There are some great blogs up for awards and I will certainly cast my little vote in the categories where I have my favourites. This blog is a finalist in the category for Chemistry, Physics and Astronomy, so if you like what you read here from time to time, consider voting for me. As well as $50 I’d probably get some kind of badge to put in my sidebar, and I totally want one of those. I think it would look really nice next to the Dopplr duck. Help me fill that gaping hole in my sidebar y’all.

See the list of finalists here and follow the link in the invitation email to exercise your democratic rights. If you need reminding of the research I’ve written about in the last few months, here are all my posts tagged “researchblogging”.

Cerro Paranal (middle right) and Cerro Armazones (middle left)

ESO announced today that their Council have recommended Cerro Armazones in the Chilean Andes as the preferred site for their next generation optical/IR observatory, the 42-m European Extremely Large Telescope. The decision came in response to the delivery of a technical report by the organisation’s E-ELT Site Selection Advisory Committee, from which Armazones emerged as the frontrunner, “because it has the best balance of sky quality across all aspects and it can be operated in an integrated fashion with the existing ESO Paranal Observatory”.

So does this means the deal is done? Apparently not. The text also tells us that ESO have received proposals to host the telescope from both Spain, who would like to see the telescope site on La Palma, and Chile, so a final run-off between these two countries now seems likely.

What has struck me about this whole site selection exercise is the different approaches taken by ESO for the E-ELT and their North American counterparts, the Thirty Meter Telescope project.

Choosing the site for a new telescope, particularly one which will represent the interests of astronomers in much of Europe, is a hugely complex process – I’ve talked about it before, here. As well as the purely scientific merit of the site for astronomical research, there are a bunch of other considerations: how accessible is a site, where would the astronomers live and work, is there access to a power grid, where is the nearest water source? On top of that there are the diplomatic and political aspects: is the government and scientific community of the host country on board, is the local population open to an invasion of foreign scientists, are there significant business interests in the region? It’s clear that picking a site for the E-ELT is a very involved process that should be handled with sensitivity, diplomacy and a great deal of political nous.

Despite all these considerations that come into play, let’s not forget about the science of site selection. Astronomers’ interest in the skies start with our own local skies, and our weather. In the last century our understanding of the influence of atmospheric conditions on astronomical observations has increased hugely. Temperature, pressure, wind, humidity and other molecular abundances from the ground up to several kilometres in height all have their unique effects on the quality of our data. With the advent of smart telescope technologies that correct in real time for environmental fluctuations, like active and adaptive optics, the need for a detailed knowledge of local conditions both on a spatial and temporal scales becomes ever more important. The huge investment needed for telescopes like the E-ELT demands that we try to get the best possible astronomical site to get the best bang for our buck euros.

Given all that, the committee’s recommendation of Cerro Armazones comes as no surpise. Located close to ESO’s existing facilities at Paranal at a shade over 3000 m in altitude, Armazones appears to be an excellent site. It only became a (presumed) candidate E-ELT site last summer, when the E-ELT’s US counterpart, the Thirty Meter Telescope, announced that their telescope would be built on Mauna Kea in Hawaii. TMT had selected Armazones as one of its frontrunner sites back in 2008, so the Mauna Kea decision freed up the spot for ESO. So in fact, if the E-ELT does go to Armazones, the European community will have benefited massively from the North Americans’ early testing of the site.

And this brings me to the researchy part of this post. I’m loving the way TMT have kept the community informed of their site testing activities. Scientists working for the project have carried out an extensive 5-year campaign at five different sites: Cerro Armazones (Chile, 3064 m) , Mauna Kea (US, 4050 m), Cerro Tolonchar (Chile, 4480 m), Cerro Tolar (Chile, 2290 m) and San Pedro Martir (Mexico, 2830 m). Last year, Schöck et al published the first of a series of 12 (!!) papers in PASP detailing the results of the campaign. This first paper is an excellent read, with a clear overview of the chosen sites and the parameters they studied. More importantly, they talk about the constraints of their work, both in terms of available instruments, calibration and data processing.

As far as I can see, four of the 12 papers have been published so far, dealing with seeing and isoplanatic angle (Skidmore et al, 2009); turbulence profiles (Els et al, 2009); turbulence coherence time (Travouillon et al, 2009). The rest are still in preparation, although much work has been presented at conferences as well (a good listing here). From what I can gather, the TMT site testing team have done a very good job at planning their campaign and gaining the best possible understanding of their equipment and data analysis methods.

In my perhaps limited view, ESO’s reports on site testing have been a bit confusing. Back in 2008, there were five official candidate sites (pdf) – including La Palma but not Armazones. Today’s announcement tells me there were indeed five shortlisted sites, but three of those are different to those on 2008’s list. I’d heard some gossip about there being more sites under consideration, but no names mentioned. It all seemed a little hush-hush, or rather, it was not something the community was being actively updated on. But maybe that just reflects my status as a lowly minion.

The best part of the TMT testing is that the team have created an online database with all their test data from the 5-year survey, free for anyone to download, with a wealth of background and context. I’ve often argued that observatories should treat their site monitoring data the same as the science data, and make them available in archives with proper formatting and metadata.

ESO have tons of astroclimatology data available on their site (see e.g. here, here) and staff were very helpful when I had questions about the data last year, but their state is rather disorganised and badly or wrongly labelled. I really hope they take a leaf out of the North Americans’ book and make available their E-ELT site test results to the community, both with detailed peer-reviewed publications and by making the data publicly accessible.

As Schöck and colleagues rightly point out in their paper, there are many ways to analyse and interpret a given dataset, and perhaps the data can be useful to scientists in ways that go beyond what the initial site testing survey had envisaged. Furthermore, perhaps data from sites that were not selected can be useful for smaller countries or institutes looking for an astronomical base but lacking the resources to fund an expensive test campaign.

The bottom line to the story is that the data from the TMT test campaign show Armazones to be a fine observing site, on first glance rather comparable to nearby Paranal – and from a purely scientific view considerably better than La Palma. I look forward to hearing about a final decision for the home of the E-ELT.

Image: ESO/M. Tarenghi

References

M. Schoeck, S. Els, R. Riddle, W. Skidmore, T. Travouillon, R. Blum, E. Bustos, G. Chanan, S. G. Djorgovski, P. Gillett, B. Gregory, J. Nelson, A. Otarola, J. Seguel, J. Vasquez, A. Walker, D. Walker, & L. Wang (2009). Thirty Meter Telescope Site Testing I: Overview arXiv: 0904.1183v1

Els, S., Travouillon, T., Schöck, M., Riddle, R., Skidmore, W., Seguel, J., Bustos, E., & Walker, D. (2009). Thirty Meter Telescope Site Testing VI: Turbulence Profiles Publications of the Astronomical Society of the Pacific, 121 (879), 527-543 DOI: 10.1086/599384

Skidmore, Warren, Els, Sebastian, Travouillon, Tony, Riddle, Reed, Schöck, Matthias, Bustos, Edison, Seguel, Juan, & Walker, David (2009). Thirty Meter Telescope Site Testing V: Seeing and Isoplanatic Angle PASP, 121 (884), 1151-1166 : 10.1086/644758

Travouillon, T., Els, S., Riddle, R., Schöck, M., & Skidmore, W. (2009). Thirty Meter Telescope Site Testing VII: Turbulence Coherence Time Publications of the Astronomical Society of the Pacific, 121 (881), 787-796 DOI: 10.1086/605295

Pretty Valaparaiso in 2005

I noticed a lot of traffic to the blog today from google searches for people looking for info on the fate of the telescopes in Chile after last weekend’s huge earthquake that has devastated the central part of the country. The bottom line is that they all seem to be fine – although let’s not forget that the damage to Chile’s infrastructure could easily pay for hundreds of VLTs. As for the lives lost, well, no hardware can replace those.

On a personal note, my only experience of earthquakes dates back to 2005, while observing at Gemini South at Cerro Pachon, near La Serena in Chile. In our week-long observing run we suffered 2 earthquakes of magnitudes 5.8 and 5.0 or so, if I remember correctly. Our telescope operator, recognising the distant rumble, gave us a few seconds’ warning that a quake was under way, giving me ample time to freak out completely. Having just escaped the London bombings a few weeks earlier, I guess my nerves were pretty shot, but it was still pretty scary. I can only imagine how terrifying a magnitude 8+ quake must be when you’re sound asleep in your home at 3 am and I truly hope I never get to find out.

Anyway, here’s a round-up of some of the statements released by the astronomy organisations with bases in the country.

ESO released a press statement on 26/02, expressing its support for the victims of the quake, and reporting that

[n]o casualties among ESO staff have been reported. At present, power cuts and network interruptions mean that communication may be limited. Disruption to staff travel plans within, to, and from Chile should be expected. We urge Visiting Astronomers with observations planned at ESO observatories to put their trips to Chile on hold until further notice. International flights to and from Santiago International Airport are currently either cancelled or diverted. Information about observing programmes will be provided at a later date.

ESO’s La Silla site, near La Serena, lost power in the quake for 10 minutes, facilities further North at Paranal and Chajnantor were unaffected.

Cerro Tololo Inter-American Observatory (CTIO), which also operates facilities near La Serena, reports no significant damage and has ensured the safety of most (though not yet all) of its staff around the country. Gemini, whose Gemini South telescope is located just adjacent to CTIO, reports similar minor disturbances but no damage.

Las Campanas Observatory, hosting amonst others the 6.5-m Magellan telescopes, suffered no damage to the telescopes either but is still gathering information on its staff and their families around the country.

Thijs de Graauw, Director of ESO’ sub-millimeter observatory ALMA in the far North of Chile,  sent a quick email to much of the Dutch community for information and reassurance. An excerpt:

For example the local (in Chile) tsunamis were completely unreported till 24 hours after the facts.
Thats why the death toll was initially so limited but then it jumped up to above 700.

Also for us here in Chile, the extent of the disaster is slowly emerging as reports were initially only from the most accessible areas.The observatories have no damage as they are far away from the quake center.
The level was so low that some me have not noticed the motion at all.
But there is observatory staff from the disaster areas and they are very worried and we are working on to get them “home”.

If anything else of note turns up I’ll add it to this post.

Importance of the Hubble archive. The number of archival papers has exceeded the number of PI-led papers since 2006 (from White et al., 2009)

I’ve been giving some thought to software development in astronomy, which is a difficult topic. All astronomers agree that good data processing, and hence good software, is crucial to doing rigorous science. To interpret observational data, to translate electrons on a detector to scientific knowledge, requires a solid understanding of the instrument, the observing conditions, and of the exact process with which the data were treated. Many large ground- and space-based observatories, like those run by ESO, Gemini and NASA, strive to provide the community with “science-ready” data. This means that the data are processed to remove all instrumental signatures, allowing astronomers to dive straight into the analysis.

The rationale is that providing science-ready data essentially makes them usable by a much wider community than those involved in the observing campaign, or those used to working with a given instrument. Indeed, a big driver behind the global Virtual Observatory initiative is the “democratisation of astronomy” by providing anyone in the world with ready-to-use astronomical data, irrespective of their location or affiliation to large organisations.

Given that many small and large observatories don’t have the resources, or simply don’t consider it a priority, to make their data available to a broad community of astronomers, the efforts of the large organisations are entirely commendable. In their paper to the Astro2010 Decadal Survey, Richard White and colleagues convincingly showed the impact of the Hubble and Chandra archives – for the Hubble Space Telescope papers using only archival data have outnumbered PI-led ones since 2006. Indeed the Hubble and Chandra observatories seem to be examples of how to process and archive data well.

But not all observatories are managing to provide “science-ready” data to the community – see for example this discussion in ESO’s Messenger from 2004 by Silva & Perón. The problem is that writing processing software requires resources and manpower, particularly given the complexity of astronomical instruments today. But developers often don’t stick around on a project long enough to go through extensive testing and debugging. Furthermore, the software developers at large organisations like ESO are not the end users of the science data, and they often lack input from the science community on the requirements for science pipelines, or feedback on their problems.

So what happens very often is that an observatory spends considerable amounts of money on the provision of pipelines to help astronomers process their data – these pipelines turn out to be (i) too complex for non-specialists to use, rendering the data useless; and (ii) not transparent or flexible enough for the specialists, who end up writing their own pipelines for processing & analysis.

Part of the problem is that the development of pipeline software is one of the last steps in the development of new instrumentation, when budgets are running low and deadlines become increasingly critical, and it’s therefore a prime target for cutting costs or saving time. In the case of instruments built for large organisations, software development is often ongoing at the time when the consortium hands an instrument over to the observatory. Whose territory the software falls under is unclear, and it has a tendency of falling between the cracks.

This can turn pipeline development into a frustrating endeavour for all involved. Software engineers care about their work and don’t like hearing that their products are of little use. Non-specialist users find it prohibitively complicated to use archive data to do science. And specialists around the world end up writing their own software, which results in a massive duplication of effort in the observing community. To me this always seemed to be a huge waste of effort and resources, crying out for an alternative model of development.

But last week I was chatting to a good astronomer friend of mine who is a seasoned observer and data analyst, and her perspective was quite different. She argued that the current model is about right: specialist observers will never ever trust a black box-type pipeline and will always prefer to write their own analysis code. Data reduction is simply part of doing robust science. The observatories should focus on providing “quick and dirty” type pipelines that allow astronomers to visualise the data, which most of them do pretty well, rather than try to make them “science-ready”. The definition of “science-ready” in any case can’t be standardised, depending entirely on the information the observer is trying to extract from the data. That kind of makes sense too, and now I’m confused.

There must be a middle ground for all this. Another paper submitted to the Astro2010 Decadal Survey by Benjamin Weiner of Steward Observatory and colleagues presents the problem in a very clear way, and they suggest several solutions. The one I particularly like is the establishment of a code repository, where astronomers can make software publicly available. Many scientists actually already post scripts they’ve written onto their webpages; for larger software initiatives a descriptive paper can provide a method for citation. A few other recent initiatives have made promising moves in that direction – although an actual repository has yet to emerge.

In the category of citable community-led software efforts, a paper was posted to astro-ph last week describing a generic data reduction package for fibre-fed integral field spectrographs called p3d, which has been tested on several instruments on 2-4-m class telescopes. These are often the observatories that do not have the resources for a large-scale software development effort, so the p3d project is a really great initiative. Last year a group of postdocs set up the Integral Field Spectroscopy wiki, which has extensive resources on the growing number of integral field spectrographs, including many links to software packages and useful code. It’s a very useful website but as with many wikis, including Wikipedia, suffers from a lack of specialist contributions – which in turn is driven by a lack of motivation to spend time contributing to them.

What is the right approach? I have no idea. The current model seems to work fine for some, but leaves others frustrated – and it’s not clear to me that the money invested in software by the observatories is optimally spent. But do we need an entirely different model, or maybe just more discussion, collaboration – perhaps more data reduction workshops to get people to share their knowledge? If you have any ideas, post them below.

C. Sandin, T. Becker, M. M. Roth, J. Gerssen, A. Monreal-Ibero, P. Böhm, & P. Weilbacher (2010). p3d: a general data-reduction tool for fiber-fed integral-field spectrographs accepted by A&A arXiv: 1002.4406v1

D.M. Silva & M. Peron (2004). VLT Science Products Produced by Pipelines: A Status Report. The Messenger, No.118, p. 2-7 (ADS)

M. S. Westmoquette, K. M. Exter, L. Christensen, M. Maier, M. Lemoine-Busserolle, J. Turner, & T. Marquart (2009). The integral field spectroscopy (IFS) wiki accompanying IFS wiki site arXiv: 0905.3054v1

Astronomer (m)e(e/a)ts Powder

As I alluded to in my previous post, last week I spent a rather fabulous week in the Rocky Mountain resort of Aspen. The Aspen Center for Physics hosted a conference, organised by Andrea Ghez, Vicky Kalogera, Fred Rasio, and Steinn Sigurdsson (of the Dynamics of Cats blog), on the Formation and Evolution of Black Holes. I don’t work on black holes myself* but am lucky enough that my significant other does, and the prospect of a week in Aspen just sounded too good to turn down.

I was planning to attend some talks and maybe blog about the meeting, but in the end the lure of the white stuff proved too strong and I spent all my time skiing. Luckily Daniel Holz, blogger at Cosmic Variance, was also in attendance and he will be writing about the meeting on CV.

The one conference activity I attended, apart from eating and drinking, was the customary mid-week public lecture in teh Aspen Opera House, which was given by the ever-enthusiastic Andrea Ghez of UCLA on her work on the supermassive black hole in the Galactic Centre. As well as being an excellent scientist, Andrea is a fun speaker and a great advocate for astronomy. You can watch the lecture online at Grassroots.tv.

Aspen is a pricey ski resort but the infrastructure and facilities are truly fantastic, if you enjoy the snow I recommend you try to go there sometime (on someone else’s grant). Through the Aspen Center for Physics, conference participants get incredibly generous discounts on lift passes, ski rentals, classes, and even food on the mountains – and these discounts extend to hangers-on like me. A really big thanks for that!

* Yet! That may change in 2011. Sort of.

Well done also to all the other finalists and in particular also to Martin Robbins’ Lay Science blog, which is a contender for the Best Lay-Level Blog – I’ll take a teeny bit of credit for that too. Martin is also up for Best Blog Post, go check out the nominated post here.

All members of Research Blogging will be invited to vote for their favourites in early March and I certainly intend to cast votes for my favourite blogs. If you want to be able to vote and write about peer-reviewed research, go sign up! I’d definitely like to see some more astronomy blogs on the site.

Planning the next .Astronomy

Carolina and I just got back from the UK, where we met up with the rest of the .Astronomy organisers to tie up some loose ends and discuss the future of our little workshop. With a few noted exceptions, participants as well as organisers seemed to enjoy the conference, and we’re keen to build on that success and put together another event in 2010. So that led us to some important questions: where, when, how and who?

In a short space of time we’ve converged on a loose plan for the next .Astronomy, and we’re confident that we can pull something together that will equal the Leiden workshop in spirit, fun and coolness. You heard it here:  .Astronomy 3 is officially under way. If you have any ideas or suggestions, get in touch!

One of the things I’ve recently been pondering when it comes to the theme of ‘Science Online’, is that we spend a lot of time talking about science online but doing a lot less of it. I’d like to bring this to the fore at the next workshop. Discussing all the great opportunities the internet has to offer in science is fantastic, but I think we need to focus more clearly on specific methods and tools that will advance astronomy research, rather than just help us talk about it.

Don’t get me wrong, talking about science online has allowed me to meet some of the most interesting and fun people I’ve come across in my (admittedly short) career. But if we want to get an entire community to listen and build successful careers for ourselves, we need to be focusing on the research. The great thing about the internet is that outreach and education can follow as a natural byproduct of doing astronomy in the open.

I’m looking forward to being able to talk more concretely about the next workshop, we have a bit more work to do before being able to make a proper announcement. More soon!

Despite Mike Brown’s best efforts, Pluto is not dead (yet). These cool new images of the tiny non-planet taken with the Hubble Space Telescope show that it is by no means a boring lump of icy rock. When comparing these images, taken in 2002-2003, to a previous set dating back to 1994, scientists noticed some striking changes. This would suggest that Pluto, just like many bodies in the solar system, shows seasonal activity and all kinds of interesting chemistry as it moves along its looong orbit around the Sun.

Image: NASA, ESA, and M. Buie (Southwest Research Institute)

Black hole/massive star pair (artist's conception)

When a physicist is on the front page of a newspaper, you know the story is either really bad, or really good. Just before Christmas, the Dutch paper De Volkskrant ran a big story on theoretical physicist Erik Verlinde, who has been making waves with his new theory for the origin of gravity. Since the story ran, Verlinde published a paper explaining his new theory to the Arxiv. In it, he postulates that gravity is an emergent phenomenon resulting from changes in entropy rather than the fundamental force of nature we currently think it is, and demonstrates this using simple thought experiments. Gravity, he says, is an entropic force – a bit like, say, osmosis.

So when Verlinde, who works at the University of Amsterdam, turned up on the colloquium  schedule of Leiden’s Lorentz Institute, I thought it was worth checking out.

Gravity has long been the problem child of the fundamental forces. Somehow, it’s everywhere, but how does it arise and how is it mediated? After the electromagnetic, weak and strong forces have been shown to fit nicely within our understanding of quantum mechanics, gravity remains a misfit, poorly understood. Its postulated carrier particle, the graviton, continues to evade detection.

In developing the theory of gravity as an entropic force, Verlinde borrows from the work of Stephen Hawking and Jacob Bekenstein, who pioneered the field of black hole thermodynamics. Black hole thermodynamics tells us that black holes have entropy, and that their entropy, or information content, is directly proportional to the area of the event horizon. This is a little odd, as it relates a property associated with a volume to its bounding area. In an generalised extension of this work, Dutch physicist ‘t Hooft in the early ’90s posited that the entropy of any volume, and thus the information it holds, is in fact proportional to its bounding surface area. This idea is known as the holographic principle, and in this picture the Universe is essentially one giant hologram.

So if a mass is moving towards the event horizon of a black hole, Verlinde explained, at some infinitesimal distance its information content will become indistinguishable from that of the black hole; it will essentially have “thermalised”. This is typically interpreted as acceleration of the mass causing a change in the black hole’s entropy. Verlinde turns this round: what if, he asks, it’s the change in entropy, the change in information on the black hole’s surface, that causes the mass’ acceleration towards the black hole?

He generalises the black hole thought experiment to a generic holographic screen in a non-relativistic space. A mass approaching the screen will change the information content of the screen as it comes infinitesimally close, and Verlinde relates the resulting change in entropy of the space to the displacement of the mass – and assuming that the characteristic temperature associated with the entropy is an Unruh temperature, Newton’s equations of motion naturally emerge. That is, at least, the story.

While I’m not enough of an expert to judge the theory critically, it’s clear that right now the arguments are too heuristic in nature – but Verlinde too acknowledges this. He’s made some assumptions based on our current knowledge to make his idea “fit”, and now has to go back to fill in the details. A certain amount of circularity, he reckons, can’t be avoided at this stage. Around the physics community, the general buzz (here, here, here) seems to be cautiously positive of Verlinde’s work rather mixed, and several papers have been posted to the Arxiv to discuss thoughts, implications and extensions to the theory – I’ve listed some of them below, and collected them on Mendeley. Interestingly, Verlinde himself has taken to responding to comments on the blogs that have offered the most in-depth analysis of the work, such as this one.

The implications of gravity and space as an emergent phenomenon rather than a fundamental force shouldn’t be underestimated, particularly in astrophysics, even if it doesn’t change our actual experience of gravity. All the things we see today as dynamic phenomena – redshift, dark energy – would be reinterpreted as thermodynamic effects.

So perhaps gravity may get to outgrow its misfit status yet – though at a steep cost, by losing its place in the elite club of fundamental forces of nature. There are many fascinating aspects to this theory. I’ll admit that since the colloquium I’ve had a bit of a crush on the idea of space as an emergent phenomenon – even if I’m not too sure what that means. Thoughts? Leave me a comment.

Reading

You can also find these papers in in a public collection on Mendeley, and I’m in the process of gathering some more background reading to add to it.

Erik P. Verlinde (2010). On the Origin of Gravity and the Laws of Newton arxiv arXiv: 1001.0785v1

Jarmo Mäkelä (2010). Notes Concerning “On the Origin of Gravity and the Laws of Newton” by E. Verlinde (arXiv:1001.0785) arxiv arXiv: 1001.3808v3

Lee Smolin (2010). Newtonian gravity in loop quantum gravity arxiv arXiv: 1001.3668v1

Liu Zhao (2010). Hidden symmetries for thermodynamics and emergence of relativity arxiv arXiv: 1002.0488v2

Jae-Weon Lee, Hyeong-Chan Kim, & Jungjai Lee (2010). Gravity from Quantum Information arxiv arXiv: 1001.5445v1

Image: ESO/L. Calçada