Detectors in Your Pocket

The Earth is under constant bombardment. Not from aliens but from extrememly energetic electrons, protons and others sub-atomic particles. Some of these come from the Sun but the origin of many is unknown. The sources of the highest energy cosmic rays have been a subject of research for many years and has led to huge cosmic ray detectors such as the Pierre Auger Observatory and HESS which monitor the showers of particles created when a cosmic ray hits our atmosphere. However, you don't need a hugely expensive cosmic ray detector to spot cosmic rays.

Everyone who has looked at raw images from a telescope's CCD camera will probably have seen the effects of cosmic ray hits. These happen when a high-energy particle, from the shower created in the upper atmosphere, hits a pixel on the CCD detector. This tends to saturate that pixel or it can even leave a little saturated track if the particle is travelling at an acute angle to the CCD chip. You tend to see more of these cosmic ray hits the higher you are above sea level as you get closer to the top of the particle shower. Most astronomers tend to find cosmic ray hits an annoyance as they can mess up your observations and measurements. The cosmic ray hits are usually removed and then forgotten about. However, I had a sudden thought this evening; there is data there. What if you could make use of all those rejected cosmic ray hits to do some science?

Most astronomical images taken with CCDs will be saved with information such as the time, the location on the ground and the orientation of the camera on the sky. If we could extract the cosmic ray detections (and directions?) from the many astronomical telescopes in existence it would probably be possible to do something interesting depending on the density of CCD detectors in time and space.

Whilst thinking about the potential for this idea, Mark Stacey from Johannesburg pointed out that someone has already thought about it and decided to use mobile phones as a massively distributed observatory. The people behind Distributed Observatory have created an Android application that uses a phone's CMOS or CCD chip to look for cosmic ray impacts and report them back to a central site. It is a neat idea and the site FAQ says the app could be left running with your phone faced down whilst charging at night. However, Mark has tried the app out and says that it eats battery life and development seemed to stop in November last year. The project is open source though so others could always contribute towards it.

Posted in astro blog by Stuart on Monday 29th Nov 2010 (18:16 GMT) | Permalink

Linking Data

This post is adapted from a post on my work site.

The world wide web has provided the ability for anyone to make a website and link it to any other. This openness, and the ground-up approach of making the sites and links, has led to the mass of interconnected web pages we see today. It is one of the strengths of the web. However, as more and more data makes its way online, computers are finding it difficult to fully understand the connections between different data sets. That is where Tim Berners-Lee's idea of Linked Data comes in. Linked Data is a way of describing and storing data on the web so that others (people or computers) can see how data on web page A is/are connected (concept-wise) to data on web page B.

I like the idea but for a while I’ve been hitting a problem. I couldn't work out how to actually go about creating Linked Data or using it. Most of the websites about Linked Data are very technical and launch into talk of specifications, schemas and ontologies at the slightest provocation. That sort of stuff scares me as it isn't usually written for people that don't already understand it and often seems to lead to an endless chain of documents to read. If, after two or three hours of reading technical documents, I still don't know how to do something basic, I tend to go find something else to do.

That is where I was with Linked Data a couple of weeks ago; nice idea but not a clue how to get started. Then, via a conversation with Doug Burke, I noticed that schools in England and Wales have been included in the UK government’s first foray into Linked Data (Scotland and Northern Ireland have separate education systems and aren’t included yet). As my new job at LCOGT has many school users in the UK (through the Faulkes Telescope Project), that seemed like a good place for me to finally get my feet wet. provides web addresses (URIs) - for each school. At a page for a specific school (e.g. Clifton High School) data about that school can be seen and, importantly, understood by special software. To get started I had to find the URI for each school that was in the LCOGT database. This involved learning some SPARQL (apparently similar to SQL or MYSQL) so that I could search their school database. It turned out that our own data quality wasn’t great with some schools being listed with slightly different names, numbers or postcodes compared to those in the government database. However, after a bit of manual effort, we got URIs for 684 schools. That meant we could start doing some interesting things.

The first thing I did was to download the longitude and latitude of every school that we had a Linked Data address for. I then gridded these and made a heat map (the redder an area, the more schools are in that bit of the country) for English and Welsh schools. The result looks fairly similar to a map showing population density so the good news is that the Faulkes Telescope Project doesn't appear to have much bias in which parts of England and Wales register.

That shows the start of what is possible once data get linked. Of course, at this point we were just consuming Linked Data and I thought I should help create some. So we added some Linked Data within the web pages for observations and users. Although not visible to a person viewing the web page it does show up in special software.

Last week I started to experimenting with sharing data properly through a special Linked Data file type known as RDF. I’m still not entirely sure of the best way to put information into RDF yet but I’m creating examples of how it might look and hoping some Linked Data experts might be able to give me some pointers (i.e. corrections rather than links to yet more documentation).

These are just the first baby steps towards making Linked Data at LCOGT. I've already started wondering what we could do if the Simbad or ADS databases provided Linked Data.

Posted in astro blog by Stuart on Monday 29th Nov 2010 (15:54 GMT) | Permalink

The First 500

Plenty of interesting astronomical things have happened recently but one particularly caught my eye this evening. I saw a tweet from @Exoplanetology exclaiming that the number of candidate exoplanets has now exceeded 500!

The first planet around a "Sun-like" star was announced in 1995 and progress was slow to start with. I remember being impressed when we passed the 200 mark back in April 2007. Since then missions such as Kepler have become exoplanet discovery machines, we have had direct observations of exoplanets, and even amateur astronomers are now able to detect exoplanets from their back gardens. How far we've come in only 15 years. I expect the next 500 will be found in a much shorter time. We should probably start thinking of some nice names.

Here's to all the scientists that have contributed to the discovery of the first 500. Cheers!

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Posted in astro blog by Stuart on Saturday 20th Nov 2010 (21:34 GMT) | Permalink
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