QUEST Community Science Blog Author: Ben Burress

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Oakland Teachers Scope Out What Galileo Saw

November 6th, 2009 by Ben Burress

Oakland Unified teachers assembling Galileoscopes at ChabotWhat was it like for Galileo, the first time he put an eye to his telescope to see things in the heavens as never before seen? As anyone who has seen a planet or a star cluster or a nebula—or the Moon—through even a small telescope knows, the sight can be quite breathtaking. For Galileo, it must have been a universe-changing experience….

Through a generous donation by a concerned citizen (concerned that kids today aren't seeing enough of the sky), Chabot just completed a pair of workshops for Oakland teachers that places in their capable hands and in their classrooms "Galileoscopes"—special telescopes designed and manufactured for the 2009 International Year of Astronomy. The Galileoscope is a low cost, simple, but good-quality telescope designed to simulate the power and field of view of Galileo's original telescope, which opened up the universe in such a profound way.

In September and October, a total of 23 Oakland teachers received training, activities, and one Galileoscope each (plus tripod), enabling them to share the experience with their students and, hopefully, spark their imagination and curiosity about the world around us in a way that nothing but astronomy does.

A look through a telescope—any telescope, big or small—does put a spark in the eye and the imagination. At least, that was my experience. Growing up in Oakland back in the 60's, I didn't have access to any small telescopes, but Chabot Observatory was only a couple miles away, and my family often went up on a weekend night for a classroom demo, a planetarium show, and thoroughly enjoyable viewing through the two antique telescopes, Leah and Rachel. Something about the actual light from Saturn or Jupiter or a distant galaxy tickling the receptors in your retina places you out there—or puts those objects directly into your brain.

The Oakland teachers now armed with their Galileoscopes will use these simple but effective tools to show their students the difference between seeing Saturn as a spot of light and Saturn as a disk with "ears" (the appearance of its rings through a Galileoscope), or the difference between Jupiter as a brighter spot of light and Jupiter as a world with a giant storm in its clouds and four smaller "worlds" (moons) in orbit around it, or the difference between the Moon as a disk with light and dark areas that make interesting shapes in our imaginations and the Moon with mountain ranges, vast plains, thousands upon thousands of craters, and shadows stretching across the landscape.

By the way, Galileoscopes can still be ordered, through the Galileoscope website, for a short time still, in case you're interested in getting your toe into the door of a much bigger universe….




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Posted in Astronomy, KQED | Please Comment

Web of Stars

October 23rd, 2009 by Ben Burress

Students in Cork, Ireland interacting live via Skype with Chabot
during real-time observing session.What do Chabot's 36-inch telescope, Nellie, and a classroom full of 14-year-old girls in Cork, Ireland have in common? In a few words, the International Year of Astronomy and the Web of Stars!

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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Posted in Astronomy, KQED | 3 Comments

Equinox on Saturn Reveals Ring Ripples

October 9th, 2009 by Ben Burress

Bumps and ripples in the otherwise flat ring system of Saturn cast long shadows at equinox. Image credit: NASA/CassiniImagine a vast, flat plain spreading out before you for tens of thousands of miles in all directions, with no Earthly curvature to give the horizon its slightly finite look. Instead, it stretches seemingly to the infinite blackness of space in one direction, and slices straight into the streaky, wind-smoothed clouds of Saturn in the other…

Hard to imagine what it would be like to float just above the rings of Saturn, but what a sight it must be! As a kid, one of my favorite astronomical pass-times was imagining the view from other places in the Solar System.

Now imagine a towering bulge of frosty mist rising up out of this super-flat plane of ice chunks, literally the size of a mountain. Such is what was beheld by NASA's Cassini spacecraft last month–albeit, from a distance–when it turned its cameras to Saturn's vast rings during the few days surrounding Saturn's equinox (August 29, 2009), giving us a view never before seen.

Equinox on Earth, when the Sun is positioned directly over our equator, happens twice a year. Due to Earth's tilted rotational axis, as we orbit the Sun the latitude over which the Sun shines directly cycles north and south between the latitudes of the Tropics. On its way north to warm our (Northern Hemisphere) summers or south to leave us in the chill, the Sun crosses the equator on the equinoxes (Fall and Spring).

The same thing happens on Saturn, with two differences. First, Saturn takes nearly 30 years to orbit the Sun, so equinox comes only about every 14 years. Second, Saturn has its system of rings that encircle the planet directly above its equator, serving as a visible extension of the equator. At Saturn's equinox, the Sun is not only directly over the equator, but sunlight strikes the rings edge-on, like a flashlight shining on a flat piece of paper from the edge, the light just grazing over the surfaces on either side.

When this happens, any deviations from the flatness of the ring system—bumps and ripples–cast long shadows across the rings, making the features much easier to see. The same thing is seen on that piece of paper with shadows from creases and bumps leaping across the page.

As seen from Earth, equinox on Saturn means the rings appear to vanish as we look at them edge-on. This behavior puzzled astronomers long ago before they understood the rings for what they are. During the August 2009 Saturn equinox, however, for the first time in history we had a bird's-eye view of the rings during equinox, from Cassini. Cassini has been in orbit around Saturn for five years now.

Cassini spotted a number of prominent shadows trailing bright spots and ridges—bumps and ripples of different sorts rising above the ring plane.

Some of the bumps–icy ring material kicked up by the gravitational disturbance of a small moonlet inside the rings–were measured at over two miles high, the height of the Rocky Mountains. Other rippling features, such as long ridges running along the direction the rings encircle Saturn, are waves created by the gravity of moons orbiting outside the ring system. Still other types of disturbances observed are possibly caused by the impact of meteoroids or chunks of ice with the rings.

Saturn's rings are tens of thousands of miles across, but are extremely thin—perhaps no thicker than the height of a four-story building! So a bump or ripple as high as a mountain is a big deal!

Ah, to be on Saturn, now that equinox is here…




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Posted in Astronomy, Partners, Physics | Please Comment

MOON Spells "Water"

September 25th, 2009 by Ben Burress

Map of Moon water; blue indicates higher concentrations of detected water molecules. Credit: NASA/Moon Mineralogy Mapper instrument.Here it comes! A veritable tidal wave of discovery on Earth's Moon….

In one short week, NASA's LCROSS (Lunar Crater Observation and Sensing Satellite) mission will quite literally come to an end—a fiery, spectacular end as it deliberately crashes into the lunar South Pole crater Cabeus A in hopes of kicking up enough material for us to detect the presence of water. If you want to see the action as it happens, come up to Chabot Space & Science Center on Friday morning, October 9, 3:00 AM to watch NASA's live simulcast and–weather and the gods of astronomy permitting–the view through Chabot's 36-inch telescope, "Nellie."

In recent months, NASA has been sending a lot of acronyms—excuse me: spacecraft—to the Moon: LRO with it's LROC, LEND, and LOLA instruments; LCROSS (which I've heard some call "LaCROSS," for the record) with its VIS, NIR, MIR, TLP, VSP, NSP—oh, the list goes on!

The fact of the matter is MOON spells "Moon." Whether or not we do end up returning humans to the Moon in the next decade, which is partly what reconnaissance by LRO and LCROSS and their arrays of acro-instrumentation is for, there are still things to be learned about our nearest neighbor in space—and water is the word at present.

Even as LCROSS and its Centaur-booster-rocket-turned-lunar-clobbering-device follow their final fatal trajectory toward Cabeus A, its launch buddy LRO, now in an orbit around the Moon and beginning to send back scientific results and images, may have already detected telltale signs of the wet stuff—which on the Moon won't be wet, but frozen solid, of course; liquid water cannot persist in the Moon's airless environment.

LRO's LEND (Lunar Exploration Neutron Detector) instrument is designed to find signs of water molecules by measuring neutron radiation emanating from the lunar surface. The Moon is constantly bombarded by high energy cosmic radiation, which forms radioactive isotopes in the soil that in turn emit neutrons. By measuring the abundance and speed distribution of the neutrons, details of soil chemistry can be inferred. The presence of light atomic nuclei–in particular the lightest of all, hydrogen, a component of water—in the soil reduces the levels of neutron emission. That drop in neutron radiation is the telltale scientists are looking for.

While LRO scientists want to make further measurements before concluding the presence water ice concentrations, observations from three other spacecraft—NASA's M3 instrument (Moon Mineralogy Mapper) aboard India's Chandrayaan-1 spacecraft and the Cassini and EPOXI spacecraft—have mutually confirmed the presence of water and hydroxyl molecules (hydroxyl is a water molecule missing one of its two hydrogen atoms) in the soils of the Moon, across much wider expanses than the confines of dark polar crater floors.

Cassini and EPOXI made measurements as they flew past the Moon to their respective destinations (Saturn, and a comet), and measurements have been made by M3 from lunar orbit. The detection of water by these spacecraft doesn't mean seas of liquid or glaciers of ice, or even blanketing layers of gaseous water vapor, but rather relatively small amounts of water and hydroxyl molecules attached to, or "stuck to," other materials in the top few millimeters of soil.

This thin "confetti" of water molecules appears to come and go with lunar daytime, forming during the cold, dark two-week-long lunar night and diminishing under the baking light of the Sun.

So, right now, MOON spells water (M3 et al), water (LRO), and possibly more water (LCROSS, on October 9th)—at least, the evidence seems to be mounting!




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Posted in Astronomy, KQED, Partners | 3 Comments

Jumpin' Jupiter! Where Did the Galileans Go?

September 11th, 2009 by Ben Burress

Three views of Jupiter before, during, and after the disappearing act by its four large moons. Credit, Conrad Jung, Chabot Space & Science CenterNow you see them, now you don't! Had Galileo spied the planet Jupiter with his telescope 400 years ago on a night such as a couple of Thursdays ago, would the history of modern astronomy have unfolded any differently? Would Jupiter's four large "Galilean" moons have been named so in his honor? Would we still think that everything revolves around the Earth?

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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Crab Nebula: Awesome Beauty From Destruction

August 28th, 2009 by Ben Burress

The Crab Nebula as seen through Chabot Space & Science Center’s 8-inch refracting telescope, Leah. Image: Conrad Jung, Chabot Space & Science CenterWhen asked what got me interested in astronomy, the stock answer I offer is my childhood experience going to Chabot Observatory and looking through the telescopes—and I'm sure that had a great deal to do with it. But, if I want to give an even shorter answer, I just say, "Crab Nebula!" and walk away….

What's the Crab Nebula? Astronomy enthusiasts are very familiar with this celestial object, or at least become so very quickly after entering the world of space. It's a supernova remnant—a torn and tortured cloud of gases expanding outward into space, the aftermath of a supernova explosion that happened almost a thousand years ago in the constellation Taurus. In fact, as I write this blog, the age of the Crab Nebula is exactly 955 years and 40 days.

How do we know with such precision when this former star went supernova? The answer, as always in science, is careful observation! The explosion of the star was witnessed by Chinese and Japanese astronomers—and possibly sky watchers of the American Southwest—who carefully observed and recorded the event. The explosion took place on July 4th, 1054 CE.

Seven hundred years later, a century after the invention of the telescope, the Crab Nebula was discovered in the same spot—first in 1731 by John Bevis, then again by Charles Messier in 1758 (August 28, in fact—the date of this blog posting!). Messier ran across it while searching for Halley's Comet, and at first mistook it for a comet. This was the reason that he began compiling his famous Messier catalog of "fuzzy" objects: a wall of mug shots of unusual suspects that resembled, but were imposters of, comets. He began his catalog with Messier 1 (M1), the Crab Nebula.

Messier 1 got its nickname of the Crab from a drawing made by observer Lord Rosse in 1844.
Today, the Crab Nebula is an expanding cloud of gas and some dust spanning 10 light years, or 60 trillion miles. The cloud is still expanding at a speed of about 1,800 kilometers per second—a speed that would get you to the Moon in just under 4 minutes! At its center is the collapsed remnant of the dead star's core, which has become the incredibly small and dense object known as a neutron star.

So why did the Crab Nebula spark my interest in astronomy? I have a specific memory of being at a summer camp and engaging in a craft activity where we cut out the pictures from a bunch of astronomy calendars and made frames and matting to display them in. I selected a few of my favorite images, which included the Dumbbell Nebula (a planetary nebula), the Veil Nebula (another supernova remnant), and, of course, the Crab. Of all these stunning astrophotos, it was the Crab that stuck the longest in my mind and on my bedroom wall, and impelled me to get my first subscription to Astronomy Magazine, and eventually my first telescope. Sometimes, our lives are guided by stars….




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Posted in Astronomy, KQED | 3 Comments

Mars Rock Talks, Opportunity Listens

August 15th, 2009 by Ben Burress

Block Island—a half-ton meteorite found on Mars by NASA's Opportunity rover.Image credit, NASA/MER OpportunityEver been driving down a lonely desert highway when you suddenly glimpse something in the corner of your eye that makes you think, "What was that?!" You brake, tires screech, you spin the wheel and make a wild U-turn, cutting into the shoulder and leaving a rooster-tail of dust as you floor the gas to get back to what you thought you saw….

Okay, dramatic desert car scene ended. That would be the Hollywood movie version of what NASA's Mars Exploration Rover Opportunity did recently, on the lonely desert highway that it's scouting on Mars.

On its determined long trek from Victoria Crater to the larger Endeavour Crater (a 12-mile span that Opportunity has completed about one fifth of over the past year), the rover passed by an X-box-sized block of iron that presented the appearance of a meteorite. It snapped a picture in passing, which was eventually transmitted to Earth and examined. By this time, Opportunity had already traveled about 180 meters beyond the block (dubbed "Block Island"). This is when the rover was commanded to backtrack all the way to the find (though it's doubtful it worked up a rooster tail).

Upon returning to Block Island—quite obviously an iron-nickel meteorite by appearance alone, but whose composition was confirmed by the rover's alpha particle X-ray spectrometer instrument—Opportunity took more pictures, including extreme close-ups with its microscope camera, which revealed surface patterns similar to those found on Earth iron-nickel meteorites that have been exposed to long-term weathering by wind and sand.

As interesting as stumbling upon a half-ton meteorite on the dusty plains of Mars' Meridiani Planum is, what this particular chunk of weathered iron is telling scientists sparks the imagination. In a nutshell, given the thinness of Mars' current atmosphere, scientists wouldn't expect a meteorite of this size to survive impact intact, at the speed it would be going. One of the possible explanations for Block Island's rock-houndable state is that when it fell to Mars, Mars' atmosphere was substantially thicker than it is now.

Further examination of the meteorite may reveal clues as to how long ago it fell through Martian skies. Evidence that Mars' atmosphere was warmer and thicker in the distant past, as well as the possibility that there was liquid water on the surface, has been mounting over the years. The age of this meteorite-fall could shed more light on the history of Mars' environment. If it fell billions of years ago, Block Island would weigh in as more evidence to support our current suspicions. If, however, we find that it fell more recently, then this could indicate that the atmosphere was more substantial later in Mars' history than we thought.

Imagine, if you will, a Mars that looks even more Earthlike than it does now: seas of water with waves rolling into shorelines, great clouds sending downpours of rain and snow onto mountains and plains, streams and rivers snaking through the landscape. Maybe, maybe, even some form of life?

All that from a rock? Yes, rocks talk, if we listen.




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Posted in Astronomy, Geology, KQED | 4 Comments

Jupiter "Nuked" By Comet? (again)

July 31st, 2009 by Ben Burress

Hot spot created by impact on Jupiter, taken by NASA's Infrared Telescope Facility in Hawaii. Picture credit, NASA. An Earth-sized hole on Jupiter! the email alerts, websites, and finally news channels were saying on Monday, July 20th. At Chabot, we were polled by at least two local news channels asking what had happened. So, what happened?

Evidently, the aftermath of some kind of collision on Jupiter was spotted by an amateur astronomer in Australia that Monday morning. He spotted a dark marking near the planet's South Pole, and alerted NASA. NASA in turn turned its large infrared telescope in Hawaii onto the scene of the crash.

There glowed the thermal footprint of the likely impact, the affected area roughly the size of the Earth. Had this impact taken place on Earth instead, the results would have been catastrophic. Fortunately this was Jupiter, half a billion miles away and large enough to absorb the impact without lasting effects. (And, owing to the fact that Jupiter is a gaseous planet with no solid surface, it would quickly heal from the trauma, not unlike that liquid-metal Terminator from the second movie of the same name.)

A significant event? Yes, in fact. But that's not all…

Rewind 15 years to July 20th, 1994, the middle of the week during which twenty-something fragments of the broken comet Shoemaker-Levy 9 were in fact colliding with Jupiter… An amazing coincidence? Yes; the two events likely have nothing to do with each other. So, then, a common event, if we're seeing two of them in the span of only 15 years? Well… not really.

When the string of fragments of Shoemaker-Levy 9 hailed down on Jupiter, it was the first time in history that humans had observed actual impacts on a Solar System body (other than perhaps the Sun–but as it turns out comets hitting that huge target are not uncommon). The Shoemaker-Levy 9 impacts, and the one on July 20th this year, left highly visible marks that lasted for days. The amateur astronomer who discovered the recent scar did so with a relatively small 14.5″ backyard telescope! So, if this sort of impact were a common event, even if the impacting comets or asteroids were never seen, the gashes they leave in Jupiter's atmosphere ought to be spotted from time to time.

Impacts—on Jupiter, Earth, and all the bodies of the Solar System—do occur, and the smaller the impacting object, the more frequently they happen. For a planet like Earth, on average a chunk of rock a few meters across enters our atmosphere about once a year, and often burns up completely or explodes before hitting the ground. A 50 meter object, again on average, is likely to strike Earth once in a century. A one-kilometer object impact averages every few hundred thousand years, and a multi-kilometer sized asteroid or comet similar to the one that wiped out the dinosaurs and which would cause global catastrophe—well, the last one of that size struck ground 65 million years ago.

As for Jupiter, being a larger target than Earth, having a much stronger gravitational pull, and being close to the asteroid belt—well, Jupiter's impact statistics should probably involve higher frequencies than Earth.
In fact, impacts like the one on July 20th are happy events for us; every time Jupiter is hit by a large object, that's one less object in the Solar System that could potentially hit the Earth in the future. So, on July 20th, Jupiter took another bullet for us.




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Neil Armstrong's Lunar Footprint Turns 40

July 17th, 2009 by Ben Burress

Neil Armstrong’s left boot print on the Moon—the celebrated ‘one small step’. Credit: NASA
What were you doing 40 years ago, on July 20th, 1969, when the first human foot (booted, not bare) made its impression on the gritty surface of the Moon? That is, if you're over 40 yourself….

I was in Oakland, lying on the green carpet of my family's living room floor, watching our black and white Zenith television set—the kind that would take a minute or so to warm up before delivering the handful of local VHF TV broadcasts within range of our aerial antenna.

Right. It was definitely another era. As archaic as the telecommunications technology may sound to those born after, oh, 1980, it was nevertheless the Space, not Stone, Age…. Never forget, the Apollo 11 landing on the Moon was the culminating moment of the whole adventure that started the Space Age.

It didn't really matter that our Zenith was a b/w set, as all the images from Apollo 11 and the Moon's surface were transmitted in black and white anyway. My eyes were riveted to the TV, the grainy, fuzzy image of the Eagle's landing strut and ladder as yet empty.

"What's taking them so long?" I complained impatiently (I was seven years old). I remember waiting for what seemed a couple of hours for the astronauts to come out.

"They're probably playing poker inside," was my dad's reply. I don't recall if I believed him or not. Finally, there was a booted foot at the top of the ladder, attached to the bulky white and gray form of a human in a space suit—Neil Armstrong, of course. And, history was made—twice: Buzz Aldrin came down the ladder soon after.

Some of you younger crowd may have been born into a world where humans walked on the Moon a long time ago, but I was born around the time it was actually happening. (In fact, I was born the year after the first human went into space; similarly my grandfather was born the year of the Wright Brothers' first aerial success—how time flies….)

On Monday, we not only mark four decades since that singular historic event, we do so at a time when there are plans afoot for humans to step onto the Moon once again.

Several robotic probes have gone Moonward in recent years, paving the way: Clementine, Lunar Prospector, and only last month the Lunar Reconnaissance Orbiter (LRO) and the Lunar Crater Observation and Sensing Satellite (LCROSS) were launched in tandem. LRO will give us our most detailed and comprehensive view of the Moon's surface appearance and conditions to date, and will help to identify future possible landing sites. LCROSS will look for water ice in a crater floor at the Moon's South Pole by impacting it with an empty booster rocket and studying what is blasted skyward. Water on the Moon would be a resource to future human missions far more valuable than gold.

Neil's left boot print is still up there, next to the Eagle's landing foot, most likely as fresh and new looking as when it was made (unless it got bulls-eyed by a one in a million meteorite strike!).

As there is no air, and thus no erosion, on the Moon, the print serves equally well as a monument to that decades-ago venture, or as a logo for the enterprise of our return. Fitting, too, as the Moon could serve as a stepping stone to destinations beyond….






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Far Out, Man: Measuring Astronomical Distances

July 3rd, 2009 by Ben Burress

Centuries ago the stars were believed to reside just beyond the planets of our solar system.It never fails to astound me how big the Universe is—how far away even the nearest stars are, let alone other galaxies scattered from here to near infinity….

How do we know how far away celestial objects are? This shouldn't be taken for granted, as it's not as straightforward as sounding the depth of the ocean floor with sonar, or determining the range to an object by bouncing radio waves off it and timing the reflection.

In fact, we have "pinged” the nearest celestial objects with radar to determine their distances very accurately. Examples are the Moon and Venus, where round-trip lightspeed travel is measured in seconds or minutes.

Before radar, the scale of the Solar System had to be determined geometrically, by observing events like Venus or Mercury transiting the face of the Sun from different locations on Earth and triangulating. Even this technique requires telescopes, which we've had only four hundred years. Before that, figuring out distances to just about everything except the Moon was mostly guesswork. In fact, it wasn't too many centuries ago that the entire Universe was believed to be not much larger than the Solar System—the Sun and it's nine…excuse me…eight planets—as we know it today.

Once the distance from Earth to the Sun was figured out, that length (the "Astronomical Unit”) in effect became a basic measuring rod for working out distances to everything else, by one means or another.

As Earth orbits the Sun, the direction from which we see stars shifts minutely, and we can observe a small change in a star's position compared to the more distant "background” stars. You can see the same effect by holding a finger in front of your face and looking at it alternately with one eye, then the other.

The geometry of this observation is a simple triangle, whose base is the distance between your eyeballs and whose legs are the lines from each eyeball to your finger. By knowing the length of the base, and observing the change in viewing angle against the background, the length of the legs (distance from your eyeballs) can be calculated.

In the case of Earth and a nearby star, the "eyeballs” are the Earth at two ends of its orbit around the Sun (six months apart) and the "finger” is the star.

But this measuring of distance by "trigonometric parallax," as it's called, only works for the nearest stars, as the minute shift in the star's apparent position diminishes with distance.

As astronomers learned more about the distance to nearby stars, they determined how to relate their temperature and mass to their actual brightness, and it became possible to estimate the distance of many stars by measuring their apparent brightness, with an understanding of how the brightness of light weakens with distance.

To measure the depths of space between us and galaxies far, far away, in which individual stars are indistinguishable from the overall galactic glow, we can turn to certain types of supernovae: individual stars that temporarily shine brightly enough to be observed and measured. Like the flare of a match struck in the dark night, the brilliance of the flash reveals how far away the striker stands.

We have built up our knowledge of the Universe's vastness over the past couple centuries, working out the problem from the near to the far. Even as science and technology have made the world on which we live smaller, it has done exactly the opposite to the Universe….




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Posted in Astronomy, KQED, Partners, Physics | 2 Comments
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