Results matching “Planck”

EBEX in Flight

Many of my colleagues in the EBEX experiment have just lit out for the west. Specifically, the team is heading off to Palestine (pronounced “Palesteen”), Texas, to get the telescope and instrument ready for its big Antarctic long-duration balloon flight at the end of the year, when we hope to gather our first real scientific data and observe the temperature and polarization of the cosmic microwave background (CMB) radiation. Unlike the Planck Satellite, which has a few dozen detectors changed little from those that flew on MAXIMA and BOOMEReNG in the 1990s, EBEX can use more modern technology, and will fly with thousands of detectors, allowing us to achieve far greater sensitivity to the smallest variations in the CMB.

Asad, one of the EBEX postdocs, involved in the experiment for several years, will be writing on the EBEX in Flight blog about the experiences down in Texas and, we hope, the future path of the team and telescope down to Antarctica. Follow along as the team drives across the country (at least twice), assembles and tests the instrument, breaks and fixes things, sleeps too little, works too hard, and, we hope, builds the most sensitive CMB experiment yet deployed. (And of course, eats cheeseburgers.)

And if you want a change from cosmology, you can instead follow along with another friend, Marc, who is trying to see if he can come to grips with writing on an iPad in the supposedly post-PC world, over at typelesswriter.

Tacos and Power Spectra in LA

One of the perks (perqs?) of academia is that occasionally I get an excuse to escape the damp grey of London Winters. The Planck Satellite is an international collaboration and, although largely backed by the European Space Agency, it has a large contribution from US scientists, who built the CMB detectors for Planck’s HFI instrument, as well as being significantly involved in the analysis of Planck data. Much of this work is centred at NASA’s famous Jet Propulsion Lab in Pasadena, and I was happy to rearrange my schedule to allow a February trip to sunny Southern California (I hope my undergraduate students enjoyed the two guest lectures during my absence).

Visiting California, I was compelled to take advantage of the local culture, which mostly seemed to involve meals. I ate as much Mexican food as I could manage, from fantastic $1.25 tacos from the El Taquito Mexicano Truck to somewhat higher-end fare at Tinga in LA proper. And I finally got to taste bánh mì, French-influenced Vietnamese sandwiches (which have arrived in London but I somehow haven’t tried them here yet). And I got to take in the view from the heights of Griffith Park:
Griffith Park view II as well as down at street level:
Signs: S La Brea and 1st St, LA And even better, I got to share these meals and views with old and new friends.

Of course I was mainly in LA to do science, but even at JPL we managed to escape our windowless meeting room and check out the clean-room where NASA is assembling the Mars Science Lab:

JPL Clean Room: Mars Science Lab I

The white pod-like structure is the spacecraft itself, which will parachute into Mars’ atmosphere in a few years, and from it will descend the circular “sky crane” currently parked behind it which will itself deploy the car-sized Curiosity Rover to do the real work of Martian geology, chemistry, climatology and (who knows?) biology.

CMB_ILC_PolMap.png But my own work was for the semi-annual meeting of the Planck CTP working group (I’ve never been sure if it was intentional, but the name always seemed to me a sort of science pun, obliquely referring to the famous “CPT” symmetry of fundamental physics). In Planck, “CTP” refers to C from Temperature and Polarization: the calculation of the famous CMB power spectrum which contains much of the cosmological information in the maps that Planck will produce. The spectrum allows us to compress the millions of pixels in a map of the CMB sky, such as this one from the WMAP experiment (the colors give the temperature or intensity of the radiation, the lines its polarization), into just a few thousand numbers we can plot on a graph.

Planck CTP cake OK, this is not a publishable figure. Instead, it marks the tenth anniversary of the first CTP working group telecon in February 2001 (somewhat before I was involved in the group, actually). But given that we won’t be publishing Planck cosmology data for another couple of years, sugary spectra will have to do instead of the real ones in the meantime.

The work of the CTP group is exactly concerned with finding the best algorithms for translating CMB maps into these power spectra. They must take into account the complicated noise in the map, coming from our imperfect instruments which observe the sky with finite resolution — that is, a telescope which smooths the sky at a scale from about half down to one-tenth of a degree — and with a limited sensitivity — every measurement has a little bit of unavoidable noise added to it. Moreover, in between the CMB, produced 400,000 years after the Big Bang, and Planck’s instruments, observing today, is the entire rest of the Universe, which contains matter that both absorbs and emits (glows) in the microwaves which Planck observes. So in practice we need to simultaneously deal with all of these effects when reducing our maps down to power spectra. This is a surprisingly difficult problem: the naive, brute-force (Bayesian), solution requires a number of computer operations which scales like the cube of the number of pixels in the CMB map; at Planck’s resolution this is as many as 100 million pixels, and there still are no supercomputers capable of doing the septillion (1024) operations in a reasonable time. If we smooth the map, we can still solve the full problem, but on small scales, we need to come up with useful approximations which take advantage of what we know about the data, usually taking advantage of the very large number of points that contribute, and the so-called asymptotic theorems which say, roughly, that we can learn about the right answer by doing lots of simulations, which are much less computationally expensive.

At the required levels of both accuracy and precision, the results depend on all of the details of the data processing and the algorithm: How do you account for the telescope’s optics and the pixelization of the sky? How do you model the noise in the map? How do you remove those pixels contaminated by astrophysical emission or absorption? All of this is compounded by the necessary (friendly) scientific competition: it is the responsibility of the CTP group to make recommendations for how Planck will actually produce its power spectra for the community and, naturally, each of us wants our own algorithm or computer program to be used — to win. So these meetings are as much about politics as science, but we can hope that the outcome is that all the codes are raised to an appropriate level and we can make the decisions on non-scientific grounds (ease of use, flexibility, speed, etc.) that will produce the high-quality scientific results for which we designed and built Planck — and have worked on it for the last decade or more.

Les autres choses (scientifique)

I’ve been meaning to give a shout-out to my colleagues on the ADAMIS team at the APC (AstroParticule et Cosmologie) Lab at the Université Paris 7 for a while: in addition to doing lots of great work on Planck, EBEX, PolarBear and other important CMB and cosmology experiments, they’ve also been running a group blog since the Autumn, Paper(s) of the Week et les autres choses (scientifique) which dissects some of the more interesting work to come out of the cosmology community. In particular, one of my favorite collaborators has written an extremely astute analysis of what, exactly, we on the Planck team released in our lengthy series of papers last month (which I have already discussed in a somewhat more boosterish fashion).


I’ve recently “upgraded” my software which seems to be playing havoc with the format of the blog. The blog is visible, and in many ways nicer than before, but I’ve lost all of my lovely formatting… I hope we’ll be back to normal soon.

In any event, you can probably ignore this and read my post about Planck’s new results instead!

Planck: First results

The Satellite now known as the Planck Surveyor was first conceived in the mid-1990s, in the wake of the results from NASA’s COBE Satellite, the first to detect primordial anisotropies in the Cosmic Microwave Background (CMB), light from about 400,000 years after the big bang. (I am a relative latecomer to the project, having only joined in about 2000.)

After all this time, we on the team are very excited to produce our very first scientific results. These take the form of a catalog of sources detected by Planck, along with 25 papers discussing the catalog as well as the more diffuse pattern of radiation on the sky.

Planck is the very first instrument to observe the whole sky with light in nine bands with wavelengths from about 1/3 of a millimeter up to one centimeter, an unprecedented range. In fact this first release of data and papers discusses Planck as a tool for astrophysics — as a telescope observing distant galaxies and clusters of galaxies as well as our own Galaxy, the Milky Way. All of these glow in Planck’s bands (indeed they dominate over the CMB in most of them), and with our high-sensitivity all-sky maps we have the opportunity to do astronomy with Planck, the best microwave telescope ever made. Indeed, to get to this point, we actually have to separate out the CMB from the other sources of emission and, somewhat perversely, actively remove that from the data we are presenting.

Over the last year, then, we on the Planck team have written about 25 papers to support this science; a few of them are about the mission as a whole, the instruments on board Planck, and the data processing pipelines that we have written to produce our data. Then there are a few papers discussing the data we are making available, the Early Release Compact Source Catalog and the various subsets discussing separately objects within our own Milky Way Galaxy as well as more distant galaxies and clusters of galaxies. The remaining papers give our first attempts at analyzing the data and extracting the best science possible.

Most of the highlights in the current papers provide confirmation of things that astronomers have suspected, thanks to Planck’s high sensitivity and wide coverage. It has long been surmised that most stars in the Universe are formed in locations shrouded by dust, and hence not visible to optical telescopes. Rather, the birth of stars heats the dust to temperatures much lower than that of stars, but much higher than the cold dust far from star-forming regions. This warm dust radiates in Planck’s bands, seen at lower and lower frequencies for more and more distant galaxies (due to the redshift of light from these faraway objects). For the first time, Planck has observed this Cosmic Infrared Background (CIB) at frequencies that may correspond to galaxies forming when the Universe was less than 15% of its current age, less than 2 billion years after the big bang. Here is a picture of the CIB at various places around the sky, specifically chosen to be as free as possible of other sources of emission:
Cosmic Infrared Background

Another exciting result has to do with the properties of that dust in our own Milky Way Galaxies. This so-called cosmic dust is known to be made of very tiny grains, from small agglomerations of a few molecules up to those a few tens of micrometers across. Ever since the mid-1990s, there has been some evidence that this dust emits radiation at millimeter wavelengths that the simplest models could not account for. One idea, actually first proposed in the 1950s, is that some of the dust grains are oblong, and receive enough of a kick from their environment that they spin at very high rates, emitting radiation at a frequency related to that rotation. Planck’s observations seem to confirm this prediction quantitatively, seeing its effects in our galaxy. This image of the Rho Ophiuchus molecular cloud shows that the spinning dust emission at 30 GHz traces the same structures as the thermal emission at 857 GHz:
Spinning Dust

In addition, Planck has found more than twenty new clusters of galaxies, has mapped the dust in gas in the Milky Way in three dimensions, and uncovered cold gas in nearby galaxies. And this is just the beginning of what Planck is capable of. We have not yet begun to discuss the cosmological implications, nor Planck’s abilities to measure not just the intensity of light, but also its polarization.

Of course the most important thing we have learned so far is how hard it is to work in a team of 400 or so scientists, whom — myself included — like neither managing nor being managed (and are likewise not particularly skilled at either). I’ve been involved in a small way in the editing process, shepherding just a few of those 25 papers to completion, paying attention to the language and presentation as much as the science. Given the difficulties, I am relatively happy with the results — the papers can be downloaded directly from ESA, and will be available on the ArXiV on 12 January 2011, and will eventually be published in the journal Astronomy and Astrophysics. It will be very interesting to see how we manage this in two years when we may have as many as a hundred or so papers at once. Stay tuned.

B/E at the Biennale

As a scientist, I am used to my work being read by my peers, and I’ve made it into the occasional magazine or newspaper article, and even the odd TV and radio slot. But last week I travelled to Venice’s Architecture Biennale for the culmination of the first phase of the Architectural Association’s Beyond Entropy art/science project (which I’ve described before). I took a vaporetto to the island of San Giorgio, and next to one of Venice’s more spectacular Palladian churches, I saw the Beyond Entropy banner hanging over the entrance:
Fondazione Cini(I took these pictures, but there are many much more professional ones taken by the AA’s Valerie Bennett.)

Before arriving, I didn’t know what to expect from the project: small-scale, low-key, amateurish? In this setting, it was clearly big and serious. And inside this lovely building were these, the prototypes for our time machine: Mechanical Energy 2

Last year I traveled to South America to witness the launch of our several-hundred million-Euro Planck satellite, surely a big and serious project. But the sight of my own work — our texts, flywheels and gyroscopes — sitting on a plywood plinth, plausibly described as something at least related to the very different creative process of art, was nearly as disconcerting (despite the lack of highly explosive rocket fuel).

I’ll leave any assessment of the overall quality to others, although it became obvious that these pieces really are prototypes for what could become more finished works, but we have a long way to go. Nonetheless, let me explicitly thank my collaborators, Shin Egashira (whom I will also congratulate on his wedding which gave him an excellent reason to not show up in Venice) and Scrap Marshall, a student at the Architectural Association who joined us toward the end of the project and did an enormous amount of practical and creative work getting our pieces together. From speaking to members of  some of the other groups, we were lucky to all be based in London, and to eventually come to see our project in similar ways, albeit from different directions; some of the more widely-dispersed groups had to deal with significantly greater practical problems, and the interpersonal ones those ended up causing.

That first day was dedicated to the AA’s visiting school, and the next day was the centrepiece: a marathon symposium of more than thirty talks, dedicated to the themes of “entropy” and “energy”. Remarkably, none of our projects addressed the ecological, societal and political aspects of these topics, while many of the speakers attacked them directly, from Richard Burdett and Reinier de Graaf’s complementary discussions of the bleak picture for energy and climate if we keep to “business as usual” in our habits of consumption and production, to Italian Green Party politician Grazia Francescato’s hopeful discussion of “Green Jobs and Green Economy”. There were a few talks on science per se, from Angelo Merlina’s brief introduction to the LHC at CERN (of which a third talked about cosmology, and a third was pre-recorded), to one of my favourites, biophysicist Tania Saxl’s description of the amazing mechanism behind the motion of rotating bacterial flagella. There was also an inexplicable prerecorded description of “parallel worlds” in film from de Gruyter and Thys, a performance from the Arazzi Laptop ensemble, and contributions from Serpentine Gallery curator Hans-Ulrik Obrist (which was interesting but mostly about himself) and Charles Jencks. Jencks tackled the overlap between science, art and architecture head-on, each as a different metaphorical system for describing and interacting with the world. This culminates in his Scottish Garden of Cosmic Speculation, a hugely symbolic landscape replete with double helixes and grassy knolls in the form of black hole spacetime diagrams (I admit I’ve also found these supposed metaphors a bit too, well, literal for my taste — with insufficient information to be effective teaching tools, but too didactic to be truly beautiful.) I think the most important thing I learned was that, in their own way, the architects are just as nerdy as us scientists, but just better looking dressed.

Also, there was plenty of fine food and free-flowing sparkling wine (which meant that I probably missed about half of the presentations).

Finally, I would like to thank everyone from the AA who made the project happen (and will continue to do so, if further funding is forthcoming): Artemis Doupa, Sylvie Taher, Esther McLaughlin, Aram Mooradian and most especially the ever-enthusiastic project director, Stefano Rabolli Pansera. Thanks also to the AA visiting students, and all of the other participants, especially Ariel Schlesinger and Wilfredo Prieto for giving me a glimpse of the Architecture Biennale through artists’ eyes.


I spent part of this week in Paris (apparently at the same time as a large number of other London-based scientists who were here for other things) discussing whether the European CMB community should rally and respond to ESA’s latest call for proposals for a mission to be launched in the next open slot—which isn’t until around 2022.

As successful as Planck seems to be, and as fun as it is working with the data, I suspect that no one on the Planck team thinks that a 400-scientist, dispersed, international team coming from a dozen countries each with its own politics and funding priorities, is the most efficient way to run such a project. But we’re stuck with it—no single European country can afford the better part of a billion Euros it will cost. Particle physics has been in this mode for the better part of fifty years, and arguably since the Manhattan Project, but it’s a new way of doing things — involving new career structures, new ways of evaluating research, new ways of planning, and a new concentration upon management — that we astrophysicists have to develop to answer our particular kinds of scientific questions.

But a longer discussion of “big science” is for another time. The next CMB satellite will probably be big, but the coming ESA call is officially for an “M-class” (for “medium”) mission, with a meagre (sic) 600 million euro cap. What will the astrophysical and cosmological community get for all this cash? How will it improve upon Planck?

Well, Planck has been designed to mine the cosmic microwave background for all of the temperature information available, the brightness of the microwave sky in all directions, down to around a few arcminutes at which scale it becomes smooth. But light from the CMB also carries information about the polarisation of light, essentially two more numbers we can measure at every point. Planck will measure some of this polarisation data, but we know that there will be much more to learn. We expect that this as-yet unmeasured polarisation can answer questions about fundamental physics that affects the early universe and describes its content and evolution. What are the details of the early period of inflation that gave the observable Universe its large-scale properties and seeded the formation of structures in it—and did it happen at all? What are the properties of the ubiquitous and light neutrino particles whose presence would have had a small but crucial effect on the evolution of structure?

The importance of these questions is driving us toward a fairly ambitious proposal for the next CMB mission. It will have a resolution comparable to that of Planck, but with many hundreds of individual detectors, compared to Plank’s many dozens—giving us over an order of magnitude increase in sensitivity to polarisation on the sky. Actually, even getting to this point took a good day or two of discussion. Should we instead make a cheaper, more focused proposal that would concentrate only on the question oaf inflation and in particular upon the background of gravitational radiation — observable as so-called “B-modes” in polarisation — that some theories predict? The problem with this proposal is that it is possible, or even likely, that it will produce what is known as a “null result”—that is, it won’t see anything at all. Moreover, a current generation of ground- and balloon-based CMB experiments, including EBEX and Polarbear, which I am lucky enough to be part of, are in progress, and should have results within the next few years, possibly scooping any too-narrowly designed future satellite.

So we will be broadening our case beyond these B-modes, and therefore making our design more ambitious, in order to make these further fundamental measurements. And, like Planck, we will be opening a new window on the sky for astrophysicists of all stripes, giving measurements of magnetic fields, the shapes of dust grains, and likely many more things we haven’t yet though of.

One minor upshot of all this is that our original name, the rather dull “B-Pol”, is no longer appropriate. Any ideas?

Talking and blogging to ourselves

(Warning, scattershot blogging echo-chamber post follows.)

Last week I went to the Science Blogging Talkfest sponsored by the Biochemical Society and led by Alice Bell from Imperial’s excellent Science Communication program.

Partially because the event was mostly attended by science bloggers themselves, there was a bit of a preaching-to-the-converted sense to the proceedings. (I tried to engage in some good-natured tweaking, pointing out that probably the greatest influence of [supposedly] science blogging has been in absurdly dragged-out climategate saga, but I couldn’t get a rise out of the audience.) But it was heartening to see just how mainstream science blogging has become.

“Only” five years ago (scare-quotes denoting an eternity of internet-time), the academic-blogosphere chattered on about an anonymous article in the Chronicle of Higher Education which contended that bloggers were essentially unsuitable to be hired as faculty members, and a couple of years after that several of my colleagues felt the need to seriously restrict their blogging while searching for permanent positions. I was heartened to see that the question of whether blogging could actually hurt someone’s career seems to be less worrying. Although Petra Boynton said that one of her previous departments were less than enthusiastic about it, most of the panelists have found that, with an increased in impact and communication in general, blogging has taken its position as an effective way to engage with the public.

One of the more novel (to me) things going on at this meeting was the Twitter backchannel: the organizers projected a running stream of tweets marked with the #talkfest tag. It was a decent mix of jokes and apposite comments, especially including erstwhile MP Dr Evan Harris’ provocative comments about whether scientists should be forced to do public engagement at all. It’s certainly good that blogging and communication don’t hurt your career — but should they be requirements for scientific advancement? Not all scientists’ talents lie in that direction, and we shouldn’t expect them to. There was also a twitter discussion of the gender makeup of the panel, which was dishearteningly 1/6 female despite an audience of at least 50% women.

When science blogging started out as its own sub-genre in the middle of the decade, no one was quite sure what it would be for. Would it be used within science as an online lab notebook, or as a substitute or adjunct to papers? That doesn’t seem to have panned out — even in the post-’net open world, the structure of science encourages secrecy, at least until the work can be packaged into what are still more or less old-fashioned papers in what are still more or less old-fashioned journals (albeit with the important twist of pre-publication posting on the arXiv in many fields). Within collaborations, however, wikis, rather than blogs, have become ubiquitous as an easy way to communicate amongst scientists who are already expert — the easy ability to add small chunks of information is exactly what is needed. (Within the Planck Satellite collaboration, we actually use a wiki as a sort of blog — we keep a reverse-chronological list of “posts” discussing our latest results.)

Instead, blogs seem to be used almost exclusively as a window into the life, methods and results of scientists, directed at a knowledgeable but lay public. Indeed, it was suggested at the talkfest that someone could make a very useful living textbook from the scattered blog posts on a given subject. I’m not so sure — one of the advantages of a proper textbook is a single voice and, more prosaically, a single notation starting from scratch— but it’s probably worth trying if someone’s got the wherewithal to do the bit-work involved.

It was especially nice to meet several of my fellow Imperial College bloggers, including biophysicist Stephen Curry (whose own post on the Talkfest also has a list of other reactions to it), whom I was somewhat embarrassed to discover actually works in the same building as I do. As always at these sorts of events, much of the amusement was during the inevitable pub visit afterwards and especially the pre-panel milling about — thanks to the organizers for the excellent combination of cupcakes and beer.

The Planck Sky Previewed

The Planck Satellite was launched in May 2009, and started regular operations late last summer. This spring, we achieved an important milestone: the satellite has observed the whole sky.

To celebrate, the Planck team have released an image of the full sky. The telescope has detectors which can see the sky with 9 bands at wavelengths ranging from 0.3 millimeters up to nearly a centimeter, out of which we have made this false-color image. The center of the picture is toward the center of the Galaxy, with the rest of the sphere unwrapped into an ellipse so that we can put it onto a computer screen (so the left and right edges are really both the same points).

The microwave sky

At the longest and shortest wavelengths, our view is dominated by matter in our own Milky Way galaxy — this is the purple-blue cloud, mostly so-called galactic “cirrus” gas and dust, largely  concentrated in a thin band running through the center which is the disk of our galaxy viewed from within.

In addition to this so-called diffuse emission, we can also see individual, bright blue-white objects. Some of these are within our galaxy, but many are themselves whole distant galaxies viewed from many thousands or millions of light years distance. Here’s a version of the picture with some objects highlighted:


Even though Planck is largely a cosmology mission, we expect these galactic and extragalactic data to be invaluable to astrophysicists of all stripes. Buried in these pictures we hope to find information on the structure and formation of galaxies, on the evolution of very faint magnetic fields, and on the evolution of the most massive objects in the Universe, clusters of galaxies.

But there is plenty of cosmology to be done: we see the Cosmic Microwave Background (CMB) in the red and yellow splotches at the top and bottom — out of the galactic plane. We on the Planck team will be spending much of the next two years separating the galactic and extragalactic “foreground” emission from the CMB, and characterizing its properties in as much detail as we can. Stay tuned.

I admit that I was somewhat taken aback by the level of interest in these pictures: we haven’t released any data to the community, or written any papers. Indeed, we’ve really said nothing at all about science. Yet we’ve made it onto the front page of the Independent and even the Financial Times, and yours truly was quoted on the BBC’s website. I hope this is just a precursor to the excitement we’ll generate when we can actually talk about science, first early next year when we release a catalog of sources on the sky for the community to observe with other telescopes, and then in a couple of years time when we will finally drop the real CMB cosmology results.

Results from the first major science papers from the Herschel Satellite were released this week at a conference in Holland. Launched almost a year ago on the same rocket as Planck, Herschel is an infrared and sub-millimeter telescope, which lets it see not only the stars that generate the visible light we see with our eyes and ordinary cameras, but also the gas and dust that absorb and re-radiate that light. That gas and dust carries information about both the birth and death of stars: the detritus of exploding stars pollutes the interstellar medium, which eventually condenses out to form new generations of stars. On larger scales, Herschel’s observations let us trace the evolution of entire galaxies, the most important tracers of large-scale structure, formed from seeds laid down somehow in the first instants of the Universe (and, bringing it all back to cosmology, which are viewed by Planck in a much earlier form).

My Imperial colleagues and Herschel scientists Dave Clements and Brian O’Halloran discuss the results in much more detail over on the Herschel mission blog,  or you can keep more up to date on twitter. But I’ll just steal some of their bandwidth and show some pretty pictures.

Most of the dots in this picture are one of those distant galaxies, lit up in the infrared due to its once and future stars:
ATLAS Survey
Image courtesy ESA/ATLAS Consortium

Closer to home, this is selection of star-forming regions, turbulent filaments of gas and dust:
Image courtesy ESA/Hi-GAL Consortium

Not coincidentally, Imperial’s Michael Rowan-Robinson, who has been doing infrared astronomy for several decades, appeared on BBC radio 4’s wonderful In Our Time this morning to discuss “The Cool Universe”: covering a century or so of infrared astronomy in forty-five minutes.

We on Planck won’t be coming out with any papers for quite a while. However, many members of the team gathered in Orsay, outside of Paris, this week, to discuss the progress of the observations (and our analyses) and, crucially, to start talking in more detail about the actual papers that we’ll be writing over the next few years. More generally, Planck is doing pretty well. It came out first in NASA’s latest round of evaluations (which is a significant achievement for a mission primarily run by ESA), and which we hope will also give further impetus to keep funds flowing in the UK. This is especially important as the length of the Planck mission is likely to be almost doubled, allowing us to extract even more science than we originally hoped.

I can’t say much more, except that we’ve got a lot of — very exciting — work ahead of us.

Beyond Entropy II

I’ve been in Geneva now for a couple of days. We spent yesterday visiting CERN, trying to inspire the artists, architects and scientists alike (I’ve collaborated with people here, but I’ve never visited before).

CERN tunnel mockup
A mockup of a section of the CERN tunnels. More pictures here.

You can also check out Peter Coles’ blog for his tall tale of CERN’s history and impressions of the project. My Imperial colleagues Roberto Trotta, Amanda Chatten and Dave Clements are also participating (and Dave is blogging, too).

The second night, after our visit to CERN and a dinner of fondue and swiss music (possibly not the high point of the trip), all of the 24 participants (eight groups each of an architect, artist and a scientist) gave a few-minute presentation on their work and interests. I was, to use the cliché, blown away by the ambition and accomplishment of everyone else involved. In particular, I am lucky enough to be working with Budapest-based artist Attila Csorgo and architect Shin Egashira, who works out of the Architecture Association, the overall initiators and sponsors of the project. Both build amazing machines. Attila’s constructions seem to me to be about the interaction of the machine and the environment, or of the components of the machine itself, whereas Shin’s involve more effort on the part of the viewer/participant (but I am sure I will get to understand their work and their practice better as I spend more time with it and them).

We spent the next day in a lovely old Swiss building, brainstorming our projects — we’re meant to come up with a “prototype” to have in place for this summer’s Architecture Biennale in Venice. Our brief was to explore the concept of “Mechanical Energy”, and we found an area of convergence in the idea of cameras, in the process of taking pictures, areas that both Shin and Attila have explored in their work.

Right now, our first idea is to combine the Planck Surveyor’s method of scanning the sky with a microphone-based sensor and camera, to make sound and light pictures of the volume surrounding the apparatus. We’re looking forward to a weekend retreat into the wilds of Dorset, to Hooke Park, a site run by the AA.

Thanks, finally, to Stefano Rabolli Pansera, the brilliant, optimistic, and enthusiastic mind behind this project, as well as all of the other people from the Architecture Association doing the hard work.

Andrew Lange, Huan Tran

The cosmology community has had a terrible few months.

I am saddened to report the passing of Andrew Lange, a physicist from CalTech and one of the world’s preeminent experimental cosmologists. Among many other accomplishments, Andrew was one of the leaders of the Boomerang experiment, which made the first large-scale map of the Cosmic Microwave Background radiation with a resolution of less than one degree, sufficient to see the opposing action of gravity and pressure in the gas of the early Universe, and to use that to measure the overall density of matter, among many other cosmological properties. He has since been an important leader in a number of other experiments, notably the Planck Surveyor satellite and the Spider balloon-borne telescope, currently being developed to become one of the most sensitive CMB experiments ever built.

I learned about this tragedy on the same day that people are gathering in Berkeley, California, to mourn the passing of another experimental cosmologist, Huan Tran of Berkeley. Huan was an excellent young scientist, most recently deeply involved in the development of PolarBear, another one of the current generation of ultra-sensitive CMB experiments. Huan lead the development of the PolarBear telescope itself, currently being tested in the mountains of California, but to be deployed for real science on the Atacama plane in Chile. We on the PolarBear team are proud to name the PolarBear telescope after Huan Tran, a token of our esteem for him, and a small tribute to his memory.

My thoughts go out to the friends and family of both Huan and Andrew. I, and many others, will miss them both.

Doctors, Deep Fields and Dark Matter

Luckily, not all the astrophysics news this week was so bad.

First, and most important, two of our Imperial College Astrophysics postgraduate students, Stuart Sale and Paniez Paykari, passed their PhD viva exams, and so are on their ways to officially being Doctors of Philosophy. Congratulations to both, especially (if I may say so) to Dr Paykari, who I had the pleasure and fortune to supervise and collaborate with. Both are on their way to continue their careers as postdocs in far-flung lands.

Second, the first major results from the Herschel Space Telescope, Planck’s sister satellite, were released. There are impressive pictures dwarf planets in the outer regions of our solar system, of star-forming regions in the Milky Way galaxy, of the vary massive Virgo Cluster of galaxies, and of the so-called “GOODS” (Great Observatory Origins Deep Survey) field, one of the most well-studied areas of sky. All of these open new windows into these areas of astrophysics, with Herschel’s amazing sensitivity.

Finally, tantalisingly, the Cryogenic Dark Matter Search (CDMS) released the results of its latest (and final) effort to search for the Dark Matter that seems to make up most of the matter in the Universe, but doesn’t seem to be the same stuff as the normal atoms that we’re made of. Under some theories, the dark matter would interact weakly with normal matter, and in such a way that it could possibly be distinguished from all the possible sources of background. These experiments are therefore done deep underground — to shield from cosmic rays which stream through us all the time — and with the cleanest and purest possible materials — to avoid contamination with both both naturally-occurring radioactivity and the man-made kind which has plagued us since the late 1940s.

With all of these precautions, CDMS expected to see a background rate of about 0.8 events during the time they were observing. And they saw (wait for it) two events! This is on the one hand more than a factor of two greater than the expected number, but on the other is only one extra count. To put this in perspective, I’ve made a couple of graphs where I try to approximate their results (for aficionados, these are just simple plots of the Poisson distribution). The first shows the expected number of counts from the background alone:

So even if there is no signal above the background, seeing two counts is not terribly unlikely. Now, here’s the likelihood function for the signal rate, given their background measurement:

It peaks away from zero, so the most likely interpretation of their experiment is that they see a signal, but it’s far from conclusive.

(I should point out a few caveats in my micro-analysis of their data. First, I don’t take into account the uncertainty in their background rate, which they say is really 0.8±0.1±0.2, where the first uncertainty, ±0.1 is “statistical”, because they only had a limited number of background measurements, and the second, ±0.2, is “systematic”, due to the way they collect and analyse their data. Eventually, one could take this into account via Bayesian marginalization, although ideally we’d need some more information about their experimental setup. Second, I’ve only plotted the likelihood above, but true Bayesians will want to apply a prior probability and plot the posterior distribution. The most sensible choice (the so-called Jeffreys prior) for this case would in fact make the probability peak at zero signal. Finally, one would really like to formally compare the no-signal model with a signal-greater-than-zero model, and the best way to do this would be using the tool of Bayesian model comparison.)

Nonetheless, in their paper they go on to interpret these results in the context of particle physics, which can eventually be used to put limits on the parameters of supersymmetric theories which may be tested further at the LHC accelerator over the next couple of years.

I should bring this back to the aforementioned bad news. The UK has its own dark matter direct detection experiments as well. In particular, Imperial leads the ZEPLIN-III experiment which has, at times, had the world’s best limits on dark matter, and is poised to possibly confirm this possible detection — this will be funded for the next couple of years. Unfortunately, STFC has decided that the next generation of dark matter experiments, EURECA and LUX-ZEPLIN, needed to make convincing statements about these results, weren’t possible to fund.


I presume that anyone reading this blog knows that today is the day when the great unwashed masses of UK Astronomers heard about our financial fate from the STFC, the small arm of the UK government responsible for Astrophysics, Particle Physics and Nuclear Physics.

For various reasons, some clear and others manifestly not, STFC is something like £70 million in the red. When all this started about two years ago, one of the main criticisms of the STFC management (beyond wondering how they could have got themselves — and us — into this predicament to begin with) was that they started to impose solutions that seemed to bear little resemblance to what the scientists themselves wanted. Trying to either genuinely ameliorate this, or at least give themselves good cover, they’ve spent much of the last year gathering input from various groups of physicists and astronomers, through a series of reports produced by scientist-led panels. These panels released their results this autumn, and STFC has supposedly used them to make decisions about the next five or so years of funding.

I was selfishly relieved to see that our work with the Planck Surveyor Satellite is rated “alpha 5”, and that our other local grants don’t appear directly affected (i.e., we weren’t drastically cut). However, STFC has “requested” (not sure what that means in this context) that even these projects reduce their costs by 15%. Other programs were not even this lucky — a not-quite-complete list of the cuts is on the STFC site. The cuts (a.k.a. “managed withdrawal”) include the UKIRT telescope, the LOFAR array, future work at the low-background facility at the Boulby mine, and future science exploitation of the XMM and Cassini missions (among many others). Alongside this, there will be a 25% cut in studentships and fellowships, although the details of this have not been revealed.

In his independent response, the Science Minister, Lord Drayson, says “we are investing record amounts into scientific research, but it is absolutely right that it is the scientists themselves, through the Research Councils, that decide how best to spend this money.” Of course we scientists don’t necessarily feel that our voices have been heard. The prioritized list of projects is available from STFC, and although it generally correlates with both the inputs from the various sub-panels and the financial outcome (in particular, many of us were pleased and relieved to see the much-criticised MoonLITE project at the bottom of the heap), there are some striking differences from at least my understanding of the panel recommendations, such as the “alpha 4” grade given to the Aurora human spaceflight program.

However, Drayson does seem to understand some of the issues: “…there are real tensions in having international science projects, large scientific facilities and UK grant giving roles within a single Research Council. It leads to grants being squeezed by increases in costs of the large international projects which are not solely within their control. I will work urgently with Professor Sterling, the STFC and the wider research community to find a better solution by the end of February 2010.” Not sure what this means, but even if we are grasping at straws, it’s the only promising news of the day.

I’ve got 11 browser tabs open just to get myself up-to-date. Here are some of them:

FInally, the #stfc twitter hashtag has been a great source of commentary, rage, and information, trending high today.

On not being able to talk about science

This week I was in the truly wonderful city of Bologna, home of possibly the oldest university in Europe. Nowadays, Bologna is also the home of IASF-BO, the Italian Istituto di Astrofisica Spaziale e Fisica Cosmica, and was hosting this year’s Planck Satellite Consortium meeting.

Of course I can’t talk about anything that was actually presented at the meeting — as I’ve mentioned before, there are strong restrictions on what is allowed to be discussed before the data become public in about three years. Indeed, that communication policy was itself the topic of considerable discussion — it turns out that at least a couple of Planck’s “highest ranking” scientists had recently been deemed to be in “non-compliance” with the policy (which may be different from actually violating the policy, but no one is quite sure…).

Luckily, there was plenty to talk about amongst ourselves between the political discussions. I reported on our efforts in London to recover Planck’s “pointing solution” — that is, to figure out where, exactly, each of Planck’s fifty or so detectors are actually looking on the sky at any given moment. This is obviously crucial to getting good science out of Planck — indeed, even though the instrument smears the sky with a resolution of about four arcminutes (about 1/15 of a degree), we want to know the pointing to roughly 10 arcseconds (about 1/360 of a degree)! But there were several hundred scientists at the meeting, so plenty to discuss, besides, over the course of the week, from Planck’s electronics to the eventual scientific results on the earliest instants of the Universe. The first hints of this science, but not much more, are present in the pictures we showed from Planck’s first-light survey. And I should point out that, despite at least one attempt — which I hesitate to even link to — there is really no science to be had in any analysis of what we’ve presented. We’re not taking three years to analyze the data just to be selfish — at least not entirely. It will take that long before we can understand the instrument well enough to interpret the data that comes out of it.

Luckily, Bologna is also known for its food, and aside from the excellent conference snacks and lunches (and a blow-out dinner at a local Palazzo from which I mostly recall the giant parmigiana wheel and the copious grappa), it was pretty easy to find excellent food at pretty much any local Trattoria (like La Montanara and the strangely-named Serghei). So now I am back, fat, happy, and with plenty of Planck work to do in the next few weeks, months and years.

Planck's First Light

I’m happy to be able to point to ESA’s first post-launch press release from the Planck Surveyor Satellite.

Here is a picture of the area of sky that Planck has observed during its “First Light Survey”, superposed on an optical image of the Milky Way galaxy:


(Image credit: ESA, LFI and HFI Consortia (Planck); Background image: Axel Mellinger. More pictures are available on the UK Planck Site as well as in French.)

The last few months since the launch have been a lot of fun, getting to play with Planck data ourselves. Here at Imperial, our data-processing remit is fairly narrow: we compute and check how well the satellite is pointing where it is supposed to, and calculate the shape of its beam on the sky (i.e., how blurry its vision is). Nonetheless, just being able to work at all with this incredibly high-quality data is satisfying.

Because of the way Planck scans the sky, in individual rings slowly stepping around the sky over the course of about seven months, with a nominal mission of two full observations of the sky, even the two weeks of “First Light Survey” data is remarkably powerful: we have seen a bit more than 5% of the sky with about half of the sensitivity that Planck is meant to eventually have (in fact, we hope to extend the mission beyond the initial 14 months). This is already comparable to the most powerful sub-orbital (i.e., ground and balloon-based) CMB experiments to date.

But a full scientific analysis will have to wait a while: after the 14 month nominal mission, we will have one year to analyze the data, and another year to get science out of it before we need to release the data alongside, we hope, a whole raft of papers. So stay tuned until roughly Autumn of 2012 for the next big Planck splash.

Pride and Science

Central London featured two important events this past weekend. First was the annual Gay Pride Parade, a riotous and joyful procession of rainbow flags, pink clothing, and (mostly) ill-fitting dresses on very large people.
Pride parade

Evil and/or misguided ChristiansSadly, the only thing that marred the good-natured, family-friendly event were the stupid protesters. But it was wonderful to see that they were just ignored, or occasionally people would point at their sad and pathetic group and just laugh (there was also a much smaller, and yet more pathetic, group of National Front protesters who deserved and received even less attention).

Planck exhibit - 1At the same time, the Royal Society, right down the road from Piccadilly Circus, hosted the annual Summer Science Exhibition, and I visited my colleagues (Stuart Lowe and Michael Bridges, here) talking Planck Surveyor science, taking infrared pictures of the visitors and handing out lots of great Planck swag.

In fact, this weekend, Planck has cooled down to just about its final temperature of 100mK (that is 0.1 degrees above absolute zero!) and has made it to its final orbit at the L2 point. So we are starting to get ready to take real data, after we spend the next month or so kicking the tires and checking her out.

Another launch

Not all CMB (Cosmic Microwave Background) experiments get launched on a rocket.

There’s a long history of telescopes flown from balloons — huge mylar balloons floating over 100,000 feet in the air. MAXIMA and BOOMERaNG, the first experiments to map out the microwave sky on the sub-degree scales containing information about the detailed physical conditions in the Universe over the first few hundred thousand years after the Big Bang. The Planck Satellite will close out that era of CMB experiments, by giving us a complete picture of the microwave sky down to less than a tenth of a degree.

But there is still more to be done, even beyond what Planck is capable of. By measuring the polarization of the microwave background at even higher sensitivities than Planck, we hope to observe the effects of gravitational radiation in the early Universe.

Last week, EBEX, one of a new generation of balloon-borne experiments designed specifically with this goal, had its maiden flight from Fort Sumner, New Mexico.

EBEX Launch, 6/11/09 from asad137 on Vimeo.

It’s worth remembering, of course, that even with a parachute, these telescopes hit the ground pretty hard. But these things are amazingly well-built, and the EBEX crew have managed to recover most of the hardware and all of the data. So now the team have some time to get the hardware and software ready to fly for a couple of weeks over Antarctica next year.

And let’s not forget that New Mexico is also the home of Roswell, where conspiracy theorists and other wackjobs have been trying to find the government cover-up of UFO sightings. Indeed, the EBEX balloon was spotted, but at least in neighbouring Arizona, they can tell the difference.

Meanwhile, another CMB experiment, PolarBear, is about to start its first set of important tests. PolarBear is a ground-based telescope, which means it can watch the sky for far longer than a balloon, at the cost of being at the bottom of the atmosphere and all of the extra noise that adds to the signal. So despite some hard times (especially here in the UK), the next generation of CMB experiments are on the way, hoping to probe all the way back to the epoch of inflation.

In the Sky (at Night)

Despite my almost eight years in Britain as an astronomer, I suppose I have to be embarrassed to admit I’ve never actually watched “The Sky At Night”, apparently the longest-running show on television (possibly in the whole world, not just the UK). But I’m watching this evening’s episode, mostly because I’m on it. I was filmed during last month’s trip to the Planck launch. As always, it was painful to realize the fat figure with the bad posture and annoying voice was actually me. But it was fun to watch Patrick Moore do his studio interviews, with a style and on a set neither of which seem to have changed since the 1970s.

But it was beautiful and moving to see the launch again, and to watch the much closer movies and pictures than I was able to get on the day. Since then, parts of Planck have been slowly turned on, cooled down, and checked out. Everything is working well so far; we’re looking forward to the first data in a little more than two months. It’s going to be a long summer.

The episode will briefly be available on BBC’s iPlayer, but more of my cringeworthy discussion of Planck in a different context is up on YouTube; check out the next post for much cooler cosmology video from a more photogenic cosmologist with a better voice.


Cross-posted on Andrew Jaffe’s Blog and the Planck Mission Blog.

Planck and Herschel are en route to their orbit at L2!

We were about 7.5 km from the launch, at the “Agami” viewing site. Here is my golden ticket:
Planck launch badge

We all milled around for half an hour, snapping pictures of friends, eminent scientists, and at least one Nobel prize winner, but it all went silent when they announced the last few minutes before launch. The inevitable and ignition was followed by a still, silent seven or so seconds, and then we saw the smoke and flames.
Herschel/Planck Liftoff
(Apologies for the poor quality; there were many people there with far more powerful zoom lenses than my meagre 2.5x.)

The rocket then pierced the clouds:
Herschel/Planck in the sky
Soon after, the booster rockets separated (which those 200x telephoto lenses could capture), and soon all left to see with the naked eye was the rocket’s trail:
Herschel/Planck contrail

For the rest, we had to watch the video feed from the control room, and, about half an hour later we finally heard what we were waiting for: first Herschel, and then Planck, had separated from the rocket and were on their own, off to L2. Four or five hours later, Planck’s instruments had been turned on, and the ESA team in Darmstadt was monitoring their progress. There’s a lot going on now, but we won’t have anything like scientific data for two or three months — and then our work is cut out for us.

Huge thanks to the instrument teams for their hard work for more than the last decade. Soon, the hard part for us scientists and data-analysts begins: four or so years of data coming down from the satellite, being cleaned and calibrated, building and rebuilding our (computer) model of the instrument, letting us build and rebuild our models of the Universe.

Thanks also to the HFI Instrument Principle Investigator and co-PI, Jean-Loup Puget and Francois Bouchet (and especially Hélène Blavot) for arranging this extraordinary opportunity for us scientists to see this part of the fruits of our work.