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.

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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

Press Release: Herschel shows galaxies had cool beginnings

Beginnings and Endings for Herschel this week:

Recently we heard the news that the Herschel Observatory has run out of Helium, required to cool the telescope

To celebrate the success of Herschel we post here a copy of the article featuring on the UK Herschel site herscheltelescope.org.uk, as a press release for Symeonidis et al. 2013 (MNRAS, 431, 2317), which was published on May 1, 2013.

Herschel shows galaxies had cool beginnings

Observations from the Herschel Space Observatory have shown that galaxies in the early Universe were cooler than those we see around us today. This indicates that early galaxies were more bloated, containing more dust, distributed over larger regions.

Around a thousand galaxies were studied, chosen because they are very distant and forming stars at very high rates. Because they are so distant, the galaxies are seen as they were when the Universe was much younger, with those studied here spanning a range of cosmic times between 1 and 10 billion years ago – a significant portion of its fourteen billion year history

Most of these galaxies are seen when the Universe was about half its current age, a period during which galaxies tended to be much more “active” than those we see around us today, with some forming stars hundreds or even thousands of times faster than our Milky Way. Although rare, such “starburst galaxies” have produced as much energy over the course of cosmic history as all the other galaxies combined. This makes them crucial for studying the history of star formation in the Universe.

Stars form from massive clouds of gas and dust, and these early galaxies have large quantities of both. Most of the dust in these galaxies is cold by human standards, at temperatures of around −240 Celsius, and so can only be seen at far-infrared wavelengths. Using Herschel’s cameras, astronomers are able to study the properties of the dust and deduce the average conditions within each galaxy.

“These galaxies are all but invisible to optical telescopes, but Herschel sees the far-infrared glow from their dust,” says Dr Myrto Symeonidis, who led and carried out the research at UCL and is currently based at the University of Sussex. “With so many galaxies in the Herschel images, we can start to look at how galaxies have changed over the history of the Universe.”

The newly formed stars in these galaxies heat up the dust, so galaxies which form stars more rapidly are expected to have higher dust temperatures overall.  But the surprise for astronomers was that the galaxies in the younger Universe appeared cooler than those seen today. “There are two explanations for this surprising result,” explains Dr Symeonidis. “Either the earlier starburst galaxies were much larger than we thought, or they contain greater quantities of dust than predicted. In either case, they are different from those we see around us today.”

These results used images and data from Herschel’s two cameras, PACS and SPIRE. By studying seemingly blank regions of sky for long periods of time, these revolutionary instruments picked out the light from thousands of galaxies in the early Universe.

“Previous assumptions have generally assumed that these early starburst galaxies were similar to those in the local Universe,” commented Prof Seb Oliver, University of Sussex, who leads “HerMES”, one of the Herschel surveys used in this study. “What we’ve shown here is that this wasn’t always the case, we need to look more carefully at the conditions in these early galaxies”.

“This work brought together some of the best data collected over Herschel’s four year lifetime, showcasing the immense advances we can make in understanding how stars form and under what conditions”, points out Dr Dieter Lutz, from the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, who leads the “PEP” survey.

“Herschel’s cameras have provided unrivalled views of the early Universe, allowing us to study the distant past in unprecedented detail,” says Prof Matt Griffin, of Cardiff University, the lead scientist of the international team which designed, built and operated the SPIRE instrument on board Herschel. “We’ve only scratched the surface of the immense Herschel data archive, and there is undoubtedly much, much more to come”, he concludes.

These results are published in the 1st May 2013 edition of the journal Monthly Notices of the Royal Astronomical Society: Symeonidis et al (2013) MNRAS 431, 2317

image1
One of the regions of sky studied by Herschel, seen towards the constellation of Ursa Major and containing hundreds of distant starburst galaxies. This patch is around the size of the full Moon as seen from Earth. Image credit: ESA/Herschel/SPIRE/HerMES
High-res
The galaxy Messier 82, the closest example of a “starburst galaxy”, seen by NASA’s Spitzer satellite. Image credit: NASA/JPL-Caltech High-res: http://www.spitzer.caltech.edu/uploaded_files/images/0008/6785/ssc2006-09a1.jpg
The galaxy Messier 82, the closest example of a “starburst galaxy”, seen by NASA’s Spitzer satellite. Image credit: NASA/JPL-Caltech
High-res