Looking Up: Stars are shining under your feet
The entire night sky before you- what a wonderful thought. Yet, this will never be unless you are an astronaut. An entire planet blocks half the sky. Ever wonder what shines under our feet, on the other side of this planet we call our home?
There was a cartoon one time about a young boy in a department store asking his mother about the escalator: 'What happens when the basement fills up with steps?'
Most realize that when the stars set in the west, they don’t just collect- or may be that is where the Sun comes from? All the stars of the night set in the west and pile up and make a big ball of light for the other side of the world where it’s daytime. Not exactly!
The Earth beneath our feet hides stars we see at night only temporarily, as we spin around daily and night returns. A section of the sky below our feet, however, never rises in the east and is locked from our view. This is the far southern sky, observable only as we travel south down around the globe. As we do, the northern sky behind us descends, and once we reach the equator, the famous North Star is just about right on the horizon. Any further south, the North Star is not seen at all.
The full sky- surrounding our planet- is referred to as the 'Celestial Sphere.' It took thousands of years for mankind to discern that the stars are not actually fixed points of light on a literal sphere, in which our world was in the center. It appears to be that way, however, just as at first glance our world seems to be flat.
That entire sphere looks like it is revolving around a point in the north, the 'North Celestial Pole,' where the North Star (Polaris) happens to be very close by. This point is where the Earth’s axis of rotation points. At any given latitude, such as where I live at 42 degrees North, the North Celestial pole is that many degrees off the north horizon. At the North Pole, the North Celestial Pole is straight up, or 90 degrees from the horizon. An entire region of the sky never sets below the horizon- within that many degrees. As seen from where I live, for instance, all the stars within 42 degrees of the North Celestial Pole – including those of the Big Dipper- constantly miss the flat horizon.
The stars we NEVER see from any given latitude are found within the exact opposite portion of sky, with the same amount of degrees from the opposite pole- in this case, the South Celestial Pole.
Only from a flat area on the equator would you be able to see the entire Celestial Sphere, at one time or another.
Once Galileo introduced the telescope to astronomy in 1609, scientists were eager to study the skies beneath their feet. One of the first astronomers to take a telescope south of the equator was Edmond Halley, who sailed in November 1676 to the south Atlantic island of St. Helena. Here, Halley measured positions of 341 southern stars. Charting was greatly expanded by French astronomer Nicolas Louis de Lacaille in 1751, who catalogued 10,035 southern stars. Fixing southern stars charts became a priority, as celestial maps from below the equator had become chaotic, with assorted proposals for new constellations, which overlapped other claims.
Just from examining southern hemisphere star charts, it is easy to see one’s early views of the sky would be confusing. While the stars of course would still rise in the east and set in the west. The sky would have seemed to have partly 'turned over.' The familiar North Circumpolar stars would be gone. In the north, stars would appear to pass from right to left, as they go east to west. The orientation of constellations would be so strange you would not easily recognize them at first. Orion, for instance, would not be in the south in February, but would be in the north- upside down!
Having learned all the constellations you could up north, your first visit to the south would bring you to virgin territory, looking south. The South Circumpolar stars would await your examination. Among them would be Crux the Southern Cross and Centaurus the centaur with its brightest star Alpha Centauri. Other highlights would be the brilliant southern portion of the Milky Way Band, and the Large and Small Magellanic Clouds, satellite galaxies of the Milky Way which are easily visible to unaided eyes on a dark night.
You will note that there is no obvious 'South Star' like our North Star. The brightest star close to the South Celestial Pole, about which the sky seems to revolve, is barely visible to unaided eyes, Sigma Octantis.
New Moon is on March 17, First Quarter Moon on March 24. From 'Down Under,' by the way, the Man in the Moon looks like he’s standing on his head!
Did you know, the soles of your shoes, and soles of shoes on a person on the exact other side of the world, are facing each other? And yet, as you ponder the heavens, both of you...
Keep looking up!
— Peter Becker is Managing Editor at The News Eagle in Hawley, PA. Notes are welcome at firstname.lastname@example.org. Please mention in what newspaper or web site you read this column.