Institute of Astronomy

Astronomy News

Celestial bodies

4 February 2015 - 4:03pm

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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Cosmic inflation's 'smoking gun' goes up in smoke

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

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4 February 2015 - 11:13am
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...

3 February 2015 - 7:05pm
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.

Call for grant applications - February 2015 round
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).

Green light for mission to Jupiter moon Europa

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2 February 2015 - 5:48pm
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30 January 2015 - 7:56pm

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Hubble's Largest-Ever Image

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30 January 2015 - 3:02pm
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30 January 2015 - 2:33pm

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Study fells cosmic inflation claim

30 January 2015 - 11:42am

Scientists who claimed to have found evidence for a cosmic super-expansion at the Big Bang made no such discovery, a soon-to-be published study will say.

NASA’s Chandra Detects Record-Breaking … s Black Hole

29 January 2015 - 7:28pm
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NASA Observatories Take an Unprecedented … ta Carinae

29 January 2015 - 7:28pm
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The tell-tale signs of a galactic merger [heic1503]

29 January 2015 - 4:47pm

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Hubble Spies a Loopy Galaxy

29 January 2015 - 4:36pm

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At first glance, galaxy NGC 7714 resembles a partial golden ring from an amusement park ride. This unusual structure is a river of Sun-like stars that has been pulled deep into space by the gravitational tug of a bypassing galaxy (not seen in this Hubble Space Telescope photo). Though the universe is full of such colliding galaxies that are distorted in a gravitational taffy-pull, NGC 7714 is particularly striking for the seeming fluidity of the stars along a vast arc. The near-collision between the galaxies happened at least 100 million years ago.

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Astrophysics: Stellar clocks

28 January 2015 - 7:15pm

Astrophysics: Stellar clocks

Nature 517, 7536 (2015). doi:10.1038/517557a

Authors: David Soderblom

A link between rotation and age for Sun-like stars has long been known, but a stringent test of it for older stars has been lacking. The Kepler mission helps to fill this gap with observations of an old star cluster. See Letter p.589

A spin-down clock for cool stars from observations of a 2.5-billion-year-old cluster

28 January 2015 - 7:15pm

A spin-down clock for cool stars from observations of a 2.5-billion-year-old cluster

Nature 517, 7536 (2015). doi:10.1038/nature14118

Authors: Søren Meibom, Sydney A. Barnes, Imants Platais, Ronald L. Gilliland, David W. Latham & Robert D. Mathieu

The ages of the most common stars—low-mass (cool) stars like the Sun, and smaller—are difficult to derive because traditional dating methods use stellar properties that either change little as the stars age or are hard to measure. The rotation rates of all cool stars decrease substantially with time as the stars steadily lose their angular momenta. If properly calibrated, rotation therefore can act as a reliable determinant of their ages based on the method of gyrochronology. To calibrate gyrochronology, the relationship between rotation period and age must be determined for cool stars of different masses, which is best accomplished with rotation period measurements for stars in clusters with well-known ages. Hitherto, such measurements have been possible only in clusters with ages of less than about one billion years, and gyrochronology ages for older stars have been inferred from model predictions. Here we report rotation period measurements for 30 cool stars in the 2.5-billion-year-old cluster NGC 6819. The periods reveal a well-defined relationship between rotation period and stellar mass at the cluster age, suggesting that ages with a precision of order 10 per cent can be derived for large numbers of cool Galactic field stars.

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