An Introduction to Astronomy Part XI: The Birth and Death of Stars. Lambert E. Murray, Ph.D. Professor of Physics. Interstellar Gas and Dust. In the late 1700’s Henry Herschell discovered “holes in the heavens” where there appeared to be fewer stars than normal.
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Lambert E. Murray, Ph.D.
Professor of Physics
Barnard 86 is a good example of one of Herschell’s “holes in the heavens”.
More Dark Nebula
H II region of the Swan in visible wavelengths
Same region in infrared wavelengths.
Notice the large number of “cool” stars, or protostars, on the right-hand-side. These are visible in the infrared because that wavelength can penetrate the dust and gas.
Notice that this model gives results similar to
the mass-luminosity data plot.
Note that the more massive, luminous stars in the cluster (at the upper left end) have already reached the main sequence, while the less massive protostars (at the lower end) have not yet joined the main sequence.
Core helium burning begins where the evolutionary tracks make a sharp downward turn in the red giant region of the diagram.
The turn-off point for each cluster gives us an estimate of the age of each star cluster. Notice the “gap” in the central part of this diagram.
Expansion upon hydrogen burn-out.
Expansion upon helium burn-out.
The shapes of the planetary nebula are quite varied, depending upon the magnetic fields associated with the star and upon previous nebula surrounding the star.
But how can it pulse so rapidly?