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Moab UT (at City Hall)
38O34’ N Latitude
109O33’ W Longitude
4048 ft - 1234 m

Cepheus: A House Fit for a King
David Prosper

Sometimes constellations look like their namesake, and sometimes these starry patterns look like something else entirely. For example, the constellation Cepheus is in the mid-northern latitudes and visible all night long as it swings around the northern celestial pole. The stars of this constellation represent Cepheus, the King of Ethiopia, sitting on his throne. However, many stargazers see a house with a pointed roof instead! Astronomers have yet another association with this northern constellation; inside its borders lies the namesake of one of the most important types of stars in modern astronomy.

The most famous, and certainly most notable object in Cepheus, is the star Delta Cephei. John Goodricke, who began observations of the star in October 1784, discovered its variable nature. More than a century later, Henrietta Leavitt discovered that variable stars, represented by Delta Cephei, possessed consistent relationships between their luminosity (total amount of light emitted), and their pulsation period (the length of time in which the star goes through a cycle of where it dims and then brightens). Once the period for a Cepheid Variable (or Cepheid) is known, its luminosity can be calculated by using the scale originally developed by Henrietta Leavitt or “Leavitt’s Law.” The Cepheid’s distance can then be estimated with a great deal of precision.

This revolutionary discovery unlocked a key to measuring vast distances across the cosmos, and in 1924 observations of Cepheids by Edwin Hubble in what was then called the Andromeda Nebula proved that this “nebula” was actually a galaxy outside of our own Milky Way! You may now know this object as the “Andromeda Galaxy” or M31. Further observations of Cepheids in other galaxies gave rise to another astounding discovery: our universe is not static but expanding!

Because of their importance in measuring cosmic distances, astronomers continue to study the nature of Cepheids. These studies, along with others, help to further refine the accuracy of distance measurements derived from observations of Cepheids. What will further observations of Delta Cephei and other Cepheids reveal about our universe? Follow NASA’s latest observations of stars and galaxies across our universe at

(The time of sunrise and sunset assumes a flat horizon. Actual time may vary depending upon the landscape.)


Nov 7 - Full Moon at 9:08pm
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Nov 23 - New Moon at 3:16am
Nov 29 - First Quarter at 6:29am

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