The American space agency's (Nasa) Dawn satellite returns its latest images of Ceres as it approaches orbit insertion on 6 March.

New maps of ‘polarised’ light in the young Universe have revealed that the first stars formed 100 million years later than earlier estimates. The new images of cosmic background radiation, based on data released today from the European Space Agency’s Planck satellite, have shown that the process of reionisation, which ended the ‘Dark Ages’ as the earliest stars formed, started 550 million years after the Big Bang.

The history of our Universe is a 13.8 billion-year tale that scientists endeavour to read by studying the planets, asteroids, comets and other objects in our Solar System, and gathering light emitted by distant stars, galaxies and the matter spread between them.

A major source of information used to piece together this story is the Cosmic Microwave Background, or CMB, the fossil light resulting from a time when the Universe was hot and dense, only 380,000 years after the Big Bang.

Thanks to the expansion of the Universe, we see this light today covering the whole sky at microwave wavelengths.

Between 2009 and 2013, the Planck satellite surveyed the sky to study this ancient light in unprecedented detail. Tiny differences in the background’s temperature trace regions of slightly different density in the early cosmos, representing the seeds of all future structure, the stars and galaxies of today.

Scientists from the Planck collaboration have published the results from the analysis of these data in a large number of scientific papers over the past two years, confirming the standard cosmological picture of our Universe with ever greater accuracy.

The imaging is based on data from the Planck satellite, and was developed by the Planck collaboration, which includes the Cambridge Planck Analysis Centre at the University's Kavli Institute for Cosmology, Imperial College London and the University of Oxford at the London Planck Analysis Centre.

“The CMB carries additional clues about our cosmic history that are encoded in its ‘polarisation’,” explains Jan Tauber, ESA’s Planck project scientist. “Planck has measured this signal for the first time at high resolution over the entire sky, producing the unique maps released today.”

Light is polarised when it vibrates in a preferred direction, something that may arise as a result of photons – the particles of light – bouncing off other particles. This is exactly what happened when the CMB originated in the early Universe.

Initially, photons were trapped in a hot, dense soup of particles that, by the time the Universe was a few seconds old, consisted mainly of electrons, protons and neutrinos. Owing to the high density, electrons and photons collided with one another so frequently that light could not travel any significant distant before bumping into another electron, making the early Universe extremely ‘foggy’.

Slowly but surely, as the cosmos expanded and cooled, photons and the other particles grew farther apart, and collisions became less frequent. This had two consequences: electrons and protons could finally combine and form neutral atoms without them being torn apart again by an incoming photon, and photons had enough room to travel, being no longer trapped in the cosmic fog.

The new Planck data fixes the date of the end of these ‘Dark Ages’ to roughly 550 million years after the Big Bang, more than 100 million years later than previously determined by earlier polarisation observations from the NASA WMAP satellite (Planck’s predecessor), and has helped resolve a problem for observers of the early Universe.

The Dark Ages lasted until the formation of the first stars and galaxies, specifically the formation of very large stars with extremely hot surfaces, which resulted in the energetic UV-radiation that began the process of reionisation of the neutral hydrogen throughout the Universe.

Very deep images of the sky from the NASA/ESA Hubble Space Telescope have provided a census of the earliest known galaxies, which started forming perhaps 300–400 million years after the Big Bang.

The problem is that with a date for the end of the Dark Ages set at 450 million years after the Big Bang, astronomers can estimate that UV-radiation from such a source would have proved insufficient. “In that case, we would have needed additional, more exotic sources of energy to explain the history of reionisation,” said Professor George Efstathiou, Director of the Kavli Institute of Cosmology.

The additional margin of 100 million years provided by Planck removes this need as stars and galaxies would have had the time to supply the energetic radiation required to bring the Dark Ages to a close and begin the Epoch of reionisation that would last for a further 400 million years.

Although the joint investigation between Planck and BICEP2, searching for the imprinted signature on the polarisation of the CMB of gravitational waves triggered by inflation, found no direct detection of this signal, it crucially placed strong upper-limits on the amount of primordial gravitational waves.

Searching for this signal remains a major focus of ongoing and planned CMB experiments. “The results of the joint analysis demonstrate the power of combining CMB B-mode polarisation observations with measurements at higher frequency from Planck to clean Galactic dust,” said Dr Anthony Challinor of the Kavli Institute for Cosmology.

Inset image: Polarised emission from Milky Way dust Credit: ESA and the Planck Collaboration

New maps from the Planck satellite uncover the ‘polarised’ light from the early Universe across the entire sky, revealing that the first stars formed much later than previously thought.

We would have needed additional, more exotic sources of energy to explain the history of reionisationGeorge EfstathiouESA and the Planck CollaborationPolarisation of the Cosmic Microwave Background

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Dark energy is thought to work on the scale of the entire universe – but if it is active on galaxies, it could explain why the Milky Way has so few satellites

Get larger image formats

Firing off a string of snapshots like a sports photographer at a NASCAR race, NASA's Hubble Space Telescope captured a rare look at three of Jupiter's largest moons zipping across the banded face of the gas-giant planet: Europa, Callisto, and Io. Jupiter's four largest moons can commonly be seen transiting the face of the giant planet and casting shadows onto its cloud tops. However, seeing three moons transiting the face of Jupiter at the same time is rare, occurring only once or twice a decade. Missing from the sequence, taken on January 24, 2015, is the moon Ganymede that was too far from Jupiter in angular separation to be part of the conjunction.

New maps from ESA's Planck satellite uncover the 'polarised' light from the early Universe across the entire sky, revealing that the first stars formed much later than previously thought.

Scientists working on Europe’s Planck satellite say the first stars lit up the Universe more than 100 million years later than was previously thought.

The New Horizons probe returns new pictures of the dwarf planet Pluto and its largest moon, Charon.

Jupiter is having a close encounter with Earth, unusual because it is edge-on.

NASA’s New Horizons spacecraft returned its first new images of Pluto on Wednesday, as the probe closes in on the dwarf planet. Although still just a dot along with its largest moon, Charon, the images come on the 109th birthday of Clyde Tombaugh, who discovered the distant icy world in 1930.

Gravitational-wave hunt enters next phase

Nature 518, 7537 (2015). http://www.nature.com/doifinder/10.1038/518016a

Author: Elizabeth Gibney

The landmark BICEP2 result has turned to dust, but the search for primordial cosmic ripples continues.

A possible close supermassive black-hole binary in a quasar with optical periodicity

Nature 518, 7537 (2015). doi:10.1038/nature14143

Authors: Matthew J. Graham, S. G. Djorgovski, Daniel Stern, Eilat Glikman, Andrew J. Drake, Ashish A. Mahabal, Ciro Donalek, Steve Larson & Eric Christensen

Quasars have long been known to be variable sources at all wavelengths. Their optical variability is stochastic and can be due to a variety of physical mechanisms; it is also well-described statistically in terms of a damped random walk model. The recent availability of large collections of astronomical time series of flux measurements (light curves) offers new data sets for a systematic exploration of quasar variability. Here we report the detection of a strong, smooth periodic signal in the optical variability of the quasar PG 1302−102 with a mean observed period of 1,884 ± 88 days. It was identified in a search for periodic variability in a data set of light curves for 247,000 known, spectroscopically confirmed quasars with a temporal baseline of about 9 years. Although the interpretation of this phenomenon is still uncertain, the most plausible mechanisms involve a binary system of two supermassive black holes with a subparsec separation. Such systems are an expected consequence of galaxy mergers and can provide important constraints on models of galaxy formation and evolution.

ESA's Rosetta probe is preparing to make a close encounter with its comet on 14 February, passing just 6 km from the surface.

Despite their red-brick finish, the corridors of the Institute of Astronomy can seem more like an art gallery than a research centre, so beautiful are the images of supernovae and nebulae hanging there. Dr Nic Walton passes these every day as he makes his way to his office to study the formation of the Milky Way and search for planets outside our solar system.

On the screen of Walton’s computer is what appears to be a map of stars in our Milky Way. In fact, it is something that is around 25 orders of magnitude smaller (that’s ten followed by 25 zeros).

It is an image of cells taken from a biopsy of a patient with breast cancer; the ‘stars’ are the cells’ nuclei, stained to indicate the presence of key proteins. It is the similarities between these patterns and those of astronomical images that he, together with colleagues at the Cancer Research UK (CRUK) Cambridge Institute, is exploiting in PathGrid, an interdisciplinary initiative to help automate the analysis of biopsy tissue.

“Both astronomy and cell biology deal with huge numbers: our Milky Way contains several billion stars, our bodies tens of trillions of cells,” explained Walton.

PathGrid began at a cross-disciplinary meeting in Cambridge to discuss data management. Walton has been involved for many years with major international collaborations that, somewhat appropriately, amass an astronomical amount of data. But accessing data held by research teams across the globe was proving to be a challenge, with a lack of standardised protocols. Something needed to be done and Walton was part of an initiative to sort out this mess.

The issue of data management in an era of ‘big data’ is not unique to astronomy. Departments across the University – from the Clinical School to the Library – face similar issues and this meeting was intended to share ideas and approaches. It was at this meeting that Walton met James Brenton from the CRUK Cambridge Institute. They soon realised that data management was just one area where they could learn from each other: image analysis was another.

Walton and his colleagues in Astronomy capture their images using optical or near-infrared telescopes, such as the prosaically named Very Large Telescope or the recently launched Gaia satellite, the biggest camera in space with a billion pixels. These images must then be manipulated to adjust for factors including the telescope’s own ‘signature’, cosmic rays and background illumination. They are tagged with coordinates to identify their location, and their brightness is determined.

Analysing these maps is an immense, but essential, task. Poring over images of tens of thousands of stars is a laborious, time-consuming process, prone to user error, so this is where computer algorithms come in handy. Walton and colleagues run their images through object detection software, which looks for astronomical features and automatically classifies them.

“Once we start characterising the objects, looking at what’s a star, what’s a galaxy, then we start to see the really interesting bigger picture. Light is distorted by gravitational mass on its way to us, so the shapes of the galaxies, for example, can tell us about the distribution of dark matter towards them. When we start counting stars, we start to see structures, like tidal streams.”

Professor Carlos Caldas, one of Brenton’s colleagues at the CRUK Institute, and now a collaborator of Walton’s, says the problems faced by medical pathologists are very similar, if at the opposite extreme of measurements. Could the same algorithms help pathologists analyse images taken by microscopes?

When a patient presents with suspected breast cancer, a pathologist takes a core of the tumour tissue – a tiny sample, less than 1 mm in diameter. The tumour samples are arranged on a block, typically together with 200 other samples taken from different patients. Each sample needs to have its own ‘coordinates’ so that the researchers know that a particular tumour came from a particular patient.

“We then cut a slice of the 200 or so cores, mount it into a slide that is stained, and take a digital picture of this slide,” explained Caldas, “but each of these high-resolution images is a few gigabytes of data, so we quickly accumulate hundreds of terabytes of data.”

By adapting the astronomers’ image analysis software, the PathGrid collaborators are able to analyse the tumour images, for example to recognise the three types of cells in the tissue samples: cancer cells, immune cells and stromal cells. Just as object identification in astronomy reveals hidden patterns and information, so the information from the slides begins to tell researchers how the different cell types relate to each other. Staining the samples to highlight elements such as potentially important proteins could also help the researchers identify new biomarkers to aid in the diagnosis or prognosis of cancers.

Equally important will be how the data is stored so that several years down the line, as researchers find new questions to ask, they can still access and analyse any of the 15,000 different tumours and their hundred stains. “We need to know that at some point in the future we can extract sample 53, for example, or find all tumours that were positive for a particular stain,” said Caldas. “Imagine if you had a million sheets of paper and you just threw them all into a room and asked someone to find page 53. They’d have to sort through all the papers to find the right one, but if you could make it glow, you’d be able to find it more easily. This is similar to what we do, except we do this digitally.”

As well as this technology allowing oncologists to ask new questions and at a much larger scale, Caldas believes that in the future it could be used as ‘digital pathology’, aiding diagnosis and prognosis even in regions with no specialist oncologists. “You could imagine a scenario where a clinician takes a biopsy and a pathologist processes and stains the slide, takes a picture and digitally relays it. This is then analysed by one of the algorithms to say if it is a tumour, identify the tumour type and say how aggressive it will be.”

Walton makes an interesting and unexpected comparison between his and Caldas’s work: “We deal with star deaths, they deal with patient deaths.” If PathGrid is successful, this might change: while the astronomers continue to watch star deaths, their collaborators will hopefully become even better at preventing many more patient deaths from cancer.

Inset image: Left - Carlos Caldas; right - Nic Walton

Astronomy and oncology do not make obvious bedfellows, but the search for new stars and galaxies has surprising similarities with the search for cancerous cells. This has led to new ways of speeding up image analysis in cancer research.

We deal with star deaths, they deal with patient deathsNic WaltonThe District

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Last March, cosmologists celebrated what seemed like evidence of gravitational waves. But 11 months later, they're nursing a hangover

A new image taken with ESO’s VISTA survey telescope reveals the famous Trifid Nebula in a new and ghostly light. By observing in infrared light, astronomers can see right through the dust-filled central parts of the Milky Way and spot many previously hidden objects. In just this tiny part of one of the VISTA surveys, astronomers have discovered two unknown and very distant Cepheid variable stars that lie almost directly behind the Trifid. They are the first such stars found that lie in the central plane of the Milky Way beyond its central bulge.

Got an idea for an outreach project, summer studentship, conference etc.? Apply for an RAS grant!

Sums of £250-5,000 are available. The next deadline is 15 February.

https://www.ras.org.uk/news-and-press/2584-call-for-grant-applications-february-2015-round


Call for grant applications - February 2015 round
www.ras.org.uk
The RAS welcomes applications for funding under its ongoing grants scheme. The deadline for the next round of grants is 15 February 2015. Applications should normally be for sums between £250 and £5,000 (restrictions apply).

Jupiter's icy moon is considered one of the most likely prospects for discovering life in our solar system – and it looks like we're going there

Not every star ends with a bang. A beautiful post-mortem portrait reveals a cloud of gas surrounding a jewel-like white dwarf

New experiments suggest that if life-bearing meteorites hit the young, molten moon, they could have been preserved until today

Despite earlier reports of a possible detection, a joint analysis of data from ESA's Planck satellite and the ground-based BICEP2 and Keck Array experiments has found no conclusive evidence of primordial gravitational waves.