Charles Burckhalter's 1900 solar eclipse image with stars marked for Relativity analysis. Credit: Chabot Space & Science Center

Elevendy-one years ago (that's a hundred and eleven to the non-Shireborne), Chabot Observatory Director Charles Burckhalter set forth on an expedition across the plains of India, risking bandits, tigers, famine, and plague, on a hunt for big game: a rare meeting of the Sun and the migrating Moon in a total solar eclipse. Little could he know, years later his then-world-class astrophotographs of the event would be used in an effort to prove or disprove the General Theory of Relativity published by Albert Einstein in 1916.

Einstein's General Theory of Relativity is the one that describes gravity, that attractive force between objects, not as some kind of invisible bungee cord but as a distortion, or warping, of space (and time) by matter. Other objects within the warped, "curved" space accelerate "downhill" along the curve, toward the mass producing the distortion. Likewise, objects moving through the gravity field are deflected, their trajectories curved toward the mass.

The trick was how to prove this theory with observational evidence. That gravity is a fact is easily demonstrated by holding up an object and then letting go of it. Gravity, whatever gravity is, accelerates it "downward"—in our case, toward the center of Earth's mass.

But how to demonstrate that gravity, as Einstein theorized, is the effect of space-time warped by matter causing objects to slide down the "uneven ground," (yeah, using a lot of quotation marks, I know) was a bit like trying to prove that gnomes are responsible for missing keys (as we all know they are, but just can't prove!)

So, an experiment was proposed to try to sort out the culprit of gravity as curved space-time, or "merely" an invisible bungee cord. If space-time is in fact warped around a massive object, then not only other material objects, but non-material forms of energy should follow along the contours of the warp and also be deflected. Light was the handiest observable, non-material form of energy available.

As the theory went, the greater the mass of an object, the greater the deflection, and the Sun was by far the most massive nearby object available. If the stars behind the Sun's vicinity could be observed to shift their apparent position—as a consequence of their light rays being deflected as they flew past the Sun on their way to Earth—then General Relativity could be observationally confirmed. And there were astronomers in both camps—pro-Relativity and pro-Invisible-Bungee-Cords—trying to observe the effect, or the lack thereof.

A total solar eclipse in 1919 made itself available only three years after Einstein published, and so became a very important eclipse to science. (And, coincidentally, occurred on almost the same day of the year, May 29, as the May 28, 1900 eclipse captured by Burckhalter–which meant that the stars whose positions were being measured, the Hyades cluster in Taurus, were the same in both cases.) In the early 20th century, before space-based satellite observatories existed, stars could not be observed close to the Sun's disk, the Sun being so bright as to drown them out completely.

But during a total solar eclipse, the Moon temporarily blocks the Sun's bright disk, briefly giving astronomers a glimpse of the starry background surrounding the Sun. Photographs of the stars' positions taken during the eclipse could be compared to those of the same stars taken at a different time of the year, when the Sun wasn't present in that location, and so the space-time distortions of gravity (if there were any) might be observed in the deflection of the stars' apparent positions.

Charles Burckhalter's expedition photos from the 1900 eclipse were accessed as part of the observational experiment—including by those on the bungee-advocacy side of the aisle. His innovations in a technique for photographing solar eclipses made his image plates quite valuable among the 1900 sets.

In the end, General Relativity was, in fact, demonstrated observationally, by Arthur Eddington and others, which opened up a whole new universe of astounding possibilities, including the origin of the universe in the Big Bang, and the existence of the mind-bending, light-devouring objects called Black Holes.

But, back in the day, Burckhalter was probably more concerned by the sounds of tigers creeping through the bush and reports of the surrounding plague epidemic as he snapped his shots of the darkened Sun above….

There are a variety of places to go stargazing in and around the Bay Area which provide magnificent views of the cosmos.

A couple weeks ago I spent the weekend geeking out with astronomy buffs and sci-fi fans at the first ever SETIcon. Organized by SETI Institute, the event was filled with a variety of fun and informative panels that re-kindled my love of astronomy. After the event, I had an insatiable desire to do some stargazing — but where to go in the Bay Area?

One of the biggest misconceptions about astronomy is that you need to buy hundreds of dollars worth of equipment to enjoy the hobby. Fortunately this is a myth, and I am going to dispel it right here and right now! Whether you already have a telescope, are interested in building a telescope or are simply discovering a new hobby that can spark the imagination of family members from 5 to 95 years old, there are a variety of opportunities to enjoy the evening sky that are not far from your doorstep.

Here are just a few (free!) options if you don’t have a telescope:

Lawrence Hall of Science in Berkeley organizes a bi-monthly stargazing event every 1st and 3rd Saturday night of the month, year-round. The next event will be on September 4th at 9 – 11pm. Starting September 18th stargazing will run from 8 – 10pm. For full details and cloudy weather cancellation notices, follow them on Twitter: @lhsstargazing

Jazz Under the Stars at San Mateo Community College is fun, family friendly event that combines jazz music and stargazing. The next event will be on September 18th from 8 -11pm.

Most counties have their own astronomy club: East Bay Astronomical Society, San Francisco Astronomical Society, San Jose Astronomical Association and San Mateo County Astronomical Society offer events every month to look up at the stars. Members are very friendly and eager to engage the community in stargazing. Check their websites for the latest details.

If you’re more serious about Astronomy and would like to spend a few nights stargazing in dark skies, the next major star party is CalStar, from October 7 – 9th midway between San Francisco and Los Angeles near Lake San Antonio. This event is an excellent way to learn from dozens of amateur astronomers, look through telescopes larger than YOU and see a variety of celestial objects. This is my favorite kind of star party!

Now if you really want to go all hard core on astronomy and gain serious nerd cred, there's a class to teach you how to make your own telescope. Believe it or not, this isn’t as hard as it seems, but it is time consuming. After a few months you’ll come out with a finished telescope that costs a fraction of what it would cost to buy. The Telescope Makers Workshop at Chabot Space and Science Center meets Friday nights from 7-10pm.

So what are you waiting for? Look up!

For more science and DIY goodness 7 days a week follow Laura on twitter.

Related QUEST stories:
Amateur Astronomers
SETI: The New Search For ET

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Live solar observing at Chabot Space & Science Center

Our weekend daytime observatory volunteer team has assembled their own live solar observatory, using a SolarMax 70 hydrogen-alpha filter telescope, a video camera, a wireless transmitter, and a large flat-panel display screen—and now that the weather is beginning to cooperate, their offering to our visitors will take place on a more regular basis.

I was up there last Sunday to see the system at work, and was very impressed. With the telescope and wireless transmitter set up outside on the observatory deck, the image of the Sun captured by the video camera was transmitted into the dome of our large telescope, Rachel, where a receiver caught the signal and piped it into the large display monitor attached to the central pier.

Even though there were no sunspots that day—and sunspots are what people generally expect to see, if anything—the Sun put on quite a show in the "hydrogen alpha" wavelength of light (a select red color emitted by hot hydrogen in the Sun's atmosphere). While the Sun's visible surface is populated by features like granules (convection cells), sunspots, and faculae, the h-alpha scope revealed a layer of the Sun's atmosphere, the chromosphere ("sphere of color", named for the bright red light emitted by the hydrogen gas).

We observed several filaments and two or three prominences on this day, even though the Sun was relatively quiet and showing little surface sunspot activity.

Filaments and prominences are the same thing, really: "clouds" of hydrogen gas in the Sun's chromosphere, shaped and contained by the force of solar magnetic fields. When seen at the edge of the Sun's disk, these clouds appear as bright flame-like structures against the dark background of space, and we call them prominences. When seen within the Sun's disk, they appear as dark streaks and strands, the cooler gases in the clouds silhouetted against the brighter surface of the Sun; in this case we call them filaments.

Each of the little puffs of prominence we saw—like bonfires surging up from the edge of the Sun—were actually enormous structures, several times the size of the Earth. And we saw them change as well; in only minutes, the structures would shift and form new shapes, reminding us that the Sun is a very active and dynamic object, always on the go.

Solar activity is now on the rise, after a multi-year lull of quiet as we passed through the bottom of the 11-year solar cycle. We are seeing sunspots on more occasions, which are revealing areas of rising magnetic activity. The activity should only increase going forward, and is expected to reach a crescendo ("solar maximum") sometime around 2012 or 2013. Then, as was the case a decade ago when Chabot Space & Science Center opened, we can expect to see a dozen or so sunspots at any given time, and many more filaments and prominences.

I hope you can make it up to Chabot on a sunny weekend afternoon and see what our volunteers are up to. Forget about that sunny beach; come up to Chabot to learn about the object that makes that beach sunny!

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Martian dunes, captured by NASA's Mars Reconnaissance Orbiter

The motor in question powers a fan in an exhibit built to demonstrate the physical processes of duning—the fluid transport and deposition of solid particulates into collections and patterns. The fan blows up a constant micro-gale within the exhibit enclosure, and visitors get to play Mother Nature by turning a handle and redirecting the wind. Meanwhile, a mass of tiny white glass beads is constantly whipped up into a fair recreation of a sand storm on planet Arakis….

After the chore of installing the new motor, I rewarded myself by enjoying the exhibit a bit. I piled up all of the sand on one side of the tank to see how the fan would redistribute it; I sent the wind from different directions, watching how the freshly blown grains were scattered across the pristine black undersurface; I placed all of the pyrite rocks, which serve as wind obstacles, in one pile. It was a lot of fun.

One thing I noticed that I hadn't paid much attention to in the past was how the dune actually moved, or migrated. Maybe I hadn't watched long enough before, or maybe it was easier to witness because I had stacked the deck by mounding the sand all in one corner, but it was fascinating to see the process.

On the windward side of the giant dune, the scouring wind picked up the sand and carried it racing to the top—slowly peeling away the front face of the dune. As soon as the sand-laden wind reached the crest and took a sudden turn downward, it was slowed a bit, becoming less able to support the sand grains, which then fell out onto the leeward side of the dune in a sandy-wind version of precipitation. The buildup of sand on the lee side eventually formed small avalanches that slid down the face in little dry floods.

In this fashion, the dune moved along, slowly being erased on its windward side and formed on the lee.

Almost coincidentally, a few days later I read a report from NASA about sand dunes on Mars. In some areas, dunes have been observed to migrate over time, while on others the patterns have remained stock-still—some of them for perhaps thousands of years, or longer.

So I had successfully created the right conditions for a migrating sand dune. What about static dunes? Well—I had noticed already that some of the pyrite rock obstacles that I placed in the sand stream formed small dunes in the wind-shadows of their leeward sides. The rocks weren't moving, and so the dunes they were nurturing and protecting remained in place.

Some of the static dune ripples observed in Meridiani Planum—where the rover Opportunity is exploring—have been explained as possibly being protected by the presence of "blueberries": tiny nodules of gray hematite that have eroded out of Martian rocks, but which themselves are erosion-resistant, and too large (1-3 millimeters) to be carried by the wind. The blueberries, as the explanation goes, embed in the sand and form a protective "armor" layer for the dune ripples, which remain safe and still in their lee.

Where else do we find dunes, other than Earth? Well, you need wind of sufficient strength and sand of sufficiently small size, for starters. We don't know about dunes on Venus; Venus has a thick enough atmosphere, but the winds may be too sluggish to whip up much of a sand storm. The only other object with a thick enough atmosphere and a solid surface is Saturn's moon Titan—and in fact we have pictures of Titanian dunes taken by Cassini.

Now I'm feeling that old itch to make another trip to my favorite place in the Solar System, Death Valley, to explore the macroscopic dunes of Stovepipe Wells . I'll send a postcard….

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Comet Wild 2, as imaged by NASA's Stardust spacecraft.

Well, at Chabot, we like to bring things down to Earth a bit—not to diminish their wonder and awe-inspiring beauty, but rather to give us a chance to connect with pieces of the Universe in a personal way that—we hope—will only enhance their wonder.

Such it is with the Personal Comet. We make them in our classrooms, and our teen volunteers—Galaxy Explorers—sometimes set up a table in our exhibits to make comets for our visitors.

Last week I was teaching a lively group of 3rd graders our class, "Shooting Stars" (I'm not the usual teacher for this class, but love teaching this one especially).

"Let's make a comet," I announced, receiving a classroomful of suddenly puzzled 8-year-old faces. "Follow me." I led the group to the back of the room and had them sit in front of our rolling comet kitchen, tying on an apron and donning the "Comet Chef" hat.

"What's in a comet?" I quizzed. Hands went up, and answers were plucked out. "Water." "Ice." "Very small pebbles."

"Good answers. Let's start cookin'…."

One by one, and two at a time, I called up volunteers (no lack of these at all) to add ingredients into the mixing bowl.

Water first—two cupfuls. What else? The Chef helped out his students a bit: pebbles are fine, but what are they?

Silicon, calcium, to name a couple—so we add a source of these: sand. Then, iron, and magnesium—two more known comet constituents. Source? Dirt! Dirt can contain these, among other things.

For the carbon in our comet, we added—carbon: black charcoal dust; just a dusting.

There is nitrogen mixed up in comets too, so we had to add some to our concoction. Our nitrogen source (other than all the gaseous nitrogen floating about us in the air) is ammonia—NH₃ (what's a little hydrogen in the compound, more or less? In fact, ammonia itself has been detected in comets, so our recipe is true).

Organic compounds—carbon based organic molecules—have also been detected in comets…so we add a couple glugs of corn syrup. Okay, that's cheating a bit, because comet organics aren't known to come from agricultural products….

And lastly, but not leastly, is the two-in-one ingredient: contained in a plastic bag, I had the class use mallets to pulverize a few cupfuls of dry ice pellets into a fine powder. This adds not only the carbon dioxide to the material makeup of the Personal Comet, but that which really makes the difference between a bowlful of slightly sweet mud and the astral nugget of a comet: COLD! Space is cold, and so is dry ice.
In goes the frigid, dry frost, and out erupts clouds of billowing vapor—very exciting stuff. Now the Chef had to work fast, stirring and mixing and shaking the brew, and then squeezing the convulsive mixture in its plastic bag, with gloved hands, into a hard, solid lump. It takes a lot of squeezing, as it turns out….

Is it done yet?

I pulled out of the bag our Personal Comet, holding it out for the kids to marvel at—and they did. The double-fist-sized, dirty whitish, somewhat gritty hard blob is covered with pits and knobs and spouting plumes vapor. And, magically, it looks almost identical to a photograph of the nucleus of comet Wild 2, taken by NASA's Stardust spacecraft some years ago.

Everyone got to touch the comet—quickly, because it was quite cold—and make a personal connection with a tiny piece of the heavens. Now, I think, these kids are armed with an experience that will make their first comet-observing experience (yet to come for many of them!) a bit deeper, as I hope when they do see the vastly awesome sight in the sky, or through the eyepiece of a telescope, they'll also remember what it's like to touch a comet, or smell a comet, or see one spouting vapor right before them, in the palm of their hand….

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Students in Cork, Ireland interacting live via Skype with Chabot
during real-time observing session.

Wednesday morning around 1:00 AM, Chabot staff astronomer Conrad Jung and I fired up the systems in the 36-inch observatory and made a Skype video call to the Blackrock Castle Observatory in Cork, Ireland. Staffers Frances McCarthy and Alan Giltinan answered—it was 9:00 AM for them, and Frances had already been up four hours to prepare for our premiere session of Web of Stars. A bus-load of girls from a local school were on their way through the downpours of rain Cork was experiencing at the time.

On our end, everything technological was working fine: Nellie, our 36-inch telescope, was stoked, motors humming and ready to drive us to faraway celestial locales; computers were singing (in their own particular way), and the webcam-Skype interlink was green. The webcam view nicely framed the telescope, making a great background for the session.

A little after 2:00 AM PDT, the girls from North Presentation Secondary School rolled into the classroom, and there was a great deal of excitement. Eight or nine of them immediately descended upon the microphone and webcam and started chirping "helloes" and "hi's" at us across the 5,000 mile gulf (what's an ocean and a continent to get in the way of the Internet?).

After the greeting buzz died down, and the girls' teacher and the facilitators at Blackrock Castle got them to their computer stations, the morning's work began….

"We regret," Conrad and I had to inform them, "that the weather at Chabot is damp, and we're completely fogged out." This was a disappointment, of course, but we had a Plan B lined up in the event of bad astronomy weather. From Conrad's archive of astrophotography, we pulled up some un-processed astronomical images from months past and dumped them to our FTP server, where Alan at Blackrock Castle immediately downloaded them to the girls' computers: Comet Lulin, the Andromeda Galaxy (M-31), the Hercules globular cluster (M-13), the Apollo 15 landing region on the Moon, the Great Nebula in Orion (M-42), and the Ring Nebula (M-57) were the fare for the session.

With the astro-image processing software Salsa-J, the Cork girls proceeded to process the images—taking each set of three color channel (red, green, blue) black and white images and combining them into composite full-color images. Throughout the 2-hour session, the girls broke away from their computers two and three at a time to come to the microphone and chat with Conrad and I—we were even treated to a song or two from the girls, one by the entire class: On the Banks of My Own Lovely Lee.

The Web of Stars program was conceived of by Blackrock Castle Observatory, and Chabot became the partner observatory through proximity to San Francisco, which is a sister city of Cork. In Ireland, classrooms competed over the summer to earn one of the six pilot observing sessions with Chabot, and the program will unfold from October through March with one session each month.

Though we had to resort to our bad weather Plan B ("B" for "bad" weather) for our kick-off session, the A plan ("A" as in "actual active astronomy") will be for us to acquire and image objects with Nellie from lists of targets sent to us by the students in Cork, and deliver them in real time to the classroom at the Castle, where they will conduct the image processing and measurement activities in lock step.

Please wish us and the students in Cork good weather!

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Kevin Cain, Digital Capture Supervisor for Maya Skies, demonstrates his innovative image-capture process that replaces expensive custom hardware with affordable consumer equipment.

The film is groundbreaking for a couple of reasons.  It’s the first time the Chabot center is using state-of-the art laser scanning technology to create one of its films.  For Tales of Maya Skies, a team of 25 people spent seven weeks scanning the ruins of the ancient city of Chichén Itzá, in Mexico’s Yucatán Peninsula.  This technology is widely used by Hollywood productions because of the flexibility it gives a creative team.  Once they’ve scanned a particular site, they can play with any one of its variables: they can create the illusion that the camera is moving in crazy ways; they can manipulate the light conditions, and they can change the look of the location in any way they want.

The creative team behind Tales of Maya Skies, made up of, among others, Emeryville nonprofit Insight, the San Francisco animation companies Digitrove and Palma VFX, the ARTS Lab at the University of New Mexico, producer Konda Mason and director Jin An Wong, are taking advantage of all the possibilities that the scanning of Chichén Itzá provides.  The audience will be immersed in full-color animations that go beyond showing the ruins of Chichén Itzá as they exist today.  Instead, through laborious historical research, the creative team has reconstructed what the monumental city must have looked like at its peak 1,200 years ago, with temples painted in bright reds, greens, blues and yellows, and incense burning and flags waving atop them.

By using the 3-D digital images created through laser scanners as the raw material for the animations in Tales of Maya Skies, the film is also breaking ground in more indirect, but perhaps even more important, ways.  Insight, the Emeryville nonprofit that oversaw the scanning at Chichén Itzá, as well as the Orinda-based CyArk, another nonprofit that worked on the project, are engaged in scanning irreplaceable sites around the world, documenting them for the benefit of the archaeologists charged with preserving them, as well as for generations to come, which might lose the real thing to natural disasters, war, or the passage of time.  CyArk’s co-founder, Ben Kacyra, has set out to use laser scanners to document 500 sites in five years.

But laser scanners, for all the wonderful detail, speed and flexibility they offer, are expensive.  They can cost anywhere from $10,000 to $150,000.  That’s why Kevin Cain, Insight’s director, has been testing an alternative system that can accomplish the same thing at a fraction of the cost. All the gear he needs is a digital camera, a flash and software, at a total cost of under $2,000.  Here’s how it works.  For every 32-square-foot swatch of an object, Cain takes 10 still photos with his camera and flash.  Then he uses the photos to reconstruct the object based on the brightness of each individual point on its surface.  The system is based on a principle of physics discovered in the 18^th century.  The high quality of today’s cheap digital cameras is what makes it possible to apply this principle to create an inexpensive image-capturing system.

“With this new technique, our ultimate goal is to be able to provide very low-cost, very usable results for archaeologists,” Cain said, “because until the price goes almost to zero, archaeologists aren’t going to be able to adopt it, just given the realities of their field.”  To illustrate those realities, Cain used the example of the work that Insight has done in Egypt for the past decade.  Each year they join a team of archaeologists for their field work at the Tomb of Ramses.  A complete yearly field season costs under $50,000, many times the cost of an inexpensive laser scanner.

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Three views of Jupiter before, during, and after the disappearing act by its four large moons. Credit, Conrad Jung, Chabot Space & Science Center

What am I talking about? About a week ago a relatively rare alignment of Jupiter and its four Galilean moons—Io, Europa, Ganymede, and Callisto—made for a brief time in which the moons disappeared, hidden behind and in front of their massive parent planet. For that brief time, Earth, Jupiter, and all four Galileans coincided on a nearly perfect line.

The event took place late in the evening on September 2nd, a little after 10:00 PM. Ganymede (the Solar System's largest moon) and Europa (the "snowball" with the probable deep liquid water oceans under its icy crust) crossed in front of Jupiter's disk, and the other pair, Io (the volcano moon) and Callisto passed behind it.

It's not uncommon for one of these moons to be out of view for a time when you aim a telescope at Jupiter. Even Galileo, on his first telescopic look at Jupiter, saw only three of them.

The disappearance of two or three of them at once is more rare, however, and a vanishing act by all four only happens a few times in a lifetime—every century, there are about 20 such alignments. The last such event prior to last week's was back in the 1980's; the next one won't happen until 2019. This event was not only observed on September 2nd by Chabot Space & Science Center astronomer Conrad Jung, but also in 1913 by then Chabot Observatory director Charles Burckhalter.

When Galileo took his newly made telescope and became the first person in history to look at Jupiter through the new invention, he saw three star-like points of light positioned around Jupiter, roughly on a common line that passed through the planet. At first he thought they might be stars, but on subsequent nights he observed that not only did these "stars" follow Jupiter's own movement through space, they changed position relative to each other. This led to Galileo's hypothesis that these were satellites in orbit around Jupiter.

The rest is history (oh, and lifelong house arrest for Galileo for suggesting that there was something in the Universe that didn't revolve directly around the Earth…).

I'm sure that if Galileo had first looked at Jupiter on one of these rare nights and saw no moons, he would certainly have discovered them the next time he looked at Jupiter—so maybe it wouldn't have changed the unfolding of historical events much. But I wonder which would have been more surprising to him: seeing the moons on the first look, or observing them to appear out of nowhere after the initial observation of a solitary Jupiter….

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Artwork from Jules Verne’s 1865 novel, From the Earth to the Moon

Sounds like something out of a Jules Verne novel… but that's exactly what NASA's up to this year with the upcoming LCROSS (Lunar Crater Observation and Sensing Satellite) mission, scheduled for launch on June 2nd and impact sometime in October– exact date TBA.

And it's not unprecedented, either: the Lunar Prospector spacecraft back in 1998/1999, whose instruments detected possible signs of water ice in craters around the Moon's poles, was crashed into the Moon's South Pole at the end of its mission. The aim was to blast up a cloud of material from the lunar surface and spectroscopically analyze the plume in search of water vapor. None was detected then, but that's where LCROSS comes in.

LCROSS will seek to verify the presence or absence of water ice and related hydrated materials buried at the bottom of a permanently shadowed crater floor on the Moon's South Pole. Water ice cannot persist on any part of the Moon's surface that is subjected to sunlight, but because of the Moon's low axial tilt with respect to the ecliptic (the Sun's apparent annual path in the sky)– only about 1.5 degrees– there are craters at the Moon's poles whose floors never see the light of day, all month long and year round. Water ice could persist near the surface in these places.

LCROSS consists of two pieces: a "Shepherding Spacecraft" that will guide the whole affair to the proper location on the Moon's South Pole, and the Centaur rocket stage that propelled the spacecraft to the Moon. The pair will separate, and the Centaur rocket will become the primary impactor, striking ground and producing a crater and plume of ejected material. Viewing the event from above, the Shepherding Spacecraft will use cameras and other instruments to analyze the plume from a distance, and will then follow the same course as the Centaur, descending four minutes after impact through the ejected plume and analyzing material samples as it falls.

Then, the Shepherding Spacecraft, too, will impact the Moon– and the plume it kicks up may well be visible through modest sized telescopes on Earth. We're planning to watch the explosion live through our telescopes at Chabot, weather permitting. Keep an eye on our website for details.

Now, back to Jules Verne for a moment. The launching of a projectile with the intent of striking the Moon was indeed the subject of one of his novels, From the Earth to the Moon, published in 1865. Fired from an enormous cannon, the goal of that post Civil War mission was to catch the attention of anyone living on the Moon, to open up a line of communication with their civilization.

My wife asked me if crashing a probe into the Moon would have any harmful effects, particularly if in fact there is any form of life (subsurface microbes or such) living there. Well, certainly, if you happen to be a lifeform living at ground zero of the impact… but the fact is the Moon is frequently struck by meteorites much larger than the LCROSS impactor anyway. To paraphrase Douglas Adams, "that kind of thing goes on all the time."

One last fun tidbit about the Jules Verne novel: the launch site for his cannon-fired projectile was a place in Florida, 50 miles south of Tampa Bay, and only about 135 miles from the Kennedy Space Center, from which LCROSS will be launched…

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A few weeks ago, this asteroid came really close to hitting Earth.

Called “2009 DD45”, the asteroid was estimated to be around the same size as the one that exploded in the atmosphere near the Podkamennaya Tunguska River in remote Siberia on June 30th, 1908, flattening 80 million trees across eight hundred square miles of remote forest. Of course, if an asteroid of this size were to hit a city or in an ocean offshore from a populated area, tens of thousands of people would likely die.

Then, just as the last of the night sky observers were completing their collective sighs of relief, on March 17th, 2009 another Tunguska-class asteroid, 2009 FH, passed by about 53,000 miles from Earth. Thankfully, neither of these asteroids actually hit us. But astronomers didn’t even observe 2009 DD45 until 4 days before its closest approach. It's orbit was calculated and it was determined that it would miss the Earth. But it's likely that asteroids of this size are fairly frequently buzzing by the Earth. And until recently, most of them have been undetected.

In 1998, NASA started the Spaceguard Survey which set out to discover 90% of those Near Earth Asteroids (NEAs) 1 km in diameter and larger. An impact by an asteroid this size would likely cause global destruction and an end to much of life as we know it so it’s definitely reassuring that 10 years after its inception, the Spaceguard Survey had found about 80% (CK) of them. But unfortunately, once we’ve found them, there’s still no international concensus or infrastructure in place in how to deflect or destroy them. But the Survey is limited by its mandate to find those mass extinction-sized asteroids as well as by the size and sophistication of the telescopes that are dedicated to searching the skies.

As former Apollo 9 astronaut, Rusty Schweickart said in a recent phone conversation, "in the process of finding the big ones, you also find a bunch of small ones, and the smaller ones are obviously far more numerous than the large ones." But it will take many more resources and new telescopes to continue searching for and tracking the smaller ones. And unfortunately, once we’ve found them, there's still no international consensus or infrastructure in place in how to deflect or destroy them. Raising awareness and building alliances amongst governments and space agencies is Schweikart's current "mission". He founded the B612 Foundation and Association of Space Explorers to tackle these goals on different fronts.

The message that I hope is conveyed with the Asteroid Hunters TV segment is that we are not immune from asteroid impacts here on Earth. Rusty Schweikart puts it best in a portion of his interview that didn’t make it into the final program:

"Well, asteroids and comets are good news and bad news, you know? But for them we wouldn’t be here, and on the other hand, if we don't actually take some action now, at some point we won’t be here anymore, because there's no question that we will be hit by asteroids, and we’ll probably be hit by, we would be hit by comets as well. Unless, we use the technology that we have and the brains that we have in order to protect the Earth from asteroid impacts, and we can do that. We can basically now, with current technology, assure that no asteroid ever hits the Earth again. That can do any serious damage."
-Rusty Schweikart

Here's a little exercise from Rusty that you can do to get a sense of what we know today about exactly what's out there:

• Go to: neo.jpl.nasa.gov/risk
• See two tables, the first table says "Recently Observed Objects" and the table below says "Objects not recently observed." You’ll notice in the bottom table that Apophis is the 4th one listed.
• Click on "Apophis". At the top you see a bunch of boxes, like the diameter at .27 km, or 270 meters.
• Down below that you see 3 lines, those are the 3 potential impacts. The first one is April 13, 2036. Go over to the right on that line you'll see the column "Impact Probability" is 2.3 x 10-5 – click on that. So there is the probability, 1 in 43,000 of that particular impact.
• Now if you go back to the main table you can do the same thing with every single one of those lines.
• Now go to the very top of the page and hit "Discovery Statistics." Scroll down to a blue and red graph "Known Near-Earth Asteroids". This shows the discovery rate beginning back in 1980 going up to almost current time. Notice the knee in that curve in 1998 – that’s when the Spaceguard Survey began.
• Scroll down to table just below the graph and look across that table to the far right side, to see that a a total of 6166 NEOs (of ALL sizes) have been discovered.

Rusty concludes that, "…what we really care about is not only the things that large, we care about things that can hurt us. Things that can hurt us go down to 40 to 45 meters or so. Instead of there being 940 of them, there are more like 600,000 of them. So the new charge for NASA, which they have so far ignored, is to find 90% of the objects 140 meters and larger by 2020. You can't reasonably set a goal to find everything down to 40 meters because it's just beyond the capability of telescopes and the money available. So NASA, working with Congress, set the goal at 140 meters. Now nevertheless, when you are looking for 140 meter objects, it’s going to take bigger telescopes than the ones to find a kilometer. Therefore we are going to find many many smaller objects as well. So 10 to 15 years from now, instead of that number on the far right hand column being 6000, it will be 1 million."

Watch the Asteroid Hunters television story online.

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