by Paul Gilster | Aug 16, 2008 | Culture and Society |
Hanny’s Voorwerp, that odd object discovered by Dutch school teacher Hanny van Arkel via the Galaxy Zoo project, has provoked press reaction all over the world. And Chris Lintott, a key player in the Galaxy Zoo’s ongoing survey of galaxies, notes the uneasiness he feels in discussing theories about the object before the paper that attempts to explain it has even gone through peer review. The speed with which the Internet allows science to be discussed can be disconcerting, as Lintott makes clear in the latest edition of the Space Carnival, conducted this week by David Chandler at his Next Generation site.
Now the Galaxy Zoo is doing good science in an obviously public fashion. Anyone can sign up to participate in the classification of the images of one million galaxies drawn from the Sloan Digital Sky Survey, and that makes participating computer users scientific collaborators. Seeing this, the Galaxy Zoo blogs about its work out of a sense of obligation to its contributors, but invariably encounters mainstream media coverage that can be misleading. Big media like ‘eureka’ moments, huge discoveries, but as Lintott notes:
“The reality of doing science day to day involves talking and arguing and thinking, and it’s in those arguments that the scientific method lurks. If you can’t defend your idea with data, whether talking to a journal’s referee, to your colleagues in the office down the corridor or even to yourself, then it doesn’t survive.”
Anyone involved in research faces the dilemma that as science becomes more open, it can be quickly misconstrued. But I agree with Lintott that having data and papers available on the Net is a huge plus. The benefit is that the more day to day science becomes visible, the more the public learns how scientists argue, using data sets, competing studies, and alternative explanations to resolve disagreements and get at the underlying facts. That moves the focus away from those ‘eureka’ moments and shifts it to the process of defending new ideas with data.
Yes, the recent perchlorate controversy invoked Net speculation that forced NASA into a premature news conference, one that seems to have left at least a few reporters disappointed. But it also sent the signal that good science can occur in more public venues, even if the excitement of the ‘big announcement’ must give way to the realization that some things take time, and the study of incoming Phoenix data remains a work in progress. Putting the scientific method into the public arena may not always make for the biggest headlines, but the results can only benefit our understanding of how the process of discovery works.
by Paul Gilster | Aug 15, 2008 | Outer Solar System |
As someone who has always been interested in how we name things, the choices on Enceladus have been particularly pleasing. On the remote Saturnian moon, place names are chosen from the The Arabian Nights, which is how we wind up with Damascus Sulcus, as seen in the photo below. A sulcus is a large fracture, a ‘tiger stripe,’ as they’re called on Enceladus. The four most prominent are named Alexandria, Cairo, Baghdad and Damascus, adding yet a further tinge of exotica to a tiny world that has already shown itself to be highly unusual.
Cassini’s August 11 flyby is, as the photo shows, paying off big. The intent was to focus in on sources for the jets that spew water vapor, ice and trace organics into space — the yellow circles in the image show two particular sources of jets. What we’re after, of course, is a closer look at geological activity in the sulci, in hopes of determining whether liquid water exists beneath the surface. The new details show that the fractures are some 300 meters deep with V-shaped inner walls, surrounded by terrain littered with blocks of ice tens of meters in size.
Image: Damascus Sulcus on Enceladus. One process that may be at work here is the sealing off of active vents by condensing water vapor, which then forces new jets to emerge elsewhere in the same fracture. Credit: NASA/JPL/Space Science Institute.
The method for getting the high-resolution images from this flyby was itself fascinating. Cassini was moving past Enceladus at 64,000 kilometers per hour, so it was necessary to compensate for the effects of that motion. Imaging team member Paul Helfenstein compared this to “…trying to capture a sharp, unsmeared picture of a distant roadside billboard with a telephoto lens out the window of a speeding car.” He goes on:
“Enceladus was streaking across the sky so quickly that the spacecraft had no hope of tracking any feature on its surface. Our best option was to point the spacecraft far ahead of Enceladus, spin the spacecraft and camera as fast as possible in the direction of Enceladus’ predicted path, and let Enceladus overtake us at a time when we could match its motion across the sky, snapping images along the way.”
Nice work!
by Paul Gilster | Aug 14, 2008 | Asteroid and Comet Deflection |
We could do with as much information as possible about near-Earth asteroids. A manned mission is a natural step, both for investigating a class of object that could one day hit our planet, and also for continuing to develop technologies in directions that will be useful for our future infrastructure in space. You would think we would know much of what we needed from examining meteorites, which generally are chunks of asteroid material, but that assumption turns out to be erroneous.
A recent paper in Nature has the story. Richard Binzel (MIT) and colleagues have been considering the properties of asteroids for a long time, looking at the spectral signatures of near-Earth asteroids and comparing them to spectra obtained from meteorites. And it turns out that most of the meteorites that fall to Earth represent types of asteroid that are different from the great bulk of near-Earth asteroids. In fact, the varied types of meteorites we find here generally resemble the mix of asteroids found in the main belt.
How can this be? Binzel’s team posits our old friend the Yarkovsky effect, mentioned surprisingly often in our archives. Uneven heating of an asteroid surface and the subsequent radiation of that heat during rotation can create imbalances that accumulate over time, adjusting an object’s orbit. And if this study is to be believed, the Yarkovsky effect works more strongly on smaller objects and much more weakly on larger ones. So efficient is the effect at small scale that it can readily move boulder-sized objects out of the asteroid belt onto a path that leads to Earth, while larger asteroids are moved much more slightly.
The largest near-Earth asteroids come from the innermost edge of the main belt, according to this theory, possibly remnants of a larger asteroid that was shattered aeons ago by collisions. In the aggregate, two-thirds of all such asteroids correspond to the type of meteorites known as LL chondrites, which represent only about eight percent of meteorites. They’re rich in olivine and poor in iron. Knowing this means we can put most of our attention onto deflecting this type of object. “Odds are,” says Binzel, “an object we might have to deal with would be like an LL chondrite, and thanks to our samples in the laboratory, we can measure its properties in detail. It’s the first step toward ‘know thy enemy.'”
So most meteorites come not from the population of near-Earth asteroids but the main belt, on a track that is made possible by the Yarkovsky effect. How we defend against an incoming asteroid may well depend upon its type, so this is a result that should be weighed carefully. Let’s hope it can also be backed up by a mission to a near-Earth asteroid in the not too distant future. The paper is Vernazza, Binzel et al., “Compositional differences between meteorites and near-Earth asteroids,” Nature 454 (14 August 2008), pp. 858-860 (abstract)
by Paul Gilster | Aug 13, 2008 | Culture and Society, Research Tools |
I want to take a momentary detour from interstellar topics to talk about how we go about doing research, astronomical and otherwise. Some years back I debated the then new trend of online peer review with an opponent who argued for the virtues of traditional print journals and their methods. At the time, what would become the arXiv pre-print site was just beginning to grow, and the benefits of having a wide audience able to examine a scientific paper before it achieved print seemed manifest. Much good research, I reasoned, would become available for scrutiny, some of it unable to get past academic referees at a specific journal but now able to be included in a broadened scientific discussion.
Even so, certain trends did worry me, some of them now manifest again in a presidential report recently cited by James Evans, a University of Chicago sociologist. The report makes a jaw-dropping claim: “All citizens anywhere anytime can use any Internet-connected digital device to search all of human knowledge.” The sheer naiveté of this claim boggles the mind, the idea that the Internet, whose holdings are top-heavy with the most recent work and all but empty of the great bulk of earlier studies other than in the form of bibliographical references, is a complete library.
Evans agrees. We have no reason to doubt (and surveys of library practice confirm) that the use of print is waning because of the manifest advantages of searching online, not to mention exotica like citing going forward, meaning an earlier paper’s references can now be buttressed with links to subsequent research that refers back to that paper, thus deepening the perspective. Interested in learning more, Evans has published the results of his survey of a database of 34 million articles, with reference to their availability and the uses to which they are being put. This is from an essay he did on the Britannica Blog about his work, and now the implications of Web availability take a darker turn:
“…as more journals and articles came online, the actual number of them cited in research decreased, and those that were cited tended to be of more recent vintage. This proved true for virtually all fields of science. (Note that this is not a historical trend… there are more authors and universities citing more and older articles every year, but when journals go online, references become more shallow and narrow than they would have been had they not gone online).
And was my idea of spreading the availability of good material outside the primary journals accurate? Apparently not, at least in sociology. For Evans also learned that researcher attention has now shifted to the most prestigious journals. The result turns out to be counter-intuitively hostile to good research: With online searching more efficient and aided by hyperlinking, what we’re actually seeing is a narrowing of the range of scholarly findings and ideas being studied by scholars. And get this:
Ironically, my research suggests that one of the chief values of print library research is its poor indexing. Poor indexing—indexing by titles and authors, primarily within journals—likely had the unintended consequence of actually helping the integration of science and scholarship. By drawing researchers into a wider array of articles, print browsing and perusal may have facilitated broader comparisons and scholarship.
And, of course, we can relate this to the non-academic experience of the average Internet user, who may find that while access to a wide range of ideas is available, the actual practice is to look at the top page of search results and little else. With Google’s page-rank algorithms making the call, people wind up experiencing largely the same number of high-profile sites, to the detriment of serendipity, that wonderful process by which we blunder into a concept that cross-pollinates into a startling new insight.
Long live the computerized database and the pre-print server concept, but can’t we work on richer indexing methods and interface possibilities to keep the research environment as fertile as possible? Evans is exploring this in his work, and speculating that advances in natural language processing may help us sharpen up the relevance of our search techniques. Beyond that, of course, we have to expand our databases themselves to include the vast storehouse of papers that have accumulated over the course of scientific investigation, many of which, when coupled with recent findings, may offer insights that would otherwise be lost. This is a future priority for the Tau Zero Foundation.
The paper is Evans, “Electronic Publication and the Narrowing of Science and Scholarship,” Science Vol. 321 No. 5887 (18 July 2008), pp. 395-399 (abstract).
Addendum: Author Nicholas Carr also looks at this issue in his Rough Type blog, from which this:
When the efficiency ethic moves from the realm of goods production to the realm of intellectual exploration, as it is doing with the Net, we shouldn’t be surprised to find a narrowing rather than a broadening of the field of study. Search engines, after all, are popularity engines that concentrate attention rather than expanding it, and, as Evans notes, efficiency amplifies our native laziness.
by Paul Gilster | Aug 12, 2008 | Outer Solar System |
Although the Cassini spacecraft has just passed no more than fifty kilometers from the surface of Saturn’s moon Enceladus, the investigation of the intriguing object will only intensify in October, when Cassini moves to within half that distance. With astrobiological interest high, Enceladus is a hot place to be. Data from the most recent flyby began streaming in to the Deep Space Network station in Canberra last night, with the downlink scheduled to continue into the afternoon of the 12th (EST).
The prime target, using every camera resource available and covering infrared, visible light and ultraviolet, is the area of the moon’s southern pole that houses the fissures now known as ‘tiger stripes.’ Under intense scrutiny will be the terrain of the fissures as well as the composition of the ice grains inside, and tuning up our data on temperature should provide a better idea of whether or not liquid water lies close to the surface. Cassini will be looking for other elements — oxygen, hydrogen or organics — mixing with the ice. “Knowing the sizes of the particles, their rates and what else is mixed in these jets,” says ultraviolet imaging spectrograph team member Amanda Hendrix, “can tell us a lot about what’s happening inside the little moon.”
Image: This graphic shows the trajectory (E4) for the Cassini spacecraft during its flyby of the icy moon Enceladus on Aug. 11, 2008, along with the trajectory of its earlier March encounter (E3). At closest approach, Cassini was 50 kilometers (30 miles) from the surface. The spacecraft’s optical remote sensing instruments imaged the fissures running across the moon’s south pole, where the icy jets originate. Credit: NASA/JPL.
We know, of course, that plenty is happening to cause the geysers of water ice and vapor that stream out of the fissures and feed Saturn’s E-ring with material. The raw images from the encounter are showing up on the JPL server, worth a look if you enjoy watching the early results of a flyby unfold (the best should be available in the early evening EST). And keep an eye on the tiger stripe known as Damascus Sulcus. Just before the flyby, John Spencer, who works on the Composite Infrared Spectrometer team that maps heat radiation from the tiger stripes, said he was anxious to see how this close pass pays off in terms of detail:
I’m most excited about the observation we’ll be attempting at about 21:11 UT, when we will try to put the CIRS short-wavelength detector right along one of the most active tiger stripes, called Damascus Sulcus, from a distance of only 4,500 km (2,800 miles). On our last flyby we saw temperatures as high as at least 180 Kelvin (-135 Fahrenheit) on this part of Damascus, from 15,000 km (9,000 mile) range, and from three times closer we might see even higher temperatures because the warm material, which we think occupies a strip just tens or hundreds of meters wide along the fractures, will fill more of our detector and give us a more accurate reading. However, this is a challenging observation because our detector consists of a linear array of ten pixels, which will be aligned parallel to the fracture. Pointing may not be perfect this close to the moon, so we may get all ten detectors, or none of them, on Damascus.
Poking around in places like the Enceladus flyby blog (from which I drew Spencer’s observation) is a lively practice when things are jumping with the spacecraft, as they are now. And we’ll see, in coming days and weeks, how the incoming temperature data back up the theory that liquid water exists somewhere within the moon.
