December 29, 2006 at 18:51 pm | Leave a Comment
The Cassini spacecraft at Saturn has been busy sending back a collection of beautiful scenes from that distant planet and its moons and rings. The folks at the NASA Cassini mission center have postI love this view of Saturn through Titan’s atmosphere.
I love this view of Saturn through Titan’s atmosphere. It’s just not something we see from Earth every day. I’m also particularly fond of the Rhea/Enceladus occultation movie they have posted. It shows a 20-minute sequence of 40 images through the Cassini spacecraft’s narrow-angle camera pointed at Enceladus. The larger moon slips right past icy Rhea in the foreground. That is definitely NOT something you’re going to see from Earth too often!ed the collection to celebrate the end of the year.
Take a few minutes to visit the Cassini site at the link above and browse through the other images they’ve posted and enjoy the New Years’ eve celebration at Saturn.
December 28, 2006 at 18:29 pm | Leave a Comment
Okay, I KNOW that some of you out there got new telescopes or binoculars as holiday gifts. Or, you got a new astronomy book. Or a picture book about space. Great! We need to keep the fires of interest in the sky alive.
No time like the present to use all that loot to study the sky. So, let’s get started. Back when I used to work at the university, I got to answer questions about the sky, asked of us by members of the public who called our department since they figured we were astronomers. We got some great questions, some kind of silly questions, and some that were misguided or the result of miscommunication in the media. But, we hardly ever got “dumb” ones. I don’t there’s any such thing as a “dumb” question, unless you count the folks who ask really silly things just to be cute. But, chances were that I’d pick up the phone (after being warned by the departmental secretary that it was a member of the public with a quesion), and I’d hear something like, “Hi, My name is XXXX and I have a really dumb question…”
Then they’d ask something perfectly reasonable like, “How can I tell the difference between a star and a planet?” Not a dumb question at all, really. Most people assume that if you look up in the sky, you’re gonna see stars and planets. And that’s usually true.
Right now (late December), the naked-eye planets are largely out of sight in the evening sky—except for Venus, which you can spot pretty low in the west after sunset, and Saturn, which rises in the east with Leo around 8 or 9 p.m. To see Jupiter and Mars, you have to get up really early in the morning and watch for them right around dawn in the southeast.
So, if you do go planet-hunting, how to tell them from the nearby stars? The best rule of thumb is to take a good star chart outside with you, one that has the planets clearly marked. You can find them in Sky & Telescope and Astronomy magazines, or online at their sites. Those maps should show you where the planets should be in the sky at the time you want to view them. I’ve included a small chart below that should be useful after about 8 or 9 p.m. local time for a week or so into the new year.
Next, once you’re outside (and remember to dress warmly if you live in a chilly climate), look in the area where your map tells you a planet should be. If the planet you want is Venus, you probably won’t be able to miss it unless it has set or the sky is cloudy. It’ll be the bright object that is often mistaken for a star (and is often called the evening star (or morning star when it’s up in the morning)). Venus should look disk-like, and shouldn’t be twinkling (although, if it’s close to the horizon, it might seem to shimmer due to atmospheric turbulence in the air near the ground).
If you’re looking for Mars or Jupiter, they’re only an early-morning sight low in the southeast right now, but the same rules of thumb holds true: planets don’t usually twinkle, but stars do. In addition, planets look disk-like, while stars look like sharp points of light.
Now, I should point out that in the S&T charts, they draw Venus and Jupiter with rays of light (starlike) coming out of them. I don’t particularly care for that, but recognize that at least you’ll get the position of the planet from the chart. Mars, on the other hand, is shown disk-like. I suppose the guys down in Cambridge are trying to show that Venus and Jupiter are bright, which they are.
Saturn, on the other hand, doesn’t appear nearly as bright. Look for it just a bit off from the star Regulus, the heart of the Leo the Lion. This is where your telescope (or a really high-powered binocular) comes in handy: aim it at Saturn and see if you can spot the rings! Depending on the magnification you’re using, the rings could just look like a couple of lumps sticking out from either side of the planet (in 3-inch telescope or 10 × 50 binoculars, for example). If so, you’re seeing it as Galileo saw it, only he called those lumps “ears” and never did figure them out. If you have stronger magnification (say a 4-inch or larger telescope), you might be able to see that they are actually rings. (Of course HOW good your view is also depends on viewing conditions (high, thin clouds? haze? a little fog? bright moonlight?) at your site.
Now, this last week of the year the evening sky is dominated by the Moon, so of course you’ll want to check that out, too. It looks way cool through binoculars, and with a small telescope trained on it you can explore lunar craters, mountains, and plains. If you were lucky enough to get a BIG telescope? Well, the Moon is yours to command.
Now, of course, there’s a LOT more out there to see. Stars, nebulae, and even a galaxy (or three) to check out. I’ll post some more charts in the coming days to help you find those, too.
For now, what’s the message here? There’s good stuff out there to look at with your astronomy loot. The sky’s waiting! As they like to say on the cruise line commercials here in the U.S., “Get out there!”
December 26, 2006 at 21:32 pm | Leave a Comment
Every year we do a holiday card and letter that we create ourselves. The front is usually a pretty picture of some kind, the inside is our annual letter, and the back is a star chart so folks can go stargazing for a week around Christmas Day and see some lovely sights.
This year we found our “pretty picture” artwork on the Hubble Space Telescope holiday card web pages. They have designed a series of printable pieces suitable for greeting cards, sort of like this one.
I think the designs they came up with are very clever and show artful use of space images as design elements. What are design elements, you might wonder. They are what they seem to be: elements of design, whether colors, image portions, graphics, sculpted text, and shapes that breathe life into a piece of artwork (and that’s really what each of these designer cards is).
I’ve used space images as elements throughhout my website and blog, and if you visit enough astronomy and space science-related blogs, you’ll see bits and pieces of space scattered through those pages, too. Look at the logo in Phil Plait’s Bad Astronomy site. There’s an actual astro-image mapped over his title letters. Or, check out The Nine8 Planets page uses images of the planets as a sort of logo in the upper left corner. Or, one of our blogrollees, Observing the Sky, is using two astro images in the banner to achieve an appropriately “spacey” look.
Pay attention as you rove the Web and see what other design elements from space have made their way into people’s blogs and online spaces. You’d be surprised at how popular space images are in the blogging world, even if the sites aren’t about space.
December 24, 2006 at 10:48 am | Leave a Comment
… the More We Find
Astronomy is a win-win proposition. You look at the sky with your naked eye and you see stars, planets, maybe a galaxy or two if you have the right observing conditions. You can always find something great to see.
If you magnify the view, you get to see more stuff that’s dimmer, farther away, and in more detail. It’s the science that keeps on giving, no matter what at what level you understand things.
If you REALLY magnify the view, say with a telescope like Hubble, you find things you’d never see with the naked eye. The top image is a view of the star Sirus, which lies just over 8 light-years away. It’s a blue-white star, and if you look at the belt of Orion and trace a line down from it to the horizon, you’ll run right into Sirius.
This star has a companion which is terribly difficult to see. It’s a white dwarf star called Sirius B. It’s not an easy star to spot because the brightness of Sirius overpowers the faint little glow of the companion. Hubble scientists managed to spot this Sirius-hugging little star by overexposing the bright star to get the dim glow of its little sibling.
The second image is a result of ongoing observations of the planet Uranus. HST scientists found a pair of rings (very thin, to be sure) circling the gas giant. We already knew that Uranus had rings, but this new discovery also tells us something is furnishing the dust that creates planetary rings. In thise case, a little moon called Mab that orbits the planet is most likely the source of the dust. Meteoroid impacts knock material from Mab’s surface, sending it into space. Ultimately it gets caught up into orbit around Uranus.
This is why I find astronomy a continual source of fascination. There’s always something new to find, to see, to learn. The universe is a great show-and-tell machine!
December 23, 2006 at 18:30 pm | Leave a Comment
I’m in a Carl Sagan state of mind tonight. No, I’m not channeling for Carl. Nobody could do that. But, I was thinking about some of his most famous phrases (and no, NOT “billions and billions”—that was a Johnny Carson schtick). The one that always seemed most evocative to me was “We are, as I like to say, starstuff.”
It seems like a strange thing, to think about coming from a star. But everything on Earth has atoms that were made inside a star. Look at your hand. It has flesh on its bones. Hard to imagine that flesh coming from the hot interior of a star. No, the flesh and bones didn’t. But the stuff that made them up did.
Your hand has atoms of carbon in it. Carbon exists in molecules that bond with other elements to make proteins, nucleic acids, enzymes, carbohydrates, and fats—all things we KNOW make up biological life. Carbon is made in the interiors of stars. Your hand also has calcium in its bones. That, too, came from a star. Heck, our own Sun has calcium in its atmosphere. And, there’s iron in the blood coursing through your veins. The iron atoms came from an ancient supernova explosion that occurred long before the Sun formed.
How do we know all this? The lives of stars are fairly well-understood in general (although many details are still being figured out). But, we do know that stars contain nuclear furnaces deep in their cores. Those nuclear “engines” fuse atoms together. Let’s take the Sun, since it’s the closest star we know of. It started its life fusing hydrogen into helium at its core. Now, the hydrogen was created in the Big Bang, so you’d expect to see plenty of that in the Sun. It gets fused into helium. And it goes from there, atoms getting smacked together to make heavier and heavier elements: carbon, oxygen, silicon and so on. As the Sun (like many stars) lives its live, it makes elements and it sends them out into space through the solar wind.
But, the good stuff happens when stars die. They exhale their outer layers, which contain healthy amounts of the elements they’ve made, into surrounding space. A star like the Sun will swell to become a red giant star, eventually sending much of its mass out to space. That includes oxygen, nitrogen, calcium, and carbon.
If a star is really huge, it will explode in a supernova. The debris of the star, its atmosphere and the elements it has been making—including iron—rushes out to space. A supernova explosion is also the cauldron of creation for elements such as cobalt, uranium, copper, mercury, gold, iodine, and lead.
All stars enrich their immediate neighorhoods with the elements they make. Then, it’s only a matter of time before those elements find their way into new generations of stars. Our own Sun was made from elements that were, themselves, created in far older stars that died and sent their elements into space. Some 5 billion years ago, a cloud of gas and dust enriched by elements from other stars coalesced to form our Sun. And, our planets formed in that cloud, from elements that—you guessed it—came from other stars. And, the elements needed for life (the carbon, oxygen, nitrogen, and iron, just happened to be along for the ride. And voila, after millions and billions of years of planetary formation and evolution, chemical reactions, and biological evolution, here we are—the end products of processes that used star stuff to create planets and favorable conditions for life to form.
So, in a sense, it’s really no surprise that we look to the stars to understand our place in the universe. Somehow we know from where we came, and I think that’s pretty elegant, indeed.
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Image of Horsehead Nebula: T.A.Rector (NOAO/AURA/NSF) and Hubble Heritage Team (STScI/AURA/NASA)
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