Category Archives: Life in Astrophysics

The Elephant in the Astrophysical Room

My name is Alvina On and I am a final-year PhD student in the Theoretical Astrophysics group in MSSL. In this post, I will blog about my experience in the XXV Winter School of Astrophysics on Cosmic Magnetic Fields.

Continue reading The Elephant in the Astrophysical Room

A Remarkable Supernova

This week we have a post by Paul Kuin (Swift UVOT team at MSSL), taking us through the breathtaking roller-coaster ride of discovery as the light from a supernova in the nearby M82 galaxy was observed.

You probably heard by now about the new supernova which was discovered in the M82 galaxy. I thought it would be nice to write about our involvement here at MSSL, and give some background story.

The first I heard about the supernova was through an Astronomical Telegram (ATEL for short) sent Wednesday the 22nd of January by Y. Cao of Caltech and collaborators who took a spectrum and identified this as a Type Ia supernova at 14 days before the peak brightness. I thought that was interesting news. We don’t see many type Ia supernovae in galaxies so nearby. The last one was SN 2011fe, which was seen in M101, the pinwheel galaxy. The supernova was discovered by our colleague Steve Fossey and his students here at UCL. I checked the Swift TOO list (a TOO is a Target Of Opportunity, requested for interesting, unexpected astrophysical events) and saw that Eran Ofek requested a Swift observation, which already had been approved.

Mark Cropper (MSSL) sent an email around alerting everyone in the lab of the discovery, and I responded that Swift was already on it, observing. Ignacio Ferreras then (MSSL) asked for more information. His student Susan Hutton (MSSL) had made a study of M82 using very deep Swift UVOT images that had just been accepted for publication! One of their data consists of sums of images in the UVOT ultraviolet filters, revealing fainter features than before.

I contacted Mike Siegel, head of the Swift UVOT team at Pennsylvania State University, who told me Peter Brown of Texas A&M was taking the lead for our team. Peter was in the process of submitting more TOOs for Swift observations in the six UVOT filters, and with the Swift ultraviolet grism (to take a spectrum of the supernova). We decided on some details via email.

A colour image of M82 with brightness in UVOT uvw2 in blue (10ks); UVOT uvw1 in green (8.7ks) and SDSS-g in red, with the position where the supernova was found as a circle. This image was taken before the supernova explosion.
A colour image of M82 with brightness in UVOT UVW2 in blue (10ks); UVOT UVW1 in green (8.7ks) and SDSS-g in red, with the position where the supernova was found as a circle. This image was taken before the supernova explosion.

In the meantime the first data had come down from Ofek’s TOO. Swift data are public and available on a quick-look site. The supernova was bright in the optical V, B, and U bands. It was also visible, though fainter, in the UVW1 band which is a filter bluewards of the U band, centered at a wavelength around 252nm, in the near-ultraviolet region (invisible to the eye!). However, the UVM2 and UVW1 bands which are at even shorter wavelengths were not yet available.

Typically, during the early stages of the explosion, the supernova has a very hot expanding photosphere. The expansion increases the brightness while the temperature goes down, but the initial temperatures are very high, putting out much of the emission in the ultraviolet. Therefore the observed faintness of the supernova in M82 in the UVW1 filter is not typical. The most likely reason for such faint UV emission is the large amount of dust that photons have to traverse to leave the dusty galaxy (which is orientated edge-on towards us).

Ignacio had in the meantime plotted the position of the new supernova on his deep image, and on a Hubble ACS optical image with better spatial resolution. I had wondered if there would be any evidence of a progenitor, but nothing special was spotted (a type II supernova would have originated from a very luminous supergiant star, whereas the progenitors of type Ia explosions are much harder to detect, consisting of a binary system, where at least one of the stars is a white dwarf). A bit later we saw other ATELs come by where others did report their searches (ATELs 5789,5794,5795).

The greyscale image is from HST/ACS (8.1 ks in F55W), zoomed in to the area around the new supernova. This image was taken before the supernova was discovered.
The greyscale image is from HST/ACS (8.1 ks in F555W), zoomed in towards the area around the new supernova. This image was taken before the supernova was discovered.

I checked a few times, but the grism observations were not yet in the Swift list of  “observations done”. By the evening we got the observation in UVW2, which showed the supernova, and later in UVM2 which did not (see the blue images below; the SN position is indicated in the uvw2 image with lines). The UVW2 filter peaks farthest in the ultraviolet of all the UVOT filters, but also has a small sensitivity bump around 420nm of about 0.4% of the peak response, also known as a “red leak”. However, the UVM2 filter response is limited to a small wavelength band around 225nm only. The first conclusion was that the contrast in brightness between the optical and ultraviolet was so large that the UVW2 detection of the supernova was probably due to the high flux of optical photons seeping through the red leak. Note that the UVW2 image was taken first, before the UVM2 one.

The next morning the grism observation was partially available on the Swift quicklook web site. I downloaded the data, and had a look at the first two images. There was a bright zeroth order in line with the spectrum, but it seemed in the wrong place. After getting the published position plotted on the image I was sure. There sat another very bright star right in the same dispersion plane as the supernova. What was going on!?

SN3

The grism disperses light into colours, and so spectra of two nearby sources in a grism image can fall over each other, and that is precisely what happened here ! It can be fixed by changing the roll angle of the spacecraft, so I quickly alerted the on-duty scientist that there was a problem. At the daily Swift planning teleconference there was some futher discussion of that issue. Since there was not much time left for the next plan upload to the spacecraft, we worked hard to resolve which angle to use for the next day. Mike Siegel was eventually asked for help and we decided on a new spacecraft roll angle. However, even the early contaminated UVOT spectrum clearly showed that there was not much emission below 290nm, since that area of the spectrum was partially uncontaminated.

SN4

The next day I got an email that NASA was going to put out a press release, and that Neil Gehrels, the Swift Project Scientist, thought that Swift should put out an ATEL with our results so far. We decided to ask Peter Brown at Texas A&M to write that. He had already done a lot of the work for that, including making some images of before and after. He also could say, based on the latest data, that there finally was a detection in UVM2. The supernova had either brightened enough, or we had accumulated enough exposure time to get a detection. He also worked with the NASA press people, and soon there was a lot on Twitter with his ATEL and NASA’s press release taken up by many outlets.

By Sunday the 26th of January, 2014, I had downloaded one of the new grism images and extracted the spectrum (plotted above). It shows the characteristic undulations due to a plethora of spectral lines from metals formed and expelled in the SN explosion (we had a blog entry in 2013 on how spectroscopy allows us to understand the composition of galaxies).

It can be seen that the flux drops off quite steeply to the blue. It will be interesting to see if summing exposures will make the spectrum in the UV visible, and what signatures there are of the absorbing material in the UV. Hopefully we will learn something from this nearby supernova Ia that helps us understand them better.

I left academia, so why come back?

Everyone who begins a PhD comes to that decision their own way. This is an explanation of the path I’ve taken and why.

My name is Megan Whewell and I started my Astrophysics PhD here at MSSL less than a month ago. My project is looking at X-rays from Active Galactic Nuclei (AGN) and using spectroscopy to discover more about them. AGN are supermassive black holes at the centre of other galaxies that are accreting matter and by doing so giving out huge quantities of radiation (hence, ‘active’).

Artist's impression of an Active Galactic Nucleus. Credit: ESA/NASA, the AVO project and Paolo Padovani
Artist’s impression of an Active Galactic Nucleus. Credit: ESA/NASA, the AVO project and Paolo Padovani

In September 2010 I began my fourth and final year of a Natural Sciences MSci degree at UCL. I’d chosen to study Astrophysics as my main subject, alongside Science Communication with History and Philosophy of Science as just less than half of my total degree. I loved this combination and always explained it to friends and family as “learning about space while learning how to talk about space!”

The Orion A star-formation cloud seen by ESA’s Herschel space observatory. The Orion Nebula is located within the central bright region of this scene, where massive star formation is most intense. Credit: ESA/Herschel
The Orion A star-formation cloud seen by ESA’s Herschel space observatory. The Orion Nebula is located within the central bright region of this scene, where massive star formation is most intense. Credit: ESA/Herschel

At this stage I’d barely thought about a PhD and instead started the year focusing on my two final year projects – research into the formation processes of massive stars (stars that have more than eight times the mass of our Sun) and designing a museum exhibition about asteroid and comet impacts on the Earth.

Many of my coursemates from Astrophysics wrote their PhD applications by Christmas that year, confident in the academic path they wanted to take, but I wasn’t yet sure. Then they had interviews, acceptances (and rejections) a few months later but I still wasn’t sure. I expected to feel relief and elation when handing in my final projects in April and didn’t expect to want to start another, much longer academic project.

‘Hand in day’ approached and I still enjoyed research, even the writing up process! ‘Hand in day’ passed but no sense of relief to be finished appeared; there was more research I’d wanted to do and I was disappointed to have reached the deadline. This certainly made me briefly reconsider a PhD but I had missed that year’s application deadlines and needed to find work.

My love of “talking about space” led me to a job at the National Space Centre in Leicester (UK), first just in Education then with split time between Education and the wider Communications department. Among many other things I taught school children about astronauts and wrote blogs about the latest Space news.

Me in the National Space Centre's Planetarium
Me in the National Space Centre’s Planetarium

It was there I learnt my first programming language, rather than dabbling in a few, but not one most people reading this will recognise. The language was called D3 and controls the planetarium there as you travel ‘live’ around a virtual universe. My favourite part of work was the satisfaction of finally getting the code right so you can watch the view as you fly away from Earth and outside of our galaxy or lift off and see the Earth rise up in front of you.

This experience, combined with a desire to continue reading academic papers (which will wear off soon I’m sure!), was what led me to apply for PhD positions after just over a year out of academia. I wanted my own project; I want to learn, explore, discover and explain things that have never been known before. For me, a PhD is the perfect way to do this and so far my time at MSSL has been living up to all I expected of it.

I hope to be able to write for MSSL Astro again, but if you want to read more about my own time at MSSL I have a personal blog here.

Day in the life of a PhD student

Hi, I’m Richelle Grisdale, and I started my PhD at MSSL about a year ago. Here’s a short summary of how it’s going so far, and what my life is like on a daily basis.

When I arrived at MSSL, I absolutely loved its lovely surroundings and the beautiful old house. I was also really looking forward to starting my project and working more independently than at undergraduate. I met my supervisor, and started work. The first few days were pretty confusing, but everyone was very friendly and it was easy to settle in to life at MSSL. My first month was spend studying by reading reviews, and becoming best friends with a very useful book called Galactic Dynamics.

Galactic Dynamics, by Binney & Tremaine. http://www.amazon.co.uk/Galactic-Dynamics-Second-Princeton-Astrophysics/dp/0691130272
Galactic Dynamics, by Binney & Tremaine. http://www.amazon.co.uk/Galactic-Dynamics-Second-Princeton-Astrophysics/dp/0691130272

Now I’m one year into my PhD. I’ve made a nice start on my project, and gotten very used to life at MSSL. In a typical week I leave my house at about 8:30 to 9am most mornings, and it takes me about 45 minutes to cycle the 6 miles to MSSL. It’s a lovely ride to the countryside. I then start with a cup of tea, and continue working on what I was doing the evening before. I meet with my supervisor about once a week, and we discuss the work I’ve done that week, which direction I should take it next, and what work I should concentrate on.

Every week we also have a series of meetings. Every other Wednesday there is journal club. Here one person picks a recent paper that they found interesting, and describes it to the others. I find it’s a great way of broadening my knowledge beyond what my project is about. On Thursdays we have a small meeting, called the Gaia meeting. This is a meeting of people who work on something to do with Gaia, and we discuss anything Gaia related. There are also regular seminars. These vary widely, some are very good, while others are quite difficult to follow!

Currently I am in Tenerife, at a summer school all about the Milky Way. One of the greatest things of being a PhD student is that you are constantly learning new things. Being at one of these summer schools is great fun, you get to meet lots of fellow astrophysics PhD students, and make new contacts. There were also a lot of very interesting lectures. These were extremely helpful as they provided me with many good references for my upcoming upgrade report.

Richelle in Tenerife
Richelle in Tenerife

In short, the life of a PhD student is pretty cool! You learn lots of interesting things, get to do independent research, and fly to cool places like Tenerife to do it!

MSSL Croquet

Post by Tom Kitching:

Early croquet game taken from "The sports and past times of the people of England by Joseph Strutt, 1834 edition published in London. Downloaded from http://en.wikipedia.org/wiki/File:EarlyCroquetSportsofPeopleofEnglandStrutt.jpg
Early croquet game taken from “The sports and past times of the people of England by Joseph Strutt, 1834 edition published in London. Downloaded from http://en.wikipedia.org/wiki/File:EarlyCroquetSportsofPeopleofEnglandStrutt.jpg

One of the nice things about working at MSSL is that the department consists not only of the building in which we work, but also the grounds in which it lies. This is particularly enjoyable during the summer, for example one can eat outside at lunchtime talking about science and looking at the amazing views for inspiration; if there is a long paper to read there are many places to sit in peace in the fresh air. MSSL also remarkably has a outdoor swimming pool (perhaps we will blog about that in the future), which is not too cold(!), and nice to use on really hot days. The various lawns in the grounds are also put to good use, football is played regularly, and in the summer the department has a Croquet tournament!

Before this summer I had never before played croquet in my life, so it was with a sense of trepidation that we formed the team Mullard Cosmology Croquet (MC^2), myself together with Dr Jason McEwen. However after the first game I realised that it is a wonderfully game, from quite simple rules very complex matches can result, full of strategy and tactics.

Image from http://www.etsy.com/listing/97418840/croquet-couple-silhouettes-hats-digital
Image from http://www.etsy.com/listing/97418840/croquet-couple-silhouettes-hats-digital

The tournament at MSSL is regularly held each summer, and its a really nice way for the different groups in the department to mix. Neville Shane is the tournament organiser and all the information is posted on a nice website here. The game we play is Garden croquet, which is the most common variant of the rules played; teams consist of two players that take it in turns to hit the ball through a series of hoops. The interesting aspect, that causes many complicated playing scenarios, is that if one hits another players ball then this results in two shots, the first of which can be used to move that players ball for example.

The tournament structure has two group stages, in which each team plays every other team in the group. The winner and runner up of each group plays the runner up and winner of the other group in the semi-finals, followed by a final show down. The MC^2 team somehow (with a good dose of luck) has managed to get through to the final, with some really close games.

The semi-final MC^2 vs. Planetary A-Team croquet lawn.
The semi-final MC^2 vs. Planetary A-Team croquet lawn.

Having such group activities in a department is very important. It creates a sense of community, it builds friendships, all things that a good science department should have. I’ve thoroughly enjoyed my croquet experiences so far, and will certainly look forward to getting out on the lawn next year.

The National Astronomy Meeting 2013

This week Alvina On, Dave Barnes and Idunn Jacobsen all PhD students at MSSL blog about the experience of attending the UK National Astronomy Meeting 2013 in St. Andrews, Scotland.

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This year’s National Astronomy Meeting was located in a (partially) warm and sunny St. Andrews, Scotland, between 1st and 5th of July. With a programme incorporating a wide range of research areas, with talks ranging from Solar physics to Cosmology to the future of instrumentation, a reported 600 registered astronomers and space scientists descended on the quiet, coastal town.

NAM 2013 Banner.
NAM 2013 Banner

We arrived on Sunday evening, which we spent getting familiar with the town. It is usually dominated by students attending the university. However, due to the summer holidays, the town centre was very quiet, and our accommodation was a 20 minute walk out of the centre, so it was even quieter.

Between Monday and Friday we enjoyed a packed programme, with parallel sessions, plenaries and public talks. The frequent coffee and lunch breaks allowed attendees to meet and greet fellow researchers, engage in discussions both within their respective fields, as well as across areas, and to view the many posters that were complimenting the talks of the parallel sessions.

The poster room at NAM.
The poster room at NAM.

With a large fraction of sessions this year allocated to UK Solar Physics (UKSP) and Magnetosphere Ionosphere Solar-Terrestrial physics (MIST) meetings, it gave us from the numerical and theoretical corners of large-scale astrophysics a glimpse of astronomy on much smaller scales than we are accustomed to. The opportunity to speak to fellow PhD- students and astronomy researchers from other institutions was great, not only to discuss the science being done, but to have the chance to discuss career paths and progress, and the general news from the science community.

NAM2013 venue

A number of social events allowed everyone to meet in more relaxed settings, such as the Whiskey tasting event. This provided both the history of Scottish Whiskey, by Dr David Wishart from the host university, and, equally importantly, ample choice in whiskies – arranged by taste and complexity analogous to the Hertzsprung-Russell diagram, for the benefit of the audience.

The conference programme commenced Monday afternoon, with registration and a plenary talk to ease us in to the week ahead. Mike Thompson from HAO Boulder gave an insight into the study of the Solar interior, including the methods of helioseismology and modelling as ways of learning more about the parts of the Sun which cannot be reached by traditional means of detection. Tuesday’s plenary talks were on cosmology, with a special focus on the recent results from the Planck satellite, from the theoretical point of view by UCL’s Hiranya Peiris, leading us through the process of obtaining the CMB map to the current 6-parameter cosmological model, and from an observational perspective by Catherine Heymans of ROE Edinburgh, emphasising the puzzle of the dark Universe.

Wednesday’s plenaries were dedicated to astronomy at slightly smaller scales: first was Rob Kennicutt Jr. (of the Kennicutt-Schmidt relation) from IoA Cambridge – who, in the morning after a night of whiskey tasting, gave an insightful talk on star formation in the Universe, and down to galactic scales, promoting upcoming data from ALMA to greatly help fill in the unknowns, especially star formation at high redshifts. In the afternoon, we continued on galactic scales, with a discussion by Andy Lawrence of ROE Edinburgh (aka the eAstronomer) on the science done with mega-surveys, focusing around AGN and the high redshift quasar population, such as the furthest quasar known to date (at a redshift of just over 7). Its massive black hole leaves us wondering how it was able to form so early on in the history of the universe, and welcomes the large quasar surveys of PanSTARRS, WISE, UKIDSS and SDSS (and we got a short reminder of the future with Gaia and Euclid).

St. Andrews from the beach!
St. Andrews from the beach!

The parallel sessions ran on average twice a day, and for each of the 11 parallel sessions, we had about six topics to choose from. The areas of science presented in each were from all corners of research represented at the conference, thus for an astrophysics PhD student, the choice would primarily fall on the most relevant session in the group. A number of people from Astro-group chaired and presented talks and posters, as did we – David and Alvina presented talks in the Heating & Turbulence session, which were received well and accumulated some good questions. In addition, David had a poster on his GCMHD+ code for cosmological simulations, for which he won the UKSP student poster competition!

On the 5-hour train home, we’re leaving St. Andrews behind in bright sunshine, and look forward to next years NAM in Portsmouth !

The absorbing life of a final-year Ph.D. student

The absorbing life of a final-year Ph.D. student

Hello, my name is Jason Rawlings and I am a final year PhD student at UCL’s Mullard Space Science Laboratory (MSSL). I am part of the astrophysics group here at MSSL and in this post I will describe the final year experiences of a Ph.D. student at MSSL.

MSSL is the UK’s largest university space research group. The lab resides in the Surrey hills and started life as Holmbury House, built in the 1870’s. The building was transformed into a space lab in the late 1960’s.

MSSL1
A couple of shots of MSSL and its environment.Image

There are many different groups here at the lab, including instrumentation, cryogenics, plasma, planetary, solar and astrophysics. In the astrophysics group, we have a wide range of research topics that include simulations of spiral galaxies, galaxy formation and evolution, X-ray binaries, high-redshift active galactic nuclei and dark matter and dark energy.

With MSSL not being located in London along with the rest of the University, being a student at the lab is a different experience to most Ph.D. students. There are about 30 students here in total and with everyone knowing everyone; this creates a close community atmosphere. Students at MSSL have the opportunity to present their work to each other in a more relaxing environment, without the presence of supervisors or other senior staff, while students in the astrophysics group attend the weekly seminars given by experts in the astronomy field. Outside academia, there are plenty of social activities for students to take part in, with visiting the many local pubs being a particular favourite. Many students also have the opportunity to live in on-site accommodation. An added feature of working at MSSL is that we are treated to a picturesque view of the natural surroundings.

Image
The view of the surrounding Surrey countryside from my office.

As part of the final year of a Ph.D. comes the daunting task of writing your thesis. To describe and condense the work you’ve done in the last 3-4 years is no easy challenge and perseverance is definitely a quality that’s needed in a finishing Ph.D. student. A thesis is broken down into different chapters, with at least three of these presenting original research by the student. Each of these should describe a different project undertaken during the Ph.D. It can help if some of your work has been published in a peer-reviewed journal as this can form the basis of a research chapter. There is a definite learning-curve when doing a Ph.D. and thankfully a lot of progress can be made in the final 12 months when one fully gets to grips with the field they study.

My interests are in infrared and radio extragalactic astronomy and the research presented in my thesis investigates the emission of photons from the formation of stars on a large scale and from active galactic nuclei (AGN)- accreting massive black holes at the centre of all galaxies (see one of our previous blogs here for more information on AGN and star formation). Both processes can emit the photons at the same wavelength and so when observing a particular galaxy, the emission can get mixed in together making it hard to tell which process is the most powerful. Fortunately, we have models that describe how the emission from each process changes with wavelength. By adding these models together and changing their relative strengths, it is possible to create various composite models. These models can then be compared to observational data. From the composite model that agrees with the data the most and the individual model with the greatest strength, one can infer which process is dominating the emission. This is a useful technique and one that I employ in my thesis for different samples of extragalactic radio sources- galaxies with powerful radio emission. The work during my Ph.D. has shown that radio sources with an AGN can have a strong component from star formation which means that they are producing stars at an exceptional rate.

Image
An artist’s impression of an active galactic nucleus. Credit: Aurore Simonnet/Sonoma State University

Throughout a Ph.D. the student encounters various milestones. Now the aim is to reach the final milestone and submit…

Ancient History on Holmbury Hill

Hello my name is Tom Kitching, I am a Royal Society University Research Fellow at MSSL, and my research is focussed mainly on dark energy and cosmic gravitational lensing. However these subjects will be saved for a future blog post :)

Part of the inspiration of the MSSL astronomy blog was that we want to try and convey what an amazing place MSSL is to work. The department is unique in its location, and in this blog we will occasionally share some of our fascination in the environment in which we work. In todays blog post I will talk about some of the ancient history of Holmbury Hill, this first blog on the history of Holmbury Hill should hopefully serve as a taster for more to come.

Holmbury Hill Fort

MSSL is situated on Holmbury Hill which has a rich history going back thousands of years! It is a very short (but quite steep!) walk from MSSL, through Hurtwood (named after the Hurtberry – or Bilberry – which grows there abundantly) to the top of Holmbury Hill. Once at the top you are not only rewarded by the amazing views stretching over the Weald to the South Downs, but also with views of the remains of an Iron Age Hill fort.

From http://www.geograph.org.uk/photo/1317389 Image http://s0.geograph.org.uk/geophotos/01/31/73/1317389_a7dc183f.jpg A view over Holmbury Hill Fort.
From http://www.geograph.org.uk/photo/1317389
Image http://s0.geograph.org.uk/geophotos/01/31/73/1317389_a7dc183f.jpg
A view over Holmbury Hill Fort.

The Iron Age (approx. 1000 BCE to 500 BCE) is the period of human history in western Europe that defines the time when Iron began to widely used in the area. This marked a significant change in technology, from the preceding Bronze Age, because Iron is harder and more resilient than Bronze. At the same time religious, artistic and sociological changes occurred. The most notable Iron Age civilisation were the Romans. On the island of Great Britain the Iron Age was a time of huge transformation, not least is that the region was invaded by the Romans, and preexisting Bronze Age tribes had to adapt. There is a lot of detailed study into this era of human history, here we’ll look at just one aspect of life during that time.

Hill forts are a generic term for settlements, created during the Bronze and Iron Ages, and can be found on top of the many rolling hills and mountains in Britain. Common characteristics are massive Earth works, banks, ditches and mounds, that are thought to have been made for defensive purposes. Within a hill fort are normally found the remains of residential structures, like roundhouses. It is unknown whether people lived in these all year round, or used them only as needed during times when defence was required. They also served as “status symbols” for tribes, and visible structures in the landscape. The fort on holmbury hill is an impressive structure, to walk around the banks and ditches one marvels at how such a structure was created 2000 years ago, and wonders what it was like to live there. The Surrey Archaeological Society have a very nice article on the Hill Fort that goes into much more detail here  http://www.surreyarchaeology.org.uk/content/holmbury-hillfort-survey-report (there is also a nice article here http://www.friendsofthehurtwood.co.uk/index.php?option=com_content&view=article&id=74&Itemid=190). There are some particularly nice quotations for example

“The results of this survey emphasise the skill with which the original builders utilised the existing topography, and also their concern that the monument should be visible from, and overlook, the expanse of the Weald to the south.” link

Indeed Holmbury Hill is one of the highest in the area at 857 feet, with a relatively steep northern face, so one can appreciate the strategic position that the builders choose. It is thought that the Hill fort was built by Belgic tribes and that it was occupied during the middle Bronze Age. The fort was apparently abandoned around the first century BCE, but for reasons unknown.

Context 

Surrey and the surrounding counties are a wonderful place to explore. To place the Holmbury Hill fort in context there are several other hill forts in the area, one of the closest is Anstiebury on the neighbouring Leith Hill. Anstiebury was also buit during the Iron Age, but it is not quite as well defined as Holmbury Hill in some respects, and in the intervening 2000 years a village has grown up around the site!

Another interesting context for the Iron Age is the network of Roman roads and villas in the area. In particular the Roman road Stane Street that ran from the coastal town of Noviomagus Reginorum, or Regnentium, later renamed Chichester to Londinium, later renamed (this translation is easy!) London. In fact there is a spur that comes off Stane Street and runs very close to Holmbury Hill.

From http://www.ordnancesurvey.co.uk/oswebsite/opendata/. Showing the area around Holmbury Hill (marked with a star) and the Roman Roads marked in Red.
From http://www.ordnancesurvey.co.uk/oswebsite/opendata/. Showing the area around Holmbury Hill (marked with a star) and the Roman Roads marked in Red.
The Roman Roads of Britain from http://en.wikipedia.org/wiki/File:Roman.Britain.roads.jpg
The Roman Roads of Britain from http://en.wikipedia.org/wiki/File:Roman.Britain.roads.jpg

‘ologies 

As an astronomer and physicist, archaeology presents a fascinating topic to explore. In fact there are many similarities with astronomy, on the technical side for example each field has a single realization of the data set being analyzed: there are only so many artefacts to be found, there are only so many galaxies in the Universe, so both need to use techniques (for example Bayesian statistics – used in Radiocarbon dating, and cosmological parameter inference) that enable a rigorous analysis in these cases. And both astronomy and archaeology inspire people to investigate the Universe around them, and ultimately help to contextualise our lives; placing us within the Universe or illuminating the history of our civilisations and our species.

From http://www.friendsofthehurtwood.co.uk/ image http://www.friendsofthehurtwood.co.uk/images/thumbnails/images-stories-gallery-pics-holmbury%20hill%20evening-408x273.jpg  A view from the top of Holmbury Hill looking East
From http://www.friendsofthehurtwood.co.uk/ image http://www.friendsofthehurtwood.co.uk/images/thumbnails/images-stories-gallery-pics-holmbury%20hill%20evening-408×273.jpg
A view from the top of Holmbury Hill looking East

On a  warm spring day Holmbury Hill seems like a a very nice place to live, it certainly is a nice place to work. We may never know exactly why people built a hill fort here, or why they left, but over 2000 years later at MSSL we continue to enjoy the environment of Holmbury Hill and can take inspiration from the stories it holds.

Live from the Euclid Meeting!

In this post we have a live report from Sami Niemi, Euclid Visible Imager Instrument Scientist, from the Euclid Consortium Annual Meeting

This blog post discusses briefly the Euclid Mission and Euclid Consortium Meeting held in Leiden on May 13 – 16, 2013.

BACKGROUND

Our very best knowledge, based on many astronomical observables, implies that the Universe we live in is made mostly out of two entities we currently know rather little about. Because we know so little about them we have decided to call them simply dark energy and dark matter. Together these two dark components constitute about 95 per cent of the energy density of the Universe. We do know that these two entities interact with light and with more common material called baryons, we are made out of, via gravity. However, because we have not managed to detect any light from either dark energy or matter (hence the name “dark”), the little knowledge we have managed to gather thusfar is based on indirect probes. It is clearly unsatisfactory to not know about 95 per cent of everything that surrounds us, but how can we make progress on something we cannot directly see?

A part of the astronomical community had acknowledged the lack of knowledge in dark matter and energy already some time ago and hence decided to propose a space mission to the European Space Agency (ESA) to study the dark Universe. After competitive process two proposals were joined to form a single space mission to help solve the mysteries of dark energy and dark matter. The Euclid mission was born.

The Euclid mission will use two complementary probes, namely weak gravitational lensing and galaxy clustering, to study the dark Universe. The launch date for the Euclid mission is 2020. But before we can unravel the mysteries of the Universe, a lot of work is required to make the mission reality.

The Euclid Concept. http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=51317
The Euclid Concept. http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=51317

EUCLID CONSORTIUM

To help make the Euclid mission reality a Euclid Consortium (EC) was founded. The Euclid Consortium consists of scientists, engineers, project managers, and technical staff and it is the largest astronomical community in Europe with about 1150 members. In the current Euclid organisation, the EC is responsible for the definitions of the scientific goals, the science requirements and the Euclid survey. It is also in charge of the design, construction, tests, integration and delivery to ESA of the imaging and spectroscopic instruments (VIS and NISP); the design, development tests, integration and operation of the data processing tools, pipelines and data centers; and the scientific analysis and interpretation of the Euclid data.

Members of the EC are working all the way from hardware to building of large cameras through development of shape and clustering measurement algorithms to finally the cosmological parameters describing the dark energy and dark matter. The Consortium therefore consists of experts from many disciplines. To fully exploit and share the expertise a Consortium level meeting is organised yearly. It is also the place to learn about Euclid and all the cool science it will enable.

EUCLID CONSORTIUM MEETING

I, Sami-Matias Niemi (VIS Instrument Scientist), am writing this blog post from the fourth Euclid Consortium Meeting held in Stadsgehoorzaal in a historic city of Leiden. In many ways the yearly EC meeting is not your typical astronomical science meeting. Firstly, about 400 people participate this years meeting, implying a large astronomical meeting. Secondly, the meeting is a mixture of technical and engineering talks and science presentations from theory to simulations and finally observations. Thus, the meeting is very multidisiplinary and provides enourmous amount of information regarding Euclid.

The Stadsgehoorzaal.  http://commons.wikimedia.org/wiki/File:Stadsgehoorzaal_Leiden.jpg
The Stadsgehoorzaal.
http://commons.wikimedia.org/wiki/File:Stadsgehoorzaal_Leiden.jpg

Now when the first meeting day is behind us, it is safe to say that this years meeting is the largest EC meeting ever. Up to six parallel splinter sessions are running simultaneously, so one must choose carefully to which ones to attend. For the morning part I had decided to catch up on the simulation activities and chose to join the Euclid Simulations splinter session.

Given that it will still be many years before Euclid will see its first light, we currently must rely on lab data and simulations. However, simulations are increasingly important in any astronomical exploitations, not only to predict the performance but also in achieving the scientific accuracy required. For example, to derive the cosmological parameters describing dark matter and energy a suite of simulations are required, so that we can be sure that we have probed the parameter space in an unbiased fashion. Without advancements, both technical and mathematical, the current brute force simulations would require billions of computer hours, so that even with the largest super computers (1 million CPUs) the simulations would still take a decade to run. Clearly advancements are needed to make the problem more manageable.

After the simulation session a few plenary talks were presented. The EC lead Yannick Mellier spoke briefly about the Euclid mission and the milestones since the last year’s meeting. Rene Laureijs (ESA) recapped the Euclid mission history since the selection six years ago, while Guiseppe Racca (ESA) enlightened us about the ESA Euclid management structure. The last plenary session, shared between Jerome Amiaux and Jose Lonrenzo Alvarez, discussed system engineering aspects of this 1 Billion Euro space mission.

In the afternoon more parallel splinter sessions discussing for example photometric redshifts, calibrations, supernova science, and science ready data and catalogues took place. I shall not go into details, but simply say that I was awed by the amount of work that has taken place since the previous meeting. I must however now stop my report, I do have a presentation to give…

Sami Niemi's Euclid VIS Presentation
Sami Niemi’s Euclid VIS Presentation

Observing the heavens from the summit of Mauna Kea

Observing the heavens from the summit of Mauna Kea

Hello, I’m Dr. Missagh Mehdipour, a research scientist at the Mullard Space Science Lab. In this post I will tell you a little bit about my first observing trip to a telescope.

As an X-ray astromoner, I am interested in studying the hottest objects in the universe which radiate in the X-ray energy band. However, as a consequence I don’t often travel to ground-based telescopes to observe them; X-ray astronomy can only be done from space since the Earth’s atmosphere absorbs the X-rays (on the upside those harmful radiations cannot reach us!). So when in the final year of my PhD the opportunity of an observing trip to a ground-based telescope came along, I grabbed it with both hands. My colleague Prof. Mat Page, and I travelled to the James Clerk Maxwell Telescope (JCMT) on the summit of Mauna Kea in the Island of Hawaii.

Fig1
Here is a fine view of Mauna Kea from close to our hotel in Hilo.

With a diameter of 15 m, JCMT is the largest single-dish telescope in the world operating in the sub-millimeter region of the spectrum. With its sensitive instruments it detects light from the coldest materials in the universe, with temperatures of only a few degrees above absolute zero. The observations that we carried out were part of a major survey to study our galaxy and the universe in sub-milimeter wavelengths. Since water vapour in the Earth’s atmosphere attenuates radiation in this part of the spectrum, the high altitude and dry conditions of Mauna Kea (an extinct volcano standing at 4200 m above sea level), makes it the ideal place for submilimeter astronomy. In fact since the creation of an access road in 1964, more than a dozen world-class telescopes have been constructed at the summet, making Mauna Kea one of the most important sites for ground-based astronomy.

 James Clerk Maxwell Telescope (image credit: Joint Astronomy Centre http://www.jach.hawaii.edu)
James Clerk Maxwell Telescope (image credit: Joint Astronomy Centre http://www.jach.hawaii.edu)

Atmospheric pressure at the summit is about 40% less than at sea level; this poses a health risk which can have a range of effects on humans from minor discomfort to life threatening conditions. Therefore we were strongly adviced about sympotoms of altitude sickness and how to prevent it and respond to it. Before travelling to the summit, we stayed at our base camp (known as Hale Pohaku, Hawaiian for “stone building”) on the slope of Mauna Kea for two night to allow us to acclimate to the high altitude. Hale Pohaku at an elevation of 2800 m is a cluster of buildings which includes few dormetories and a main building containing a caferteria, offices, recreation facilities. The many cinder cones and lava rocks in the surrounding areas are testement to the former volcanic activity of the mountain.

Here is a view from top of a cinder cone looking down at the base camp. The zigazagging dirt road to the mountain top can be seen in the distance.
Here is a view from top of a cinder cone looking down at the base camp. The zigazagging dirt road to the mountain top can be seen in the distance.

Our observing program ran for 7 consecutive nights; we would leave our base at 6 pm each night and return by 8 am the following day. After the first two nights, staying up all night became easy! For safety reasons, no one is allowed to spend more than 14 hours above the base camp in a 24 hour peroid. The drive from Hale Pohaku on the winding dirt road to the summit takes about 20 minutes. The view from the top is spectacular; we often saw tourists driving up the mountain to catch a glimpse of the beautiful sunset.

Some of the telescopes at the top of Mauna Kea, including JCMT shown on the far left hand side.
Some of the telescopes at the top of Mauna Kea, including JCMT shown on the far left hand side.

In the couple of days we had before and after our observing run, we visited some amazing places in the Big Island. One interesting location is the Volcanoes National Park. The park is full of mind-bogglingly huge crators and fascinating lava fields. The cracks on the ground from which steam and sulphur gases are expelled are a reminder the region is an active geothermal area. The diverse and beautiful landscape of Hawaii Island makes it a unique place definately worth visiting!

A huge crater in the Volcanoes National Park
A huge crater in the Volcanoes National Park