Results tagged “astrophysics”

Leon Lucy, R.I.P.

I have the unfortunate duty of using this blog to announce the death a couple of weeks ago of Professor Leon B Lucy, who had been a Visiting Professor working here at Imperial College from 1998.

Leon got his PhD in the early 1960s at the University of Manchester, and after postdoctoral positions in Europe and the US, worked at Columbia University and the European Southern Observatory over the years, before coming to Imperial. He made significant contributions to the study of the evolution of stars, understanding in particular how they lose mass over the course of their evolution, and how very close binary stars interact and evolve inside their common envelope of hot gas.

Perhaps most importantly, early in his career Leon realised how useful computers could be in astrophysics. He made two major methodological contributions to astrophysical simulations. First, he realised that by simulating randomised trajectories of single particles, he could take into account more physical processes that occur inside stars. This is now called “Monte Carlo Radiative Transfer” (scientists often use the term “Monte Carlo” — after the European gambling capital — for techniques using random numbers). He also invented the technique now called smoothed-particle hydrodynamics which models gases and fluids as aggregates of pseudo-particles, now applied to models of stars, galaxies, and the large scale structure of the Universe, as well as many uses outside of astrophysics.

Leon’s other major numerical contributions comprise advanced techniques for interpreting the complicated astronomical data we get from our telescopes. In this realm, he was most famous for developing the methods, now known as Lucy-Richardson deconvolution, that were used for correcting the distorted images from the Hubble Space Telescope, before NASA was able to send a team of astronauts to install correcting lenses in the early 1990s.

For all of this work Leon was awarded the Gold Medal of the Royal Astronomical Society in 2000. Since then, Leon kept working on data analysis and stellar astrophysics — even during his illness, he asked me to help organise the submission and editing of what turned out to be his final papers, on extracting information on binary-star orbits and (a subject dear to my heart) the statistics of testing scientific models.

Until the end of last year, Leon was a regular presence here at Imperial, always ready to contribute an occasionally curmudgeonly but always insightful comment on the science (and sociology) of nearly any topic in astrophysics. We hope that we will be able to appropriately memorialise his life and work here at Imperial and elsewhere. He is survived by his wife and daughter. He will be missed.

On the Dark Side?

A few weeks ago, I took part in a “Big Questions” debate with Subir Sarkar, a colleague from Oxford, on Dark Energy and the Fate of the Universe. For those of you who couldn’t attend, a related podcast is available, you can download my meagre slides, and it’s been mentioned on Physics World, as well as by a fellow blogger who referred to me as a “Dark Side proponent”. Unlike the perhaps more contentious previous debate on the origin of the Universe (i.e., the existence of god), we decided to allow the audience to vote on the outcome, usually not the way scientific questions are decided. Of course I take such a petulant tone since, in fact, I lost…

I am amused and actually a little disturbed that my position is seen to be simultaneously radical — I am advocating the idea that the universe is dominated by an all-pervasive repulsive fluid — and conservative — just jumping on the same bandwagon as my colleagues.

In fact, I (we) are just doing science: we’ve made some measurements of the Universe and its constituents. Our simplest theories, that the Universe is dominated by what we could call “normal” matter, simply don’t fit the data, since normal matter requrires that the expansion of the Universe be slowing down (decelerating) over time.

Indeed, several different lines of observational argument all lead separately to this contradiction with the simpler theories: the Universe as a whole would be older than the objects in it; distant objects are dimmer; and present-day structures are growing more slowly. These problems and other related ones can be solved if we open up our theories to allow the expansion of the Universe to be accelerating. And how can we implement that idea? What is the physics behind acceleration? Well, the simplest possibility is just to reinstate Einstein’s own “cosmological constant”. Other possibilities are a so-called “scalar field” or even some modifications to Einstein’s theory itself. All of these nowadays fall under the rubric of “dark energy”, originally coined by Mike Turner of the University of Chicago in the 1990s when the evidence for such a concordance model was beginning to grow. I don’t know which of these possibilities is true, nor even whether these ideas will stand the test of time. But despite a decade of attempts to find other explanations for the observations without resorting to dark energy, none have so far succeeded.

So that’s why I plumped for Dark Energy — it’s the simplest, perhaps only, explanation of our cosmological observations.

As part of Imperial College Astrophysics’ ongoing series “The Big Questions”, I’ll be in discussion with Subir Sarkar of Oxford here at Imperial on Tuesday, 21 July 2009. We’ll be debating the fate of the Universe, and, more specifically, the existence or otherwise of Dark Energy, which appears to be causing the Universe to accelerate in its expansion.

I expect this will be less metaphysical — but perhaps no less contentious! — than the previous debate, between Professor Michael Rowan-Robinson from Imperial and the Rev. Dr John Polkinghorne KBE FRS on “The Origin of the Universe”.

Tickets are free, but please register in advance.

The Big Questions -- Fate of the Universe.png

Gemini telescope: back for the UK

In an unexpectedly rational decision, STFC (UK astronomy’s funding council, if you haven’t been paying attention) and the board of the Gemini telescope, have come to some sort of agreement to reinstate UK observing time for the time being, with the further statement from Gemini that “The Board asks that the Chair and Designated Members, including the UK, meet face-to-face at the earliest opportunity to further discussion of possible continued UK involvement in Gemini.” (Via Andy Lawrence.)

UK Gemini telescope bid rejected

Many others have been doing their best to disseminate information on the UK Physics funding crisis (especially Sheffield Prof Paul Crowther) but it’s probably worth pointing out the latest repercussion (which has already been picked up by the BBC): despite a bid to remain involved at a reduced level, it looks like the UK will be forced to completely withdraw from the Gemini telescope consortium. This is particularly dangerous for astronomers here, as Gemini-North was the only large telescope (about 8 meters in diameter) in the Northern Hemisphere to which the UK had access. Now, half the sky will be inaccessible, at least at the highest sensitivities and with the most advanced instruments. (Realistically, this will likely force us to collaborate with European, Asian and American colleagues, and probably to give up leadership roles in these projects.)

Meanwhile, committees are meeting, the government is holding hearings, and we scientists are being quietly advised that, essentially, you attract more flies with honey than vinegar, so we’d better not start pondering the thought that, perish forbid, anyone had actually made a mistake getting to this increasingly difficult position. Let’s hope that whatever is going on behind the scenes is better than what we’re seeing out front.

UK Physics on the chopping block

Today we heard that the (bizarrely agglomerated) UK Department for Innovation, Universities and Skills will be significantly cutting the physics budget that comes through the Science and Technology Facilities Council (STFC). STFC was formed earlier this year out of PPARC (Particle Physics and Astrophysics) and the CCLRC (which ran big facilities like the Rutherford Appleton Lab). When it was formed, we were told this would enable better science. But it seems we may have been sold a bill of goods: the science program is being saddled with what is, essentially, CCLRC’s debt, in the form of an £80 million shortfall that will fall disproportionately on academic research. And therefore, of course, on physics departments and, inevitably, physics education.

The Delivery Plan has just been announced, but of course the spin is all on the overall increase to funding, not these cuts. Happily (and a little surprisingly) the BBC highlighted the impact on physics in its usual stroppy manner.

Andy Lawrence has been following the news of the impending cuts over the last few weeks. Chris Lintott and Stuart have some more details. The headline cuts seem to be: withdrawal from the International Linear Collider (particle physicists’ next big instrument after the LHC at CERN), cessation of all support for ground-based solar-terrestrial physics facilities (i.e., telescopes and instruments that investigate the sun and its impact on the earth from the ground), and “revisiting the on-going level of investment” in gravitational wave detection, dark matter detection, the Clover CMB experiment and the UKIRT telescope. The UK will pull out of the Isaac Newton Group of telescopes.

Most important for me, so-called post-launch support for existing space missions (such as the Planck Surveyor CMB Mission, although it was never explicitly mentioned in the plan) will be cut by around 30%. This is a very cynical ploy: we will undoubtedly be so excited by the data from missions like Planck that we will donate our time, gratis, just to make sure that it gets analyzed.

There do appear to have been some small victories. Rather than a full termination as mooted last week, STFC plans “to withdraw from future investment in the twin 8-metre Gemini telescopes and we will work with our international partners to retain access to Gemini North.” So at least UK astronomers will have access to a world-class telescope in the Northern hemisphere. Most importantly, “Science Minister Ian Pearson said [on the BBC] funding arrangements would be reviewed,” — which we hope means actual compromises are possible — although of course he “did not promise extra money.”

More PhD goodness

Congratulations to Joe Zuntz, recipient of Imperial Astrophysics’ latest Doctorate for successfully defending his entertainingly-titled Ph.D. Thesis, “Cosmic Microwave Background Power Spectrum Estimation and Prediction with Curious Methods and Theories”. Joe had been my student since 2004, working on topics from hard-core data analysis with the MAXIPOL team to exploring the repercussions of exotic theories such as the Causal Set idea for unifying quantum mechanics with relativity (which, alas, he has shown is unlikely to be able to match our current observations). Joe has already moved over to a postdoctoral fellowship at Oxford where he is sure to (continue to) prosper. Congratulations, Dr. Z!

Doctor Rock Star, and his younger peers

Congratulations to Dr Brian May, PhD, for successfully defending his PhD thesis, “Radial Velocities in the Zodiacal Dust Cloud”. At the time of his defense, I was up in Durham, lecturing to the mostly younger incoming class of STFC-supported UK grad students. Best of luck to them, too, and let’s hope they can finish before their funding runs out in three or four years and so won’t have to make do with a less interesting career like Brian’s.

More rock-star astrophysics

Combining as it does my vocation with my avocation, it’s impossible to resist an easy post about our favorite rock-star PhD student, especially when he’s made the Guardian’s Leader (aka Editorial) page and the front of the BBC News site (complete with a spiffy pic of the rock star with our new head of group). Less than three nervous weeks for Brian to prepare for his PhD viva! Of course, I should point out that, like parents and their kids, we love all of our students equally, even the ones who haven’t made platinum records, written West End musicals and books on astrophysics, and inspired Wayne’s World.

Hard Rock in the Solar System

The Zodiacal Light is a fuzzy glow visible in the morning and evening sky, stretching along the line along which the constellations of the zodiac appear — the ecliptic that we now know to be the plane made up of the sun and the orbits of the planets. Observations of the zodiacal light show it to be due to reflections from dust in the plane, dust thought to be mostly the detritus of collisions between and among asteroids, comets, and more distance objects from the Kuiper Belt.

This week we in the Imperial astrophysics group were treated to a talk on the zodiacal light by Brian May, the group’s newest postgraduate student (and one of the eldest). Brian started his Imperial PhD in the early 1970s, but decided to leave to play guitar, eventually, on the roof of Buckingham Palace. Last year, he decided to return to astrophysics and, perhaps amazingly, has finished his PhD thesis under the supervision of Michael Rowan-Robinson, the former head of our group and current President of the Royal Astronomical Society. He was actually lucky in his choice of topics: it hasn’t been a major research area since his last astronomical work three and a half decades ago but is coming to the fore again as we start seeing similar dust clouds orbiting distant stars, and as we worry about the obscuring properties of the local dust as we peer through it with ever-more-sensitive instruments, such as the Planck Surveyor.

For someone so, um, inexperienced in public speaking (or at least in giving scientific presentations), Brian gave a very good distillation of the history of the field (including the missing 35 years while he was indisposed) including his own work, and his own interpretations speculating that some of the light may be due to our movement through an even larger cloud of interstellar dust.

As is customary, we took Brian May (still “Mr. May” until he gets his PhD later in the Summer) out to dinner with members of the group, and he even joined us afterward for a pint at one of our locals. He paid for a round, and he was extremely gracious to the crowds who stared, pointed, and came up to chat. He was also accompanied by his chauffeur, a very nice guy who was also one of the… widest… men I’ve ever seen (and who seemed happy to sit in the very nice Lexus while Brian ate and drank with us).

Who would have through astrophysics would give me a taste of the rock’n’roll lifestyle?

Big Smoke Science

In his comment on last week’s post, fellow physicist blogger Tommaso lets me know that he’ll be attending a meeting that we’re hosting here at Imperial College next week, Outstanding questions for the standard cosmological model. We’ll be casting a critical eye over current cosmological models and data, but I expect most of us will come to the conclusion that the whole structure is surprisingly weather-sturdy.

In fact if you’re any sort of astrophysicist, particle physicist or cosmologist, Imperial Physics is likely to have a meeting for you in London over the next few months. In addition to “Outstanding Questions”, we’ll have

  • A meeting making plans for XEUS, April 2-4. XEUS is the X-Ray Evolving Universe Spectroscopy mission, an X-Ray telescope satellite under consideration by the European Space Agency;
  • PASCOS (Particles, Strings and Cosmology) 07, July 2-7, the latest in a series of meetings examining the interface between theoretical particle physics and cosmology; and
  • From IRAS to Herschel-Planck, July 9-7. This is a special meeting, in honor of Professor Michael Rowan-Robinson on his 65th Birthday. Michael is currently the head of our Astrophysics group, and is one of the founders of the field of sub-millimeter and infrared astronomy, using long-wavelength photons to observe those parts of the Universe often hidden behind clouds of dust — veiled stellar nurseries where indeed a significant fraction of the stars were formed in the universe’s first few billions of years. IRAS was the first large-scale infrared satellite, and Herschel (along with its sister spacecraft, Planck, about which you’ve heard plenty here) will be the next ambitious project to observe the whole sub-millimeter sky.
Hope to see you in London…


The Oakland Tribune has an article about Marc Davis, a professor at Berkeley.

When I was doing research there, I was lucky to have Marc in the office next door: a brilliant astrophysicist who has done as much as anyone of his generation to understand the large-scale structure of the Universe, he is more recently one of the principal designers of the DEEP survey, mapping the distribution of galaxies as they were when the Universe was less than half its present age. Moreover, Marc certainly didn’t live up (or down) to the stereotype of the pasty, unathletic office-bound scientist — he was ebullient, athletic, charming, driven — but still a nice, lovely guy.

In 2003, only fifty years old,Marc suffered a stroke, leaving him paralyzed on his right side. Since then, he has fought back, managing to ski in Lake Tahoe, bicycle up and down the Berkeley hills (and continue pushing his science forward). It’s hard to avoid getting soppy or sentimental when faced with what Marc has gone through, what he’s accomplished, and how far he may still have to go.