Using the Sky

Our Link to the Celestial Realm

I just got back from a lecture gig on board a study-cruise program in the Mediterranean. We visited Italy, Greece, Turkey, and the Greek Islands, and the theme of the educational program was “Gods and Heroes”.  My job was to talk to people about the ancient connections to the sky that the Greeks and Romans (in particular) had in ancient times. In contrast to today, when we get all our time information from gadgets like watches and cell phones, our calendars hang on the wall, and we don’t even think about whether it’s night or day, ancient people had no mechanical means of understanding the sky.  They used it, but they didn’t really get what it was they were seeing. At least, not in the scientific sense that we do today.

Yes, they were incredible observationalists and their charts were the basis of astrology, which was the predecessor to the science of astronomy.  But, the ancients only really had what they could see with the naked eye. They had a one-dimensional view of the sky — things appeared in it, sometimes they seemed to move against the backdrop of stars, and there was no scientifically rigorous study of the celestial realm.  People weren’t stupid back then — they just had different priorities (like survival) and belief systems (“things in the sky must be gods and goddesses”).

A Greek sundial dating back to 3 BC. Used by permission; link: http://en.wikipedia.org/wiki/File:SunDialAiKhanoum.jpg

So, the Sun, for example, became more than a bright shiny thing in the sky. People imagined that it had a purpose, it had a reason for being there — and, being humans — they endowed it with human and superhuman powers.  They created a god/goddess in their own image and then made it bigger, mightier, and mysterious.

Of course, we all have a link to the Sun today — it’s what helped us devise the units of day and night.  It provides warmth and stimulates life processes.  So, it’s no surprise that such a powerful influence on the planet would have been an object of worship among ancient people.  Heck, some people worship the Sun today — I often refer to them as the “SPF 50 Cult”.

It didn’t take long for people to figure out that the Sun could be used as a timekeeper, a way to mark the passage of days. Along with the Moon’s cycle of phases — it became the basis for what eventually have become the various world calendars. The ancients used the sky as a tool to capture time, to define their daily lives, and as a place for their gods/goddesses/heroes/villains.  In a sense, it provided not just orderliness, but entertainment and a sense of cultural unity (“We all believe in Ra, the Sun God, therefore we are people of the Sun God”.)

Today, of course, we know the Sun is a star. There’s nothing mysterious about it. There are certainly parts of its processes that scientists are still working to understand and explain — that’s the nature of the science of solar physics. But, as a former deity — well,  the Sun’s WAY bigger than that. It’s more real to us as a star and we have a very good idea of how stars work (mechanically and astrophysically).  And, we know where it lies in the hierarchy of stars that make up the stellar city we live in — the Milky Way.

Still, it was a lot of fun to go back to the “ancient world” for ten days and look at things like the Sun and Moon and planets through the eyes of those who lived in those times. The work they did in charting the sky, the apparent motions of the Sun, Moon, planets, and stars, were the cartographica basis for the sky charts we use today. And, if certain “natural philosophers” among the ancient peoples around the world hadn’t looked up and wondered “What is that we see?” about sky objects, we wouldn’t have the science of astronomy to help us understand the universe in the straightforward, rigorous way we do today.

Planet or Not…

Pluto Has Moons

The Pluto system. Courtesy STScI/NASA/ESA

That distant world called Pluto has surprised astronomers again, yielding up yet another moon.  Pluto’s largest moon is Charon and was discovered in 1978.  Two more — Nix and Hydra — were found in 2005. The new one, called P4 (for now), is quite small, somewhere between 13 to 34 kilometers across, and small enough that it was probably missed in earlier images of the system taken by Hubble Space Telescope. This latest HST image was taken as part of  a search for ring material around the distant dwarf planet, in support of the New Horizons mission, which is en route to Pluto.

So, how would Pluto, itself a small world like many others in the outer solar system, get moons?  The current thinking is that a collision between Pluto and another world early in the history of the solar system would have flung material out into orbit. Eventually, the pieces and parts would have coalesced back together, forming the family of moons we see today.

When I read this story, the first things I wondered were “Why search for rings around Pluto?”  and “Where would the material for Plutonian ringlets come from?”  A long-ago collision would have provided material for rings, but by now, that material would have been cleared away or coalesced into moons, such as Nix, Hydra, P4 (and maybe even Charon?).  To maintain a ring system, you need a constant source of material being tossed out to space.  At Pluto, that source may well be material “chipped away” from the icy surface by the impacts of tiny micrometeoroids.  That would provide chips of ice to form a faint, thin ring. If it exists, it hasn’t yet been detected. But, HST would be the best instrument we have at this time to find the ring.  Once New Horizons gets there, it may well “see” the ring, if it exists.

I like it when HST finds things like this. It’s a continuing reminder that the venerable telescope has a lot of life in it yet; and will keep surprising astronomers with new finds.