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:
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:
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.
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?
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).
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:
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.
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.
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.
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.
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.
Planck and Herschel are en route to their orbit at L2!
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 10.9.8.7.126.96.36.199.2.1 and ignition was followed by a still, silent seven or so seconds, and then we saw the smoke and flames.
(Apologies for the poor quality; there were many people there with far more powerful zoom lenses than my meagre 2.5x.)
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.
Today we saw the rollout of the gargantuan Planck/Herschel Ariane 5 rocket, when they move it from its assembly building to the launchpad. Spectacular!
There are plenty more pictures, and some movies, which I’ll try to edit and post shortly. At the end of the day, I was interviewed and inadvertently kidnapped by Chris Lintott and the BBC Sky at Night team. But I am here to tell the tale (and better fed for it) and ready for the — very — big day tomorrow.
Live coverage of the launch, scheduled for 2:13pm on 14 May, at:
Today was spent in Cayenne — the capital of French Guiana, where most of the hotels are located, and Kourou — home of ESA’a Centre Spatial Guianaise. We climbed up a nearby peak for a look over the Spaceport, but mostly we saw hand-sized spiders and a hazy view of what some very large if indistinct structures.
Closer up, we (about a hundred scientists, obviously more than the ESA staff were used to) got a tour of the facilities, starting in the “Jupiter II” control room where the launch will actually be, um, controlled:
We also saw the launch sites for the Vega and Soyuz rockets, and of course for our own Ariane 5:
But better will be tomorrow, when we get to see the rocket — our rocket — rolled the few kilometers from its current building to the pad in preparation for Thursday’s (hoped-for) launch.
With less than a week to go before its planned launch, The Planck Surveyor Satellite has been loaded into the fairing of its Ariane 5 rocket along with its sister satellite, Herschel. It is scheduled to be rolled out to the pad on May 13, and the launch window opens on May 14 at 13:12 GMT. Within three months, it will be at the Lagrange 2 (L2) point, from where it can watch the sky with the Sun, Earth and Moon all comfortably shielded from view.
Once there, Planck will scan the sky for at least 14 months. But don’t expect to see much out of the mouths (or blogs, or printers) of Planck scientists for a while: we’ve got a full year thereafter to analyze the data, followed by a year’s “proprietary period” during which we’ll do our best to extract the most exciting science. But until then — the first rule of Planck is: you do not talk about Planck. The second rule of Planck is: you DO NOT talk about Planck. (Luckily, Herschel expects to release its pictures of the infrared and submillimetre universe much more quickly.)
For now, the European Space Agency, the UK’s Science and Technology Facilities Council, and of course us Planck scientists ourselves have been gearing up both for the scientific data — and the press.
ESA has a Herschel and Planck launch campaign page with a nifty live countdown (which users of Apple’s Safari browser can make a dashboard widget out of). Last week, STFC held a pre-launch press event in London, which got us some coverage in The Independent, The Daily Mail, The Telegraph, The Times, as well as BBC Radio and TV news. (And Sky at Night will have coverage from the launch.) We’ve also been covered in New Scientist (complete with always-exciting quotes from me).
If this media saturation isn’t enough, you can check out the page dedicated to Planck in the UK, Follow Planck on Twitter (and Herschel too), read the Planck Mission Blog (there’s one for Herschel, too).
As for me, I’m taking a break from this term’s teaching — off to French Guiana next week for the launch (barring further delays). For those of you less lucky, it will be visible on satellite tv and streamed by ESA. I’ll do my best to keep up the twittering and blogging, probably cross-posting from here to the Planck Mission Blog. Wish us luck!
The Planck Surveyor Satellite has finished its assembly and testing in Liège, Belgium, and this week was loaded onto a Volga-Dnepr Antonov AN-124 plane, and sent to Kourou, French Guiana, location of the Centre Spatial Guyanais (one of the few places near the Equator politically connected to Europe). It’s due to be launched in tandem with Herschel on April 16. Here are some pictures of the “Planck Transport and Storage Container” making its way on a “Convoi Exceptionnel” to the airstrip. These photos came to me third-hand, so my apologies and thanks to the unknown (to me) photographer.
No time for a full blog post, but I wanted to point out the results of the STFC Consultation, now available.
Some of my favorite projects like AstroGrid seem to have not fared too well (the consultation panel rated it highly, but PPAN, responsible for the final ranks, disagreed). Nonetheless, Imperial Astrophysics projects like Planck, Herschel, Scuba II, UKIDSS, LISA Pathfinder and XMM Newton appear to have survived the cut. However,
It is important to stress that these reports are not the final conclusions of the Programmatic Review. These conclusions will be reached by STFC Council using these reports to inform their decision-making.More later as the repercussions become clear.