In Their Own Words

This column includes excerpts from various papers that introduce concepts that will build upon in future issues of the Cosmic Times. The quotes may be a little difficult to understand, as they are taken directly from published papers by the listed authors. Here is a little more on these excerpts and why we have chosen to include them:

• "Periods of 25 Variable Stars in the Small Magellanic Cloud" – Miss Henrietta Leavitt

  Cepheid variables are mentioned briefly in the article titled "Mount Wilson Astronomer Estimates Milky Way Ten Times Bigger Than Thought". Their true significance will be realized in the 1929 issue of the Cosmic Times. Leavitt discovered that the Cepheid variables she looked at in the Small Magellanic Cloud (a companion galaxy to our own) had a remarkable and predictable relationship between their period (the time it took to cycle once from bright to dim back to bright) and their luminosity. This might not be remarkable, except that since they were all part of the Small Magellanic Cloud, they could be considered to be at approximately the same distance. This, in turn, meant that the relationship was intrinsic to the stars and not a trick of the eye. See the 1929 and 1955 issues for more on this relationship and its significance.

• "Spectroscopic Observations of Spiral Nebulae" – V. M. Slipher

  Vesto Slipher discovered, in 1912, that Andromeda, a spiral nebulae (which we now know is another galaxy) had a redshift, meaning that it had a velocity with respect to the Earth. He continued to measure the spectra of other spiral nebulae, and found that they had a net positive velocity. In other words, they had a net velocity away from the Earth.

• "The Relation of the System of Stars to the Spiral Nebulae" – G. F. Paddock

  As mentioned above, astronomers did not know that the spiral nebulae were galaxies separate from our how; however, some astronomers had speculated as much, but the evidence was scant. This research suggests another small piece of evidence in favor of the spiral nebulae as entities outside our galaxy. Slipher had found that the spiral nebulae had an average radial velocity of +400 km/sec. However, no other type of object in our galaxy had a radial velocity of over +50 km/sec. This was a huge discrepancy.