The eclipse might have been underwhelming in London. But in Svalbard, a Norwegian archipelago far north of the Arctic Circle, the skies were clear, and the eclipse was total. Sitting on a hillside ten kilometres outside Longyearbyen – the northernmost town in the world – is Kjell Henriksen Observatory.

UCL’s Atmospheric Physics Laboratory has instruments at the observatory – and during the eclipse, three UCL scientists (Anasuya Aruliah, Ian McWhirter and PhD student Amy Ronksley) operated them remotely from overcast London.

The instruments study the properties of the uppermost reaches of the Earth’s atmosphere. Near the north and south magnetic poles, Earth’s magnetic field plunges into the atmosphere. The charged particles of the solar wind which are deflected before reaching the atmosphere in the rest of the world are able to interact with atmospheric gases here.

These interactions lead to the phenomenon known as the aurora borealis – or northern lights – and their southern counterparts.

UCL’s instruments at the observatory measure winds and temperatures at an altitude of 240km, where the air is only one ten billionth the density of that at ground level. They do this by detecting the wind’s effect on the aurora.

The two main components of the aurora are green light, produced at an altitude of 90km, and red light, at 240km altitude. Both come from oxygen atoms whose electrons have been excited by the solar wind. As the electrons return to their usual orbits, they produce light of extremely precisely defined colours – much like neon signs or lasers do.

These colours let the scientists determine the speed and temperature of the gases in the upper atmosphere.

They determine the speed by observing how the colour shifts almost imperceptibly towards blue or red, when the wind is blowing towards or away from the observatory. (This phenomenon, known as the Doppler Effect, is also what causes the shift in the pitch of an ambulance siren as it drives past.)

They determine the temperature thanks to the oxygen atoms’ vibration. As the atoms vibrate to and fro, a miniature Doppler Effect makes the light appear slightly redder for the time the atom is moving away, and slightly bluer for the time it is moving towards the observer. This means the light is no longer a perfectly pure shade of red, but encompasses a tiny range of colours – a process known as spectral broadening. The hotter a gas is, the greater the movement, and the greater the spread of colours.

By measuring Doppler shifts and spectral broadening, the UCL instruments produce a complete weather map for the atmosphere at the edge of space.

Alongside the instruments is a colour camera with a fisheye lens, which can see from horizon to horizon, and which produces photos such as the one shown above.

Such measurements can only be done at night, not just because the auroral emissions are swamped by sunlight during the day, but because the sensitive cameras in the instruments would be damaged by sunlight. The eclipse provided a unique, albeit brief opportunity to observe during daytime. Preliminary analysis of the data has indicated strong daytime winds in the upper atmosphere during totality.

And although the scientists weren’t able to see the aurorae they hoped to catch a glimpse of, a fisheye picture they took during the eclipse does show how a small ‘umbrella’ of darkness sat directly above Svalbard, while bright sunlight was visible on the horizon in all directions.

As well as simple scientific curiosity, scientists study the uppermost reaches of the atmosphere (known as the thermosphere) for some very practical reasons. Most satellites orbit within this region, and better data on its properties can help engineers plan their orbital corrections and manoeuvres. Moreover, the interaction between the thermosphere and the solar wind is also a key element of ‘space weather’, which can disrupt electrical and communications infrastructure on the ground.

The information gathered by atmospheric physicists at UCL and elsewhere is helping to improve the computer models of how the upper atmosphere behaves, so that we can better understand these phenomena.

Related links:

• Reports from the team on the UCL Astrophysics Group website
• Kjell Henriksen Observatory on Facebook
• University Centre in Svalbard

 

Hello, I’m Tom Kitching, a cosmologist at UCL’s Mullard Space Science Laboratory. My research involves using the distorting effect of curved spacetime on the images of galaxies to map dark matter in the Universe. In some new research, my collaborators and I have pinned down the nature of dark matter to an unprecedented level of accuracy.

Dark matter is a substance that fills the Universe, and accounts for nearly 95% of all matter that exists – but we have no idea what it is. The name dark matter is however a bit of a misnomer. Dark matter is in fact transparent and doesn’t emit or absorb ordinary light at all. However it does interact with light in a very special way: its gravitational pull bends the light rays around and through it, in a similar way to how a magnifying glass does.

Our new research out now uses that bending effect, known as gravitational lensing, to make maps of dark matter around galaxy clusters.

Galaxy clusters are particularly interesting places because dark matter, galaxies, and hot X-ray gas are all being smashed together as the Universe evolves. What we observe is a snapshot of these collisions, which are the biggest most energetic collisions in the Universe.

By mapping the different components of these collisions we can determine the physical properties of the dark matter. To date this approach had only ever been applied to only a few clusters of galaxies. In our research we applied to this to 72.

With this very large sample we determined that dark matter has to exist in galaxy clusters with a probability of 100,000,000,000,000:1. This is the most definitive detection of dark matter ever.

Using this very information rich data set we managed to measure how dark matter interacts with its self: a property known as its cross-section.

The cross-section measures what happens when two particles bump into each other. From the Earth we can test whether dark matter bumps into ordinary matter and what happens, which gives us clues to what dark matter is. But it’s only in space, around galaxy clusters that we can test what happens when dark matter bumps into itself, a crucial piece in the puzzle. By using this data we measured the cross-section to be smaller than previous experiments.

Related links

• Press release on the UCL Mathematical & Physical Sciences website
• European Space Agency press release (features extra pictures and video)

The Solar Orbiter project has moved a step closer to reality, with the completion of its structural thermal model (STM) this month. UCL is heavily involved with this European Space Agency mission, with the university’s Mullard Space Science Laboratory leading the development of parts of its scientific payload.

The spacecraft is being built at Airbus Defence & Space in Stevenage, just north of London.

The STM is a full-scale model of the spacecraft, which is used for extensive pre-flight testing. Its appearance, structure and design are virtually identical to what will launch in 2018 – the main difference is that the delicate (and costly) electronics are replaced by dummy components that mimic their physical size, weight and properties.

The extensive pre-flight testing, covering potential hazards such as vibration, G-forces and heat resistance (crucial for a solar mission) will be carried out on the STM, to identify potential issues with the flight model before it’s too late.

UCL leads the development of two of the scientific instruments that will fly on board Solar Orbiter.

The Extreme Ultraviolet Imager, with Louise Harra as a co-PI, will image the atmosphere of the Sun, which is heated by our star’s magnetic field. The solar atmosphere is far hotter than the Sun’s surface – an apparent paradox – and Solar Orbiter will aid scientists in their efforts to shed light on precisely why this is.

The Solar Wind Analyser, led by Chris Owen, will study the particles that make up the solar wind. The solar wind is a constant stream of charged particles churned out by the Sun and blown out into the far reaches of the Solar System. It cannot be studied from the ground, as the particles are deflected by the Earth’s magnetic field.

One of the unique features of Solar Orbiter, over all other solar observation missions to date, is that it will give an unprecedented perspective on the Sun. During its mission, it will use Venus fly-bys, each time getting a small nudge from the planet. This will gradually move Solar Orbiter out of the plane of the Solar System – where Earth and all the other planets lie – and by about six years into the mission, it will be in a position to look down onto the poles of the Sun. These have never been seen before, and they are crucial to understanding the Sun’s magnetic field.

Solar Orbiter will also fly telescopes closer to the Sun than any spacecraft before and be able to observe features such as sunspots evolve for weeks at a time, thanks to an orbit that follows the rotation of the Sun.

Solar Orbiter will fly inside the orbit of Mercury, at barely over a quarter of the Earth’s distance from the Sun. This means extremely powerful Solar radiation, bright light and intense heat. Part of the engineering challenge of building the spacecraft is its heat shield, which protects Solar Orbiter’s delicate electronics, shielding them from temperatures of 600 degrees and keeping the internal temperature down to a much more manageable 60 degrees.

The instruments can poke through small openings in the heat shield so as to observe the Sun’s surface without being fried.

Solar Orbiter is scheduled for launch in 2018. The launch vehicle will be provided by the United States. Like many space missions, this is a project of international cooperation.

Links

• An album of freely-useable high-resolution images of Solar Orbiter

 

 

 

These two photographs were taken in the quad during the eclipse. The first at 9:25 the second at 9:31am.

During this time the light dropped by a factor of 16: dropping from an Exposure Value (EV) value of 11 to 7, or 4 stops, to the photographers amongst you.

My eyes told me it got “a bit darker”, the reality was far more!

The clouds didn’t part, but there was a great turnout for the eclipse party in the quad this morning. (So great that all the smartphones made eduroam a bit unreliable – sorry for the occasional breaks in the stream.)

Thanks everyone for coming – and see you for the next big one in 2026!

It’s a setup worthy of Heath Robinson. In a faraway galaxy, a high energy cosmic ray interacts with a photon, producing a series of particle decays eventually releasing a neutrino. The neutrino then crosses billions of light years of space, punching through dust, gas and nebulae without effect. Eventually it reaches Earth, plunges through our atmosphere and finally meets something it cannot pass through: our planet.

When it reaches Earth, scientists hope to detect it. But the complications are only beginning.

High energy neutrino impacts are rare. A cubic kilometre of matter should typically see one roughly once every century. When it does, it triggers a brief and not particularly bright flash of microwave radiation – at the same wavelength and intensity as the flashes from piezoelectric cigarette lighters.

Detect these rare flashes, and you can detect the impact of neutrinos.

Scientists are patient people, and science is no stranger to large and expensive experiments. But building a detector of a cubic kilometre in size, far away from any sources of accidental interference – then waiting potentially a century or more to see a single result – is not reasonable.

Scientists need, somehow, to use the Earth itself as a giant detector, to increase the odds of seeing one.

Searching for somewhere remote enough that the faint signal doesn’t get drowned out, big enough to act as a natural detector, and dry enough not to absorb the microwaves, has taken UCL’s Ryan Nichol to Antarctica three times in the last decade.

There, ANITA (Antarctic Impulsive Transient Antenna), the instrument he works on, circles the South Pole, suspended from a balloon, monitoring a million cubic kilometres of ice for the telltale flash of microwaves that would signal a neutrino detection.

***

Scientists are targeting neutrinos because of what they tell us about cosmic rays.

Cosmic rays are fast-moving particles – usually protons and ions – that bombard the Earth’s upper atmosphere. Some of these move at exceptionally high speeds, up to 99.99999999999999999999% of the speed of light, giving them vast amounts of kinetic energy. A single one of these particles can have the same energy as a cricket ball travelling at 55 miles per hour. But frustratingly, their origins are shrouded in mystery. They must come from some kind of high-energy phenomenon – such as supernovae, black holes or the centres of galaxies – but we can’t figure out what.

Ultra-high energy cosmic rays can travel a long way, but they can’t travel infinitely far. They can interact with photons (light particles), which are everywhere in the Universe, even the vacuum between galaxies. This means that cosmic rays eventually – after about a hundred million light years – come to a halt.

As a result, all the cosmic rays detected in Earth’s upper atmosphere come from a region that includes our galaxy and a few neighbouring ones, but not from the hundreds of billions of galaxies that lie further away. This is by no means a small volume of space, and yet astronomers have come up empty handed when trying to pinpoint the origins of high energy cosmic rays within our cosmic neighbourhood. They need a way of broadening the search.

By looking for high energy neutrinos instead – which are launched like billiard balls by cosmic rays when they interact with photons, but which, unlike them, can cross the void of space without interacting – particle physicists like Nichol hope to extend the search radius from a few tens of millions of light years to several billion.

This should give them a large enough sample to begin to plot where the highest energy cosmic rays are coming from, and see if they can match this up with known objects in the sky that could be causing them.

But first, they need to develop a reliable way of spotting the neutrinos, which is where ANITA comes in.

And for ANITA to do its job, Nichol needs to get to Antarctica. Even in this age of easy international travel, this is not simple. Without any permanent inhabitants, Antarctica has no towns, isn’t visited by scheduled airlines, and even in the brief Antarctic Summer, is still cold and battered by extreme weather.

***

Nichol’s base of operations in Antarctica is McMurdo Station, the largest scientific research station on the continent. It looks like a cross between a mining town and a scruffy university campus – with halls of residence, cafeterias serving mediocre food, and social life centred on a few slightly disreputable bars.

Located on the coast, and served by several runways, McMurdo is one of the gateways to the constellation of smaller research stations dotted around Antarctica. Its summer population tops 1000 – not just researchers, but engineers, cooks, cleaners, drivers – but most of the scientists are just passing through, waiting for connecting flights to more remote stations where they will carry out their research.

For one group of scientists, though McMurdo is perfectly placed: those carrying out research using balloons. High in the sky above the base, a constant, predictable wind blows. Release a balloon into this, and it will gently float in a giant circle around Antarctica, before returning to where it started about two weeks later.

For the first couple of days after ANITA is released, McMurdo base is still in range. ANITA floats high in the atmosphere, around three times the altitude of commercial airliners, and so the base, with all the radio interference that comes from it, remains above the horizon for a long time. But once out of range, the only interference is the occasional chirp from communications satellites high above. ANITA silently watches the ice, recording vast amounts of data, and storing it for analysis later on.

The first two flights have not conclusively detected any high energy neutrinos yet. There has been one tentative detection, but the scientists would want to see several before being confident that they hadn’t just seen a false positive.

This may all change soon. The third flight’s results are on their way home now – and taking a suitably convoluted route back. The December 2014 observations had to be cut short after the balloon blew off course, and the ANITA experiment was jettisoned onto the ice.

Rescued by helicopter and returned to an Australian base, ANITA is now waiting to board the icebreaker Aurora Australis for the journey to Tasmania. The research team hope to get it back next month.

The most recent ANITA mission featured more sensitive instrumentation than the previous two. Given this, the scientists are hopeful – though not certain – that they will get some more tangible results than previous years. They estimate that they should detect somewhere between 0 and 5 high energy neutrino events in this year’s data. So, barring bad luck, the planning, the cold and the years of hard work may just pay off.

***

So if you’re part of the ANITA team, that’s how you detect the highest energy cosmic ray in the Universe. All you need is for it to interact with a photon, emitting a neutrino that flies across billions of years of space before colliding with a water molecule, emitting a flash of microwaves. And for the flash of microwaves to be detected by a sensor suspended from a balloon floating 35km over the most remote and inhospitable region of the world, for the detection to be recorded onto a hard disk, for the hard disk to be dropped onto the ice, then rescued by helicopter, shipped by icebreaker and flown back to the lab, to be decoded by a physicist.

It’s simple, really.

Related links

• ANITA
• Ryan Nichol
• UCL High Energy Physics
• Article on the recovery of the ANITA instrument after its crash landing (including further photos)

Photos

• High resolution photos of McMurdo Station and the ANITA experiment are available from the Faculty of Mathematical & Physical Sciences Flickr library

 

UCL has played a key role in the development of the Dark Energy Survey’s instrumentation, including building a series of lenses that form a crucial component of the Dark Energy Camera. UCL’s Ofer Lahav also serves as co-chair of the Dark Energy Survey science committee.

The Dark Energy Survey team published a new result this week that shows the power of the instrument.

The Milky Way is surrounded by a few dozen dwarf galaxies. Some of these are easy to spot, like the Large Magellanic Cloud, which is visible even to the naked eye as a pale blob in the Southern Hemisphere’s sky, clearly separate from the Milky Way.

Others are much harder to spot, as it is virtually impossible to distinguish their stars from the ones in the foreground, which are part of the Milky Way. Now, the Dark Energy Survey has discovered what appears to be several more. This image shows the challenge in identifying them:

The image shows one of the candidate galaxies, known as DES J0335.6-5403. It sits around 100,000 light years from Earth, and has very few stars, only around 300 could be detected, compared to an estimated 200 billion stars in the Milky Way.

The team were, however, able to analyse the image and mask all the stars that belong to our Milky Way. And when you do that, the dwarf galaxy suddenly jumps out at us:

Although UCL’s involvement in this study was only minor, it shows the power of the instrument and its contribution to the science over the past decade.

• Full details of the research can be found in a news story on the Fermilab website.

Readers familiar with UCL will immediately recognise the Slade School of Fine Art – the North Wing on UCL’s historic (and grade I listed) quadrangle. What they may not know is that the building, which dates back to the 1870s, was originally also home to UCL’s Department of Chemistry.

It was in this building that some of UCL’s most famous contributions to chemistry were made: William Ramsay and his successor J Norman Collie both worked here.

In fact, as far as we can work out, it is the building in the world which has seen the discovery of the greatest number of chemical elements. Ramsay discovered argon, neon, krypton and xenon while working here, as well as isolating helium (which had been seen in the spectrum of the Sun, but not observed here on Earth) and radon. These elements are together known as the noble gases, and Ramsay’s discoveries secured for him the 1904 Nobel Prize in Chemistry – UCL’s first.

In 1913, the year of Ramsay’s retirement, UCL’s Chemistry department moved to a new purpose-built lab immediately behind its old home. The building – which still houses some of the department’s laboratories and offices – is now named after another towering figure in chemistry: Kathleen Lonsdale.

After a century of heavy use and piecemeal remodelling, the building is looking a little tired . A multi-million pound complete refurbishment of the building is planned to begin later this year.

Links

• UCL Chemistry

High resolution image

• A high-resolution image can be downloaded from Flickr

 

Guest post by Anita Heward

The potential for exoplanet research to inspire students and widen participation at university from under-represented groups will be highlighted today at 11 Downing Street.

Dr Clara Sousa Silva, who completed her PhD at UCL last year, has been invited to give a four-minute presentation during an event hosted by the Chancellor for Your Life and Researchers in Schools (RIS). Clara is currently participating in the RIS teacher training and professional development programme.

The programme builds links between universities and schools by training researchers that have completed PhDs to become classroom teachers, while supporting them for 20% of their time to pursue academic interests. Clara is training as a physics teacher at Isleworth and Syon School for Boys and, through the RIS programme, is continuing aspects of her research into atmospheric characterisation of cool stars and exoplanets.

Clara also heads up the education programme for Twinkle, a UK space mission that will characterise exoplanet atmospheres using an instrument led by UCL.

EduTwinkle will draw on Clara’s experiences with RIS and the Brilliant Club to foster a productive relationship between space exploration and British schools, increase girls’ uptake of STEM subjects at A-level and higher education and to widen participation at universities from under-represented communities.

• Anita Heward is press officer for the Twinkle Space Mission