It’s snowing!

Not in Leiden, obviously, but it is on the Königstuhl mountain next to the city of Heidelberg, Germany. Near the top of this 567-metre high mountain (1859 ft.) lies the Max Planck Institute for Astronomy (MPIA), where I’m visiting a colleague for a week.

We already got some snow yesterday morning, but at only half an inch, it wasn’t too exciting. The more interesting bit yesterday was the dense fog hovering over the upper part of the mountain. The clouds were hanging so low that they covered the MPIA, and much of the Königstuhl, like a thick grey blanket. With visibility down to about 50 metres (160 ft.), the bus driver must have had a hard time hauling his vehicle up the slopes. Making it even tougher is the fact that some of the roads are essentially single lane, and the bus can only pass oncoming traffic at specific passing places. That can be tricky already in clear weather. Fortunately, no accidents occurred.

This morning, as we started up the mountain, there was quite a bit of white visible amongst the greens and browns of the forest at the top. Ascending further, it turned out to be a lot more than yesterday. A good four inches had fallen overnight, making for a truly beautiful landscape. The road was still in good condition, as it had been well cleared and salted. The clouds are hanging higher than yesterday, so I have a great view from my office now. It’s a shame I have to work today.

I will be attending a conference on chemistry in space in Hong Kong next year. Yesterday I filled in the registration form and payed the conference fee online with my credit card. I also signed up for an optional tour of Hong Kong at the end of the conference, and payed that one as well. Within a few minutes, I got an email from the conference organizers confirming the receipt of my registration and payment.

Half an hour later, my cell phone rang. It was my credit card company! They wanted to know if I had just made two payments to an address in Hong Kong. Apparently, the transactions had set off their alarm bells. They quoted the sums and I told them everything was in order.

Now, on the one hand, I’m glad they keep an eye out for suspicious transactions. The world seems to be full nowadays of people robbing bank accounts and abusing credit cards through the internet. I’d rather not have that happen to me. On the other hand, it’s a weird feeling that my credit card company (though certainly well-intentioned) keeps such close tabs on what I’m using my credit card for. It’s a question that’s been asked many times: how much privacy are we willing to give up for extra security? Pretty much everything we do nowadays is recorded, or can be. Phone calls, email, travelling, shopping, browsing the internet, making payments: it’s difficult to do any of that without leaving a trace. It’s something most people take for granted. I know I do. And do I care? No, not really. Not enough to try and do something about it, anyway. I just hope the powers that be use all the data they’ve gathered about me wisely.

Two papers on which I’m the third author recently got accepted for publication in Astronomy & Astrophysics, the major European journal for all astronomical and astrochemical research. Both of them make use of the infrared emission model for polycyclic aromatic hydrocarbons (PAHs) that I developed over the past three years. My own (first-authored) paper, describing this model in more detail, was published in A&A earlier this year.

The first of the two new papers, “Dust sedimentation in protoplanetary disks with PAHs”, looks into the effects of dust settling on PAH emission from protoplanetary disks. Dust tends to fall towards the midplane of a protoplanetary disk due to gravity, and larger dust grains do so more quickly than smaller ones. Since PAHs can be considered very small grains, they should stay up at higher altitudes for longer times than the rest of the dust. This is expected to enhance the PAH emission features with respect to the continuum emission. However, this enhancement is not found in observations. The paper discusses turbulence and coagulations as possible answers to this discrepancy. The research was led by Kees Dullemond, who did his PhD in Leiden and is now at the Max-Planck-Institut fü Astronomie in Heidelberg, Germany.

The other paper was written primarily by Vincent Geers, a fellow PhD student here in Leiden. He will graduate next Tuesday and this paper is the basis for one of the chapters of his thesis. Titled “Spatially extended PAHs in circumstellar disks around T Tauri and Herbig Ae stars”, it describes highly detailed observations of PAH emission from protoplanetary disks around solar-type stars. Vincent found that the PAH emission is extended on a scale similar to the size of these disks. This shows that PAHs are present throughout the disk and emit everywhere, as predicted by theoretical models.

The abstracts and full texts are available from my list of publications.

There was a total lunar eclipse last night, but the moon was almost eclipsed too much. The sky had been going from almost fully clear to almost fully overcast and back throughout the afternoon and early evening. No one knew for sure whether the moon would be visible during the eclipse, which would last from 10.30pm to 2.11 am, with the total phase occurring between 11.44pm and 0.58am.

We got a good start, with only a few scattered clouds at 10.30pm. The shadow of the Earth was clearly visible on the moon’s lower left, slowly creeping across the rest of the surface. I was out with my bike, camera and tripod, trying to get a few pictures in between the clouds, and meanwhile riding around looking for a good (dark) location to catch the total phase from. That brought me to parts of Leiden I’d never been before, including what I later discovered to be a bike racing track.

With some ten minutes to go before totality (where the moon is entirely in the Earth’s shadow), I set up my tripod on an empty parking lot just outside the city limits. The illuminated part of the moon continued to shrink and shrink and shrink… and then disappeared entirely.

Behind a pack of clouds.

At 11.42pm, two minutes before totality, a seemingly endless stretch of clouds came in from the west and obscured the moon. I felt robbed. Granted, a lunar eclipse is not nearly as spectacular as a solar eclipse, but I’d never seen one before (contrary to a solar eclipse; I saw the 1999 total eclipse in Belgium) and I was looking forward to seeing the moon turn a dark brownish red. Alas, no such luck. To make matters worse, it started raining and I had wondered off quite far from home. I was soaked to my underpants by the time I got back, but I wasn’t about to give up just yet.

The rain subsided a bit, so I changed into a dry jacket and a dry pair of shoes, and went out again. Before long it had stopped raining again and the clouds got a bit thinner. Eventually they broke altogether and I got a ten-minute window to behold the fully eclipsed, dark red moon. After that the clouds returned and it started raining again, but I didn’t care. I’d seen the eclipse.

The partially eclipsed moon at 11.04, 11.14 and 11.30pm (40, 30 and 14 minutes before totality) and the fully eclipsed moon at 0.39am (55 minutes into the 74-minute total phase). The poor quality is due to the limited capabilities of my camera.

Clouds came in again around 0.45am to make the rest of the eclipse invisible from Leiden.

Bad news for astronomers and fans of gorgeous astronomy pictures. The most important camera on the Hubble Space Telescope, the Advanced Camera for Surveys (ACS), has broken down. Again. It’s the third outage in less than a year and the problem seems to be worse than the last two times. A NASA Anomaly Review Board will try to determine what happened and whether the camera can be turned back on.

More details are available in the article “Telescope News: Advanced Camera for Surveys Suspends Operations” on the Hubble website (retrieved Jan. 30, 2007):

Hubble’s Advanced Camera for Surveys (ACS), the instrument whose work has dominated the telescope’s observation program, is currently not operating.

On Jan. 27, Hubble went into a self-protective hibernation called “safe mode.” This happens whenever Hubble’s computers measure a serious anomaly in the spacecraft’s operation. A pressure sensor located in the section of the telescope that houses the science instruments had detected a rise in pressure. At the same time, an electrical fuse blew in the ACS, probably as the result of a short circuit.

Hubble is currently out of safe mode and functioning normally. Science operations will resume this week.

Hubble still has significant science capabilities. The Near Infrared Camera and Multi-Object Spectrograph (NICMOS), the Wide Field Planetary Camera 2 (WFPC2), and the Fine Guidance Sensors (FGS) are all working. ACS was installed in 2002 and has met its expected lifespan of five years.

NASA has convened an Anomaly Review Board to attempt to identify the precise cause of the ACS problem and determine whether it is safe to return ACS to operation. It will also help establish whether there is any prospect for repairing ACS, if it cannot be turned back on, during the upcoming mission to service Hubble in 2008.

In the likelihood that ACS remains inoperative, several steps will allow NASA to proceed with the best possible science program with the telescope.

Observations that had been scheduled for the still-working instruments will be moved, when possible, into the time slots left empty by ACS’s breakdown. All the current ACS programs will be reviewed to determine which observations might be transferred to other instruments — most likely WFPC2.

My first paper, which I submitted late November last year and which got a favourable referee rapport just before Christmas, has now been accepted for publication in Astronomy & Astrophysics. A preprint is available on arXiv.org as of yesterday, under ID astro-ph/0701606.

Did you know that Brian May, guitarist of Queen, used to be, in a way, a colleague of mine? Or rather, that he still is one?

May was working on a PhD in astronomy at the Imperial College London in the 1970s, but quit when Queen rose to fame. He was studying zodiacal light, the faint glow that is visible above the horizon under favourable circumstances after twilight or before dawn. It is produced by sunlight reflecting off dust particles within the solar system. (May can undoubtedly tell you much more about it than I can.) As part of his thesis work, May performed observations on Tenerife, resulting in his co-authoring two scientific papers (one, two). Even more interesting, the first of these two was published in the very prestigious Nature journal.

As of last year, May is once again working on his thesis, hoping to finally earn his astronomy doctorate after a thirty-year break. It’d be cool if he succeeds!

Astronomy meets linguistics! The American Dialect Society picked plutoed, from the verb to pluto, as 2006′s Word of the Year:

In its 17th annual words of the year vote, the American Dialect Society voted plutoed as the word of the year, in a run-off against climate canary. To pluto is to demote or devalue someone or something, as happened to the former planet Pluto when the General Assembly of the International Astronomical Union decided Pluto no longer met its definition of a planet.

Pluto’s demotion to dwarf planet is getting this little ball of rock and ice more fame in a single year than in all 76 years combined since it was first discovered!

On the verge of Christmas break, the editor of Astronomy & Astrophysics sent me a nice present: my paper on the chemistry and infrared emission of polycyclic aromatic hydrocarbons around young stars, submitted last month, has been judged favourably by the referee. Following a couple of minor revisions, it will be accepted for publication. The comments from the referee should not take too much time to address, so we can probably submit the revised manuscript early next year.

After several months of steady (but somewhat slow) progress, I finally submitted the first paper of my PhD project last week. Its purpose is two-fold: (1) to describe the key chemical reactions affecting polycyclic aromatic hydrocarbons (PAHs; large organic molecules) in gas/dust disks around young stars; and (2) to study the effects of their chemistry on the infrared emission we observe from such stars/disks. If that sounds like gibberish to you, just be assured that it is Very Important Science (really!), yet unlikely to affect humankind in any major ways within the current century. (It might have big consequences in the next one, though.)

If you do know what PAHs and disks around stars are, and if you want to know all the details, I’m happy to direct you to this PDF file, which is the version I submitted to the journal Astronomy & Astrophysics. Please note that my paper has not been refereed yet, so the final version may deviate significantly from the current one.

Interestingly, the PAH model I describe in my paper has already been put to use in two other papers. Vincent Geers, a fellow PhD student here in Leiden, used it to analyze actual observations from PAHs in disks. Klaus Pontoppidan, a postdoc at Caltech and a former Leiden PhD student, used it to analyze the young star VV Ser and its surrounding gas/dust cloud. You can find their papers online as well: Vincent’s work and Klaus’s work. Vincent’s paper includes me as one of the co-authors, while Klaus’s paper mentions my model in the acknowledgements.

I will be attending a two-day conference in Belfast, Northern Ireland in early January, and I hope to get a chance to present my research there in a short talk. It would be cool if I can! (It would also be pretty scary, since I’ve never given a talk at a conference before, but I’ve got to do it at some point…)