From Imperial College London: “New type of photosynthesis discovered”

Imperial College London
From Imperial College London

15 June 2018
Hayley Dunning

1
Colony of cells where colours represent chlorophyll-a and -f driven photosynthesis. Dennis Nuernberg

The discovery changes our understanding of the basic mechanism of photosynthesis and should rewrite the textbooks.

It will also tailor the way we hunt for alien life and provide insights into how we could engineer more efficient crops that take advantage of longer wavelengths of light.

The discovery, published today in Science, was led by Imperial College London, supported by the BBSRC, and involved groups from the ANU in Canberra, the CNRS in Paris and Saclay and the CNR in Milan.

The vast majority of life on Earth uses visible red light in the process of photosynthesis, but the new type uses near-infrared light instead. It was detected in a wide range of cyanobacteria (blue-green algae) when they grow in near-infrared light, found in shaded conditions like bacterial mats in Yellowstone and in beach rock in Australia.

As scientists have now discovered, it also occurs in a cupboard fitted with infrared LEDs in Imperial College London.

Photosynthesis beyond the red limit

The standard, near-universal type of photosynthesis uses the green pigment, chlorophyll-a, both to collect light and use its energy to make useful biochemicals and oxygen. The way chlorophyll-a absorbs light means only the energy from red light can be used for photosynthesis.

Since chlorophyll-a is present in all plants, algae and cyanobacteria that we know of, it was considered that the energy of red light set the ‘red limit’ for photosynthesis; that is, the minimum amount of energy needed to do the demanding chemistry that produces oxygen. The red limit is used in astrobiology to judge whether complex life could have evolved on planets in other solar systems.

However, when some cyanobacteria are grown under near-infrared light, the standard chlorophyll-a-containing systems shut down and different systems containing a different kind of chlorophyll, chlorophyll-f, takes over.

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Cross-section of beach rock (Heron Island, Australia) showing chlorophyll-f containing cyanobacteria (green band) growing deep into the rock, several millimetres below the surface. Dennis Nuernberg

Until now, it was thought that chlorophyll-f just harvested the light. The new research shows that instead chlorophyll-f plays the key role in photosynthesis under shaded conditions, using lower-energy infrared light to do the complex chemistry. This is photosynthesis ‘beyond the red limit’.

Lead researcher Professor Bill Rutherford, from the Department of Life Sciences at Imperial, said: “The new form of photosynthesis made us rethink what we thought was possible. It also changes how we understand the key events at the heart of standard photosynthesis. This is textbook changing stuff.”

Preventing damage by light

Another cyanobacterium, Acaryochloris, is already known to do photosynthesis beyond the red limit. However, because it occurs in just this one species, with a very specific habitat, it had been considered a ‘one-off’. Acaryochloris lives underneath a green sea-squirt that shades out most of the visible light leaving just the near-infrared.

The chlorophyll-f based photosynthesis reported today represents a third type of photosynthesis that is widespread. However, it is only used in special infrared-rich shaded conditions; in normal light conditions, the standard red form of photosynthesis is used.

It was thought that light damage would be more severe beyond the red limit, but the new study shows that it is not a problem in stable, shaded environments.

Co-author Dr Andrea Fantuzzi, from the Department of Life Sciences at Imperial, said: “Finding a type of photosynthesis that works beyond the red limit changes our understanding of the energy requirements of photosynthesis. This provides insights into light energy use and into mechanisms that protect the systems against damage by light.”

These insights could be useful for researchers trying to engineer crops to perform more efficient photosynthesis by using a wider range of light. How these cyanobacteria protect themselves from damage caused by variations in the brightness of light could help researchers discover what is feasible to engineer into crop plants.

Textbook-changing insights

More detail could be seen in the new systems than has ever been seen before in the standard chlorophyll-a systems. The chlorophylls often termed ‘accessory’ chlorophylls were actually performing the crucial chemical step, rather than the textbook ‘special pair’ of chlorophylls in the centre of the complex.

This indicates that this pattern holds for the other types of photosynthesis, which would change the textbook view of how the dominant form of photosynthesis works.

Dr Dennis Nürnberg, the first author and initiator of the study, said: “I did not expect that my interest in cyanobacteria and their diverse lifestyles would snowball into a major change in how we understand photosynthesis. It is amazing what is still out there in nature waiting to be discovered.”

Peter Burlinson, lead for frontier bioscience at BBSRC – UKRI says, “This is an important discovery in photosynthesis, a process that plays a crucial role in the biology of the crops that feed the world. Discoveries like this push the boundaries of our understanding of life and Professor Bill Rutherford and the team at Imperial should be congratulated for revealing a new perspective on such a fundamental process.”

See the full article here .


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Imperial College London

Imperial College London is a science-based university with an international reputation for excellence in teaching and research. Consistently rated amongst the world’s best universities, Imperial is committed to developing the next generation of researchers, scientists and academics through collaboration across disciplines. Located in the heart of London, Imperial is a multidisciplinary space for education, research, translation and commercialisation, harnessing science and innovation to tackle global challenges.

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From Imperial College London: “Scientists spot erupting jets of material as black hole tears a star apart”

Imperial College London
From Imperial College London

14 June 2018
Hayley Dunning

1
NRAO/AUI/NSF

Astronomers have for the first time directly imaged a fast-moving jet of material ejected as a supermassive black hole consumed a star.

Scientists have previously detected a few cases of black holes destroying stars, but this is the first time they have imaged a bright jet of material from the event.

The way the jets were detected means researchers are hopeful they can spot more similar events. Such events may have been more common in the early universe, so studying them may help scientists understand the environment in which galaxies developed billions of years ago.

The results, led by the University of Turku in Finland and the Astrophysical Institute of Andalucia in Spain, and including Imperial College London researchers, are published online today in the journal Science.

Only a small number of this kind of stellar deaths, called tidal disruption events (TDEs), have been detected. Physicists thought that material pulled from the doomed star would form a rotating disk around the black hole, emitting intense X-rays and visible light, and also launch jets of material outward from the poles of the disk at nearly the speed of light.

Now, these jets have been observed as a black hole, which is 20 million times more massive than our Sun, shredded a star more than twice the Sun’s mass. Astronomers tracked the event with radio and infrared telescopes in a pair of colliding galaxies called Arp 299, nearly 150 million light-years from Earth.

Epic project

Dr Dave Clements, from the Department of Physics at Imperial, said: “This project has been quite an epic, with observations and analysis spanning 13 years. It all started when my colleague Professor Peter Meikle came into my office in 2005 and said ‘something odd is happening in Arp299’.”

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GIF by Imperial College London

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ARP299 by NASA/Chandra

Astronomers using the William Herschel Telescope in the Canary Islands had discovered a bright burst of infrared emission coming from one of the colliding galaxies in Arp 299.


ING 4 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, 2,396 m (7,861 ft)

Follow-up observations with the National Science Foundation’s Very Long Baseline Array (VLBA) revealed a new, distinct source of radio emission from the same location.

NRAO/VLBA

Infrared and radio waves are those emitted beyond the visible light spectrum. The astronomers had expected to see visible light and X-rays (below the visible spectrum) created by the TDE, but think they only observed infrared and radio waves because of the amount of dust in the galaxy.

See the full article here .


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Imperial College London

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From ICL: “Intense laser experiments provide first evidence that light can stop electrons”

Imperial College London
Imperial College London

07 February 2018
Hayley Dunning

1
By hitting electrons with an ultra-intense laser, researchers have revealed dynamics that go beyond ‘classical’ physics and hint at quantum effects.

Whenever light hits an object, some of the light scatters back from the surface of the object. However, if the object is moving extremely fast, and if the light is incredibly intense, strange things can happen.

Electrons, for example, can be shaken so violently that they actually slow down because they radiate so much energy. Physicists call this process ‘radiation reaction’.

This radiation reaction is thought to occur around objects such as black holes and quasars (supermassive black holes surrounded by a disc of gas). Being able to measure radiation reaction in the lab will therefore provide insights into processes that occur in some of the most extreme environments in the universe.

Radiation reaction is also interesting to physicists studying effects beyond ‘classical’ physics, as the equations (known as Maxwell’s equations) that traditionally define the forces acting on objects fall short in these extreme environments.

Now, a team of researchers led by Imperial College London have demonstrated radiation reaction in the lab for the first time. Their results are published today in the journal Physical Review X.

They were able to observe this radiation reaction by colliding a laser beam one quadrillion (a billion million) times brighter than light at the surface of the Sun with a high-energy beam of electrons. The experiment, which required extreme precision and exquisite timing, was achieved using the Gemini laser at the Science and Technology Facilities Council’s Central Laser Facility in the UK.

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STFC Central Laser Facility

Photons of light that reflect from an object moving close to the speed of light have their energy increased. In the extreme conditions of this experiment, this shifts the reflected light from the visible part of the spectrum all the way up to high energy gamma rays. This effect let the researchers know when they had successfully collided the beams.

Senior author of the study, Dr Stuart Mangles from the Department of Physics at Imperial, said: “We knew we had been successful in colliding the two beams when we detected very bright high energy gamma-ray radiation.

“The real result then came when we compared this detection with the energy in the electron beam after the collision. We found that these successful collisions had a lower than expected electron energy, which is clear evidence of radiation reaction.”

Study co-author Professor Alec Thomas, from Lancaster University and the University of Michigan, added: “One thing I always find so fascinating about this is that the electrons are stopped as effectively by this sheet of light, a fraction of a hair’s breadth thick, as by something like a millimetre of lead. That is extraordinary.”

The data from the experiment also agrees better with a theoretical model based on the principles of quantum electrodynamics, rather than Maxwell’s equations, potentially providing some of the first evidence of previously untested quantum models.

How to make intense light

Study co-author Professor Mattias Marklund of Chalmers University of Technology, Sweden whose group were involved in the study, said: “Testing our theoretical predictions is of central importance for us at Chalmers, especially in new regimes where there is much to learn. Paired with theory, these experiments are a foundation for high-intensity laser research in the quantum domain.”

However, more experiments at even higher intensity or with even higher energy electron beams will be needed to confirm if this is true. The team will be carrying out these experiments in the coming year.

The team were able to make the light so intense in the current experiment by focussing it to a very small spot (just a few micrometres – millionths of a metre – across) and delivering all the energy in a very short duration (just 40 femtoseconds long: 40 quadrillionths of a second).

To make the electron beam small enough to interact with the focussed laser, the team used a technique called ‘laser wakefield acceleration’.

The laser wakefield technique fires another intense laser pulse into a gas. The laser turns the gas into a plasma and drives a wave, called the wakefield, behind it as it travels through the plasma. Electrons in the plasma can surf on this wake and reach very high energies in a very short distance.

See the full article here .

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Imperial College London is a science-based university with an international reputation for excellence in teaching and research. Consistently rated amongst the world’s best universities, Imperial is committed to developing the next generation of researchers, scientists and academics through collaboration across disciplines. Located in the heart of London, Imperial is a multidisciplinary space for education, research, translation and commercialisation, harnessing science and innovation to tackle global challenges.

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From ICL: “Leukaemia treatment can be made more effective by using a drug for iron overload”

Imperial College London
Imperial College London

21 December 2017
Hayley Dunning

1
Healthy bone marrow (yellow) invaded by leukaemia (red), with blood vessels in cyan. Credit: Delfim Duarte

Chemotherapy for one type of leukaemia could be improved by giving patients a drug currently used to treat an unrelated condition, new research shows.

Acute myeloid leukaemia (AML) is an aggressive cancer that stops healthy blood cell production. Chemotherapy is the standard treatment, but improvements are needed as the five-year survival rate in patients older than 60 is only 5-15 per cent.

Now, by studying how leukaemia cells infiltrate bone marrow, where blood cells are created, researchers led by a team from Imperial College London have made a crucial discovery.

Studying mice and human samples, they found that certain areas in the bone marrow support blood stem cells, and when these are overtaken by leukaemia cells, these stem cells are lost and production of healthy blood is significantly reduced. This can cause anaemia, infection, and bleeding in patients, and affects the success of chemotherapy.

Crucially, the team also discovered that a drug already approved to treat a condition known as iron overload can protect these important bone marrow areas and allow blood stem cells to survive. Their results are published today in the journal Cell Stem Cell.

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Conceptual image from real data of yellow leukaemia invading the bone marrow, dislodging red normal blood cells and destroying cyan blood vessels and blue osteoblasts. Credit: Delfim Duarte

The study’s lead author, Dr Cristina Lo Celso from the Department of Life Sciences at Imperial, said: “Since the drug is already approved for human use for a different condition, we already know that it is safe.

“We still need to test it in the context of leukaemia and chemotherapy, but because it is already in use we can progress to clinical trials much quicker than we could with a brand new drug.”

The researchers are now hoping to team up with clinicians to begin human trials of the drug for AML. Understanding whether this drug is a viable option should take less than five years, as opposed to the 10-15 needed if an entirely new drug is developed.

Protecting blood vessels

The team conducted the study by filming the invasion of leukaemia cells into bone marrow in mice. This approach allowed them see both large overviews and incredible details of the bone marrow, revealing phenomena happening deep inside the bone marrow – a view usually inaccessible to direct observation in patients.

The group discovered that one of the spaces hit particularly hard by leukaemia were special regions of blood vessels where blood stem cells reside. These are the basic blood cells that can become all other types of blood cells, including red and white, generating billions of new cells every day of our life.

For this reason, these special blood vessel regions are vital for producing new healthy blood, and their destruction by leukaemia allows the disease to progress. The loss of these vessels was confirmed in humans by studying patient tissue samples.

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Blood vessels decreased in bone marrow full of leukaemia (shown with arrows). Credit: Delfim Duarte

To see if they could protect the vessels, the team tested a drug called deferoxamine. The drug is used to treat iron overload, which can happen for example when a person receives multiple blood transfusions.

Deferoxamine has also been used in the treatment of myelodysplasia, a disease related to leukaemia where young blood stem cells do not mature into healthy blood cells. Other researchers who contributed to this project, and are now based at Imperial, Max Plank Munster, and Oxford Kennedy Institute, showed that this drug increases bone marrow vessels in aged mice.

Dr Lo Celso’s group now found that the drug had a protective effect on the blood vessels in AML, allowing the rescue of healthy blood stem cells. Moreover, the enhanced vessels improved the efficiency of chemotherapy.

Delfim Duarte, a physician and PhD student who performed most of the experiments published today, said: “Our work suggests that therapies targeting these blood vessels may improve existing therapeutic regimes for AML, and perhaps other leukaemias too.”

See the full article here .

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Imperial College London is a science-based university with an international reputation for excellence in teaching and research. Consistently rated amongst the world’s best universities, Imperial is committed to developing the next generation of researchers, scientists and academics through collaboration across disciplines. Located in the heart of London, Imperial is a multidisciplinary space for education, research, translation and commercialisation, harnessing science and innovation to tackle global challenges.

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From ICL: “A lead candidate for immunotherapy may increase tumour growth in certain cancers”

Imperial College London
Imperial College London

12 May 2017
Hayley Dunning

1
Boosting a part of the immune system known to have anti-tumour properties may actually help tumours grow in cancers linked to chronic inflammation. No image credit.

Cancer immunotherapies boost aspects of the body’s normal immune system, to help fight tumours. They are part of a fast-evolving field of research and medicine, with several types of immunotherapies currently in clinical trials.

Now, a research team at Imperial College London has found that in a mouse model developing liver cancer, one immunoreceptor – attractive candidate for immunotherapies – promoted rather than delayed tumour growth.

The researchers believe this could have implications for the effectiveness of immunotherapy in combating human cancers caused by inflammation, such as some liver and colon cancers. The study, funded by the Wellcome, Trust was published in Nature Communications earlier this year.

Lead author Dr Nadia Guerra from the Department of Life Sciences at Imperial, said: “Immunotherapies have shown unprecedented successes in treating cancer patients with advanced forms of cancer, especially metastatic melanomas. These therapies are now being tested in various type of cancer and novel combination approaches are being developed at a very fast pace.

“Nonetheless, there are still challenges ahead to optimise those therapies and reduce adverse effects. Scientists and clinicians are working at identifying cancer patients that would benefit the most from those therapies to increase success rates and hopefully achieve complete remission.”

How immunotherapies tackle cancer

The part of the immune system involved in the study is called NKG2D (Natural Killer Group 2 member D). NKG2D is a type of immunoreceptor – a molecule present on the surface of the body’s immune cells that recognises signals from normal cells that are distressed.

For example, if a normal cell is infected with a virus, it will display molecules on its surface that the NKG2D immunoreceptor can detect. The immune cell then directs a lethal hit that destroys the infected cell.

Dr Guerra first showed ten years ago that this mechanism also works against cancerous tumours – demonstrated by the fact that tumours grew faster in mice that had their NKG2D activity supressed.

However, NKG2D contributes to inflammation and has been found to play a role in chronic inflammatory disorders, such as Crohn’s disease. In this case, the NKG2D misfires and attacks normal cells instead of damaged ones.

The paradoxical effect of inflammation

The team looked into whether NKG2D’s roles in chronic inflammation and cancer could help tumours to grow in these types of cancer.

To do this, they used a mouse model of liver cancer driven by inflammation. Human and mouse NKG2D receptors are very similar, so the results are thought to be relevant to human liver cancers.

They found that the tumours actually grew faster in mice with functional NKG2D than in mice that lacked NKG2D. Dr Guerra said: “NKG2D is a potent anti-tumour agent, but we have found that it might actually have the opposite effect in tumours that arise and/or grow from a background of chronic inflammation.”

In these environments, the liver tissue undergoes cycles of damage and repair continuously as it is fought by NKG2D, making the cells more at risk of developing genetic mutations.

Dr Guerra said: “The paradoxical effect of NKG2D we discovered exposes the need to selectively target the types of cancer that will benefit from NKG2D-based immunotherapy. What is beneficial in fighting one type of cancer might have the opposite effect in another.

“We need to be more precise when administering a chosen therapy to a particular type of cancer. Our data unravels a conceptual shift that will inform which cancer these new therapies can benefit the most, and help match the best therapy to each patient.”

See the full article here .

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Imperial College London

Imperial College London is a science-based university with an international reputation for excellence in teaching and research. Consistently rated amongst the world’s best universities, Imperial is committed to developing the next generation of researchers, scientists and academics through collaboration across disciplines. Located in the heart of London, Imperial is a multidisciplinary space for education, research, translation and commercialisation, harnessing science and innovation to tackle global challenges.

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From ICL: “Fledgling stars try to prevent their neighbours from birthing planets”

Imperial College London
Imperial College London

22 March 2017
Hayley Dunning

1
Artist’s impression of an evaporating protoplanetary
disc. Image:NASA/JPL-Caltech/T. Pyle (SSC)

Stars don’t have to be massive to evaporate material from around nearby stars and affect their ability to form planets, a new study [MNRAS] suggests.

Newly formed stars are surrounded by a disc of dense gas and dust. This is called the protoplanetary disc, as material sticks together within it to form planets.

Stars of different shapes and sizes are all born in huge star-forming regions. Scientists know that when a protoplanetary disc around a relatively small star is very close to a massive star, the larger star can evaporate parts of the protoplanetary disc.

However, it was thought this was only the case where very large stars shone on the protoplanetary disc. Now, researchers led by Imperial College London have discovered that a protoplanetary disc shone on by only a relatively weak star is also losing material. The protoplanetary disc studied, called IM Lup, belongs to a star similar to our Sun.

The researchers estimate that the disc will lose about 3,300 Earth’s worth of material over its 10-million-year lifetime, despite the light from the nearby star being 10,000 times weaker than stars usually caught stripping discs.

Lead author Dr Thomas Haworth from the Department of Physics at Imperial said: “Because the light shining on this disc is so much weaker than that shining on known evaporating discs, it was expected that there would be no evaporation. We have shown that actually these stars can evaporate a significant amount of material.

“This result has consequences if we want to understand the diversity of exoplanet systems that are being discovered. This phenomenon could significantly affect the planets that can form around different stars. For example, light from nearby stars could limit the maximum size a solar system can be.”

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IM Lup’s ‘fuzzy halo’

The IM Lup system was studied recently by Dr Ilse Cleeves at Harvard, who discovered an unexplained ‘halo’ of material around it.

Working with Dr Cleeves, and researchers from the Max Planck Institute and the University of Cambridge, Dr Haworth modelled the flow and chemistry of the system to determine if the halo was the result of a nearby weak star heating up the system and evaporating away material.

They found that the halo is the result of evaporation, as material streams away and is lost to space. The team think the reason this disc is being strongly evaporated is that it is very wide.

When talking about solar systems or discs, distances are usually measured in astronomical units (AU), with one astronomical unit being the distance from the Sun to the Earth. The distance out to Pluto is about 40AU, whereas IM Lup’s disc reaches out to about 400AU.

This means the star cannot hold on to the disc’s outer parts so strongly, as its gravity would be much weaker that far out, leaving the fringes at the mercy of evaporation.

Dr Haworth said: “Our calculations show that if the disc started at 700AU in size, it would halve in size in the first million years of its life. Since IM Lup is less than a million years old, we’ve caught it in the act of rapid shrinking.”

See the full article here .

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Imperial College London

Imperial College London is a science-based university with an international reputation for excellence in teaching and research. Consistently rated amongst the world’s best universities, Imperial is committed to developing the next generation of researchers, scientists and academics through collaboration across disciplines. Located in the heart of London, Imperial is a multidisciplinary space for education, research, translation and commercialisation, harnessing science and innovation to tackle global challenges.

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From ICL: “Scientists confirm the universe has no direction”

Imperial College London
Imperial College London

22 September 2016
Hayley Dunning

1
The universe is not spinning or stretched in any particular direction, according to the most stringent test yet.

Looking out into the night sky, we see a clumpy universe: planets orbit stars in solar systems and stars are grouped into galaxies, which in turn form enormous galaxy clusters. But cosmologists assume this effect is only local: that if we look on sufficiently large scales, the universe is actually uniform.

The vast majority of calculations made about our universe start with this assumption: that the universe is broadly the same, whatever your position and in whichever direction you look.

If, however, the universe was stretching preferentially in one direction, or spinning about an axis in a similar way to the Earth rotating, this fundamental assumption, and all the calculations that hinge on it, would be wrong.

Now, scientists from University College London and Imperial College London have put this assumption through its most stringent test yet and found only a 1 in 121,000 chance that the universe is not the same in all directions.

Oldest light in the universe

To do this, they used maps of the cosmic microwave background (CMB) radiation: the oldest light in the universe created shortly after the Big Bang.

CMB per ESA/Planck
CMB per ESA/Planck

The maps were produced using measurements of the CMB taken between 2009 and 2013 by the European Space Agency’s Planck satellite, providing a picture of the intensity and, for the first time, polarisation (in essence, the orientation) of the CMB across the whole sky.

Previously, scientists had looked for patterns in the CMB map that might hint at a rotating universe. The new study considered the widest possible range of universes with preferred directions or spins and determined what patterns these would create in the CMB.

A universe spinning about an axis, for example, would create spiral patterns, whereas a universe expanding at different speeds along different axes would create elongated hot and cold spots.

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Four potential CMB patterns for universes with direction. No image credit.

Dr Stephen Feeney, from the Department of Physics at Imperial, worked with a team led by Daniela Saadeh at University College London to search for these patterns in the observed CMB. The results, published today in the journal Physical Review Letters, show that none were a match, and that the universe is most likely directionless.

Cosmology is safe

Dr Feeney said: “This work is important because it tests one of the fundamental assumptions on which almost all cosmological calculations are based: that the universe is the same in every direction. If this assumption is wrong, and our universe spins or stretches in one direction more than another, we’d have to rethink our basic picture of the universe.

“We have put this assumption to its most exacting examination yet, testing for a huge variety of spinning and stretching universes that have never been considered before. When we compare these predictions to the Planck satellite’s latest measurements, we find overwhelming evidence that the universe is the same in all directions.”

Lead author Daniela Saadeh from University College London added: “You can never rule it out completely, but we now calculate the odds that the universe prefers one direction over another at just 1 in 121,000. We’re very glad that our work vindicates what most cosmologists assume. For now, cosmology is safe.”

The work was kindly supported by the Perren Fund, IMPACT fund, Royal Astronomical Society, Science and Technology Facilities Council, Royal Society, European Research Council, and Engineering and Physical Sciences Research Council.

See the full article here .

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Imperial College London

Imperial College London is a science-based university with an international reputation for excellence in teaching and research. Consistently rated amongst the world’s best universities, Imperial is committed to developing the next generation of researchers, scientists and academics through collaboration across disciplines. Located in the heart of London, Imperial is a multidisciplinary space for education, research, translation and commercialisation, harnessing science and innovation to tackle global challenges.

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