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All posts for the month December, 2006

Peeking at Saturn through Titans atmosphere

Peeking at Saturn through Titan's atmosphere

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.

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.

Night sky chart by TheSpacewriter. (Click on the image to get a larger version

Night sky chart by TheSpacewriter.

Sunset viewing chart by Sky & Telescope.

Sunset viewing chart by Sky & Telescope.

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).

Dawn sky chart by Sky & Telescope

Dawn sky chart by Sky & Telescope

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!”