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Selected readings 5/31/10

Monday, May 31, 2010

Interesting reading and news items.

Please leave some comments that indicate which articles you find most interesting or that identify topics you would like to read about, and I will try to include more articles of a similar nature in the future

These items are also bookmarked at my Diigo account.

Seeing Aliens Will Likely Take Centuries
Although our telescopes will likely become good enough to detect signs of life on exoplanets within the next 100 years, it would probably take many centuries before we could ever get a good look at the aliens. "Unfortunately, we are perhaps as far away from seeing aliens with our own eyes as Epicurus was from seeing the first other worlds when, 23 centuries ago, he predicted the existence of these planets," said astrobiologist Jean Schneider at the Paris Observatory at Meudon. [Space.com, 4/29/10]

Only a matter of time, says Frank Drake
The search for extraterrestrial intelligence began in earnest 50 years ago, led by a young American astronomer named Frank Drake - a man, who is still confident we'll eventually find extraterrestrial civilisations. [COSMOS Magazine, 4/7/10]

A review of the Drake Equation
Which is the more shocking proposition: that our galactic neighbourhood is riddled with advanced alien civilisations? Or that we humans are a solitary beacon of intelligent life in a silent universe of almost incomprehensible vastness? Either prospect is enough to keep you awake at night. Yet one of these two statements is likely true. We just don't know which one. [COSMOS Magazine, 4/7/10]

What's up with nanotech?
While nanotechnology — working at a scale that is one-thousandth the width of a human hair — may have faded from the public’s imagination, the field has made substantial progress in recent years, opening new frontiers in electronics, medicine, and materials. [Boston.com, 3/29/10]

Scientist who cloned Dolly the sheep sees revolution in disease treatment in 20 years
The scientist who cloned Dolly the sheep believes that a new approach to the production of stem cells could revolutionise the treatment of inherited diseases such as Parkinson’s and motor neurone disease “within ten to twenty years”. [Times Online, 3/26/10]

Next Big Thing in English: Knowing They Know That You Know
This layered process of figuring out what someone else is thinking — of mind reading — is both a common literary device and an essential survival skill. Why human beings are equipped with this capacity and what particular brain functions enable them to do it are questions that have occupied primarily cognitive psychologists. [New York Times, 3/31/10]

Telescope arrays give fine view of stars
Radio astronomers have relied on interferometry for more than half a century, but optical astronomers have lagged behind. Now, optical interferometry has come of age. [Nature News, 4/7/10]

Protein folding: The dark side of proteins
Almost every human protein has segments that can form amyloids, the sticky aggregates known for their role in disease. Yet cells have evolved some elaborate defences. [Nature News, 4/7/10]

A New Clue to Explain Existence
Physicists at the Fermi National Accelerator Laboratory are reporting that they have discovered a new clue that could help unravel one of the biggest mysteries of cosmology: why the universe is composed of matter and not its evil-twin opposite, antimatter. [New York Times, 5/17/10]

Fermilab scientists find evidence for significant matter-antimatter asymmetry
The dominance of matter that we observe in the universe is possible only if there are differences in the behavior of particles and antiparticles. Although physicists have observed such differences (called “CP violation”) in particle behavior for decades, these known differences are much too small to explain the observed dominance of matter over antimatter in the universe and are fully consistent with the Standard Model. If confirmed by further observations and analysis, the effect seen by DZero physicists could represent another step towards understanding the observed matter dominance by pointing to new physics phenomena beyond what we know today. [SymmetryBreaking, 5/18/10]

How Many Sparks in the Genome?
The first two categories include stretches of DNA that are useful. The second two include stretches that are useless. Now comes the hard part: figuring out just how much of the genome is made up of each. [The Loom, 5/19/10]

Supermassive Black Holes Can Kill Whole Galaxies
Astrophysicists have found that when a supermassive black hole quickly devours gas and dust, it can generate enough radiation to abort all the embryonic stars in the surrounding galaxy. [ScienceNOW, 4/15/10]

The Search for Genes Leads to Unexpected Places
Dr. Marcotte and his colleagues have discovered hundreds of other genes involved in human disorders by looking at distantly related species. They have found genes associated with deafness in plants, for example, and genes associated with breast cancer in nematode worms. [New York Times, 4/26/10]

Life on Titan: stand well back and hold your nose!
Research by astrobiologist William Bains suggests that if life has evolved on the frozen surface of Saturn's moon, Titan, it would be strange, smelly and explosive compared to life on Earth. [Physorg.com, 4/14/10]

Perhaps a longer lifespan, certainly a longer 'health span'
Organisms from yeast to rodents to humans all benefit from cutting calories. In less complex organisms, restricting calories can double or even triple lifespan. It's not yet clear just how much longer calorie restriction might help humans live, but those who practice the strict diet hope to survive past 100 years old. [Physorg.com, 4/15/10]

Hubble Space Telescope clocks up 20 years
It was an instrument that much of the astronomical community didn't want, but times change: to get time now on the Hubble Space Telescope, which is celebrating its 20th anniversary this week, an astronomer usually faces competition from at least 11 other eager scientists. [Nature News, 4/22/10]

Origin of Life Chicken-and-Egg Problem Solved
Scientists have wondered how the first simple, self-replicating chemicals could have formed complex, information-rich genetic structures, when replication was originally such an error-prone process. Every advance would soon be lost to copying errors. According to a new study, the answer may lie in the fundamental nature of those chemicals. The errors may have triggered an automatic shutdown of replication. Such stalling would allow only error-free sequences to be completed, giving them a chance at evolving. [Wired, 4/22/10]

A Skeptic Questions Cancer Genome Projects
Fueled by hundreds of millions of grant dollars, biomedical researchers have begun sequencing the genomes of thousands of tumor samples in the past few years, linking up scores of labs and sequencing centers in a massive effort to identify the genes behind major cancers. But a leading cancer geneticist this week questioned whether this strategy still makes sense. [ScienceInsider, 4/23/10]

Black holes and qubits
While string theory and M-theory have yet to make readily testable predictions in high-energy physics, they could find practical applications in quantum-information theory. [CERN Courier, 5/5/10]

Neutrinos: Clues to the Most Energetic Cosmic Rays
ARIANNA, a proposed array of detectors for capturing the most energetic cosmic rays, is being tested in Antarctica with a prototype station built last December on the Ross Ice Shelf by a Berkeley Lab team. By detecting neutrino-generated signals bounced off the interface of water and ice beneath the shelf, scientists hope to pinpoint the still unidentified sources of ultra-high-energy cosmic rays. [Physorg.com, 4/20/10]

In praise of the Y chromosome
David Page, director of the Whitehead Institute and professor of biology at Massachusetts Institute of Technology, says research indicates the much-maligned Y chromosome plays a more critical role in genetics than previously believed. [Physorg.com, 4/20/10]

The Evolution of the End
Immortality comes with some fairly significant disadvantages. A large complex organism requires a good bit of resources and the environment offers only so many available niches in which organisms of a set design can live. If the landscape is already saturated by unaging oldsters doing their timeless thing, there's little room for new and at least possibly improved models to take the stage. For most organisms, the areas where life is most tenuous is at the ends; both predators and disease take the hardest toll on the very young and the very old. If there are no old, then additional stress could be placed on the newcomers, further cutting turnover in a population. That means little chance for newbies, with their occasional mutations and interesting new combinations of genes. For immortals, evolution runs in slow motion. [Daily Kos, 5/30/10]

The Rise of the Mind
When and where did the cognitive abilities of modern humans arise? It's a big question -- one debated by anthropologists for decades. It's an even bigger question for an undergraduate thesis, but senior Logan Bartram has a leg up on this ambitious project: he helped unearth artifacts that are playing a critical role in shaping our knowledge about human origins. [Physorg.com, 4/22/10]

Airport security: Intent to deceive?
To Honts, the decade since the 11 September attacks has been one of lost opportunity. Calling SPOT an "abject failure", he says that the government would have done better to invest first in basic science, experimentally establishing how people with malintent think and respond during screenings. That work, in turn, could have laid a more solid foundation for effective detection methods. [Nature News, 5/26/10]

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The Glow of the Lagoon Nebula

Saturday, May 29, 2010

The Glow of the Lagoon Nebula
Gas and dust condense, beginning the process of creating new stars in this image of Messier 8, also known as the Lagoon Nebula. Located four to five thousand light-years away, in the constellation of Sagittarius (the Archer), the nebula is a giant interstellar cloud, one hundred light-years across. It boasts many large, hot stars, whose ultraviolet radiation sculpts the gas and dust into unusual shapes. Two of these giant stars illuminate the brightest part of the nebula, known as the Hourglass Nebula, a spiralling, funnel-like shape near its centre. Messier 8 is one of the few star-forming nebulae visible to the unaided eye, and was discovered as long ago as 1747, although the full range of colours wasn’t visible until the advent of more powerful telescopes. The Lagoon Nebula derives its name from the wide lagoon-shaped dark lane located in the middle of the nebula that divides it into two glowing sections.

Lagoon Nebula – click for 1280×1303 image

Soul Nebula

Wednesday, May 12, 2010

Soul Nebula (4/2/10)
This WISE mosaic is of the Soul Nebula (a.k.a. the Embryo Nebula, IC 1848, or W5). It is an open cluster of stars surrounded by a cloud of dust and gas over 150 light-years across and located about 6,500 light-years from Earth in the constellation Cassiopeia, near the Heart Nebula (partially seen in the WISE image of Maffei 1 & 2).

The cluster of stars, IC 1848, formed about a million years ago from the material of the nebula. Winds and ultraviolet light from these young stars are excavating a cavity in the cloud. Parts of the cloud that are more dense than their surroundings are being eroded more slowly and form giant towers, or pillars of dust and gas, which all point toward the central star cluster. It’s reminiscent of the landscape of Badlands National Park in South Dakota. Material at the interior edges of the cavity is also being compressed by the winds and radiation from the star cluster. This triggers new star formation in those areas. The pillars inside the Soul Nebula are each about 10 light-years tall and have stars forming at their tips.

Soul Nebula – click for 800×418 image

Where the action is in black hole jets

The object known simply as 3C 279 is rather distinctive for several reasons, in spite of the rather unassuming name. For one thing it's an active galaxy – that is, it has a supermassive black hole at its center, and that black hole is sucking in surrounding matter at a rate high enough to generate as much energy as all stars the in the galaxy where it resides combined. Only about 1% of visible galaxies are active galaxies like 3C 279.

But that's not all. 3C 279 is also a radio galaxy, a subset of only about 10% of active galaxies that also feature strong radio-frequency emissions. Such strong emissions are generally thought to be produced by a violent outflow of matter from the vicinity of the black hole in the form of narrow jets. The flow is so violent that matter in the jets reaches velocities close to the velocity of light.

And if that's not enough, one of the jets of 3C 279 is pointed almost straight at us. Only a few percent of active radio galaxies are oriented that way, by chance. Because we're looking essentially straight into the most active part of the object, with basically no dust or gas to obscure the view, 3C 279 appears especially luminous – the term for such an object is "blazar".

Although its jet is aimed right at us, there's nothing to be particularly concerned about, since 3C 279 has a redshift of z=0.536, which means it's actually about 6.5 billion light years away.

3C 279

I just wrote at some length about active galaxies, here, in some detail, so you might like to review that if you need to refresh your memory on many basics of the subject. There may be some aspects of the present discussion that will make more sense in light of that.

Even though 3C 279 came to the attention of astronomers over 40 years ago, because of its unusual apparent brightness and radio emissions, it is not an especially powerful active galaxy, as those things go. The central black hole is estimated to have a mass around 6×108 M, somewhat short of 109 M that is typical of the largest quasars.

The peak velocity of matter in the jet of 3C 279 has been inferred to be about 99.8% of the speed of light, which is "relativistic" by anyone's definition. In other words, this velocity is v=0.998c. It's customary to express this velocity as β = v/c = 0.998. The inference is based on apparent (but not real) "superluminal" (faster than light) motion of jet-related material. This is a common phenomenon seen in active galaxy jets that are nearly parallel to our line of sight. A related quantity, the Lorentz factor, is defined as γ =  (1-β2)-1/2, so in this case γ ≈ 16. That'll play a role in an important calculation later.

Since astronomers have been interested in 3C 279 for over 40 years, it's been studied a lot, although that's been difficult, because of its rather large distance. Radio galaxies like this produce electromagnetic emissions all the way from radio frequencies on up to gamma rays – spanning 11 or 12 orders of magnitude in photon energy, from under .001 eV to over 100 Mev. Many of those frequency ranges can be observed only from instruments in space, so until recently it hasn't been possible to observe a single object continuously for long periods of time in many bands. This has now been done for the blazar 3C 279 – and perhaps by chance something rather interesting showed up, which could only have been observed in an active galaxy whose jet is nearly parallel to our line of sight.

A change in the optical polarization associated with a γ-ray flare in the blazar 3C 279
It is widely accepted that strong and variable radiation detected over all accessible energy bands in a number of active galaxies arises from a relativistic, Doppler-boosted jet pointing close to our line of sight. The size of the emitting zone and the location of this region relative to the central supermassive black hole are, however, poorly known, with estimates ranging from light-hours to a light-year or more. Here we report the coincidence of a gamma (γ)-ray flare with a dramatic change of optical polarization angle. This provides evidence for co-spatiality of optical and γ-ray emission regions and indicates a highly ordered jet magnetic field. The results also require a non-axisymmetric structure of the emission zone, implying a curved trajectory for the emitting material within the jet, with the dissipation region located at a considerable distance from the black hole, at about 105 gravitational radii.

The main thing that this paper reports is an "event", evidently some sort of disturbance affecting the jet, manifested in the spectrum of 3C 329. The event was most pronounced in the γ-ray part of the spectrum, which – in this object – is the dominant and also the most variable part. The γ-ray flux of 3C 279 can vary over an order of magnitude, and at one point – the beginning of the event – the flux increased rapidly from an already elevated level to its maximum value, then dropped a little more slowly, over a span of 20 days, to its minimum.

Other parts of the spectrum were also affected, but not so dramatically. Flux in ultraviolet, optical, and near infrared bands also decreased from somewhat elevated levels during the same 20 days, though there was no spike up at the start. There was, however, little change in the X-ray and radio bands during this period.

There was one additional dramatic change in the same period. The percentage of polarization in optical emissions (blue) dropped from 30-40% down to 10% before recovering at the end of the period. And at the same time, the direction of polarization changed smoothly over the 20 days by about 180°.

Since our line of sight is nearly parallel (to within about 2°) to the jet, it is difficult to distinguish where in 3C 279 different emissions originate. Strong γ-ray emissions are typically associated with jets (when present), but a key question that the paper examines concerns what part of the jet the dramatic changes in γ-ray flux could have been associated with. Was it relatively close to the black hole, or much farther out?

It's not too surprising that there was little change in X-ray flux, since that's normally associated in active galaxies with the "corona", which is symmetrically distributed in a region with a radius of a few hundred light years around the black hole. Radio emissions, however, do generally originate from the jets, but often from "lobes" at very large distances from the center. In this case it would seem that the source of radio emissions had little to do with the "event".

On the other hand, since distinct changes in ultraviolet, optical, and infrared flux – as well as the dramatic change in polarization – occurred at exactly the same time as the γ-ray "event", it's natural to suppose that whatever caused the disturbance affected a part of the jet where these emissions originated.

So what can be said about the size and (perhaps) location of the disturbance? The key fact is that the event was observed to last 20 days. However, since we're dealing with matter moving at a relativistic velocity, it doesn't at all follow that the disturbance affected only a portion of the jet about 20 light days in extent. It's not hard to calculate the "actual" size of the disturbance, but it does take a little work.

Suppose we let r0 be the distance along the jet from the central black hole at which the disturbance began, and r1 be the distance at which the state of the jet has returned to "normal". Then r1 >r0. The distance d = r1 - r0 is what we want to compute. If v is the average velocity of matter in the jet when the event occurred, then we have already noted v = 0.998c, so that β =v/c = 0.998.

Note that d is the distance in our reference frame. The time (in our frame) it takes light to travel that distance is d/c. If we assume that the matter within the jet that's subject to the disturbance is moving with velocity v, then the time it takes the leading edge of that matter to go the same distance is d/v. Since c > v, d/v > d/c, so by the time the leading edge reaches r1 it is lagging behind the corresponding photons by a time interval Δt = d/v-d/c > 0. Since we're aiming only for an approximation, assume for simplicity that the spatial extent of the disturbance (from leading to trailing edge) is small compared to d. Then the photons from the time the disturbance began at r0 will reach us by the same interval Δt ahead of the photons from the time the disturbance ended, when the affected matter was at r1.

So the data we have to work with are just β and the observed elapsed time between the start and end of the event: Δt ≈ 20 days. We'll get an expression for d in terms of Δt.

We have Δt = d/v-d/c = (d/c)(c-v)/v = (d/c)(1-β)/β. Multiplying that by (1+β)/(1+β) gives Δt = (d/c)(1-β2)/[β(1+β)]. Using 1-β2 = 1/γ2 and solving for d gives d = γ2cΔtβ(1+β). But in this example, β≈1, so d ≈ 2γ2cΔt.

Plugging in actual numbers, Δt≈1.7×106 seconds, c≈3×108 m/sec, and γ2≈256 gives d≈2.6×1017 m. A light year is about 9.5×1015 m, so d is about 27 light years. That's quite an extensive part of 3C 279's jet that is affected by the disturbance.

Another way to appreciate the size of that number is to compare it to the Schwarzschild radius of the black hole, rs=2GMBH/c2. MBH is roughly 6×108 M, so with G=6.67×10-11 m3 kg-1 sec-2 and M=1.99×1030 kg, we find rs≈1.8×1012 m. Thus the size of the disturbance is more than 100 thousand times the black hole's Schwarzschild radius – 5 orders of magnitude.

So, now that we have some idea of the impressive extent of this "disturbance", is it possible to draw any conclusions about what caused it?

To begin with, keep in mind that we have assumed the matter that is disturbed is propagating along the jet with velocity v=0.998c. That assumption is the reason the estimate of d is so large, because of the factor γ2. If v≪c, then β≈0 and γ≈1, so that d ≈ cΔt ≈ 5×1014 m – about a factor of 500 smaller. In this latter case the disturbance affects the jet only in a small zone at a distance of r0 from the black hole, and the matter "flows through" this zone without much long-lasting effect. This could happen, for example, if there is a narrow knot in the magnetic fields that keep the jet constricted.

The evidence that this latter possibility is not in fact what's happening is that the polarization of light turns around by 180° in almost perfect synchrony with the event in which γ-ray flux has a large bump. This implies that there's a large-scale bend in the jet at that point, so that the direction of the jet crosses over our line of sight. This apparent change of direction persists far longer than the event itself.

Of course, that hypothesis still doesn't explain either the γ-ray flare or the change of direction itself. It is possible, for instance, that the jet encounters, at an oblique angle, some large concentration of matter that deflects the jet. Perhaps the jet passes very close to another black hole. We simply don't know.

There was no guarantee that we could quickly learn how to explain all the behavior of black hole jets with ease – so the observational effort must continue, with increasingly sensitive equipment and larger data sets.

Abdo, A., Ackermann, M., Ajello, M., Axelsson, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Baughman, B., Bechtol, K., Bellazzini, R., Berenji, B., Blandford, R., Bloom, E., Bock, D., Bogart, J., Bonamente, E., Borgland, A., Bouvier, A., Bregeon, J., Brez, A., Brigida, M., Bruel, P., Burnett, T., Buson, S., Caliandro, G., Cameron, R., Caraveo, P., Casandjian, J., Cavazzuti, E., Cecchi, C., Çelik, �., Chekhtman, A., Cheung, C., Chiang, J., Ciprini, S., Claus, R., Cohen-Tanugi, J., Collmar, W., Cominsky, L., Conrad, J., Corbel, S., Corbet, R., Costamante, L., Cutini, S., Dermer, C., de Angelis, A., de Palma, F., Digel, S., do Couto e Silva, E., Drell, P., Dubois, R., Dumora, D., Farnier, C., Favuzzi, C., Fegan, S., Ferrara, E., Focke, W., Fortin, P., Frailis, M., Fuhrmann, L., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Gehrels, N., Germani, S., Giebels, B., Giglietto, N., Giommi, P., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Grenier, I., Grove, J., Guillemot, L., Guiriec, S., Hanabata, Y., Harding, A., Hayashida, M., Hays, E., Horan, D., Hughes, R., Iafrate, G., Itoh, R., Jackson, M., Jóhannesson, G., Johnson, A., Johnson, W., Kadler, M., Kamae, T., Katagiri, H., Kataoka, J., Kawai, N., Kerr, M., Knödlseder, J., Kocian, M., Kuss, M., Lande, J., Larsson, S., Latronico, L., Lemoine-Goumard, M., Longo, F., Loparco, F., Lott, B., Lovellette, M., Lubrano, P., Macquart, J., Madejski, G., Makeev, A., Max-Moerbeck, W., Mazziotta, M., McConville, W., McEnery, J., McGlynn, S., Meurer, C., Michelson, P., Mitthumsiri, W., Mizuno, T., Moiseev, A., Monte, C., Monzani, M., Morselli, A., Moskalenko, I., Murgia, S., Nestoras, I., Nolan, P., Norris, J., Nuss, E., Ohsugi, T., Okumura, A., Omodei, N., Orlando, E., Ormes, J., Paneque, D., Panetta, J., Parent, D., Pavlidou, V., Pearson, T., Pelassa, V., Pepe, M., Pesce-Rollins, M., Piron, F., Porter, T., Rainò, S., Rando, R., Razzano, M., Readhead, A., Reimer, A., Reimer, O., Reposeur, T., Reyes, L., Richards, J., Rochester, L., Rodriguez, A., Roth, M., Ryde, F., Sadrozinski, H., Sanchez, D., Sander, A., Saz Parkinson, P., Scargle, J., Sgrò, C., Shaw, M., Shrader, C., Siskind, E., Smith, D., Smith, P., Spandre, G., Spinelli, P., Stawarz, L., Stevenson, M., Strickman, M., Suson, D., Tajima, H., Takahashi, H., Takahashi, T., Tanaka, T., Taylor, G., Thayer, J., Thayer, J., Thompson, D., Tibaldo, L., Torres, D., Tosti, G., Tramacere, A., Uchiyama, Y., Usher, T., Vasileiou, V., Vilchez, N., Vitale, V., Waite, A., Wang, P., Wehrle, A., Winer, B., Wood, K., Ylinen, T., Zensus, J., Ziegler, M., Uemura, M., Ikejiri, Y., Kawabata, K., Kino, M., Sakimoto, K., Sasada, M., Sato, S., Yamanaka, M., Villata, M., Raiteri, C., Agudo, I., Aller, H., Aller, M., Angelakis, E., Arkharov, A., Bach, U., Benítez, E., Berdyugin, A., Blinov, D., Boettcher, M., Buemi, C., Chen, W., Dolci, M., Dultzin, D., Efimova, N., Gurwell, M., Gusbar, C., Gómez, J., Heidt, J., Hiriart, D., Hovatta, T., Jorstad, S., Konstantinova, T., Kopatskaya, E., Koptelova, E., Kurtanidze, O., Lahteenmaki, A., Larionov, V., Larionova, E., Leto, P., Lin, H., Lindfors, E., Marscher, A., McHardy, I., Melnichuk, D., Mommert, M., Nilsson, K., Di Paola, A., Reinthal, R., Richter, G., Roca-Sogorb, M., Roustazadeh, P., Sigua, L., Takalo, L., Tornikoski, M., Trigilio, C., Troitsky, I., Umana, G., Villforth, C., Grainge, K., Moderski, R., Nalewajko, K., & Sikora, M. (2010). A change in the optical polarization associated with a γ-ray flare in the blazar 3C 279 Nature, 463 (7283), 919-923 DOI: 10.1038/nature08841

Further reading:

Extreme Jets Take New Shape (2/17/10)

Fermi pins down a colossal accelerator (2/18/10)

Astrophysics: Cosmic jet engines (2/18/10)

Related articles:

Active galaxies and supermassive black hole jets (4/25/10)

Winds of Change: How Black Holes May Shape Galaxies (4/19/10)

Galactic black holes may be more massive than thought (6/8/09)

Black hole outflows from Centaurus A (2/6/09)

Evidence that quasars are powered by black holes (10/21/06)

The wind from a black hole (7/8/06)

Selected readings 5/8/10

Saturday, May 8, 2010

Interesting reading and news items.

These items are also bookmarked at my Diigo account.

The Search for Genes Leads to Unexpected Places
Dr. Marcotte and his colleagues have discovered hundreds of other genes involved in human disorders by looking at distantly related species. They have found genes associated with deafness in plants, for example, and genes associated with breast cancer in nematode worms. [New York Times, 4/26/10]

Are we there yet?
Years of effort and roughly 10,000 people have made the Large Hadron Collider the most powerful particle accelerator in the world. This collaborative feat of technology promises to change the way we understand the universe. Now the world is watching, waiting to see what so much effort will yield. Even at an initial collision energy of 7 trillion electronvolts-half its full capacity-the LHC is in a position to make important discoveries. [Symmetry, 4/1/10]

Moving beyond silicon to break the MegaHertz barrier
We're rapidly closing in on a decade since the first desktop processors cleared the 3GHz mark, but in a stunning break from earlier progress, the clock speed of the top processors has stayed roughly in the same neighborhood since. Meanwhile, the feature shrinks that have at least added additional processing cores to the hardware are edging up to the limits of photolithography technology. [Nobel Intent, 3/26/10]

How huge particle detectors actually detect tiny particles
The detectors in colliders like the Large Hadron Collider and Relativistic Heavy Ion Collider work by looking at some of the items that come rocketing out of the collisions, producing the sort of traces shown here. Given that data, it's possible for physicists to work their way backwards in order to figure out what went on in the collision itself. [Nobel Intent, 3/29/10]

The software brains behind the particle colliders
In the instant that its detectors register the events associated with a collision, the challenges move from the hardware realm into software, as the LHC will literally produce more data than we can possibly handle. We have to figure out what to hang on to in real time, and send it around the globe via dedicated connections that aggregate multiple 10Gbp/s links; those on the receiving end need to safely store it and pursue the sorts of analyses that will hopefully reveal some new physics. [Nobel Intent, 3/30/10]

Lasing Beyond Light
Now, at age 50, the laser has extended its dominion far beyond the realm of light. Physicists have succeeded in building lasers that emit different kinds of waves. Laserlike “hard” X-ray pulses, for example, can freeze atoms in their tracks, providing a ringside view of chemical reactions. And phonon lasers vault the technology out of the electro­magnetic spectrum altogether, creating coherent beams of sound. [Science News, 4/23/10]

Master of the Cell
RNA interference, with its powerful promise of therapy for many diseases, may also act as a master regulator of most-if not all-cellular processes. [The Scientist, 3/29/10]

Obesity: the role of the immune system
Obesity is one symptom of several, which together constitute what is now termed metabolic syndrome. Morbid obesity is also associated with a host of other symptoms including high blood sugar, high blood lipids, insulin resistance and liver disorders. The root causes of which are traced back to excessive food consumption, reduced physical activity and in some cases, genetic predisposition. [Byte Size Biology, 4/25/10]

Evolving a code: A molecular fossil's tale
Every living cell on earth carries a molecular fossil: the ribosome. In a recent paper published in PNAS, researchers from California open the drawer and dust off this ancient molecular machine. The structure of the ribosome seems to provide hints about the origin of that universal feature of life: the genetic code. [Thoughtomics, 4/18/10]

Can Life on Titan Thrive Without Water?
The standard definition of a "habitable world" is a world with liquid water at its surface; the "habitable zone" around a star is defined as that Goldilocks region — not too hot, not too cold — where a watery planet or moon can exist. And then there's Titan. Saturn's giant moon Titan lies about as far from the standard definition of habitable as one can get. The temperature at its surface hovers around 94 degrees Kelvin (minus 179 C, or minus 290 F). At that temperature, water is a rock as hard as granite. And yet many scientists now believe life may have found a way to take hold on Titan. [Space.com, 3/23/10]

Neutrinos: Clues to the Most Energetic Cosmic Rays
“The most energetic cosmic rays are the rarest, and they pose the biggest mystery,” says Spencer Klein of Berkeley Lab’s Nuclear Science Division. He compares the energy of an ultra-high-energy (UHE) cosmic ray to a well-hit tennis ball or a boxer’s punch – all packed into a single atomic nucleus. ... Sources capable of producing such high-energy nuclei have not been clearly identified. One clue to the origin of the highest-energy cosmic rays is the neutrinos they produce when they interact with the very cosmic microwave photons that slow them down. [Berkeley Lab News Center, 4/19/10]

Bizarre models for human diseases
The search for models of human diseases might just have become easier, thanks to a data-mining technique that screens genetic databases to find subtle links to organisms as distant from humans as plants. The new tool integrates information from existing databases that associate gene mutations with observable traits in a range of species, including humans, mice, yeast, worms and plants. And the method identifies genes in the non-human species that are more likely than by chance to contribute to human disease. [Nature News, 3/22/10]

Addicted to Fat: Overeating May Alter the Brain as Much as Hard Drugs
Like many people, rats are happy to gorge themselves on tasty, high-fat treats. Bacon, sausage, chocolate and even cheesecake quickly became favorites of laboratory rats that recently were given access to these human indulgences-so much so that the animals came to depend on high quantities to feel good, like drug users who need to up their intake to get high. A new study, published online March 28 in Nature Neuroscience, describes these rats' indulgent tribulations, adding to research literature on the how excess food intake can trigger changes in the brain, alterations that seem to create a neurochemical dependency in the eater-or user. [Scientific American, 3/28/10]

Fatty foods can be addictive like crack—at least for rats
Obesity may be a result of a reduced sensitivity to the "rewards" of calorically dense food, fostered by eating too much of the stuff too often, according study published in Nature Neuroscience this week. A group of researchers gave some rats different levels of access to tasty and highly caloric "cafeteria" foods, while training them to respond to aversive stimuli. Rats who had been given the most access to the good stuff ignored any indications of negative consequences and kept right on eating. [Nobel Intent, 3/30/10]

Fast machines, genes and the future of medicine
Some experts say the world is on the cusp of a "golden age" of genomics, when a look at the DNA code will reveal your risk of cancer, diabetes or heart disease, and predict which drugs will work for you. Yet the $3 billion international Human Genome Project, whose first phase was completed a decade ago, has not led to a single blockbuster diagnosis or product. [Reuters, 3/30/10]

Bursting the genomics bubble
For scientists, the Human Genome Project (HGP) might lay the foundation of tomorrow's medicine, with drugs tailored to your genetics. But a venture capitalist would want medical innovations here and now, not decades hence. Nearly ten years after the project's formal completion, there's not much sign of them. [Nature News, 3/31/10]

Human genome at ten: Life is complicated
As sequencing and other new technologies spew forth data, the complexity of biology has seemed to grow by orders of magnitude. Delving into it has been like zooming into a Mandelbrot set — a space that is determined by a simple equation, but that reveals ever more intricate patterns as one peers closer at its boundary. [Nature News, 3/31/10]

The trouble with genes
Scientists were shocked when they found out how few 'old-fashioned' genes we actually have - about the same number as the humble nematode worm (Caenorhabditis elegans). In fact, almost all multicellular creatures with the complexity of a worm or greater have about 20,000 genes. But for Mattick, the death knell of the traditional concept of the gene was triggered by another revolution altogether - that of the digital information age. [Cosmos, 4/12/10]

Genome of a killer
What we call cancer is actually a class of 200 diseases in different tissues, which are all caused by cells that have started to multiply out of control. Most treatments are drastic and invasive, such as chemotherapy and surgery. "Cancer is extremely complex, but we are beginning to understand how this complexity works, in terms of which genes are important," says oncologist Victor Velculescu. [Cosmos, 4/27/10]

10 Years on, ‘The Genome Revolution Is Only Just Beginning’
Almost 10 years after the celebrated completion of the human genome’s first draft, the expected revolution in medicine and research has only partly come to pass. The human genome’s sequencing has profoundly influenced basic research and the refinement of genome-reading tools. But those advances have had only limited medical impacts. [Wired, 3/31/10]

Einstein’s theory fights off challengers
Two new and independent studies have put Einstein’s General Theory of Relativity to the test like never before. These results, made using NASA’s Chandra X-ray Observatory, show Einstein’s theory is still the best game in town. Each team of scientists took advantage of extensive Chandra observations of galaxy clusters, the largest objects in the universe bound together by gravity. One result undercuts a rival gravity model to General Relativity, while the other shows that Einstein’s theory works over a vast range of times and distances across the cosmos. [Symmetry Breaking, 4/15/10]

What are 'mini' black holes?
‘The simplest black holes are objects with a singularity in the centre and that are surrounded by an ‘event horizon’,’ explains Cigdem Issever of Oxford University’s Department of Physics. ‘Once something comes closer to the black hole than the radius of the event horizon, it is not able to leave: even light can’t escape and so the name ‘black hole’ was given to these objects by John Archibald Wheeler back in 1967.’ [Physorg.com, 3/29/10]

A Grand Unified Theory of Artificial Intelligence
In the 1950s and '60s, artificial-intelligence researchers saw themselves as trying to uncover the rules of thought. But those rules turned out to be way more complicated than anyone had imagined. Since then, artificial-intelligence (AI) research has come to rely, instead, on probabilities -- statistical patterns that computers can learn from large sets of training data. [Physorg.com, 3/30/10]

Charting Creativity: Signposts of a Hazy Territory
They hope to figure out precisely which biochemicals, electrical impulses and regions were used when, say, Picasso painted "Guernica," or Louise Nevelson assembled her wooden sculptures. Using M.R.I. technology, researchers are monitoring what goes on inside a person's brain while he or she engages in a creative task. Yet the images of signals flashing across frontal lobes have pushed scientists to re-examine the very way creativity is measured in a laboratory. [New York Times, 5/7/10]

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VISTA’s infrared view of the Cat’s Paw Nebula

Monday, May 3, 2010

VISTA’s infrared view of the Cat’s Paw Nebula
The Cat’s Paw Nebula, NGC 6334, is a huge stellar nursery, the birthplace of hundreds of massive stars. In a magnificent new ESO image taken with the Visible and Infrared Survey Telescope for Astronomy (VISTA) at the Paranal Observatory in Chile, the glowing gas and dust clouds obscuring the view are penetrated by infrared light and some of the Cat’s hidden young stars are revealed.

Towards the heart of the Milky Way, 5500 light-years from Earth in the constellation of Scorpius (the Scorpion), the Cat’s Paw Nebula stretches across 50 light-years. In visible light, gas and dust are illuminated by hot young stars, creating strange reddish shapes that give the object its nickname. A recent image by ESO’s Wide Field Imager (WFI) at the La Silla Observatory (eso1003) captured this visible light view in great detail. NGC 6334 is one of the most active nurseries of massive stars in our galaxy.

NGC 6334 – click for 1280×1280 image

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