Daniel Pope

Earth’s location in our Solar System is often referred to as the “Goldilocks” position – not too cold, not too hot, but just right.

It is understandable that when our ancient ancestors started to study the night sky they assumed that our Earth was the stationary center of all there was. Kepler’s Sun centered system with Earth and the other planets traveling elliptical orbits about our Sun was not widely accepted until the middle of the 1600s. Earth was no longer the center – so – what was our location? Kepler had shown that the Sun was the new center and that Earth was the third planet from our Sun. This was a huge leap and required a big change in how people visualized Earth and its place in our Cosmos. There were those who began to wonder whether or not our Sun was the ‘true’ center of our Cosmos. Where were we – really?

Based on observational data in the early 1900s Harlow Shapley made estimates of distances to and distributions of stars in our sky. He proposed that our Sun was not at the center of the stars we see in our sky. He calculated that our Solar System is about 25,000 to 30,000 light years from the center of our Milky Way Galaxy. We are far from being the center of our Milky Way Galaxy. Others proposed that what appeared to be clouds of gas were in fact distant galaxies similar to our Milky Way. This was confirmed by Edwin Hubble’s work in the 1920s. It was quickly realized that our Milky Way Galaxy was not the center of the Cosmos. Since that time the idea of finding ‘the’ center has been abandoned in favor of other models for thinking about the shape of our Cosmos.

So, we are not at the center but with just our naked eye we can start to get an idea of our orientation in our Cosmos.

When we look at the North Star (North Celestial Pole) we are looking out the top of our Earth or perpendicular to Earth’s equator. When we look at the North Ecliptic Pole we are looking out the top of our Solar System or perpendicular to the plane of our Solar System. When we look at the North Galactic Pole we are looking out the top of our Milky Way Galaxy or perpendicular to the plane or main disk of our Milky Way Galaxy.

When we look at the North Galactic Pole we see the faint and fuzzy constellation Coma Berenices (KOH-mah bear-eh-NEE-seez). Coma Berenices (Berenice’s Hair) did not exist prior to 240 BC. Unlike so many stories about the constellations this one involves real people who really lived. From 246 BC until 221 BC Ptolemy III and his wife, Berenice II, were the King and Queen of Egypt. Egypt was at the height of its influence, perhaps best exemplified by its world famous Library in Alexandria. The king found it necessary to lead his army off to war. Berenice was naturally concerned about his health and well-being. She pledged that if he returned successful then she would cut off her long beautiful hair and place it in the temple of Venus. The king was gone for a few years but did return triumphant and in good health. Berenice kept her promise by placing her hair in the temple, but it disappeared from the there almost immediately. Ptolemy and Berenice were quite angry and we can assume the temple guards and their superiors were in serious trouble. The court astronomer, Conon, devised an explanation. He took the King and Queen to look at the night sky and explained that the goddess, Venus, was so moved by Berenice’s gesture and beautiful hair that she placed the hair in the night sky for all the world to see. Conon pointed to what had been the fuzzy tuft at the end of the tail of Leo the Lion. Thus, in 240 BC, Leo lost the fuzzy end of his tail. It takes some imagination to see these faint stars as hair, especially in our less than dark skies but it is a nice story.

When we look toward Coma Berenices we are looking away from the dust and clouds of gas that obscure our view in the main disk of our Milky Way. When the Hubble Space Telescope was aimed toward Coma Berenices and the North Galactic Pole it took a picture of perhaps the most dense cluster of galaxies in our Cosmos. There are thousands of galaxies in the comparatively small region of space in this Hubble image.

One name for the full Moon in April is the Planter’s Moon. Next week we will take a last look at the winter constellations as we watch them slip behind us and toward our western horizon.

Clear skies