Archive for November, 2009

2012 - A Scientific Reality Check

Tuesday, November 10th, 2009
Donald Yeomans
Donald Yeomans

There apparently is a great deal of interest in celestial bodies, and their locations and trajectories at the end of the calendar year 2012. Now, I for one love a good book or movie as much as the next guy. But the stuff flying around through cyberspace, TV and the movies is not based on science. There is even a fake NASA news release out there… So here is the scientific reality on the celestial happenings in the year 2012.

Nibiru, a purported large object headed toward Earth, simply put - does not exist. There is no credible evidence - telescopic or otherwise - for this object’s existence. There is also no evidence of any kind for its gravitational effects upon bodies in our solar system.

I do however like the name Nibiru. If I ever get a pet goldflish (and I just may do that sometime in early 2013), Nibiru will be at the top of my list.

The Mayan calendar does not end in December 2012. Just as the calendar you have on your kitchen wall does not cease to exist after December 31, the Mayan calendar does not cease to exist on December 21, 2012. This date is the end of the Mayan long-count period, but then – just as your calendar begins again on January 1 - another long-count period begins for the Mayan calendar.

The Galileo spacecraft's view of the Moon and Earth
On December 16, 1992, 8 days after its encounter with Earth, the Galileo spacecraft looked back from a distance of about 6.2 million kilometers (3.9 million miles) to capture this remarkable view of the Moon in orbit about Earth. Image credit: NASA/JPL
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There are no credible predictions for worrisome astronomical events in 2012. The activity of the sun is cyclical with a period of roughly 11 years and the time of the next solar maximum is predicted to occur about May 2013. However, the Earth routinely experiences these periods of increased solar activity – for eons - without worrisome effects. The Earth’s magnetic field, which deflects charged particles from the sun, does reverse polarity on time scales of about 400,000 years but there is no evidence that a reversal, which takes thousands of years to occur, will begin in 2012. Even if this several thousand year-long magnetic field reversal were to begin, that would not affect the Earth’s rotation nor would it affect the direction of the Earth’s rotation axis… only Superman can do that.

The only important gravitational tugs experienced by the Earth are due to the moon and sun. There are no planetary alignments in the next few decades, Earth will not cross the galactic plane in 2012, and even if these alignments were to occur, their effects on the Earth would be negligible. Each December the Earth and Sun align with the approximate center of the Milky Way Galaxy but that is an annual event of no consequence.

The predictions of doomsday or dramatic changes on December 21, 2012 are all false. Incorrect doomsday predictions have taken place several times in each of the past several centuries. Readers should bear in mind what Carl Sagan noted several years ago; “extraordinary claims require extraordinary evidence.”

For any claims of disaster or dramatic changes in 2012, the burden of proof is on the people making these claims. Where is the science? Where is the evidence? There is none, and all the passionate, persistent and profitable assertions, whether they are made in books, movies, documentaries or over the Internet, cannot change that simple fact. There is no credible evidence for any of the assertions made in support of unusual events taking place in December 2012.

For more information on the silliness surrounding December 2012, see:

Cassini’s Swoop over Enceladus: First Morsels of Science Coming Back Now

Thursday, November 5th, 2009
Bonnie J. Buratti
Bonnie J. Buratti

Phew! We made it through the deepest swoop yet down into the plume of Enceladus, the encounter we call “E7″ because it’s the seventh targeted flyby of Enceladus.

But now we have our work cut out for the next few weeks as we pore over the data, painstakingly analyzing every signal to understand the composition of the plume and its structure.

So far, we know the Visual and Infrared Mapping Spectrometer (VIMS) was able to get images and data in a variety of wavelengths of light and saw that the plume extends out to at least 1,000 kilometers (600 miles).

Raw image of Cassini's Nov. 02, 2009 flyby of Enceladus
Cassini captured this raw image on its Nov. 02, 2009, flyby of Enceladus. The camera was pointing toward Enceladus from approximately 10,000 kilometers (6,000 miles) away. Image credit: NASA/JPL/Space Science Institute.
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We also have striking images of the moon crowned by its glorious plume, which Cassini captured right before its plunge. The images illustrate well that the spectacular plume spewing from the south polar region is composed of many much smaller jets.

The images and VIMS data both show that as the moon becomes less and less illuminated by the sun (similar to when our moon approaches the phase known as “new moon”), the plume gets much brighter. These data will be valuable for understanding the detailed structure of the plume and where it connects to the surface.

We have also learned that the density of the plume appears to be less than half of that predicted. Still, the heart of the plume measured on this flyby was about three times denser than the sparser parts of the plume we flew through previously.

There is more good news. We will be able to do the Enceladus flyby on April 28, 2010, on the spacecraft’s reaction wheels. This means we will be able to perform the Radio Science Subsystem experiment with Cassini’s main antenna to understand the interior of Enceladus under the hot south polar region.

During this experiment, antennas from the Deep Space Network (DSN) on Earth will be tracking the spacecraft to see how much Enceladus tugs on it. By measuring this tug, scientists will be able to answer such questions as: How much is the shape of the moon deformed by tidal forces from Saturn? Is there an unusually dense mass under the south pole? (The higher the mass, the larger the tug?)

We know that heating by tidal forces is what drives the plumes, but we’re not sure exactly how. In addition to a possible liquid subsurface ocean, Enceladus may be harboring a dense mass underneath its surface that helped to start and maintain the moon’s current activity.

Just wanted to share our excitement about the reams of data we’re combing through. Now, back to work!

Rocks and Stars with Amy: Hi Ho, Hi Ho, It’s Into Space We Go

Thursday, November 5th, 2009

By Amy Mainzer

Rocks and Stars with Amy

With WISE a mere month away from liftoff, it’s probably a little late to be asking why we need to send it into space. But it’s worth taking the time to explain why we go to all the trouble of sending something up on a rocket. While it’s really cool to go into space, we’re not just sending WISE up there for the fun of it. In this case, there’s no other reasonable way to accomplish the mission’s science goals: surveying the entire sky in infrared, finding the nearest star to our sun, and finding the most luminous galaxy in the universe. We can’t do this from the ground.

artist concept of WISEIt turns out that the main culprit that drives us into space and into an orbit more than 500 kilometers (about 360 miles) above the Earth’s surface is our atmosphere. As wonderful as our atmosphere is for life on Earth, it wreaks havoc on astronomical images in many ways. For one, shifting pockets of warm and cool air drifting above a telescope — or a human observer– cause stars to twinkle. While pretty, this twinkling makes it difficult to get a good measurement of a star’s true brightness (or, in astronomical terms, its “photometry”). The twinkling also reduces the telescope’s sensitivity and resolution by enlarging the images it produces, making them blurrier and less sharp. This is true for all kinds of telescopes not just infrared ones.

Secondly, the atmosphere acts like a sponge at many wavelengths, soaking up light from the stars so that it never reaches the ground at all. Everybody’s seen a rainbow at one time or another, and that range of colors — from violet to red — spans the maximum range of wavelengths that our eyes can see. But that is only a small fraction of the entire spectrum of light that’s really out there in the universe. Our sun puts out most of its radiation in visible light, and most of that visible light makes it through our atmosphere to the ground. However, our atmosphere is only partially transparent to infrared wavelengths. Filled with water vapor, carbon dioxide, and methane, our atmosphere absorbs almost all infrared light, so most of the infrared light emitted by distant stars, asteroids, and planets doesn’t make it to observers on the ground. These molecules grab infrared light and trap it, preventing it from passing through the atmosphere (which is why they are called greenhouse gases). To see anything at all in most infrared colors, we have to get entirely above the Earth’s atmosphere.

The final problem posed by our atmosphere for infrared astronomers is that it — and the Earth itself — is warm. Infrared light is characteristically emitted by room-temperature objects. Objects like you and I glow brightly in infrared light, and so does the Earth and its atmosphere. If you could see in infrared light, the night sky would look as bright as daylight! So when we’re trying to detect the faint heat signatures of distant astronomical objects, a glowing, warm atmosphere is almost impossible to see through. This is why we must cool the WISE telescope to a mere 12 degrees above absolute zero (minus 438 Fahrenheit). Being in space with a cold telescope makes such a huge difference that the relatively modest-size WISE telescope, which is 40 centimeters (16 inches) in diameter, is equivalent in sensitivity to literally thousands of 8-meter (26-foot) telescopes on the ground. That small WISE telescope packs a punch.

So with that cleared up, we’re just about ready to put WISE into the nose cone and crane it up onto the Delta II rocket that’s waiting for us on the launch pad. Let’s go see some stars!