FirstLight Astronomy Club

33°29.6'N / 117°06.8'W / 1190 ft.

The Seven Sisters

Every year at this time, and throughout the winter months, there are some places in the sky that draw our attention like a flame lures moths. One attraction, of course, is the mighty constellation of Orion. Another might be Sirius, that intensely bright star to the east of him. But another inevitable eye-catcher is that little group of stars just to the "right" of Orion, the little cluster called the Pleiades.

Known to most people groups for millennia by many names, our name - the Pleiades - comes from the Greek myths about Atlas and his seven daughters. Hence, our alternate epithet for the cluster, The Seven Sisters.

It takes little imagination to see why, in astronomy, the Pleiades are called a "star cluster." But star cluster in astroland, specifically an "open" cluster like the Pleiades, implies more. It tells us that the stars there were born and raised at essentially the same time and place. The sisters in this family started forming about 100 million years ago.

And there are far more than the half dozen or so we can see with the naked eye, or even the dozens we can see through binoculars. There are over a thousand stars there, all traveling through the galaxy together like a flock of seagulls.

One particular bit of space trivia allows the Sisters to appear even more beautiful in photographic images taken of the area. At the moment they are traveling through a galactic cloud of dust and gas. When a star has a cloud around it, its light can be deflected in strange ways.

A star gives off all kinds of wavelengths, the whole rainbow of colors, just like our sun. But when that light passes through very small, microscopic bits of dust, the blue end of the spectrum gets scattered about quite well. Some of those scattered blue photons get thrown in our direction. So, the Pleiades looks like it's swimming through a veil of blue light. Coincidentally, this same effect is why our skies are blue; many of the blue photons of our sun's light get scattered in our atmosphere and - voilà! - blue skies.

One more thing about the Sisters: They are not the Little Dipper. The Little Dipper is an asterism over in Ursa Minor which includes the pole star, Polaris, aka the North Star.

Regardless of what you want to call it, take time this winter to grab a pair of binoculars and focus on the Pleiades, and find images online if you can. The Sisters are a sparkling bit of cosmic beauty.

Giving Thanks

It's Thanksgiving time again. But with unemployment what it is, the economy not quite where we all hoped it might be, and all of us cutting corners, it might be a good idea this year to focus on the everyday things, in the heavens and on earth, for which we should be thankful. Let's take a look at some of these gifts as a friendly, gentle reminder that there really is a lot to be grateful for.

The air we breathe on this planet every moment of our life could not be a better mix. Most of it is composed of the almost inert gas, nitrogen. Only about 20% of it is life-giving oxygen, which is exactly how much we need for a beautiful life on this orb. Much more and any fires on the planet flame out of control in a heartbeat, any less and complex life like our own slows or stops.

There is just enough carbon dioxide - less than a percent - to keep the plants alive and yet still act as a warm blanket on the planet. And the amount of water vapor is just enough to give us our miraculous water cycle. It's not too much so as too heat us all up since water vapor is a greenhouse gas like carbon dioxide, nor is it so paltry as to parch the planet into a desert wasteland.

Our perfect surface is such a collection of wonders it would take a book to write of all its amazing characteristics. Suffice it to say now that our continents, seas, plate tectonics, mountains, volcanoes, quantity of land and oceans - everything under our feet - are all made to order for a pleasant time on this rocky planet. There is not a better combination of air, sea, and land that we know of. And we have it! Next time you look around at the beauty of nature you can bet it is probably designed to perfection and could not be otherwise.

But don't stop at our planet for things to be thankful for. Above our heads are the sun and moon. Our sun, that great giver of heat and light, is not your average star. Most stars, by far, are smaller, less energetic wimpy stars not well-suited to provide for a planet like ours. Many stars are bigger and spew out far more lethal doses of radiation than our star could dream of.

The moon, our own solitary satellite, keeps our planet balanced on its axis and holds the tides in perfect check. Moreover, both the sun and moon are at the just-right distances to do their work to perfection.

These are just a few of the hundreds of everyday things around us that we have been genuinely blessed with, but which we often take for granted. And these glorious stalwarts are above and beyond any trials that our present state of things can throw us. Be thankful!

Invisible Ring

Recently a new, monstrously big ring was found around Saturn. That was big news in itself. But it raised a legitimate follow-up question: How could astronomers have missed it all these years? Are they blind? Well, yes, in a way they are.

We've known about those other, more famous rings around Saturn ever since Galileo and subsequent astronomers trained their telescopes towards our sixth planet. Even a cheap department store telescope can make out those beauties. But we were all using scopes that capture and focus photons of visible light. Those are the only photons we can detect with our eyes. There are many - I mean many - more kinds of photons out there.

We have all at least heard about gamma rays, X-rays, ultraviolet, infrared, and radio waves. They, too, are all composed of photons, the same tiny bundles of energy that make up visible light. But whereas our eyes have been designed to react to the photons of visible light, we are literally blind to all the others.

For the record, gamma, X-rays, and ultraviolet from space pack more energy than the visible light we receive and they are almost all stopped by our savior of an atmosphere. On the other hand, infrared and radio waves are all wimps as far as energy is concerned. The atmosphere stops almost but not all of those photons. All of the visible wavelengths, however, can make it through.

In order to "see" photons that do not make it through the atmosphere we have to send special telescopes above the atmosphere, into orbit. There the full spectrum of photons can be seen if our instruments, our "eyes," are properly designed to pick them up. That's why we have X-ray and ultraviolet and infrared telescopes up there now - to complete the full picture of what is going on out there.

I'll bet you can guess why we could not see the new giant ring until now. It is because we literally cannot see it from here. The Saturnian rings we all know and love are made of big chunks of ice and they reflect the sun's visible light magnificently. But this new mega-ring is made of a thin wisp of tiny dust particles. They only give off just the tiniest amount of infrared radiation.

Astronomers, for reasons beyond the scope of this article, had suspected the big ring to be there. But they didn't find it until they made visible that which was invisible by training the infrared space telescope, Spitzer, on where they thought the ring should be. And behold, it was there.

Modern-day technology is making it possible for us to discover the deeper beauties of the cosmos previously unseen. This is a new Golden Age of astronomy.
Temecula Valley High School / Temecula, CA · Some images © Gemini Observatory/AURA Contact Me