Tuesday, May 29, 2007

Messier Sky

6/3/07 – 6/9/07
by C. Zaitz

It is my opinion that summertime is the very best time for evening sky watching, whether you are a casual looker, an interested observer or a hard-core “Messier object” junkie. I’ve been all three at various times, but summer is the time when we can spend more quality time outside at night, gazing upward, finding your “fix” in the stars. Beyond knowing the constellations, if you really want to get to know the universe, finding Messier objects is a good way to do it. (Messier doesn’t refer to the chaos of the sky, it’s the last name of French astronomer Charles Messi “ay.”)

Monsieur Messier was an observational astronomer at the end of the 18th century who was very interested in finding new comets. This was a popular past time for an astronomer seeking to be immortalized by getting a comet named after him. However, Messier was annoyed with the countless fuzzy clouds in space that were easily confused with fuzzy comets. Messier catalogued over 100 “nebulae,” which were thought to be some sort of cloud within the galaxy. He hoped to save himself and other comet hunters the confusion of wondering if the faint fuzzy was indeed a fame-inducing object, or merely another “cloud.”

The existence of other galaxies beyond the Milky Way was not known until William Herschel and others continued cataloguing the fuzzy objects. The Herschel General Catalogue of Nebulae, listing over 5,000 objects, gave way to the New General Catalogue (NGC) in 1888, which contained nearly 8,000. Soon their true nature became clear- these clouds were not of the Milky Way at all, but each a separate “island universe” like our own. And Messier’s catalogue of galaxies, nebulae and supernovae remnants gave him more fame than any comet would have. Amateur astronomers world-over know of Messier and his wonderful catalogue of deep space objects. The NGC does not immortalize its author, but contains Messier objects as well as many more interesting destinations for the observer with time and telescope on hand.

The summer skies hold many Messier objects, known by their “M” number. Many of them have very pretty nicknames. For example, M57 is the Ring Nebula, M101 is the Pinwheel Galaxy and M104 is the Sombrero Galaxy. Other nick names are not so lovely; such as the Blackeye galaxy (M64), the Crab Nebula (M1), and the Dumbbell Nebula (M27). Cute name or not, one of the most beautiful sights to see in the late spring and summer is M13, the lovely globular cluster of stars in Hercules. A globular cluster is a tightly packed group of older stars. In M13 there are estimated to be over a million stars in a sphere of space about 100 light years across. You can see the Hercules cluster with binoculars, but it truly is best seen through a telescope.

M57, the Ring Nebula in Lyra is also a pretty sight in a telescope. It is the first planetary nebula ever discovered. It looks like an ethereal smoke ring in the black sky, but it is the outer shells of a dying star, suffering the same fate as will our sun, in some 5 billion years.

There are many more such objects within view of a typical amateur telescope, and summer amateur group star parties are the best way to see these sights, and to get to know those folks who can help you discover the universe of Messier deep space objects.

Until next week, my friends, enjoy the view.

Wednesday, May 23, 2007


5/27/07 – 6/2/07
by C. Zaitz

The earth is cooling. It had to. When it formed some 4.6 billion years ago, it was way too hot for any life to form. In fact, it’s taken a lot of time to cool enough for rhinos and beavers and gazelles to be able to roam freely without burning their hooves and paws and giant feet. Much of earth’s history has been spent cooling and changing into the planet we know and love. Unfortunately, earth doesn’t know and love us. It keeps changing, whether or not the life forms occupying its surface can survive it or not. It cares not whether its atmosphere grows thick or thin, whether its waters are pure, or if its movements will disrupt the parasites on its edge.

We know that huge volcanic eruptions and earthquakes can cause widespread destruction. They are caused by the movement of the plates of crust and mantle. Deeper within the earth lies the mechanism for creating an invisible shield, a barrier against the killing radiation from the sun. The earth has a fairly strong magnetic field, created and maintained by the movements of its liquid metallic outer core. The field extends out into space like a giant protective web. We have learned about the nature of our magnetic field from looking at the bottom of the ocean at the mid-Atlantic ridge. As magma flows out from the crack between two separating tectonic plates, little bits of magnetic material align in the direction of earth’s magnetic field. It hardens and the magnetic record is solidified. We can read the ocean floor like a book, and it’s telling us that over time the magnetic field of the earth changes. Sometimes it is aligned as it is now, but other times it’s completely switched. The north magnetic pole is sometimes in the southern hemisphere! What’s nerve-wracking is that while it’s switching, it can weaken and be non-existent for awhile. Our mid-Atlantic story book is telling us that it may be time for another switch. Or even more harrowing, as the earth cools and the outer core solidifies, the magnetic field may disappear forever.

Though we don’t often notice the effects of the magnetic field in our daily lives, it does provide an invisible barrier from the harsher radiation from the sun. We’re all familiar with the northern lights, which are caused by high energy solar radiation interacting with our atmosphere, spiraling in along the magnetic field lines near the poles. But what we’re not aware of is the daily bombardment of high energy particles from the sun that are deflected away from us. Without our magnetic field, we would be exposed to much more radiation than we’re used to, and it could be very harmful to all life forms on earth.

Between earth’s mantle and the cold, stark emptiness of outer space, lie the layers of geology that hold our history. Creatures have come and gone in the 3 billion year history of life on earth. It started with single celled organisms and has proliferated in the multifarious beings of today. But the creatures that were around 100 million years ago are not necessarily the ones we see now. Life has changed, often in big sweeping changes caused by the earth itself. Our magnetic field may be an important part of the plot of how life on earth changes, and we may be in store for the next chapter in the book. I hope it has a happy ending!

Until next week, my friends, enjoy the view.

Tuesday, May 15, 2007

The Short and the Long

5/21/07 – 5/27/07
by C. Zaitz

I just had one of those milestone birthdays- you know, the ones that are supposed to be more special than the rest because the number is getting so high that you have to celebrate just being alive. It made me think of the age of things. Biologically, things happen on a pretty short time scale. 70-80 years is not that long when you take into consideration how long rocks live. In astronomy we talk about ages of stars, in geology we talk about the ages of rocks and planets. In human lifescales, those numbers are incomprehensible. We have no feeling for how long it takes a rock to form, much less a star. It seems like eternity to wait for your tomatoes to ripen or for your hair to grow out after a bad cut!

Though humans have a relatively short lifespan, we are still around long enough to watch things grow and develop, die and transform. Plants and animals live in our time scale, though we marvel at the 2,000 year old sequoias and ancient cedars. But things we think of as everlasting, like rocks or stars, are not eternal. All rocks move through a cycle, from being sand sediments on the surface, to being metamorphised as the pressure of layers upon layers of rock change its character, to suffering the igneous fate of melted rocks, turning into magma and reforming on the surface as lava basalt, only to be worn away again as sand and sediment. Eons pass and the dirt just keeps changing form, nothing destroyed or created, but morphing from one form to another.

The same thing happens with stars. Our sun was once diffuse gas and dust, our own planet not more than a breath of cosmic debris, sprinkled with rare elements fused in the death throes of an ancestor star. Gravity and pressure brought everything around, and our solar system will go for at least as long as it already has, some 4.5 billion years. Then it will die, only to form something new in the next “billenia.” Will it be something completely different? A double star or part of a new open cluster of stars? Or maybe a familiar life-harboring solar system?

We happen to be living in a very particular time when we as a species can begin to understand all the cycles of life and death around us. How unique and incredible for us. It’s not surprising we’re so curious about the universe, since we see our own selves reflected in the life cycles, in the growing and dying of everything around us. I think we study these cycles to try to understand what happens when we, too, die. Will we be born again in some “next cycle?”

From an old southern banjo tune:
Little birdie, little birdie,
come sing to me your song.
I've a short while to be here,
and a long time to be gone.

Little birdie, little birdie,
What makes you fly so high?
It’s because I am a true little bird
and I do not fare to die.
I guess I like to think that nothing really goes away. We all get older and will all die, but even black holes give up their dead eventually. Nothing seems to be destroyed, and it all comes back around again, sometimes in the near future, like perennial flowers, and sometimes in the long run, like planets with life.

Until next week, my friends, enjoy the view.

Wednesday, May 09, 2007

A Weighty Subject

5/13/07 – 5/20/07
by C. Zaitz

My husband recently lost about 35 pounds due to having a very overactive thyroid gland. After an intense potion of radiation, it calmed down, so we started going back to the gym for workouts. He picked up a 35 pound weight and gave it to me to feel how much weight he’d lost. It seemed very heavy, but he carried it around for years. I started to think about weight and how we measure it, and how hard it is to lose it.

Weight is a combination of how much gravity pulls down on us, and how much “us” there is. Often in everyday life we confuse “mass” and “weight.” Mass is an intrinsic property of something, measured in pounds or kilograms. It’s how much “stuff” there is. If our mass was 150 kg on earth, it would still be 150 kg on the moon. But we wouldn’t weigh as much there, because the moon has much less gravity than earth. To get our weight, we would have to multiply our mass by how much gravity our “ground” has. Since we all live on earth and have nearly the same amount of gravity tugging on us, we forget the fact that weight and mass are different things.

Interestingly, if there were no floor or surface to stand on, you wouldn’t feel weight at all. If the floor wasn’t “pushing” back on you as hard as gravity is pulling you toward the center of the earth, you would just fall in, feeling no weight at all. This is “free fall” or “weightlessness.” It’s hard to do on earth, but the astronauts in orbit are very familiar with it. The astronauts and the space station might not have any “weight” in orbit, but they certainly have mass, which takes energy to move. That’s why it takes a lot of fuel to move stuff around even in “weightlessness.”

The fun comes when we figure out how much we’d weigh on other planets. Which would you choose, big planet or small? A 150 pound person would weigh 57 pounds on Mars. On the moon, you’d weigh a mere 25 pounds. But things get weird when you go to one of the giant, gassy planets. You’d think a mammoth planet like Saturn, a planet that could engulf earth 760 times, would have an enormous amount gravity. It does, but the farther you get from the center, the force of gravity lessens exponentially. Saturn has about 95 times more mass than earth, but its radius is 9.4 times that of earth. The math works out that on the “surface” or visible gassy outer atmosphere of Saturn, you would weigh approximately what you do on earth. The same is true of Neptune and Uranus. Jupiter is the most massive planet, 318 times more than earth, but its radius is over 11 times earth’s. Its surface gravity turns out to be about 2.5 times that of earth’s. Our 150 pound person would only weigh 375 pounds on Jupiter. Not bad for the biggest planet of them all. On Saturn, this same person would weigh a svelte 137 pounds. So you can actually “lose” weight by going to Saturn. Not to mention the weight you’d lose by eating freeze-dried peas for the three years it would take to get there.

If you’d like to check your own weight on the planets, you can go to: http://www.exploratorium.edu/ronh/weight/index.html to plan your weight loss/gain itinerary.

Until next week, my friends, enjoy the view.

Wednesday, May 02, 2007

Saturn in Leo

5/6/07 – 5/12/07
by C. Zaitz

Sometimes I take comfort in the thought that, as crazy as life gets here on earth, the planets are making their planetary journeys ‘round the sun in their own time. Each planet has its own pace, and the slowest, calmest naked-eye planet is Saturn. Right now Saturn is passing in front of the constellation Leo. Some folks say that this fact can be life altering.

For fun I looked up what astrologers have to say about the planet Saturn being “in” Leo. Because Saturn orbits so slowly, it spends more than two years in any one of the zodiac constellations. Saturn was the god of change, of destroying the old to make way for the new, so astrologers say. In his modern personification, he’s a teacher, and his tests are often difficult and life changing.

Astrologically, people born when the sun was “in” Leo tend to be leaders, and very involved with ego. So to have such a “destructive” planet in Leo seems to spell disaster for the top cats. But astrologers also say that if you are willing, Saturn’s life-changing presence can open up new doors and clean your inner house. That’s a lot of deep advice from the distant gas planet and the even more distant, boiling hot gas stars that make up the constellation of Leo. Recently I showed Leo to some 4th graders. They said that Leo looks like a smiley face or a pony or a balloon. This is not a very distinguished description of Leo, but nevertheless, kind of true. In general, constellations like Hercules or Sagittarius look nothing like a giant hero or a centaur. So to assign such lofty characteristics to a group of stars scattered through space is amusing to me. Of course, it’s crafty humans that come up with the characteristics, the shapes and the connections. And it’s searching humans that read their horoscopes and make connections with their own lives. It’s kind of interesting that not only do planets reflect sunlight back to us, but they reflect our own hopes and dreams, problems and possible solutions, back to us from afar.

As far as Saturn being “in” a constellation, right now is about 8 times the distance from the earth to the sun. It takes light about and hour and half to reach us from Saturn. Stars are much farther away. The brightest star in Leo, Regulus, is nearly 80 light years away from us. The planet actually moves “in front of” the stars of the constellation as it orbits, but it sounds more mysterious and inviting to say Saturn is “in” Leo, especially if you call that part of the sky a “house.”

If you want to see Saturn in Leo, look toward the south after sunset, about halfway up the sky, and look for the “sickle” or the backwards question mark shape of stars. That is the front part of Leo, if we imagine the round sickle blade as his head and golden mane. Saturn will be just to the right or west of the sickle. This spring, Saturn’s rings are prettily displayed for anyone with a telescope. Whether or not Saturn brings life altering events for you, you can still let the beauty of the reflected light dazzle your eyes and your mind. And that can be life altering as well, especially if it moves you to use the credit card to buy a new telescope!

Until next week, my friends, enjoy the view.