October 24, 2003 at 16:31 pm | Leave a Comment
I got a press release from my friends over at Sky Publishing Corporation, publishers of Sky & Telescope Magazine. Now’s the time to plan ahead for viewing the next total lunar eclipse of 2003. Read on for details!
“On Saturday night, November 8-9, 2003, the full Moon will pass through the Earth’s shadow for skywatchers throughout the Americas, Europe, and Africa, and in parts of Asia. For the Americas, this will be the second lunar eclipse of 2003; the first took place the night of May 15-16.
But the total phase of November’s eclipse will be unusually brief, lasting only 25 minutes as the Moon skims barely inside the southern edge of our planet’s dark shadow.
Skywatchers in eastern North America will see the entire eclipse during dark evening hours. Those living in the western half of North America will find the eclipse already in progress as the Moon rises around sunset.
All of Europe and most of Africa will see the eclipse in its entirety much later Saturday night. Observers in eastern and southern Africa, the Middle East, and southern Asia will see the eclipsed Moon set around sunrise on Sunday morning.
[For a nifty table of times and visibility, click here.]
A total lunar eclipse occurs when the Sun, Earth, and Moon form a nearly straight line in space, so that the full Moon passes through Earth’s shadow. Unlike a solar eclipse, which requires special equipment to observe safely, you can watch a lunar eclipse with your unaided eyes. Binoculars or a small telescope will enhance the view dramatically.
As the Moon moves into the outer fringe, or penumbra, of Earth’s shadow, it will fade very slightly — imperceptibly at first. Only when the leading edge of the Moon is at least halfway into the penumbra is any shading visible at all.
The real show starts when the Moon’s leading edge first enters the shadow’s dark core, or umbra, and the partial eclipse begins. For the next hour and 34 minutes, more and more of the Moon will slide into dark shadow.
The total eclipse begins when the Moon is fully within the umbra. But it likely won’t be blacked out. The totally eclipsed Moon should linger as an eerie dark gray or coppery red disk in the sky, as sunlight scattered around the edge of our atmosphere paints the lunar surface with a warm glow. This is light from all the sunrises and sunsets that are in progress around Earth at the time.
Each total lunar eclipse is different. Sometimes the Moon looks like an orange glowing coal, while at other times it virtually disappears from view. Its brightness depends on the amount of dust in the Earth’s upper atmosphere at the time, which influences the amount of sunlight that filters around the Earth’s edges.
Because the Moon passes just inside the umbra, totality will be very short and the Moon’s southern edge, in particular, should remain fairly bright. After only 25 minutes the leading edge of the Moon will emerge back into sunlight, and the eclipse is again partial. In another hour and 33 minutes the last of the Moon emerges out of the umbra.
Details about this event, and the solar eclipse visible from Antarctica, Australia, and New Zealand on November 23-24, appear in the November 2003 issue of SKY & TELESCOPE magazine.
The next total eclipse of the Moon falls on May 4-5, 2004, and is visible from central and south Asia, the Middle East, and the eastern two-thirds of Africa. North Americans will see their next lunar eclipse on October 27-28, 2004.”
October 21, 2003 at 17:03 pm | Leave a Comment
In 1990 I wrote a planetarium show about a space cat. His name was Larry (after our own Lawrence E. Katt, who was with us from his birth in 1982 until his passing in 1999) and he had all kinds of adventures. Now we have three other cats (Pixel, Miranda, and Lazarus Long), and they’re all sort of astro cats in one way or another. Pixel is named after a Robert Heinlein cat character who plied the spaceways with Maureen Johnson Long. Miranda is so named because her mottled coloring reminded us of the Uranian moon Miranda.
And Laz (our newest addition) is named after another Robert Heinlein character who also plied the spaceways through a number of novels. What is it about cats and space? Would they do well on long voyages, in weightlessness? Would they travel well? I’ve always wondered about taking a cat on a cruise ship. Seems like a good companion to have on those days when all you want to do is slip into your cabin and relax…
Of course there are cats in astronomy. The constellations Leo Major and Leo Minor come to mind.
Aside from the constellations, cats show up in the cosmological tales of such civilizations as the Aztec, where their Jaguar God Tezcatlipoca rules the stars as god of the night sky and the winds of night. His name really means “smoking mirror”, which gives him a sort of magical aspect.
And of course, there is Bastet, the cat deity who was both goddess and protectress of cats and the people who lived with and cared for cats. While not exactly a deity associated with the stars, she was important in her own right — and I like to think of ancient Egyptians out stargazing with their cats by their sides!
So, how do cats figure in today’s stargazing? Hard to tell. Probably they don’t care much about what their humans are doing outside, as long as food regularly appears and the humans let them out to help during backyard stargazing sessions. I have a friend who used to brag that he kept a kitten in each pocket to keep his hands warm during long periods at the telescope. Our own cats don’t go outside (we live near a wooded area that is home to many critters that see cats as a tasty main dish), but they do like spend time indoors crawling around on the telescope base for my Dob and sleeping on the case for my 6″ Sovietski scope. But perhaps our cats are the exception. Maybe your cats go out stargazing with you ” and spend their evenings watching YOU scan through Leo or Lynx looking for excitement, adventure, and deep-sky objects! They’re great observers too — while you’re watching the universe, they’re watching YOU.
October 20, 2003 at 23:29 pm | Leave a Comment
People of a “certain age” might remember all the old jokes about “x-ray eyes” in science fiction stories. Truth is, if we had X-ray eyes, we’d look vastly different than we do as human beings. And we would have had to evolve in the light of a star that gave off massive amounts of X rays and on a planet that didn’t shield us from that radiation. Like I said, if we did, we’d look very different.
Just because we can’t see X rays with our naked eyes doesn’t mean that things in the universe don’t give them off. To be sure, our Sun does give them off — but not as strongly as some objects do. There is some evidence — found by studying starbirth nurseries like the Orion Nebula — that the Sun’s infancy might have been quite a stormy one, marked by blustery stellar winds, outflowing jets, and a much higher amount of X-ray emissions than it shows now. The cause of those emissions and how long they lasted are topics that currently fascinate astronomers who study the early lives of stars.
To chart x-rays coming from stellar newborns, astronomers pointed the Chandra X-Ray Observatory at the Orion Nebula and found bright X-ray sources among the stellar babies just coming to life in that cloud of gas and dust. The x-ray image above shows about a thousand young stars in a 10 light-year-wide region of the Orion Nebula star cluster. These newborns are just blazing away with x-rays produced in the upper atmospheres of these stars. These are regions where the temperatures are millions of degrees hot. The bright stars in the center are part of the Trapezium — an association of stars less than a million years old. Young stars, such as those found in Orion, are known to be much brighter in x-rays than middle-aged stars such as the Sun.
Why are these stars so bright in x-ray emissions? Astronomers think that all the x-ray activity stems from violent flares in strong magnetic fields near the surfaces of these young stars. Although astronomers have known about the high magnetic activity of young stars for a while, the actual physical causes and evolution of the activities are still being figured out. A region rich in hot, young stars — like the Orion Nebula — provides a perfect laboratory to study the active phases of a newborn star’s life.
We’ve come a long way since people could only look up into the sky with naked eyes and wonder about what they saw. Now we explore the sky with multi-wavelength eyes, seeing things that are stranger and more wonderful than the old “x-ray eyes” sci-fi dramatists could ever imagine. Whenever I look at Orion now, I imagine it in infrared, optical, and x-ray wavelengths of light — and marvel at the things astronomy has to teach us.
October 19, 2003 at 11:31 am | Leave a Comment
In the last installment, I started a discussion about the Orion Nebula. Since it’s such an interesting place, I think I’ll talk about it a little more — it’s got so much to explore!
Astronomers refer to the Orion Nebula as an HII region because it is largely made up of hydrogen gas (H2), with a dash each of helium, oxygen, nitrogen, and traces of other elements. When the Orion birth clouds are are heated by nearby stars, they glow (emit light) in various colors — transforming it into a glowing emission nebula. The starbirth nursery may look serene in this image, but the nebula is an incredibly active place. Stellar winds scoop out caverns around the newborns, jets of superheated gas streak out from the stars, and lumpy-looking cloud textures are carved out by the combined actions of jets and winds. In the center of the nebula lies a cluster of newborns less than a million years old. None of these stars are likely to have planets — yet, and even if they did, their brightness would make it extremely difficult to find the tiny planetary pinpoints. Yet, there are things forming here that we can spot if we use an infrared-sensitive instrument to do the searching.
Hubble Space Telescope gazed at the central cluster of stars in the Orion Nebula with its optical camera and infrared NICMOS instrument, revealing bright stars in visible light — and hidden among them — about 50 of the so-called “substellar objects” that we all know as brown dwarfs glowing in infrared light. They’re the bright star-like objects in the image on the right. These are too cool to be stars, too hot to be planets and difficult to see, unless you happen to have infrared eyes.
Could our own neck of the galaxy have looked like this about 5 billion years ago? If so, when you gaze at the Orion Nebula, you may very well be see what baby pictures of the Sun and its stellar siblings could have resembled, if there’d been anybody around to do the looking!
October 18, 2003 at 21:11 pm | Leave a Comment
When you go out to find Orion later this year, it’s a safe bet that what you see through your binoculars or small telescope (or even the naked eye) will be limited to optical wavelengths of light — that is, the light your eyes are most sensitive to. That makes sense, since that’s what “optical” means. But, what if you had eyes that were sensitive to infrared light — specifically to the 1.2 to 2.2 micron infrared wavelength range, and you could zoom in on the constellation Orion and the nebula that lies just beneath the three stars that make up the belt of Orion? You might see something that looks like this 2MASS image.
I’ve discussed the Nebula in this blog before — it’s one of my favorite places to study in the winter sky (and is a familiar summer sight for southern hemisphere stargazers). The nebula contains one of the closest star formation regions in our neck of the galaxy. Small wonder that it’s one of the most heavily studied areas of the sky. Every major observatory ranging from the likes of Hubble Space Telescope to the smallest amateur facility has a picture or some data set relating to this nebula.
The visible part of this nebula is only a small part of a huge cloud of gas and dust spread out across the region of the galaxy where the nebula and its “trapezium” of newborn stars inhabit. The whole complex is called the Orion A Molecular Cloud and it is a huge storehouse of containing the raw materials for star formation. Newborn stars already formed in this “stellar nest” are lighting up the rest of the cloud, which enables us to see it from across 1,500 light years of space.
This 2MASS infrared view of the Nebula looks quite different from the many colorful optical light images we’re all used to seeing in books, magazines, and spread out across the planetarium dome. The light we see with our eyes and in those optical photos is given off by glowing gases in the nebula, or reflected off of dust grains. Those gas and dust clouds hide other objects in the nebula. In infrared light the obscuring clouds of dust are more transparent, allowing us to see deeper into the Orion Nebula and revealing the otherwise hidden stars and other objects scatted throughout the region. None of the reddest objects in this picture can be seen in visible light!
If you’d like to look at other familiar sky objects with an infrared eye, take a look at the 2MASS web site. What you see will give you a greater appreciation for how the universe looks through infrared eyes!
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Copyright 2013, Carolyn Collins Petersen
Image of Horsehead Nebula: T.A.Rector (NOAO/AURA/NSF) and Hubble Heritage Team (STScI/AURA/NASA)
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