Your estimate for the average distance between stars is reasonable. Your estimate for the average distance between galaxies is…
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How Repeatable is the Position of a Star in the Sky From One Year to the Next?
Since the Earth completes one orbit around the Sun every year, it returns to the same position after 365.256…
What Causes Nebulae to Form?
There are actually several types of nebulae which are created by a variety of processes, including those associated with…
What Process Gives the Helix Nebula its Apparent Pole-On-View Structure?
You are right in that the properties of the ejected material from the star and the fact that the…
Can You Tell the Difference Between Stars by Looking at Their Spectra?
We can tell the difference between different types of stars by looking at their spectra. In fact, spectral classification…
How Well is the Distance to Gl-581 Known?
Gl-581 is an M3 dwarf star whose distance is derived from its apparent parallactic motion of p = 159.52+-2.27…