The landing site for Philae, the lander component of the Rosetta mission, has been chosen and is marked here with a white cross. Photo credit: ESA

The Rosetta mission, which for the past decade has been on a long and convoluted journey to Comet C-G, has recently reached its destination. It is the only artificial object ever to enter orbit around a comet, and is currently circling around it at an altitude of around 30km. (The cometary nucleus itself is around 4km across.)

Part of Rosetta’s mission is to measure the properties of the plasma (electrically charged gas) that surrounds the comet. To this end, the spacecraft features a suite of five sensors built by the Rosetta Plasma Consortium, a scientific collaboration that includes UCL’s Prof Andrew Coates.

But as well as measuring the plasma around the comet, Rosetta will attempt something never achieved before: it will release a lander that, later this year, will touch down on the comet’s surface. The European Space Agency has today announced the site that the lander, known as Philae, will aim for: a spot known as Site J, pinpointed in the photo above with a white cross. The landing site was chosen as the best compromise between safety (the surface of the comet is uneven in places and could damage the probe) and scientific interest (some parts are more active than others).

Copyright: ESA images are free to use providing they are credited, do not imply endorsement by ESA, do not feature identifiable individuals, and are not used in advertising or promotional materials.

Links

• UCL Mullard Space Science Laboratory
• Article on the ESA website

High resolution images

• Download high-resolution images from Flickr

Cover of Phobos: Close Encounter Imaging from the Viking Orbiters

This week’s Picture of the Week comes from UCL’s planetary science archives, and their rich collection of early NASA space images. Many of these are not available anywhere online, and some of them are hidden behind rather unpromising covers (see above).

The Viking missions to Mars, two identical spacecraft launched a few weeks apart in 1975, are well known for making the first successful landings on the surface of the red planet. But the Viking orbiters were important too, mapping the surface of the planet and observing its moons, Phobos (fear) and Deimos (dread).

This NASA book from 1984, entitled Phobos: Close Encounter Imaging from the Viking Orbiters is a comprehensive album of the observations the programme made of Phobos, the larger of the two moons.

This picture shows a typical spread, produced during the flyby of Phobos on May 26, 1977 by Voyager Orbiter 1.

Phobos from Viking 1

Although it is the larger of the two moons of Mars, Phobos is still very small, and seems likely to be an asteroid captured by Mars’ gravity, rather than a moon formed at the same time as its parent planet.

A fraction of the size of Earth’s Moon, its gravity is not strong enough to have pulled it into a sphere, leaving the irregularly-shaped object visible here.

A Russian mission to land on Phobos and return a sample to Earth, Fobos-Grunt, malfunctioned shortly after launch in November 2011 and never left Earth orbit.

Links

• UCL Regional Planetary Image Facility
• Snapshots from Space History (more photos from UCL’s planetary science archives)
• UCL Centre for Planetary Sciences
• Videos and photos of Phobos and Deimos seen from the Martian surface, taken by the Curiosity Rover

High resolution image

• Download high-resolution images from Flickr

This image shows one possible scenario for the distribution of light in the cosmos. Photo credit: Andrew Pontzen/Fabio Governato

Figuring out what the structure of the universe is surprisingly hard. Most of the matter that makes up the cosmos is totally dark, and much of what is left is in tiny, dim galaxies that are virtually impossible to detect.

This image shows a computer simulation of one possible scenario for the large-scale distribution of light sources in the universe. The details of how light (and hence galaxies and quasars) is distributed through the cosmos is still not a settled question – in particular, the relative contributions of (faint but numerous) galaxies and (bright but rare) quasars is unknown.

A faint dwarf galaxy

(New research from UCL cosmologists published last week shows how we should be able to find out soon.)

However, astronomers know that on the largest scales, the universe is structured as a vast web made up of filaments and clusters of galaxies, gas and dark matter separated by huge, dark voids. Observational astronomy is making strides forward in mapping out these structures in gas and light, but the smallest galaxies – less than a pixel across in the image above – might never be seen directly because they are simply too faint.

A Hubble image of a nearby faint dwarf galaxy (right) shows the challenge involved in observing these objects even when they are in our galaxy’s vicinity.

These computer models are one way of trying to extrapolate from what we know to what is really there. New research from UCL now shows how we can also use future observations of gas to find out more about this elusive population of tiny galaxies.

This simulated image shows the distribution of light in an area of space over 50 million light-years across. The simulation was created by Andrew Pontzen of UCL and Fabio Governato of the University of Washington.

Links

• UCL Physics & Astronomy
• UCL News story on finding the origin of the universe’s light
• In depth profile of the research on the UCL Mathematical & Physical Sciences website

High resolution image

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The Dark Energy Survey, which has just begun its second year of observations, is gathering data about one of the most puzzling phenomena to be discovered in the past century: that the universe is not only expanding, but is doing so at an ever faster rate. Some as yet unknown force dubbed ‘dark energy’ is driving this acceleration.

Dark energy affects the appearance and evolution of the universe on very large scales. The Dark Energy Survey aims to find out more about this phenomenon by studying measuring four key cosmological probes:

• The number of galaxy clusters;
• The distances to faraway supernovae;
• The bending of light by gravitational lensing;
• and the pattern of the distribution of galaxy clusters across the universe.

Observing these requires sharp images that can detect very distant (and hence faint) objects, and so the the images collected by the Dark Energy Camera, the survey’s workhorse, are often quite stunning.

This image of the NGC 1398 galaxy was taken with the Dark Energy Camera. This galaxy lives in the Fornax cluster, roughly 65 million light-years from Earth. It is 135,000 light-years in diameter, just slightly larger than our own Milky Way galaxy, and contains more than a billion stars. Credit: Dark Energy Survey.

To mark the beginning of the second year of DES’s five-year observing run, the team have published a gallery of the most attractive images from the first year of operation, including the image of galaxy NGC 1398, pictured above. The complete the gallery is at the end of this post and in the faculty Flickr gallery.

UCL is deeply involved in DES, and Prof Ofer Lahav, Vice-Dean (Research) of Mathematical & Physical Sciences, is chair of the DES UK board and co-chair of the DES international science committee.

More information on UCL’s involvement in the DES science programme is available in an article on the UCL news pages.

Gallery

Copyright: Dark Energy Survey photos are free to use providing they are credited to the Dark Energy Survey. Any queries on reuse should be sent to Fermilab Visual Media Services at vismedsr@fnal.gov.

Links

• UCL Physics & Astronomy
• Dark Energy Survey
• UCL News story on the Dark Energy Survey

High resolution images

• Download high-resolution images from Flickr

In Fermilab, just outside of Chicago, an intense beam of neutrinos leaves a particle accelerator. Less than one hundredth of a second later, the neutrinos reach Northern Minnesota, over 700 kilometres away. Here, scientists and engineers are developing a number of large experiments to help them understand the properties of neutrinos – currently an area of considerable uncertainty in the world of physics.

One of these is a device known as CHIPS-M, pictured here at dawn on 1 August, just before it was deployed underwater in the flooded Wentworth-W mine pit in the background.

The CHIPS-M detector at dawn, on the day it was deployed in the flooded mine pit in the background. Photo courtesy Jerry Meier (University of Minnesota)

(This pit belongs to Cliffs Natural Resources who have kindly granted access and the land where the detector and control-shed are sitting has been provided by PolyMet Mining.)

This neutrino detector may look large (it is a 3.5m x3.5m cylinder), but it is in reality a small-scale prototype for a device which will be many times larger. The team developing the instrument is led by Prof Jennifer Thomas (UCL Physics & Astronomy).

Neutrinos barely interact with normal matter. Even though we know vast numbers of them pass through the Earth thanks to their production in nuclear reactions in the Sun, detecting even a single neutrino is extremely challenging, and larger detectors improve the odds of seeing one by increasing the amount of matter in their path.

Neutrino detectors can work in a number of ways. CHIPS-M works through detecting Cerenkov radiation which is produced in the water inside it. Like all methods of detecting neutrinos, it is indirect.

CHIPS-M consists of a large bag storing 50 tonnes of water, equipped with highly sensitive detectors, like the ones used in the IceCube Experiment in Antarctica,  that can pick up the tiniest flashes of Cerenkov radiation. When a muon-neutrino enters water, very occasionally, it will interact with the water and produce  a charged muon. Sometimes the muon-neutrinos oscillate into electron neutrinos and they can produce a charged electron. Both of these charged particles, if they have enough energy,  move through the water faster than light can. The electromagnetic wake these particles leave behind them is visible as a brief flash which can be picked up by the detectors.

In order to minimise false-detections caused by cosmic rays, energetic particles that come from space, CHIPS-M is placed 60 metres deep at the bottom of a flooded mine pit: the water above it shields it from some of this interference as indeed does the orientation of the photo-detectors inside the bag.

The CHIPS-M detector being lowered into the mine pit and filled with water. In the boat is UCL physicist Prof Jennifer Thomas. Photo courtesy Jerry Meier (University of Minnesota)

And yet despite this shielding, over the year-long experiment, it is estimated that it will detect around 170,000 cosmic rays and just 20 neutrinos. Any positive identification of neutrinos in this period is in reality just icing on the cake, though – the primary objective of CHIPS-M is as a test-rig for technologies that will be used in future, for instruments far larger and more sensitive than this.

Links

• UCL High Energy Physics
• Fermilab

High resolution images

• Download high-resolution images from Flickr

Artist’s concept of Mars 2020, a proposed NASA mission to Mars. UCL is part of the consortium building the stereoscopic camera. Photo credit: NASA (public domain)

Mars 2020 is a planned NASA Mars rover, which will be built to an almost identical design to the Curiosity rover currently exploring the Martian surface. NASA has just announced the scientific payload, and it will include Mastcam-Z – a stereoscopic zoom camera which will be built by a consortium that includes UCL.

Mastcam-Z is the pair of square ‘eyes’ on the bottom of the rover’s ‘head’ as shown on this diagram.

Labelled diagram showing the location of the instruments on Mars 2020, a proposed NASA mission to Mars. UCL is part of the consortium building the Mastcam-Z stereoscopic camera. Photo credit: NASA (public domain)

UCL are responsible for developing a test environment for laboratory simulations of stereo measurements, and deriving accuracy estimates for rover operations from this. Prof Andrew Coates (UCL Mullard Space Science Laboratory), who is one of the co-investigators (scientific leaders) on the project will also play a leading role in science requirements specification and exploitation, and comparison with other missions including ExoMars.  His scientific focus will be atmosphere-surface interactions.

Many congratulations to the whole team, and in particular to Prof Coates, on this success.

UCL is already leading the consortium building PanCam, the main panoramic camera on the European ExoMars probe, which will launch in 2018.

We’ll check back in on the progress of both of these projects as the design, construction and testing moves forward.

Links

• Mars 2020
• NASA news release
• UCL Mullard Space Science Laboratory

High resolution images

• Download high-resolution images from Flickr

A two-photon event captured in the ATLAS experiment at CERN. This is one of the experiments that analyse particles accelerated and collided in the Large Hadron Collider, and played a key role in the discovery of the Higgs Boson. Photo credit: CERN (CC-BY-SA 4.0)

Peter Higgs, who predicted the existence of the Higgs Boson in the 1960s, is usually associated with the University of Edinburgh, where he spent most of his career. But we want to claim just a little credit for ourselves: Higgs briefly worked as a lecturer in UCL’s Department of Mathematics in 1960 (four years before postulating the existence of the particle that bears his name), and was awarded an honorary degree by UCL in 2010 (three years before winning the Nobel Prize in Physics). Clearly there is a correlation.

A more concrete and less contrived contribution by UCL to the discovery of the Higgs Boson comes from UCL’s involvement in the ATLAS experiment at CERN. Along with the CMS experiment (also at CERN), ATLAS finally provided concrete experimental corroboration of the existence of the Higgs particle in 2012.

A rendering of an experiment using ATLAS provides this week’s UCL Science Picture of the Week.

Numerous UCL physicists have been involved with the ATLAS project over the  years, and when the collaboration’s paper setting out the evidence it had found for the Higgs Boson was published, 24 members of the Physics & Astronomy department were listed among the (many) authors on the paper.

Jon Butterworth, head of physics at UCL and a major participant in the ATLAS collaboration, will be hosting an evening of particle physics at UCL on 20 August 2014. Introducing the Large Hadron Collider, a virtual visit to CERN hosted by David Miller of Chicago University, a talk by TEDx speaker Lily Asquith about sonificiation of LHC data, and a Q&A session in which you can ask all your burning particle physics questions, the event is free and suitable for everyone from ages 12 up.

Links

• Booking page for ‘An Evening of Particle Physics’ with Prof Jon Butterworth
• ATLAS collaboration paper
• UCL Physics & Astronomy
• UCL High Energy Physics research group

High resolution image

• Download a high-resolution image from Flickr
• Download a high-resolution image from CERN Document Server

CERN have made available thousands of pictures, videos and photos of their work that are well worth checking out, all of which are totally free for educational and informational use. They even have a collection of photos – including this one – which are available under Creative Commons licences, which have even fewer restrictions on their reuse.

Intensity landscape of x-ray speckles.

Counterintuitively, scrambling X-rays can help scientists make better X-ray images.

New research from an international collaboration including Pierre Thibault (UCL Physics & Astronomy) uses the random speckles of scrambled X-rays to produce improved images of objects when X-rays are passed through them.

The location and brightness of the speckles encodes information about the object being studied, allowing a detailed image to be reconstructed.

Today’s Picture of the Week shows the intensity (shown as the height and colour) and position of X-ray speckles detected in an experiment that was carried out as part of this research.

Photo credit: I. Zanette (TUM). This photo may be freely reproduced for the purposes of news reporting of this research, but it is not released under a Creative Commons licence.

Links

• Press release on the research, including further images
• UCL Physics & Astronomy

High resolution image

• A high resolution image is available on Flickr

We hear a lot about 3D printing as the future of manufacture, but it’s also finding many applications in research.

Today’s picture of the week shows three of the uses researchers at UCL Engineering are finding for additive manufacture.

Examples of research objects created using 3D printing at UCL Engineering

On the left, a model submarine printed by a student in Naval Architecture lets them see their designs in 3D. In the middle, UCL computer scientists experiment with the exciting new problem of creating virtual models that can be printed out with movable, posable parts; and on the right, a section of 3D printed skull, recreated from scans by researchers at UCL Medical Physics based within UCLH, enables surgeons to plan their operations.

Just for fun: old school meets new tech: a chimp skull from UCL’s Bioanthropology Collections next to a high-tech 3D print of a modern human from UCL Medical Physics. Will 3D printed skulls be the future of anatomy teaching?

All of these models were printed using a method called Selective Laser Sintering (SLS). This is a kind of 3D printing that uses lasers to melt bits of a polymer powder together in the shape of a cross-section through the object you want to print. Then, a layer of power is added on top, and another layer melted. If it is resting on powder, that powder will just brush off when the plastic model is removed: if it is resting on a previously melted bit, it will stick to it.

This is a more expensive way to 3D print than the hobby-level 3D printers which are more commonly seen, which basically squeeze out layers of plastic like toothpaste, stacking them up into shapes . However, it allows the printing of more complicated shapes, with overhangs and interpenetrating parts – so it’s really handy for detailed research uses. UCL has a number of 3D printers, some free for all our staff and students to use in our open access Makespace.

Semiconductors are the basis of almost all the electronics we are used to today. Transistors are tiny switches (often microscopic) which govern how electricity flows through a device, thanks to their variable electrical conductivity. Putting many transistors in sequence means the flow of electrons through the circuit can begin to follow logical rules and make calculations – the basis of all computing. Even small devices like smartphones can today contain over a billion transistors squeezed onto the tiny chips inside them.

But electronics existed before semiconductors. The transistor was invented in the late 1940s, and only became widely used in the mid 1950s, a decade after the invention of electronic computers.

Early electronic devices, including the first computers such as Colossus and ENIAC, relied instead on thermionic valves.

A small electronic valve manufactured by Mullard. (This is the same Mullard that endowed UCL’s Mullard Space Science Laboratory). Photo: O. Usher (UCL MAPS)

Dating back to the early 20th century, valves can carry out the same functions as semiconductors do today, acting as switches and diodes. But the principles they work on are totally different – instead of exploiting the quantum properties of semiconductors, valves use brute force: glowing hot filaments that flood the valve with electrons.

This means they are extremely energy-inefficient – the ENIAC computer, with just under 18,000 valves (compare this to over a billion transistors in an iPhone) drew 150 kilowatts of power. A typical oven uses around 2 kW, a modern laptop computer uses less than 0.1 kW.

This high power consumption also means that valves look a lot like another device with a glowing filament, appalling energy efficiency and vast production of waste heat: the filament light bulb. (Like old-style light bulbs, valves also regularly burn out and need to be replaced.)

A selection of larger thermionic valves found in UCL Chemistry. Photo: O. Usher (UCL MAPS)

Valves were widely used for electronic applications in university labs until their relatively sudden obsolescence in the 1950s left unused stocks in store rooms. They still occasionally turn up when cupboards are cleared out – including a large haul of several crates of mint-condition valves recently found in UCL’s Department of Chemistry, pictured here. These are of little use for research today, but they are of great historical interest, not least for restoring and repairing old electronic devices.

Dekatrons (counting tubes) were widely used in early computers including the Harwell Dekatron Computer, which is now at the National Museum of Computing.

For this reason, the valves have been donated to the National Museum of Computing at Bletchley Park.