosity class: A classification of a star according to its luminosity within a given spectral class....