Astronomy Chapter 20 question and answers 2022

In a photo like the Hubble eXtreme Deep Field (Figure 20.1 in your text), we see galaxies in many different stages of their lives. In general, which galaxies are seen in the earliest (youngest) stages of their lives? the galaxies that are farthest away Which of the following statements about types of galaxies is not true? Elliptical galaxies are bluer and contain more dust than spiral galaxies. 00:27 01:33 The most basic difference between elliptical galaxies and spiral galaxies is that ______. elliptical galaxies lack anything resembling the disk of a spiral galaxy Hubble's galaxy classification diagram (the "tuning fork") ______. relates galaxies according to their shapes but not according to any evolutionary status. Although it is highly unlikely to happen, suppose that we suddenly discovered that all these years we'd been wrong about the distance from Earth to the Sun, and it is actually 10% greater than we'd thought. How would that affect our estimate of the distance to the Andromeda Galaxy? It would mean the distance to the Andromeda Galaxy is also 10% greater than we thought. Suppose we observe a Cepheid variable in a distant galaxy. The Cepheid brightens and dims with a regular period of about 10 days. What can we learn from this observation? We can learn the distance to the galaxy. In 1924, Edwin Hubble proved that the Andromeda Galaxy lay far beyond the bounds of the Milky Way, thus putting to rest the idea that it might have been a cloud within our own galaxy. How was he able to prove this? By observing individual Cepheid variable stars in Andromeda and applying the period-luminosity relation. Assume that Hubble's constant is 22 kilometers per second per million light-years. How fast would we expect a galaxy 100 million light-years away to be moving? (Assume the motion is only as a result of Hubble's law.) away from us at 2,200 km/s Does Hubble's law work well for galaxies in the Local Group? Why or why not? No, because galaxies in the Local Group are gravitationally bound together. Why are white dwarf supernovae more useful than massive star supernovae for measuring cosmic distances? White dwarf supernovae all have roughly the same true peak luminosity, whereas massive supernovae come in a wide range of peak luminosities. Suppose an elliptical galaxy is so far away that we cannot see even its brightest stars individually. Which of the following techniques might allow us to measure its distance? We could use a white dwarf supernova as a standard candle. You observe the peak brightnesses of two white dwarf supernovae. Supernova A is only 1/4 as bright as Supernova B. What can you say about their relative distances? Supernova A is twice as far away as Supernova B.