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A daily view of all the goings-on at ASTRON and JIVE.

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  • 08/25/16--17:00: A very inclusive picture
  • © Madroon Community Consultants (MCC)

    This picture brings together a remarkable range of species at the weekly gathering of the secretive Pesse Institute. See whether you can identify them:

  • A departing hero (don't be a stranger).

  • A couple of beaming newly-weds (congratulations!).

  • Some of this year's excellent crop of summer students.

  • A young buck from NOVA (rare, but encouraged).

  • A bright light from DOME.

  • A leader of JIVE, and his lady (once they were newly-weds here too).

  • A stalwart from ASTRON, and his dog.

  • A contented dinosaur, and his lady (our perennial hostess).

    The picture was taken at 22:30, the hallowed moment that marks the start of the second part of the evening program. The champagne was libated to toast the happy couple, who will settle in Beilen. They are prime candidates for keeping the wednesday flame burning, in the fullness of time.

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  • 08/29/16--17:00: Dubbel feest!
  • © Hemel en Dampkring, 1951

    The parabolic reflector shown here - 30 m in diameter - was the largest single antenna ever built for radio astronomy in the Netherlands. If it still existed (it was dismantled many years ago), it would this year have reached retirement age(*).

    Curiously, the man on the rim of the dish himself celebrates something special this month. He is Hugo van Woerden, Professor Emeritus, long-time member of the board of NFRA (ASTRON's predecessor), and he has just turned 90. Tomorrow (Aug 31st) there will be a special celebration for him in Groningen.

    Huug, we are all thankful for the many years you have worked with and for SRZM/NFRA/ASTRON, and that you have much more staying power than the antenna! Gefeliciteerd met je 90e verjaardag!

    (*) Editor's note: Perhaps Kootwijk was not the optimal site for a super-sensitive antenna for detecting faint radio whispers from the Universe. The cathedral-like building in the background houses a powerful transmitter that was used to exchange radio messages with Indonesia, on the other side of the globe. Radio astronomical observations were soon moved to quiet Drenthe, i.e. to Dwingeloo (1956), Westerbork (1970) and Exloo (2010).

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    © ASTRON/JIVE. Photo from Minnie Mao

    The annual ASTRON/JIVE summer student Wadlopen(*) event took place on August 12.

    This time we could not get to the island of Ameland due to recent bad weather. But the cloudy day with occasional light rain did not preclude a perfect outing for the intrepid radio astronomers that followed Commander Bob on a circular path through mud, sand, and sea water.

    The students could make new friends during the wadlopen, meeting crabs, oysters, or shrimps. Although not all of them survived to their stomachs...

    (*) The shallow sea between the north shore of the continental Netherlands and its distinctive string of protective islands is called the Wadden sea. Crossing it at low tide, squelching over the bottom of the sea, is a must-do experience.

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  • 08/30/16--17:00: Farewell, tot kijk!
  • © ASTRON

    Dear Colleagues - today is my last day in the employ of NWO.

    It has been a great privilege to serve NWO and both ASTRON/JIVE for the last 20 years.

    The progress both institutes have made is impressive - ASTRON (and indeed the Netherlands as a whole) is playing a leading role in the realisation of the SKA in terms of its technical design, its scientific specification and especially as the recognised coordinator and initiator of the European SKA Regional Science Data Centre (the recent success of the AENEAS proposal, under Michael Wise's coordination is the icing on the cake!). We are also involved in an exciting future-oriented collaboration with the Chinese and other Dutch colleagues to build a low-frequency radio astronomy package that will fly on the upcoming Chinese far-side lunar mission - Chang'e-4. This, together with our continuing development of advanced aperture array technologies, places ASTRON at the fore-front of next generation radio telescope developments, including SKA-2. Meanwhile, the WSRT is on the brink of a fantastic new wide-field capability via the APERTIF upgrade, and LOFAR is widely recognised as the premier low-frequency radio telescope in the world. Our own astronomy group flourishes in a way we could only have dreamt of 10 years ago - the many successes we have enjoyed in competing for individual research awards both at home and in Europe has been quite staggering. In addition, we have enjoyed the enormous growth of a vibrant radio community at the universities, in Leiden, Groningen, Amsterdam and Nijmegen where are links and engagement are strong.

    JIVE is also well-established as an ERIC with the potential to grow significantly via ear-marked EC funding, with an eye towards the exciting opportunities associated with a new and impressive (South) African (SKA) VLBI capability.

    The DOME project (a collaboration between IBM and ASTRON) has been pivotal in the Netherlands optimal positioning in the SKA ICT global planning, and a follow-up to this initiative is in the works.

    The NOVA IR/Optical Group has also flourished during this period - it's with some pride that Dwingeloo is now a major centre for two of the greatest and most hotly anticipated observatories of the 21st Century - the E-ELT and the SKA.

    CAMRAS is enjoying a beautifully refurbished Dwingeloo Telescope, and organises an impressive programme of activities that involves radio amateurs, amateur radio astronomers, education (STEM), public outreach, art and culture in the broadest possible sense. Much to my own delight, there is also a fledgling SETI capability being developed.

    All-in-all, I think I leave Dwingeloo with ASTRON, its telescopes and the other organisations it hosts in better shape than ever before. It's a state of affairs that we can all take great pride in. Naturally, it is very hard to leave an institute like ASTRON without a certain tinge of regret but I also look forward to the new challenges and opportunities Manchester, Jodrell Bank and the UK in general present. I have greatly enjoyed my time in Dwingeloo and the Netherlands - I met many wonderful people here and made some very good friends. The Netherlands and the Dutch people have a very special place in my heart.

    I hope to be a frequent visitor to the Netherlands and Dwingeloo in the future. The ASTRON JIVE Daily Image pages will also help me keep in touch with what is going on here - let me take this final opportunity to encourage all of you to submit your results and various events to these pages!

    [The image above shows the "standard" farewell picture all ASTRON and JIVE employees receive on their departure from Dwingeloo - the signatures of all staff represent a snapshot of the organisation at a particular epoch in time. An analysis of all the signatures could probably fill a thesis or two but what I notice is (i) incompleteness(!), (ii) an interesting use of colour by Bob Campbell, (iii) the large fraction of signatures that are actually legible, (iv) a singular personal note from Marjan T, (v) one signature presented upside down by Harro and (vi) a cheeky reference to Ajax by Anno!

    I expect I am still missing a lot - take a look and do your own analysis!]

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    © Swinburne Astronomy Productions

    I will give a history of Fast Radio Bursts, talk about where the field is today, what we know and what we don't know, what the controversies are and what the future of the fast-evolving field is. If proven to be at cosmological distances, FRBs have the potential to measure the baryonic fraction of the Universe and have a say on Dark Energy.

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  • 09/01/16--17:00: A thank you to Roy Smits
  • © ASTRON

    Roy Smits achievements reflect those of the rise of pulsar astronomy in the Netherlands. His steady work has been one of the driving forces ensuring that we have such a lively research field today. Roy joined ASTRON in 2009 as a postdoc in the LEAP (Large European Array for Pulsars) project and as a WSRT support scientist. For LEAP he worked on the monthly WSRT pulsar observations and he was instrumental in the development of the LEAP beamformer. For the pulsar group he maintained the PuMa II pulsar instrument. Around 2 years ago Roy switched to the Astronomy Group and has since then led the design and commissioning of the pulsar-timing back-end for WSRT. Roy has in addition contributed to ASTRON's various outreach activities such as "Girl's day at ASTRON", given countless tours of WSRT, ASTRON and the Dwingeloo Telescope, and visited high schools to promote astronomy. He has also organized game evenings and other social activities for ASTRON employees, summer students and visitors. Roy is a person with tons of ideas, always helpful, a great communicator and he brings lots of positive energy into every team he is in. He will be much missed at ASTRON and his colleagues wish him all the best for his future.

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    © ASTRON

    The daily image of today shows that the collaboration between CSIRO and ASTRON is going very well. The picture shows Gijs Schoonderbeek from ASTRON at the right and his new room mate Andrew Brown from CSIRO on the left. After almost three months of working together intensively, they are still laughing. They have been working on a new digital platform called Gemini. This FPGA board will form the basis of the SKA-Low correlator and beamformer architecture. The board design is finished and the board is currently in production.

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  • 09/05/16--17:00: The Cat's Eye Nebula NGC6543
  • ©

    Most well-known pictures of the Cat's Eye Nebula are high-resolution (Hubble) images of the central part of this planetary nebula. But the nebula is much larger than that, because it has a much fainter outer shell.

    From my observatory, the object is favorably placed only for a short period each year. Just after the "grey nights" of summer, it emerges above the roof of my house, but only for a few hours. Later in the year it is out of view again, so imaging it requires a bit of luck.

    In this image, the bright central part of the nebula is overexposed; it even shows diffraction spikes. Eventually, I will have to add some shorter integrations to fill in this gap and get a nice HDR image. Please click on the image for a full-size view.

    As a bonus, the field also contains NGC6552, a very nice barred spiral galaxy with a ring.

    The image is an LRGB composite of nine 600s integrations each for R,G and B, and ten 600s integrations for the luminance channel, made with my 400mm telescope and a cooled CCD camera.

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    © Floor Broekgaarden, Zsolt Paragi, Ilse van Bemmel

    During a gamma-ray burst (GRB) a pair of opposite ultra-relativistic jets are produced, that decelerate while interacting with the surrounding medium and produce broadband synchrotron radiation, the so-called 'afterglow', which in case of radio is in general visible from days up to months.

    Directly measuring the size of the jet and its evolution is important for constructing and testing theoretical models. Since GRBs are found at cosmological distances but their jets are smaller than a parsec in size, obtaining resolved images, even with VLBI, is extremely difficult and has only been done in one extremely nearby and luminous case: GRB030329.

    The goal of my summer project was to constrain the image size of GRB130702A, a relatively nearby GRB (redshift z = 0.145), that we observed with e-EVN for 13 hours, 14 days after the burst.

    The diffraction limit of our observations was 3 milliarcseconds (mas), but we could constrain the size of our jet to have an upper limit of 0.35 mas, one tenth of the diffraction limit. This was done by assuming a source intensity profile, and (model)fitting different source sizes to the visibility data (Marí-Vidal et al. 2012).

    However, we experienced that the degree of phase errors, influence the robustness of this modelfitting a lot, i.e. the outcome of modelfitting is strongly correlated with the degree of phase errors.

    In the top panel we have plotted one of the analytical models for the size of the jet at a certain moment of time. The size of the afterglow that is predicted, depends on the medium that it is propagating through (k=0 for inter stellar medium, k=2 stellar wind). Which also means that observing the size of the jet can constrain the environment of the GRB.

    In the lower panel are the histograms of the distributions of sizes of our Monte Carlo simulations shown for with phase errors of 1 sigma equal to 10 degrees (l) and 30 degrees (r). The scattered sizes in the right plot clearly shows that modelfitting is not robust when dealing with large phase errors, which is often the case in the longest baselines of the e-EVN. However, the future SKA will have smaller phase errors and will therefore be a promising new instrument for resolving more GRB jet image sizes, and deriving more physically parameters of GRBs.

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    © AAMID Consortium

    Mid-Frequency Aperture Arrays are an enabling technology for SKA Phase 2 and are being developed by the AAMID consortium. Recently, the project passed the SRR milestone. The objective of the SRR has been to deliver a properly defined set of science requirements that have been well established within the scientific community, and to trace down these science requirements to AAMID and MFAA system requirements. In addition, system architectures and a detailed status update of the technology developments has been presented, together with an evaluation of the technology readiness levels of the various sub-systems.

    The image above shows the Review Panel and the MFAA team. The panel consisted of Anna Scaife (chair, University of Manchester), André van Es (SKAO), Russell Gough (CSIRO), Francois Kapp (SKA South Africa) and Jeff Wagg (SKAO).

    Thanks to the constructive feedback from the panel and the various discussions we can further improve the quality of the MFAA documentation. The Consortium is now ready to proceed to the Preliminary Design phase.

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  • 09/08/16--17:00: LOFAR's view on pulsar sky
  • © Anna Bilous

    Imagine you are a sentient alien creature with a pair of superb radio eyes, capable of discerning even the most minute splashes of radio emission... how would the night sky look to you? The image above may give a clue to that. On top of the diffuse black-and-white Galactic background, the swarm of color dots provides a one-second glimpse into the life of 158 northern pulsars, with the course of time slowed down by a factor of 10.

    These pulsars were observed within the LOFAR Pulsar HBA Census -- a large project which aims at creating the first uniform low-frequency (110-188 MHz) portrait of all known non-recycled pulsars in certain regions of the sky. All 196 pulsars with well-known positions within the grey lines(*) were observed, regardless of their estimated brightness and scattering level. Only 38 of those pulsars escaped detection (still dots with black edges).

    The first paper in the census series (Bilous et al. 2016) describes the general set-up of the project, and presents the first basic results: calibrated average pulse profiles (reflected by the size of the dot varying with time) and the dispersion measures (DM, shown as color, increasing from blue to red). DM is a quantity proportional to the amount of matter in the interstellar medium along a given line of sight.

    Because of the advantageous frequency position, the census observations yielded DMs that are 10 times more precise, on average, than those in the standard ATNF pulsar catalogue. The obtained flux density values helped to constrain the shape of pulsar spectra. For 48 of the census pulsars, spectral fits were published for the first time.

    The observations within the LOFAR Pulsar HBA census resulted in a unique data set, useful for studying both pulsar emission and the interstellar medium. Data analysis is continuing, so watch this space for many more interesting results in the future.

    (*) The horizontal gray lines indicate the plane of our galaxy. The curved gray line indicates the part of the sky than can be observed by LOFAR.

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    © Vlad Kondratiev

    Studies of millisecond pulsars (MSPs) at low radio frequencies are very valuable as they expand our ability to probe the compactness of radio emission regions in pulsar magnetospheres by comparing radio emission properties between MSPs and non-recycled pulsars. However, until recently there have been only a few studies of MSPs at frequencies below 200 MHz, mainly due to the high background sky temperature and large pulse broadening (caused by both scattering and dispersion in the interstellar medium). At the same time, as result of Fermi discoveries and ongoing pulsars surveys, the number of known MSPs in the Galactic field grew substantially over the past few years.

    Here we present the results of LOFAR MSP census. Within this project, we accumulated the largest sample of MSPs ever observed at frequencies below 200 MHz with a single radio telescope, with half of the detected MSPs being observed for the first time at these low frequencies. Out of 75 MSPs, observed in the frequency range 110-188 MHz, we detected 49, and three of those MSPs were also detected at 38-77 MHz.

    In our paper (Kondratiev et al. 2016, A&A, 585, 128) we present the average pulse profiles of the detected MSPs, their dispersion measures, effective pulse widths, and flux densities, and compare these with higher observing frequencies. A qualitative comparison of the LOFAR MSP profiles with those at higher radio frequencies shows constant separation between profile components. Similarly, the profile widths are consistent with those observed at higher frequencies, unless scattering dominates at the lowest frequencies. This is very different from what is observed for normal pulsars and suggests more compact emission region in the MSP magnetosphere.

    "Postal stamps" of the LOFAR total-intensity average profiles from the best individual observations are shown here. The horizontal axis shows the pulse phase, and the vertical axis is the flux density in arbitrary units.

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  • 09/12/16--17:00: Summertime
  • © Rik ter Horst

    It is a bit risky to point a telescope into the direction of the sun, but sometimes it's worth the risk! This scene was captured a few weeks ago from Noordpolderzijl in the north of the province of Groningen. The sunset in itself was already quite impressive but in combination with a passing stranger it becomes even more interesting ;-)

    Imaged through a 130 mm F/11.5 Schmidt Cassegrain Telescope and a Canon EOS 550D camera under a very clear sky. 1/4000 sec on 100 ISO.

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    © Vlad Kondratiev

    We proudly announce that Pulsar Pipeline (PulP) is now ready for the new LOFAR cluster CEP4 and awaits to be fully integrated into the LOFAR framework. With CEP4 all pipelines including the PulP should accomodate several significant changes since the previous CEP2 era. Namely, they should support cluster workload manager SLURM, make use of the Global File system where raw observational data are accessible from any of CEP4 compute nodes, and also run within a Docker container specifically designed and tuned for the corresponding pipeline. Having these many substantial changes also put additional difficulties for the debugging and testing. On top of that necessary changes were needed to be done to incorporate Pulp into the LOFAR framework for pipelines to be run automatically.

    As of now PulP is fully suited to be run on CEP4. It can be run both manually and automatically within the LOFAR framework. The same code with different cluster settings can be used to process the pulsar data on 4 different LOFAR clusters: CEP2, CEP3, Dragnet, and now CEP4. It was successfully tested for different data modes: complex-voltage data, Stokes I, and Stokes IQUV; both for a single tied-array beam and multiple beams, as for example for LOTAAS pulsar survey and system Fly's Eye observations. Currently, Pulp is given to Science Support for further tests within the LOFAR framework and performance characterization.

    Images show two happy men who worked hard to have Pulsar Pipeline on CEP4, together with their CEP4/PulP-related screenshots.

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    © Photo: Steven Bloemen

    The MeerLICHT telescope achieved first light here in Dwingeloo on the evening of September 13, 2016. The telescope was built by the NOVA Opt-IR group and serves as the prototype telescope for the BlackGEM Array. The image quality that was obtained during the first night was excellent! The first tests were performed with a Canon 5D camera. The 110 Mpix science CCD will be installed next week.

    The telescope will be tested further in the coming weeks. In October, it will move to Radboud University in Nijmegen to be merged with its mount and electronics. After thorough characterisation and testing, it will be commissioned at Sutherland (South Africa) in the beginning of 2017. The telescope will always co-point with the MeerKAT radio array to provide optical data of the sources for which radio data has been taken.

    The PI institutes of the MeerLICHT project are the University of Cape Town (Prof. Patrick Woudt) and Radboud University (Prof. Paul Groot). For more information, see

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    © ASTRON

    The Fourth LOFAR Data Processing School was organized and hosted by ASTRON between 5-9 September 2016. The event was sponsored by ASTRON, the International LOFAR Telescope (ILT), and BALTICS, which is a project granted through the H2020-TWINN-2015 call and is aimed at twinning the Latvian institute VIRAC with ASTRON and the University of Manchester.

    The School has provided a week of lectures and tutorials to introduce the LOFAR system to users and new members of the collaboration who will analyze Cycle data. The topics ranged from the capabilities of the basic station hardware to the software pipelines and science products they produce. Particular emphasis was given to long-baseline imaging topics. Compared to previous LOFAR Schools, more time was reserved for tutorials. Moreover, 'Q&A' sessions were introduced in the programme. These helped the participants to ask more questions and properly understand all topics, including the most complex ones. The best images made by the participants after the imaging tutorials were awarded a prize. 47 students attended the event, together with lecturers, tutors, and helpers. The social events included a School dinner at ASTRON, a GPS competition, and a visit to the LOFAR core.

    Here you see the school picture, taken on the third day of the school at the LOFAR Superterp. For the participants, the LOC, and SOC, it has been an intense, fruitful, and successful week. The School LOC thanks all the people who contributed to the school!

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  • 09/18/16--17:00: IC342, a dusty spiral
  • ©

    IC 342 is an intermediate spiral galaxy in the constellation Camelopardalis. The galaxy is near the galactic equator (zone of avoidance) where dust obscuration makes it a difficult object for both amateur and professional astronomers to observe, though it can readily be detected even with binoculars. The dust of the Milky Way makes it difficult to determine the precise distance; modern estimates range from about 7 Mly to about 11 Mly.

    The galaxy is one of the brightest two galaxies in the IC 342/Maffei Group of galaxies, one of the galaxy groups that is closest to the Local Group. The galaxy was discovered by William Frederick Denning in 1895. Edwin Hubble first thought it to be in the Local Group, but later it was demonstrated that the galaxy is outside the Local Group.

    In 1935, Harlow Shapley declared that this galaxy was the third largest spiral galaxy by angular size then known, smaller only than the Andromeda Galaxy (M31) and the Triangulum Galaxy (M33), being wider that the full moon. (Modern estimates are more conservative, giving the apparent size as one-half to two-thirds the diameter of the full moon). IC342 has an H II nucleus. (source: Wikipedia)

    The image consists of 23, 600s integrations, 6 each for RGB, and 5 for Luminance, acquired from a backyard in Beilen, with a 0.4m reflector equipped with a cooled CCD. Image calibration and processing was done with PixInsight.

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    © Yuping Huang, Aard Keimpema, Benito Marcote, Zsolt Paragi

    The radio transient sky remains relatively unexplored in the sub-second timescale. Known forms of these transients include single pulses from pulsars, Rotating Radio Transients (RRATs) and Fast Radio Bursts (FRBs). Most of these pulses have been discovered by large single dish telescopes, which cannot provide precise localizations due to their limited angular resolutions. The European VLBI Network (EVN), combining large collecting elements and superior angular resolution, is well-suited for searches and localizations of these pulses. In particular, searching for and localizing Fast Radio Bursts will enable us to identify their locations within their hosts and thereby unveiling their currently unknown origin.

    In this summer project, we develop techniques to search for and localize single pulses with the European VLBI Network (EVN) data and apply them to repeating sources (a pulsar and a RRAT) to understand the limitations and uncertainties of these techniques. Shown in A) is a dispersed, astrophysical signal alongside the 80Hz calibration signal at Effelsberg. These calibration signals, resembling pulses, should be removed to allow for searches for truly astrophysical pulses. B) is a sample output of the source detection program we developed, showing the source at the center of the 2 arcmin x 2arcmin map with 0.5 milliarcsec resolution (i.e. a huge map). C) is the "dirty image" around where the source is detected in B); the pulse is clearly visible as the most prominent peak. In this fashion we obtain a position for each pulse. D) shows a histogram of all our measurements from a repeating source, PSR B0525+21; it demonstrates that localizations with milliarcsecond precision is attainable with the EVN.

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    © Roy van der Werp

    At the HR & Communications department it is a given that when it is someone's birthday, he or she hands out cake and will, in return, receive a small birthday gift. In principle the birthday boy or girl bakes a cake as a treat.

    On September 19 the bar was raised by Carin Lubbers. As you can see in the picture, it is no longer enough to just bake something. Decorating the cake has become an important aspect as well.

    FIY: The cake tasted excellent there is nothing left ;-)

    We look forward to eating more creations, and hopefully other colleagues will feel the challenge as well.

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    © JvL

    Astronomy has a singularly visual and attractive role in encouraging scientific curiosity in the wider public. The ability of astronomy to stimulate students (and specifically, girls) to choose physics or technical studies is especially interesting, as the Dutch cabinet has declared it aims to strengthen The Netherlands' position in the world's top five most-competitive knowledge economies. Because it is highly visual and thought-provoking, astronomy is uniquely suited to engage young students in the physical sciences.

    Through high-school physics curriculum progress, we are succeeding in bringing astronomy to adolescent-age students. Through the Physics Education Renewal, astronomy is now part of high-school materials. For 5 VWO (16-yr olds) this includes e.g., the power radiated by the Sun, its spectrum, and the Planck curves; but also the CMB. For 6 VWO (17-yr) olds, topics are as advanced as Gravition, Astrophysics (including sections on Westerbork, LOFAR, and pulsars!), Quantumphysics and even Special Relativity. So, note one of the Dutch standard physics series "Pulsar", above. Astronomers involved include coordinator Jaap de Vreeling (NOVA), and authors Alex de Koter, Peter Barthel and Henny Lamers. There is a copy in Joeri's room for anyone interested.

    By next holding lectures in the refresher courses that high-school physics educator take, we invest time in teaching the teachers, in "number multipliers". For the central region of the Netherlands, Wijers, van den Heuvel and Van Leeuwen teach this yearly post-graduate course. Through that approach we have reached tens of thousands of learners.

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