It seems the sky is falling…

Imagine driving in your car on a lovely Friday morning and seeing a flaming ball of death streaking across the sky and coming, as best you can tell, right at you.

This view from a Russian dashboard camera shows a terrifying view of the fireball as the meteoroid entered the atmosphere and hurtled over the city of Chelyabinsk. Credit: Discovery News

That’s what terrified citizens in the lovely Russian city of Chelyabinsk experienced on the morning of Friday, February 15. The multitude of videos and photos of this meteor are simply horrifying since many of them give the impression that this huge chunk of flaming interplanetary death is about to smash right into the camera. Not only did this fireball make a scary visual impression, but it packed a very literal punch as well. As the meteoroid hurtled through the atmosphere at 40,000 mph, the heat and pressure it felt caused it to break apart with a huge amount of energy, the equivalent of 470 kilotons of TNT (or 30-40 times the power of the atomic bomb dropped on Hiroshima). The deposition of that huge amount of energy into the sky caused a pressure wave that blasted the city. Over 1,000 people were injured by the blast, mostly due to cuts and scrapes from glass as windows shattered. Scientists have now come to the conclusion that the initial object was only 17 meters wide– that’s about the size of a tractor trailer. That’s pretty small cosmically speaking. Imagine the damage that could have been inflicted if something larger had hit the atmosphere. The last time a meteor had significant large-scale impact was in 1908, again in Russia. This impact, known as the “Tunguska event“, is the largest impact ever recorded- 20-30 times larger than the one that happened this month. This meteoroid, which is estimated to have been about 100 meters wide (the size of a football field), blew up in the air and released 10-15 megatons of energy, leveling 830 square miles of trees. Witnesses to the event said that the heat and pressure from the explosion made their skin feel like it was on fire.

The 1908 Tunguska event, the largest impact near or on Earth ever recorded, leveled trees over 830 square miles. Credit: nightsky.org

Luckily the 2013 Russian meteor was much smaller, so windows got knocked out but buildings weren’t leveled. The object was actually so small that astronomers didn’t even see it coming. NASA has a whole division of people who track objects that could potentially come close to Earth, it’s known as the Near-Earth Object Program. Unfortunately, for scientists to be able to see an object it needs to be large enough to reflect an observable amount of light. That didn’t happen here.

The meteor also came as a bit of a shock since scientists were so focused on another Near-Earth Object called 2012 DA14. This 45-meter wide asteroid was scheduled for a flyby of Earth on the same day, February 15. This relatively small piece of space rock flew closer to the Earth than any other celestial body. It was 17,200 miles away at its closest approach, that’s closer than satellites in geosynchronous orbit and much, much closer than the Moon. Although scientists were certain that DA14 wouldn’t impact the Earth, they were very excited to use the close flyby as an opportunity to study the asteroid.

This collage of 72 individual radar-generated images of asteroid 2012 DA14 was created using data from NASA’s 230-foot Deep Space Network antenna at Goldstone, CA. Credit: NASA

Of course it was ironic that after weeks of assuring the public that there was no threat of an impact from DA14 another huge impact happened in Russia the same day. Scientists from NASA’s Meteoroid Environment Office concluded that the Russian meteor and DA14 were totally unrelated, having come from two very distinct trajectories/orbits. This means it was a huge cosmic coincidence that they just happened to occur on the same day…weird.

This plot of the orbits of the Russian meteor and asteroid 2012 DA14 show that the two bodies came from very different parts of the solar system and were unrelated. The Russian meteoroid most likely originated from the Asteroid Belt out past Mars. Credit: NASA/Space.com

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The Cosmic Distance Ladder, part 1…

For the past few months, I’ve been spending a lot of time in my position as Manager of the UNH Observatory, in helping to prepare for the 2012 New England Fall Astronomy Festival. The event, lovingly known as NEFAF, is a family-friendly astronomy-related event that will be hosted by the UNH Physics Department in partnership with the New Hampshire Astronomical Society. As you can imagine, this is quite an undertaking, but in an incredibly exciting turn of events, we just found out that Dr. Alex Filippenko, noted astronomer from UC-Berkeley and member of the research team that won the 2011 Nobel Prize in Physics, will be giving the keynote talk at NEFAF 2012! In addition to being a highly acclaimed professor, Filippenko is also the co-author of an extremely popular astronomy textbook and a frequent contributor to the documentary series The Universe on The History Channel.

Dr. Alex Filippenko, the newly announced keynote speaker for the 2012 New England Fall Astronomy Festival to be held at the UNH Observatory.

That extremely exciting news has inspired me to do a couple of posts about the expansion of the universe, the area of research that Dr. Filippenko works on. But before we can really get into talking about that, we need to cover a very basic aspect of astronomy, but something that most non-astronomers don’t really know about. I was at a public session at the Observatory this weekend when a guest who had never studied astronomy before asked me what she thought might be an “ignorant” question: she wanted to know how exactly astronomers knew the distances to objects in space. This is by no means an ignorant question, in fact it’s a very fundamental and very involved question that really gets at the very nature of astronomy.

Astronomy by definition is an observational science. Unlike many other scientific disciplines, astronomers can’t really do experiments in a laboratory (although some do). But the stereotypical astronomer can’t throw his subject (a star or galaxy) on a lab bench and dissect it or set up an experiment to test it, so astronomers need to observe and record data. Okay, so we observe light, that tells us what something looks like, where it is, and how bright it is. Big deal, is that really that helpful scientifically. Well, not really. So we have to come up with ways to get more information from observing the light. The main way we do that is by breaking the light up in a spectrometer, an instrument that breaks light down into a spectrum of colors. This breakdown of light can reveal an abundance of new information including what the object is made up of, how hot it is, how fast and in what direction it’s moving, how old it is, and more.

The question of how astronomers calculate the distance to an astronomical object varies depending on how far away the object is. Because most of these techniques only work up to a certain distance, there is actually a progression of different approaches that astronomers use to measure distance to celestial objects. This list of methods of measuring astronomical distances is known as the Cosmic Distance Ladder (or less poetically, the extragalactic distance scale).

A graphical representation of the distance-measuring techniques that make up the Cosmic Distance Ladder. “1 A.U.” is 1 astronomical unit or approximately 93 million miles, the distance from the Earth to the Sun. A “pc” is a parsec, equal to 3.2 lightyears (206,265 A.U.) or about 20 trillion miles. “Mpc” stands for “Megaparsec” or millions of parsecs. Credit: University of Rochester

In our solar system

The first step in our exploration of the universe was to our own celestial neighborhood. The first step was precise measurement of the size scale of the solar system, which started with the determination of the distance between the Earth and the Sun. As I’ve explained before, this measurement was originally calculated via observations of transits of the planet Venus across the disk of the Sun. Early on in the 20th century, observations of asteroids also played an important role in this measurement. But today the distance from the Earth to the Sun, defined as 1 Astronomical Unit or “AU”, is measured with high precision using radar ranging. By bouncing a radar beam off another planet, usually Venus, and measuring the time that beam takes to return to Earth, scientists can very accurately determine the difference in the size of the two planets’ orbits. Using that difference and the ratio of the two orbital sizes, we can very easily calculate the distance the Earth must be from the Sun. We use a similar process even closer to home. During the Apollo missions of the late 1960s-early 1970s, astronauts deployed the lunar laser ranging experiments, arrays of mirrors that allowed scientists to measure the distance to Earth’s only natural satellite with extreme precision using lasers. This radar ranging is how we’ve calculated the distance to most of the objects in our solar system. More recently, we can also use spacecraft in orbit around other planets as a tape measure by measuring the time it takes for a signal to travel from the spacecraft to its controllers on Earth.

Another  way we can get measure the distance to the planets and to nearby stars is a phenomenon known as stellar parallax. This method is less accurate than radar ranging for planets, but is very good for stars in our local stellar neighborhood. Parallax is something you experience almost every day. Hold your thumb up at arm’s length. Close one eye, then open that one and close the other. Notice how your thumb appears to shift with respect to the objects far off in the distance? That’s parallax! Astronomers take measurements of a planet or star a two points in Earth’s orbit (6 months apart) and measure the angular shift of an object with respect to the background stars between those two measurements. Then, because we know the distance the Earth is from the Sun, we can use some basic geometry to calculate the distance to that star or planet in the foreground.

This diagram shows how parallax is used to find the distance to planets in our solar system and nearby stars. Scientists make two observations 6 months apart, measuring the angle that an object (the red dot) makes with regard to the background stars between the two observations. Then using the distance from the Earth to the Sun (1 A.U.) and some simple geometry, the distance to the object (d) can be calculated. Credit: Hyperphysics

It was using parallax, that Italian astronomer Giovanni Domenico Cassini was able to roughly calculate the distance to Mars in 1672. His calculation was a little bit off though, because instead of taking two measurements 6 months apart, he sent his colleague to Cayenne, French Guiana (on the northern coast of South America) to make observations while he stayed in Paris. Then Cassini could make the same parallax calculation using the known distance between the two observation points (~4400 miles) instead of the distance from the Sun to the Earth. This single direct measurement of the distance to Mars, which is now easily calculated and heavily used by missions such as Curiosity, actually allowed for the calculation of the distances to all the planets. Since geometry and Kepler’s Laws governed the basic ratios the Sun-planet distances, you only needed to measure one Earth-planet distance to be able to easily calculate them all. This major contribution and several others in planetary science (including the discovery of four of Saturn’s moons and joint discovery of Jupiter’s Great Red Spot) prompted NASA to name the Saturn-bound spacecraft mission after the him.

Giovanni Domenico Cassini

[To be continued…]

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Outer Space: The Movie!…

A few posts ago I spotlighted Saturn’s rings and its tiny icy moon Enceladus. Now you should check out this movie from NASA called Outer Space. The short movie is comprised of still images of Jupiter and Saturn and their moons taken by the Cassini and Voyager spacecraft.

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Saturn’s rings explained…

This natural color image of Saturn was created from a series of images that were taken by the Cassini spacecraft during its encounter with the planet in October 2004. Credit: NASA

Of the five planets visible to the naked eye from Earth, Saturn is the furthest and slowest moving across the sky. That’s actually how Saturn got its name; the ancient Greeks named the planet after Chronos (Saturn to the Romans), the father of Zeus (Jupiter) and the God of time (a reason why chronos is a root of time-related words, as I explained in an earlier post). Galileo was the first to resolve and discover the rings of Saturn when he looked at it through his telescope in 1610. It’s incorrect status as the only ringed planet in the solar system survived until well into the latter half of the 20th century. In 1977, Saturn was joined in the ringed planet club by Uranus, after scientists observed a star passing behind the planet, a phenomenon called an occultation. Most unexpectedly, the star’s light blinked on and off nine times before disappearing behind the disc of the planet; this proved that although the rings were too dim to be seen from Earth, the material was present. Only a few years later, Voyager 1 discovered the rings of Jupiter and it wasn’t until the mid-1980’s that another stellar occultation proved the existence of  Neptune’s ring system. So it’s true, all of the gaseous outer planets, or “gas giants”, have rings, but Saturn’s are by far the most visually impressive and the only ones visible from Earth. So that leads us to a very interesting and mysterious question…why? What makes Saturn’s rings special?

As telescopes on Earth have become more and more advanced and we continue our extensive exploration of the solar system, we have pieced together a much more comprehensive understanding of Saturn’s rings than Galileo had 400 years ago. Although the rings look solid and sheet-like from Earth, we now know that the rings of Saturn are actually comprised of billions of particles of rock, ice, and dust ranging in size from microscopic to meters-wide. The brighter, more dense regions of the rings have more material to reflect light while the dark regions or “gaps” are much more scarcely populated. The debris that makes up the planet’s rings are in a very well-defined plane, only a few tens of meters thick, but extending almost 130,000 km (80,778 mi) above the planet’s surface. The gallery below shows the evolution of our understanding and imaging of Saturn’s rings.

But many questions still remain about why Saturn’s rings are so much brighter than the other gassy planets. The answer scientists think, lies with the sixth-largest of Saturns 60+ moons: a small, icy world called Enceladus (shown below).

Saturn’s 6th largest moon, Enceladus, as imaged by NASA’s Cassini spacecraft. The blue fissures in the surface seen in the southern hemisphere are known as tiger stripes. Credit: NASA

Enceladus is roughly 500 km  in diameter (14% of the Moon) and 1.1 × 10²º kg in mass (0.2% of the Moon), but what it lacks in stature it makes up for in output. Literally. Discovered by William Herschel in 1879 (only 2 years before his discovery of the planet Uranus), Enceladus first came into the spotlight for scientists in early 1980. As John Spencer recalls in a recent article in Physics Today, that was

“…when scientists using Earth-based telescopes acquired new images of a faint outer ring of Saturn—the E ring—which had been discovered in the 1960’s. Those images revealed that the E ring’s brightness peaked at the orbit of Enceladus. They also showed that unlike Saturn’s other rings, the E ring scattered sunlight more efficiently at shorter wavelengths, which indicated that the ring was dominated by particles not much larger than the wavelength of light. Sputtering by charged particles in Saturn’s magnetosphere would erode away such micron-sized particles on time scales of decades to hundreds of years, so something had to be replenishing the ring on comparable time scales. The peak in ring density at Enceladus pointed to that moon as the likely source.”

Since then interest in the small ice-world increased exponentially and as a result Enceladus became a primary target of investigation for the joint NASA/ESA mission of the Cassini spacecraft. After only slightly whetting their appetite with two flybys of the small moon in early 2005, researchers decided to make a third flyby at a much closer range, 170 km (105 mi) instead of the planned 1000 km (621 mi). The dramatic results from this third Enceladus flyby in July 2005 were released in a special March 2006 issue of the journal Science. It was this flyby that got the high-resolution images seen above and first discovered the “four prominent parallel fractures, dubbed tiger stripes, surrounded by an intensely tectonically disrupted landscape” that the image depicts. In an even more interesting find, Cassini caught evidence of multiple plume jets erupting from the four tiger stripe fractures seen near Enceladus’s south pole.

Multiple plume jets erupting from the four tiger-stripe fractures near Enceladus’s south pole are visible in this Cassini image. The jets appear not only on the edge of Enceladus’s disk but also where they rise up into sunlight from sources on the night side of the moon. CreditNASA/JPL/SSIMosaic: Emily Lakdawalla

These plumes (shown above), currently ejecting mass at an astounding 200 kg/s, have two observable components: micron-sized ice grains and gas (99% water vapor). It is speculated that the water vapor and ice crystals that are being deposited into Saturn’s ring system by Enceladus are what have kept the planet’s rings so bright and reflective for so long.

In spite of all of this other extremely intriguing science, the most interesting thing for scientists is Enceladus’ potential for life. As one of the few places in the solar system where we know water exists, Enceladus has become a key target in the search for extraterrestrial life. Scientists speculate that liquid water might occur in several places on the tiny moon: as a global ocean between the silicate core and the ice crust, as a more local south polar sea beneath the ice shell), or as localized bodies of water in the ice shell itself.

Here is Saturn’s tiny icy moon Enceladus, imaged by NASA’s Cassini spacecraft. Just above the smaller moon we can see the planet’s rings and Saturn’s largest moon, Titan, looming in the background. Credit: NASA/JPL-Caltech/Space Science Institute

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Earth is not alone…

Continuing the lunar trend after my last post, which highlighted new multimedia from NASA that reviewed the stages of the Moon’s development and a tour of the Moon’s most notable features, now I’d like to share some more recent news about Earth’s only natural satellite…or so we thought.

Leading theories about the creation of the Moon is that an object about half the size of Earth (roughly Mars-sized) collided with the Earth roughly 4.5 billion years ago. This cataclysmic, near-Earth-ending impact (models show that an impactor only 10% larger would have completely destroyed the planet) ejected a large amount of debris that settled into a ring system around Earth. As the Earth cooled and gravity pulled the planet’s mass into its roughly spherical shape (technically an “oblate spheroid“), pieces of debris in that ring system began to collide and combine, eventually collecting almost all of the debris and forming the Moon. But now, as NPR reports, an international collaboration of researchers from the University of Hawaii, University of Finland, and Observatoire de Paris have written a computer simulation that calculates how many small asteroid-like objects may actually be in captured orbits around Earth. Their results, published in a recent issue of the scientific journal Icarus, conclude that at any given time, Earth may have one or more smaller captured objects, or additional “moons”, in orbit around it. The idea of a captured moon is not a new one, most scientists agree that the two irregularly-shaped moons of Mars, Phobos and Deimos, are most likely captured asteroids whose orbits were disturbed while out in the asteroid belt and were captured by the Red Planet after they strayed too close to it. And of course having a single moon would make Earth unique, of the 6 planets which have moons (Mercury and Venus lack them), Earth is the only planet with a singular moon, or so we thought. But even if these other natural satellites are in orbit around earth, will we consider them moons or will the International Astronomical Union (IAU) make some new kind of classification of “dwarf moons”?

The moons of Mars, Phobos (left) and Deimos (right) are thought to be captured asteroids. Credit: Encylcopedia Britannica

Speaking of the good ol’ IAU, as I detailed in one of my earliest posts, “Alas, poor Pluto“, part of the 2006 decision that de-planetized Pluto defined that a “planet” must clear its orbit of debris. I also mentioned that such a vague definition could leave open an argument for Jupiter to be demoted as well since it has Trojan asteroids which share its orbit. Well now, some could argue that Earth might not technically be a planet anymore either. A new study by NASA’s Wide-field Infrared Survey Explorer (WISE) mission located a Trojan asteroid that shares Earth’s orbit. As NASA explains, “Trojans are asteroids that share an orbit with a planet near stable points in front of or behind the planet. Because they constantly lead or follow in the same orbit as the planet, they never can collide with it. In our solar system, Trojans also share orbits with Neptune, Mars and Jupiter. Two of Saturn’s moons share orbits with Trojans.” Details about the tiny Trojan, designated 2010 TK7, were published in the July 28 issue of Nature. 2010 TK7, seen in the star field below, is only 1,000 feet (300 meters) in diameter is in a highly irregular orbit as it follows Earth around the Sun (click here for an animation of the little guy’s odd orbit). Thankfully though, the smart folks at NASA have done their research and the asteroid’s orbit is well-defined and for at least the next 100 years, so we know that it will not come closer to Earth than 15 million miles (24 million kilometers), which is more than 50 times the distance from the Earth to the Moon. So no end of the world asteroid impacts…from this asteroid, but I’ll leave that conversation for another post.

Earth’s only known Trojan asteroid, 2010 TK7, is shown here, in the green circle, among a field of stars. The asteroid was found by NASA’s WISE mission. Credit: NASA

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Getting your rocks off…

Hello all you loyal readers out there, sorry for the lack of posts this summer, but it’s just so nice outside and it’s hard to see with the sunlight reflecting off my screen. In any case there’s a lot going on down in Washington regarding budgets and debt and all that good economics stuff (read: things that I don’t really understand or care to), so I figure I’ll just ignore that and talk about some fun space stuff!

  • First off, as this blog has been (or attempting to) chronicling for most of the summer, NASA finally ended the Space Shuttle program after the successful return of the final mission of Atlantis on July 21. The shuttle ran an amazing 30 year history and is still to this day the most sophisticated vehicle ever constructed by man. NASA and the U.S. government now have to wait and hope (with bated breath and some hard finger crossing) that private companies quickly ramp up the development and advancement of private launch capabilities. Several big-time frontrunners in the commercialization of space exploration (SpaceX, Orbital Sciences, etc.) have hit major setbacks, failures, and are going way over budget.
  • Next up, here is a very cool picture from the Opportunity rover on Mars. Yes, that’s right Opportunity found metal on Mars! How cool is that!??!! But yeah, not the giant pieces of scrap metal that are in the background, NASA is actually interested in that strange metallic-looking rock in the foreground to the left. That’s the real prize. The scrap metal (which I  half expected to see wrecked R2-D2 and C-3PO somewhere near…) is not some failed attempt at Martians to reach space, it’s actually Opportunity‘s own heat shielding that was abandoned during the rover’s descent back in 2004. The rock though, found to be made mostly of dense metals iron and nickel, is thought to be just as alien to Mars as Opportunity‘s heat shielding. Scientists believe the rock to be a meteorite much like the vast number found in Antarctica here on Earth.

It’s not the scrap metal here that interests scientists, but the small metallic rock in the left foreground. Credit: APOD

  • In a news story that is too weird to be made up, a man recently released from jail, is finally having the story told of how he stole moon rocks from NASA (similar to the NJ heist?). A new book, Sex on the Moon: The Amazing Story Behind the Most Audacious Heist in History by Ben Mezrich (the author of the books Bringing Down the House and The Accidental Billionaires, the movies behind 21 and The Social Network respectively), focuses on the story of then-24-year-old Thad Roberts, a former Mormon from Utah, who stole an entire safe full (not just the rocks in the safe, but the ENTIRE safe) of moon rocks from a lab at NASA’s Johnson Space Center in Houston back in 2002. Why, you ask, would the wanna-be astronaut pull off such an audacious crime? For the love of a girl he’d met only three weeks prior…so he claims. In any case the article and book detail the robbery and how the couple celebrated the crime on the 33rd anniversary of first moon walk by being intimate ON the rocks (hence the pun of this post’s title). The short summary is, people are weird, but this book HAS to be a page-turner.

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Space rock stings and heated things…

Hey there everybody. Well, since yours truly was not Raptured this weekend, I guess I should probably post something. Here are some of the things going on in the world of NASA.

This amazing shot shows Endeavor silhouetted against the breaking dawn. Credit: CBS News

  • The much anticipated final launch of the Space Shuttle Endeavour finally happened last Monday, May 16. But now Commander Mark Kelly and his crew have a bit of an issue on their hands. Saturday morning the crew discovered that one of the 20,000+ tiles that cover the exterior of the shuttle and protect it from the extreme heat experienced during atmospheric reentry has been damaged. Immediately for many, this will bring back terrible memories of the 2003 Columbia tragedy, when the shuttle and its seven crew members were lost during reentry because of damage that one of the heating tiles had incurred during launch. NASA and the astronauts have and will continue to run tests to diagnose the severity of the damage, but LeRoy Cain, the deputy program manager and chairman of the mission management team, said that the tile had been cleared and that there was no danger to the shuttle from the damaged tile because the structure beneath the tile will still only reach an estimated 219 degrees Fahrenheit–below its maximum temperature capacity of 350 degrees. Let’s hope he’s right and the crew and shuttle will be safely returning on June 1. NASA also announced the date of the final shuttle launch; Atlantis is slated to make its final launch on July 8.
  • At the end of a previous post, I had recapped a precarious situation where NJ officials misplaced a collection of moon rocks brought back from the lunar surface by Apollo 17. Well, just recently police arrested a California woman for attempting to sell a moon rock on eBay. Apparently the bust came after the woman made a $1.7M deal for the rock with an undercover NASA agent. The rock was taken into custody (along with the culprit) and its legitimacy will be tested by NASA officials (are they also the undercover agents or do you think that’s a separate department?). It’s for just such a situation that we need to set up an galactic branch of INTERPOL, maybe GALAPOL? Or really it would just be the solar system (SOLAPOL?) or just for the Moon (LUNAPOL?)…
  • Finally, here’s a very interesting and very well-written article from Forbes magazine that talks about the risks that NASA is making by betting so much on the success of Elon Musk’s SpaceX and other start-up commercial launch companies. The extremely interesting article takes a look at SpaceX’s track record and includes an interesting look at the company’s unique business strategy that plans to drastically cut launch prices. However, as the article indicates, delays and failures at SpaceX and other private launch companies has many politicians, NASA employees, and NASA fans (like myself) worried about where the Obama Administration is steering the American space program.

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