21. What is the Hertzsprung-Russell diagram? Why is it useful? Describe the diff
ID: 3162988 • Letter: 2
Question
21. What is the Hertzsprung-Russell diagram? Why is it useful? Describe the different kinds of stars and their particular properties using the H-R diagram.
22. How do stars form? What are their masses? How does the life of a massive star
23. What causes a supernova? What are some of the objects left behind afterwards? Use the “guest star” of 1054 AD as an example.
24. Stars end their lives ending up as white dwarfs, neutron stars or black holes. What determines their different fates and why? (Why don’t they all keep collapsing to a point and become black holes?)
25. What is the “Principle of Relativity?” Why does this force us to reevaluate our notion of time?
26. What are the different types of galaxies seen in our universe? Briefly describe our Milky Way galaxy.
27. How do we know the Universe is expanding? How did the discovery of an accelerating universe change our view of what it contains? What will be its ultimate fate and why?
28. Are there other universes? What does that even mean? How might the possibility of myriads of other universes explain why our universe is exactly like it is, perfect for life like ours!
Explanation / Answer
The Hertzsprung–Russell diagram, abbreviated H–R diagram or HRD, is a scatter plot of stars showing the relationship between the stars' absolute magnitudes or luminosities versus their stellar classifications or effective temperatures. More simply, it plots each star on a graph measuring the star's brightness against its temperature (color).
It is useful for represents a major step towards an understanding of stellar evolution or "the way in which stars undergo sequences of dynamic and radical changes over time".
group A. It shows a general trend from cool, dim stars in the lower right corner up to hot, extremely bright stars in the top left corner. Our Sun is one such example. Others include Cen, Altair, Sirius, Achernar and Barnard's Star.
group B are mostly 6,000 K or cooler yet more luminous than main sequence stars of the same temperature.These stars are referred to as giants. Examples include Aldebaran and Mira.
group C are even more luminous than the giants. These are the supergiants, the largest of stars with extremely high luminosities.
group D. From their position on the H-R diagram we see that they are very hot yet very dim. Although they emit large amounts of energy per square metre they have low luminosity which implies that they must therefore be very small.Sirius B and Procyon B are examples.
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