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!

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.

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….

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…

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.

The footage of the August total eclipse that we got from the Exploratorium and used in our story is incredibly beautiful. The red images of the sun that you'll see are created by a telescope that views the sun in a wavelength of hydrogen gas. "The sun is mostly made of hydrogen gas," said Doherty, "and this is a deep red wavelength called hydrogen alpha." You can watch the entire China 2008 eclipse on the Exploratorium's web site. And Doherty recommends trying to view the next two total solar eclipses live. They will be visible on July 22, 2009, from Shanghai, China, and on July 11, 2010, from Easter Island. But if your budget doesn't allow you to travel that far, you can always wait until 2017, when a total eclipse will be visible in Washington and Oregon and all the way across the United States to South Carolina. Or you can plan to visit the Exploratorium or the Chabot Space and Science Center on any of those three days, to watch the eclipse through their live feed.

Watch the Eclipse Chasers television story report online.

The 1992 'Peekskill' meteorite and its point of
impact in Peekskill, New York. Credit: "Pierre Thomas

The first thing I tell people is that I'm not a meteorite expert, but that I have a contact who is. This rarely discourages them from wanting to bring their rocks in for a look.

The first sample was brought in by a family who said they collected the chunk of iron from Lake Tahoe. This one actually looked promising to my mostly untrained eye: a fist-sized chuck of magnetic metal, with pits and holes and an overall melted look. I took some pictures to send off to our regional expert and told the family I'd call them to let them know what he said. The response to the pictures was pretty certain: it wasn't a meteorite, but a chunk of metallic slag. I was told that this is a common mistake; that often bits of slag from old foundries or other sources are taken for meteorites.

The second sample brought to me didn't really strike me as a meteorite, by appearance. It was metallic, but not magnetic; it was pretty heavy for its size; it didn't have any obvious signs of melting, and no real pits or holes-other than one, deep, tunnel-like hole the width of a finger. It didn't appear jagged or shrapnel-like, as fragments from an exploding metallic meteorite often do. Finally, it had wide, flat facets that looked much more like the result of natural rock cleaving as pieces of Earth's crust break apart.

I went ahead and performed a density measurement on the sample. It was pretty heavy, so our sensitive balance scales wouldn't handle the load. Instead, I resorted to our "learn your weight on other planets" scale-the one that tells you how much you would weigh on the Moon, Mars, and other planets, in addition to your Earth weight. (I found this scale useful when I had a package to mail and needed to know the weight; by selecting the Moon weight of the package, I would pay only one-sixth the normal Earth rate!)

The double-fist-sized sample was 11.3 pounds, which converted to 5126 grams. Then, I selected a graduated beaker from our lab, filled it with water and submerged the sample. Reading the difference in water level with and without the sample, I measured a volume displacement of 750 cc. So, the density-mass divided by volume-turned out to be about 6.83 grams/cc. That's twice the typical density of silicate-type rocks (stone), and fairly close to that of pure iron.

I sent the owner off with my appraisal that the rock didn't present the appearance of a meteorite, and though the density was in neighborhood of that of iron, the appearance (black, inside and out) and non-magnetic nature suggested some other metal or metal-stone mixture. As always, I encouraged him to seek an expert appraisal.

Let's face it, all rocks found on Earth are ultimately of extraterrestrial origin-though what we regard as Earth rock has been on Earth for many billions of years, and shaped, reshaped, and metamorphosed by eons of weathering and geological activity. Meteorites, then, are only the newcomers….

Depiction of a major alignment of
the five visible planets in 1059 BCE.

Photo By Ben Burress

There are some pretty good "lineups" coming soon to skies above you.

First of all, "lineups," or alignments, go on in the heavens all the time, though most often they are alignments of objects too faint to easily notice, if at all. With that said, this summer holds some significant alignments of some of the brightest objects in the sky.

First on my hit list is the upcoming Saturn-Mars "near-miss". Though these two planets are not coming physically close to each other (the closest actual distance they come to each other is about 750 million miles), they will align so closely along the same line of sight that on July 11^th they will appear only ¾ of a degree apart-that's not much greater than the width of a Full Moon. The best time to see this pairing is after sunset on the evenings of July 10, 11, and 12, over the western horizon.

The next big ticket alignment is on August 1^st, when the Moon and the Sun occupy the same spot in the sky-the event we call a Total Solar Eclipse. As it happens, we won't be able to see this eclipse directly from the United States, as it will only be visible in Asia. However, NASA will be broadcasting live coverage of the eclipse from Northern China. We'll be showing NASA's broadcast in our planetarium at Chabot Space and Science Center, in case you'd care to come up and enjoy the spectacle. Don't let the fact that the live event goes on around 4:00 AM keep you away…it's worth getting up for!

A bit further out on the calendar is the September alignment of three planets: Venus, Mars, and Mercury. In the dusky twilight of mid-September evenings the three will be gathering. The closest grouping of the trio is on September 11^th, when they will be within about three degrees of each other-close enough that you can just about cover all three with your thumb. Mercury and Mars won't be very bright in the twilight-but Venus, bright enough to spot easily, can help guide your eye to the other two. Using a pair of binoculars will help a lot-but make sure you don't point them that way until after the Sun sets….

In ancient times (and in some cases not so ancient times), different cultures around the world have viewed alignments like these in different ways. Eclipses-both solar and lunar-were regarded by many cultures as bad omens, or bad occurrences (such as the Sun being devoured by a celestial animal-dragon, dog or other-in the case of a solar eclipse).

Planetary alignments were also given special consideration, sometimes being regarded as auspicious (for good or bad-usually the latter). One major alignment of the five visible planets (February 26, 1953 BCE) was believed to have "mandated" the creation of the Hsia Dynasty in China-the first great Chinese Dynasty. (Then, four centuries later, Mars, Mercury, Jupiter and Saturn apparently conspired to bring down that same dynasty-at least, their alignment on December 20, 1576 BCE was interpreted as an indicator of the dynasty's corruption, and it was overthrown by a revolt of believers…).

However you regard the lining up of celestial bodies (astronomically, astrologically, or aesthetically), these alignments are pleasing to watch, and times to reflect upon the constant and cyclic movement among the heavens. Enjoy….

School groups tour the Oakland Schools Science Fair
projects at Chabot. Ben Burress, Chabot Space & Science Center

The science projects of students from a range of schools in Oakland are on display at Chabot Space & Science Center for a couple of days-a long-time tradition I know, because when I was in elementary school (Glenview Elementary in Oakland) I participated in the Science Faire every year and wound up with my First Grade project (Which Straw Works Best-longer or shorter?) on display at Chabot Observatory on Mountain Blvd.

So I went out into our halls to browse the rows of free-standing cardboard displays (all pre-fabbed display boards; in my day we'd make our own from boxes, staples, and glue!) to see what today's young minds are thinking about science. In particular, I was looking for any that dealt with astronomy.

As usual, I saw a range of science topics, presentations styles, decoration, and grade levels. I saw the cadre of "standard" science projects that get done every year (the tabletop volcano, the floating egg, the electric potato, and the like).

I also saw some that I'd not seen before. There was one where the question asked was who has more germs, boys or girls? The experimenter took swab samples from behind the ears and from the hands of the students in her fourth grade class and grew germ cultures, which were all displayed before the presentation board in little plastic Petri dishes. What was the result? Do you want to know? Well, by this experiment at least, the girls won over the boys in having more germs from both sample sites….

But what of the astronomy? In all of the couple hundred project displays, only three of them were astronomy projects. This doesn't surprise me too much, since astronomy is for the most part an observational, not experimental, science and doesn't lend itself to the kinds of things kids like to get their hands into. And of my own elementary school science faire projects, not one of them dealt with astronomy, so I really can't complain!

What were they? One dealt with observations of Moon phases, asking the question is there a pattern to the way in which the Moon's shape changes from day to day. One asked why do the planets of the Solar System take different periods of time to orbit the Sun, and why do they have different temperatures. Finally, one asked the ultimate Inconvenient Truth sort of question: What would happen to Earth if the Sun suddenly turned off? (That would be inconvenient!) The answer to that one was, not long, since just about everything we do requires energy derived ultimately from the Sun.

The results of my own observation project, walking down the halls of Chabot and seeing what's up in the minds of our youth, was a happy success: the curiosity and scientific enthusiasm of our budding scientists appears to be alive and well.

Illustration of a blast of solar wind impacting
Earth's protective magnetic field. Credit: NASA

Did you know that the Sun also has an atmosphere, and that the Earth is inside it? In fact, the Sun's envelope of gases extends well beyond the orbit of Pluto, out to the regions of the solar system where the 3-decade-old Voyager spacecraft are only now reaching.

"Space weather" refers to the conditions in space caused by the outflow of electrically charged gases (plasma) coming from the Sun—what we call the "solar wind." The term "space weather" may conjure images of cosmic tornadoes, astral lightning bursts, and some Star Trek version of a galactic hurricane– but actual space weather is nothing so Earthly and familiar.

First of all, the "air" in space is nothing like the atmosphere we draw our breath from. Earth air, at the surface, is made of nitrogen, oxygen, argon, carbon dioxide, water vapor, and other trace elements, and is relatively dense. "Space air" is mostly hydrogen– ionized hydrogen at that (meaning stripped of its electrons and so electrically charged; the separated electrons are also blowing along in the solar wind).

Second, the gases of the solar wind are extremely rarified. Despite the talk of a solar atmosphere, solar wind, and space weather, space within the solar system is still almost a complete vacuum. At Earth's distance from the Sun, the average density of the solar wind is somewhere between 6 and 9 atoms (mostly hydrogen) per cubic centimeter. If you spread out the gas contained in an ordinary party balloon to this same thinness, it would fill a volume of space over 10 miles across!

Third, the solar wind, for all its sparseness, blows fast! Depending on conditions of space weather, the flow of solar wind past the Earth can speed along anywhere from 200 to 900 kilometers per second! Earth's fastest winds slug along at only a few hundred kilometers per HOUR.

So how does space weather—the changing conditions of the solar wind—affect us on Earth? How might you, personally, have experienced, directly or indirectly, the effects of the Sun's gentle breeze?

The most familiar phenomenon caused by space weather is Earth's beautiful auroras —the northern and southern lights. Interactions between the solar wind and Earth's magnetic field and electrically charged particles trapped in it excite atoms in the upper atmosphere to emit light. And it's not just a softly glowing night light: the most powerful auroras can generate up to a trillion Watts of power!

Solar wind "storms" can not only produce more active auroras, but can cause fluctuations in Earth's magnetic field whose effects can be felt on the ground. These "geomagnetic storms" usually pass unnoticed, perhaps causing a tiny change in the direction that compass needles point– but have also been known to overload electrical power grids and cause blackouts.

In the space around Earth, solar storms have been known to damage or disable satellites, and can put unprotected astronauts at risk. Space walks on the International Space Station are scheduled for times when space weather is – so to speak -"sunny and calm."

Thinking about space weather on Earth might seem like worrying over Atlantic hurricanes here in the Bay Area—but with more and more human activity taking place beyond the confines of our atmosphere, this is a very real and vital concern, and is taken very seriously.

Benjamin Burress is a staff astronomer at The Chabot Space & Science Center in Oakland, CA.