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All posts for the month November, 2011

What We can Learn from Near Earth Objects

This radar image of asteroid 2005 YU55 was obtained on Nov. 7, 2011, at 11:45 a.m. PST (2:45 p.m. EST/1945 UTC), when the space rock was at 3.6 lunar distances, which is about 860,000 miles, or 1.38 million kilometers, from Earth. Credit: NASA/JPL-Caltech (Click to enlarge.)

A couple of weeks ago many people were startled to learn that a space rock—an asteroid called 2005 YU55—was about to pass just inside of our Moon’s orbit. This tumbling piece of debris is big enough that a decent-sized ocean liner could fit inside it, and its 1.22-year orbit occasionally brings it close to Earth. This time, we were in no danger of an impact from it during the November 8th flyby.

Scientists took the opportunity to study the asteroid in great detail. The radio astronomy community was all over it. The Arecibo radio telescope, the Very Long Baseline Array, the Green Bank Telescope, and the Goldstone telescopes all focused on 2005 YU55. The Herschel Space Telescope also looked at the asteroid in far-infrared light, which helps us understand the temperature of the asteroid and what it’s made of.

In particular, astronomers used the Goldstone Deep Space Antenna to bounce radar signals off the asteroid and then examine the data to see what this baby looked like. The movie below shows a series of the highest resolution radar “images” ever taken of a near-Earth object. The movie consists of six frames made from 20 minutes of radar data, and is a work in progress. Word is there will be another, more detailed movie released here after astronomers get through analyzing all the data—perhaps in a week or two.

2005 YU55  rotates on its axis once every 18 hours, so what you see below is five repetitions of the same loop, and the loop shows the rotation faster than in real time.

What About NEOs?

So, I’ve had people ask me what NEOs mean. The close passage of this one raised concerns again about what we would do if such a rock were headed straight toward our planet. Obviously if it had hit Earth, 2005 YU55 would have dug out a crater about six kilometers across (nearly four miles) if it had impacted on solid ground. The consequences could have been pretty severe. Of course, the asteroid didn’t hit, for which we all breathed a sigh of relief.

But, that’s not to say that Earth is safe from a collision with one of these orbiting space rocks. It turns out the solar system is peppered with them, and in particular, the region we inhabit (the inner solar system) has a good-sized population of these rocks. They’ve BEEN around since the earliest history of the solar system. In fact, populations of such objects were spread out across much of the proto-solar nebula. They were the precursor “worldlets” that combined and collided to form the larger bodies such as Earth, the Moon, and so on. What we have now are the ones that didn’t participate in that early solar system tango to create worlds. They still zip around in their own orbits, and occasionally get close enough to another world (like Earth) to pose a collision threat.

There are communities of scientists who track these objects (once they’re discovered) and do a good job of assessing the chances of impact, near misses, and close encounters. You can read their work at the Web page for NASA’s Near Earth Object Program , the Minor Planets Center , and at the European Space Agency’s NEO’s pages here and here.

There are a number of search programs called asteroid surveys that constantly watch the sky and catalog just about everything that moves. They are scattered around the world, and you can see a list of the major ones here.  These surveys aim to find as many NEOs as possible, down to the limits of what they can see. Planned future surveys will need to use ever-more sensitive detectors to find smaller and dimmer objects with orbits intersecting Earth’s.

So, what can we learn about these NEOs as they whiz by? The radar imaging you saw in the movie here tells scientists something about the surface characteristics of an object. That is, is it cratered, does it have other surface features like hills or outcrops? What is its shape? Sometimes they can figure out what its surface is made of—that is, the minerals that make up a rocky asteroid, for example. And, by sussing out the composition and “look and feel” of these asteroids, we learn more about the raw materials that made up Earth and other worlds. We find out what conditions were like in various parts of the solar system during the early days when these types of objects were forming, colliding, and contributing themselves to build larger worlds. So, in a sense, these asteroids are historical treasure troves that give us a look at the early history of the solar system. In another sense, the ongoing discovery of NEOs also tells us about their distribution—that is, how many of them there are and WHERE their orbits are in the inner solar system.

NEOs have always been there, folks. As I mentioned above, the solar system was born with an inventory of these guys, and over time they collide with planets and Sun. The inner solar system’s collection of NEOs is constantly being replaced by asteroids that migrate from the main Asteroid Belt, or from objects that are bumped from their orbits out near Jupiter and Saturn and sent inward toward the Sun.

Currently we’ve discovered most of the larger ones. In recent decades, we’ve developed much better detectors to find the smaller near-Earth objects (the size of city blocks, for example). Most are so small and so dim (their surfaces can be as dark as charcoal, which makes them hard to spot, particularly when they’re little guys).

Once a NEO is discovered, scientists have to make many observations of it to pin down its orbit very accurately. This is like watching a plane land: the more observations you have of that plane, the more accurately you can figure out its path to its landing site. In the days after a NEO discovery, scientists are very careful to point out that their calculations of the object’s orbit and trajectory are preliminary AND that the orbital parameters will change as more observations come in. This is completely normal and nothing to worry about. Yet, I often see people, particularly in the media or as part of the conspiracy theory crowd ignoring that fact and getting all upset because they think scientists are hiding information or aren’t telling the truth.

The truth is that calculating orbits, particularly when you want to figure out whether or not something will impact us, requires observations over a long period of time, and those observations should be very precise. It’s not an overnight job— it’s like any other quality work—it reflects the amount of time and effort put into it. We pay our scientists well to do their jobs, and so it’s only fair to LET them DO their jobs without having people screech about it.

I’ve also seen a lot of nonsense on the Web about how NEOs can change our magnetic fields or shift our polar axes or how they are being hidden by NASA/ESA/whoever. Such speculations are the work of people who either don’t know much about the reality of NEOs (or about the laws of physics for that matter) or don’t care to know because they can get more attention by making stuff up and then posting their “fantasies” on the Web. That’s the politest way I can term such nonsense. There’s good, solid science behind the discovery and characterization of NEOs, and I wish people would pay more attention to THAT. The universe is always much more fascinating and wondrous than our imaginations can dream up.

So, to sum up: NEOs are fascinating rocks from space. Sure, they can pose a threat, and we should be looking for ways to mitigate that threat. But, in the larger sense, NEOs hand us a unique chance to learn more about our neck of the woods, by giving us a look at what was once the undiscovered country of small bodies of the solar system.

(Special thanks to Dr. Paul Chodas at NASA/JPL for his insights on these NEOs. If you want to read more commentary about NEOs, check out David Ropeik’s discussion of impact risks here , and Alan Boyle’s comments on CosmicLog at MSNBC. Both of their blog entries were written after a workshop about communicating risks of NEO impacts, sponsored by the Secure World Foundation that I and a number of other scientists and writers attended this past week.)

They Aren’t Going to Be Harming Us

Earth is NOT doomed. Yeah, I know this is going to come as a complete disappointment to the folks who insist the universe is out to get us via the auspices of giant killer solar flares and rogue comets. It ain’t gonna happen. Lucky for all of us, the universe is sticking to the laws of physics.

The Valentine's Day 2011 solar flare. Courtesy NASA/SDO/SOHO

Let’s start with the so-called giant killer solar flares. Yes, increased solar activity, including flares and coronal mass ejections (outbursts from the Sun), is a concern. This is because we’re heading into a period of maximum solar activity (something the Sun goes through periodically), and we are expecting more solar flares and coronal mass ejections.

This is pretty much normal for the Sun, despite some of the screaming headlines on conspiracy theory Web sites about “mysterious” solar flares and what they supposedly mean for mankind.

In reality, solar activity is not mysterious. It’s not confusing scientists, nor is it being directed by aliens (yes, I saw that on a Web site). Solar activity is part of what our star does.  Solar physicists (the experts on solar activity) are really starting to understand some of the mechanisms of solar flares, for example, thanks to solar-observing satellites such as SDO, STEREO, and SOHO.  But, giant killer solar flares? Those are a product of overworked imaginations of people who don’t understand the basic principles of physics and the Sun.  For one thing, there isn’t enough energy in the Sun to power a monster fireball that could hang together long enough to travel 150 million kilometers between the Sun and Earth.

Sure, solar flares can be strong enough to create space weather disturbances that can stimulate auroral displays above our poles. All that means is that the energy transfer from Sun to Earth is strong enough to excite gases in our upper atmosphere, which causes them to glow. This happens a lot, and not just on Earth. Aurorae have been seen on such planets as Jupiter and Saturn, for example. Same principle at work there, too.

In some cases, the space weather can mess a bit more with our upper atmosphere, which affects some of our technology—such as telecommunications and GPS signals. (For more information about space weather, visit the Space Weather FX Web site at MIT. It contains a series of very nicely produced videos (if I do say so myself) about the effects of space weather. Very timely and very educational.) Studying solar flares is an important step in understanding the whole Sun and the cycles it goes through, and I, for one, look forward to seeing what astronomers learn about our star during this next solar cycle.

The other great story that’s been making the rounds among the “we’re gonna die” crowd is about Comet Elenin. It is (or was, actually) a perfectly harmless comet making a swing past the Sun (as many comets do). A few folks got all hot and bothered by their own misconceptions about the comet’s orbit and they worried that all kinds of disasters would occur on or to Earth, all caused by the comet. I read some of these…ummm… pseudo-scientific rants. To be honest, I never could figure out what the fuss was about. And some of the uneducated hyperbole was… laughable.

Comet Elenin as seen by HI1-B on Aug. 6, 2011. As Comet Elenin passed to within just 7 million kilometers of the STEREO (Behind) spacecraft, NASA rolled the spacecraft to take a look at it (Aug. 1, 2011) with its wide angle HI-2 instrument. Though the observation lasted only a little over an hour, the fuzzy looking comet can be seen moving across a small portion of the sky. STEREO will be taking these one-hour observations every day through August 12. The comet is seen by the HI-2 telescope between August 1-5, and by the higher resolution HI-1 telescope between August 6-12. From August 15 onward, the comet enters the HI-1 telescope's nominal field of view, at which time we should enjoy continuous viewing of the comet. Over time, we expect the comet to be visible in the SOHO C3 coronagraph on September 23 for six days and possibly STEREO's COR2 coronagraph as well between August 20 and September 1. Courtesy NASA/STEREO mission.

As it turns out, there never was anything to be worried about. Comet Elenin came as close as 72 million kilometers to the Sun and never got closer than about 34 million kilometers to Earth. For reference, the Sun and Earth are 150 million kilometers apart; Venus and Earth are close as about 38 million kilometers apart when they are closest to each other in their orbits. So, Elenin was never in any danger of smacking into us.  It faced far more danger from its close approach to the Sun.

As it passed near the Sun, Elenin broke up into a traveling collection of ice chunks and bits of dust. It’s now scattered along its former orbit.  According to Don Yeomans, the comet expert at the Near-Earth Objects Program Office at Jet Propulsion Lab in California, about two percent of new comets passing by the Sun break up like this. This is because most comets are made up of ice, rock, dust and other stuff that are all held together in a loosely bound conglomeration that can be easily disturbed by the pull of gravity from a nearby planet or the Sun. This is all perfectly natural and nothing to be worried about.And, trust me, comets can’t screw with Earth’s axis or change our magnetic fields or do any of the stuff that they’ve been accused of by some of these pseudo-scientists.

Look, the solar system is an interesting place scientifically. We continue to explore it and learn more about it. Everything we learn is from observations and the applications of basic scientific laws. The more we look, the more we discover, quite simply because we keep creating better and better tools with which to study the cosmos. This is great, and it’s what science is all about: figuring stuff out from the evidence in front of us, using scientific principles to do so.

Science doesn’t make the solar system weird or mysterious or frightening or alien. People with a vested interest in having you believe (and the operative word here is “believe”) their untested, unscientific assumptions about things they don’t quite seem to understand may drive a few folks to read ranting Web sites. I’m sure it feeds the egos of those people who have books to sell or tales to tell. But, it’s really not the way that sane, rational people view the cosmos. And, it’s certainly not the way science works.  The universe is grand and wonderful enough without making up inane stuff about it.

Come Along for the Ride

Astute readers of this blog may recall that I’m married to one of the premier space music composers on the planet. No, really, it’s true. Working under the nom-de-plume Geodesium, Mark C. Petersen (also my business partner at Loch Ness Productions), has been composing planetarium space music for more than 35 years and he’s built up quite a specialized fan base for his music.

cover for Geodesium 11th album: Arcturian Archives

The 11th in a series of well-respected Geodesium albums.

Yesterday, 11/11/11 was more than numerological curiosity. It marked the day we released his 11th album of space music, called Arcturian Archives. It’s really an aural journey through a fascinating period in our lives and in planetarium technological history. In 1980s and 1990s, Mark created custom Geodesium music for some special planetarium shows — part system demo and part cosmic journey. The resulting soundtracks influenced his musical stylings in seminal ways, cementing in the minds of many his place as one of the top space music composers for domed theater shows.

This album captures the musical tenor of those times. Beginning in the 1980s, planetarium hardware companies were creating new ways to present content on the dome, and in the keyboard world, new digital synthesizers were coming out that had many musicians (Mark included) panting to get their hands on them.  The result of these technological changes shows up in this music.

Many of these tracks have never been heard before, outside of the few planetarium performances for which they were commissioned. And, here are three elaborate renditions of popular orchestral works:  Pachelbel’s Kanon in D, Resphigi’s Pines of the Appian Way, and (to my mind) a driven and thrilling version of Holst’s “Mars, the Bringer of War” from The Planets.

Aside from being Mark’s chief critic (and believe me, he returns the favor when I need somebody to give my writing a critical eye), I also wrote up his album liner notes and talked with him at great length in a piece called “Interview with the Artist” that is featured on the album’s Web page.  Some of the music accompanied some of the first “outside” planetarium show scripts I wrote for clients such as the St. Louis Science Center (mentioned prominently in Mark’s interview).  At the time, I had yet to go back to grad school, and I was working my way from science writing for newspapers to creating touching and engaging shows for the domed theater. And, Mark has always been right there, providing the soundtrack for my—and other people’s—flights of exploration into the cosmos. So, it’s my turn to give him the recognition he deserves for his music and his services to the domed theater community over the years. I look forward to more albums and more great shows!

If you’re interested in buying the album, check out our Website at Loch Ness Productions. It’s also available through the usual places: Amazon.com, iTunes, CDBaby, and other sources. You can preview the music below.