THE SOUTHWORTH PLANETARIUM
207-780-4249 www.usm.maine.edu/planet
70 Falmouth Street Portland, Maine 04103
43.6667° N 70.2667° W
Altitude: 10 feet below sea level
Founded January 1970
Julian date: 2458744.5
2019-2020: XIII
We put the tagline at the end of today's DA
THE DAILY ASTRONOMER
Thursday, September 19, 2019
The Underground Stars
Today we return to Pandora's Jar, the vessel in which we store the astronomy questions that we are determined to answer. Granted, a couple people seem to suffer through an interminable wait to have their questions answered because we consider the drafts we write in response to be horribly inadequate. (Yes, I know, most of our posts are like that!) So, to these patients subscribers we offer our gratitude and sincerest apologies. We have NOT forgotten about you.
Today's question pertains to the stars: not those above our heads, but those below our feet.
"Are there more stars below the ground or in the sky?"
-N.E, Naples
Let's imagine that we transformed the planet into a transparent glass sphere. Let's further pretend that we snapped off that troublesome Sun so as to allow us to see outer space in all directions. We would notice starry black skies in every direction, almost as if we were "floating" in a boundless starfield. In fact, our planet IS floating in a boundless starfield. Or. more correctly, our planet is moving around a star that is traveling through the spiral arms of a galaxy containing billions of stars. The image below shows the closest stars to the Sun. Notice that they are located in all directions.
Stars beneath our feet: We often don't think of stars "floating" in space, as we're accustomed to observing them adorning our sky. In fact, all the stars we see in the sky, including the Sun, are moving through the Milky Way Galaxy. The image above shows the positions of the closest stars to the Sun. There are as many stars "below" Earth as "above" it.
It is impossible to determine if more stars exist below us than above us. However, we do know that the Sun is moving along an undulating curve while it travels around the galaxy so that the solar system is alternately "above" and "below" the galactic plane. We can think of the galaxy as being a disc about 1000 light years in thickness and 100,000 light years in diameter. Astronomers are not exactly certain as to our position relative to this plane, but believe that our solar system is 76 - 110 light years above it. So, by this measure, there are more of the galaxy's stars beneath our feet than above our heads.
However, the Universe harbors more than 200 billion galaxies scattered in all directions. If we decided to conduct a thorough census of all the stars, we would find -193,450 years later- that there are just as many galaxies in all directions and therefore we wouldn't see more stars or galaxies in any particular direction. This planet lends us the comforting sensation of standing on a steady ground, even though we are all literally moving through an unbounded void extending in every direction for billions of light years.
Spider webs are not webs.
They are the life paths of myriad luminous micro-sprites who are confined to the regions we perceive as the webbings, just as we are confined to the streets, buildings and pathways of the world. They lead very short lives before they transform into spores that the wind conveys to alternate universes that we see as other spider webs. They move so quickly during their lives that their light seems to create a solid pattern, just as fan blades can produce the illusion of either a solid disc or no disc at all. When you stare at a spider web, even if it is just for a moment, you're observing a scintilimon -the collective noun for micro-sprites numbering greater than 625, which is the square of 25, the base unit of their numbering system derived, likely, from the 25 photon emitting globules that line the circumference of their heads- of luminous micro sprites living out their entire lives in what to us is a flash, but to them is a protracted life span in which they are as beset with travails as we are. If you're staring at a spider web, the micro sprites are perceiving you as a constellation: immortal and unchanging. They see you as the one immutable aspect of their lives so that the micro sprites who first beheld you in their infancy while awakening to the strange cosmos will in their old age (ten seconds later for you) be comforted by your presence as they prepare to lapse off into what for them is the undiscovered country but, to us, is the glistening spider web along a nearby tree.
Photo by Susan C.H. Siu
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