Test image from Gaia: Slightly shaky to start with, but it’ll get there. (Image: ESA/DPAC/Airbus DS)
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Largest ever space camera is ready to map a billion stars

The European Space Agency's Gaia telescope is so powerful, it see stars with power akin to measuring the width of a human hair at a distance of 500 km.

After its successful launch in December, the European Space Agency’s (ESA) Gaia has now taken up its position in space and is ready to survey the skies. With the help of two onboard telescopes focused onto the largest ever space camera, Gaia is estimated to catalogue nearly one billion stars in its 5-year mission.

Like Hipparcos before it, ESA’s Gaia will map stars in the Milky Way. It will do this by measuring the brightest billion objects and determine their three-dimensional distribution and velocities. It also has the ability to measure the temperature, mass, and chemical composition of these billion objects.

Gaia will be able to discern objects up to 400,000 times dimmer than those visible to the naked eye. The positional accuracy of its measurements are akin to measuring the width of a human hair at a distance of 500 km.

The process will involve scanning each part of the sky an average of 70 times over its five-year mission lifetime, which means scanning the entire sky twice every 63 days, once through each of the two telescopes, making it a powerful tool for spotting time-evolving phenomena such as binary systems, supernovae, and exoplanets. Compared to Hipparcos, Gaia will be able to measure 500 times the number of stars, extending to objects 1000 times dimmer than the dimmest that Hipparcos could catalogue.

The technology that makes this possible is the largest camera ever launched into space – 940 million pixels. That is why a lot of effort before launch was on figuring out exactly how to get the huge amount of data Gaia will produce back down to Earth.

When a picture is taken a number of charged-coupled devices (CCDs) – the stuff most digital camera sensors are made off – are dedicated to spotting objects before they fall onto the main focal plane. This allows the instrument to track the objects as they pass and only retain small regions around the object, reducing the file-size needed to be sent to Earth. In five years it will send only 100 TB of data. Once the data arrives to Earth, there is a system in place to analyse the data and distribute alerts to ground-based observatories if anything quickly evolving and potentially interesting is spotted, such as supernovae.

The catalogue produced by Gaia is expected to contribute to many areas of astrophysics, multiply our database of exotic objects such as exoplanets, white and brown dwarfs, and supernovae many-fold, contribute to more precise measurements of General Relativity, help to constrain the measurements of the presence and location of dark matter, and give us more accurate information about our galactic neighbourhood and its evolution.

Gaia was successfully launched on 19 December. After a month’s transit, it is now in orbit at about 1.5 million km away from Earth. By virtue of its position opposite the Sun from the Earth and its large sunshield, it will be able to see objects as close as 45 degrees from the Sun, allowing it to spot asteroids with orbits that lie between the Earth and the Sun, which are candidates for Earth collision, and very difficult to observe from the ground.

Staff on the ground are conducting in-orbit testing, during which the exact orbital parameters are determined, and all systems are tested for performance. Calibration images have been obtained, and the ground team is working on procedures to resolve a few remaining issues, such as reducing contamination on the CCDs and dealing with sunlight diffracted around the sun-shield.

Beyond the alert system allowing quick ground-based follow up, the first proper Gaia catalogue will take two years to complete and will be made available to the wider scientific community. Following this, new iterations will be issued about once a year, which will add more precisely determined characteristics of these objects. It is expected that Gaia’s database will have many new discoveries waiting to be mined from it, fuelling astronomers for decades to come.

Ben Dryer has received funding from the UK Space Agency to perform Gaia data analysis.

This article was originally published on The Conversation. Read the original article.The Conversation

Reuters/New Statesman composite.
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When it comes to social media, we all have a responsibility to avoid sharing upsetting images

If Twitter is the new journalism, we are all editors – and responsible for treating our fellow humans with dignity.

“I wish I hadn’t seen that”, my colleague says from across the desk. It’s been an hour since the first reports came in of a shooting outside Parliament, and the news agency Reuters has started posting photographs of injured people, knocked down by the terrorist as he drove across Westminster Bridge.

In one, a brunette woman leans over a victim whose blood is beginning to stain the wet pavement. Lying on her back, she is framed by scattered postcards sold for tourists which have been knocked to the floor. She is clutching the arm of the woman helping her, but her eyes are staring dead into the photographer’s lens.

Another photograph – the one that my colleague is referring to – disturbs me even more: a man who has fallen (or been pushed?) off the bridge onto a stairwell. He is face down in a pool of blood, his left leg at an unnatural angle. It is impossible to tell if he is alive or not.

Briefly, before I scroll past, I wonder if someone, somewhere is seeing the same picture and experiencing a shock of recognition as they recognise their friend’s clothes.

And then there is one picture which I now cannot find on Twitter, but which, lying in bed last night, I could not stop thinking of: a woman’s legs extended from under the wheel of a bus, her skirt hiked up to show her underwear, her shoes missing.

We are a desk of journalists covering an attack on the Houses of Parliament, so I keep scrolling. It is only later, in an article by the Telegraph, that I learn a junior doctor has declared the woman dead.

Of course, the shock of seeing images like these is nothing compared to what war reporters, doctors or police go through on a regular basis. But a 2015 study at the University of Toronto found that extended exposure to violent or disturbing material can have a severe effect on journalists’ mental health.

The impact can be particularly confusing when one does not anticipate seeing violence.On social media, we increasingly encounter images this way: without warning and without a chance to steel ourselves. This is particularly a problem when it comes to members of the public, whose jobs don’t require them to look at shocking material but who can nevertheless be exposed to it just by virtue of using a social media network.

It is for this reason that, shortly after Reuters published their photographs of the Westminster victims, prominent journalists began posting asking their colleagues not to retweet them. Some protested the fact that Reuters had published them at all.

In today’s media landscape, news moves fast and social media faster. Where a picture editor would have previously had until their print deadline to decide which images to run, now photographers are able to send their work back to the office almost instantaneously, and editors must make a snap decision about what to release.

Deciding what images to use can be a difficult call – especially under pressure. On the one hand, there is the urge to not turn away, to bear witness to the full magnitude of what has happened, even if it is shocking and upsetting. On the other, there is the need to treat fellow human beings with dignity, and particularly to avoid, where possible, showing images of victims whose families have not yet been informed.

Social media makes this process even more difficult. Once released online, photographs of the Westminster attack were quickly saved and re-posted by private individuals, stripped of context or warning. One can choose not to follow the Reuters Pictures account, but one cannot necessarily avoid seeing an image once it is being retweeted, reposted and recycled by private accounts.

As the line between traditional news and social media blurs and we increasingly become participants in the news, as well as consumers of it, our sense of responsibility also shifts. On Twitter, we are our own editors, each charged with making sure we extend dignity to our fellow humans, even – especially – when the news is dramatic and fast-moving.

I was glad, this morning, to encounter fewer and fewer photographs – to not see the girl lying under the bus again. But at 3am last night, I thought about her, and about her family; about them knowing that journalists on desks across Britain had seen up their loved one’s skirt during the last moments of her life. It was, without putting too fine a point on it, no way to encounter a fellow human being.

Over the next few days, we will find out more about who the victims were. The media will release images of them in happier times, tell us about their jobs and careers and children – as is already happening with Keith Palmer, the policeman who we now know died on the Parliamentary Estate.

It is those images which I hope will be shared: not just as a way to resist fear, but as a way of acknowledging them as more than victims – of forging a different connection, based not in horror and voyeurism, but in a small moment of shared humanity.

There is no shame in being affected by graphic images, however removed one “ought” to feel. If you would like someone to talk to, Mind can provide details of local services.

The BBC also provides advice for those upset by the news.

Find out how to turn off Twitter image previews here.

Stephanie Boland is digital assistant at the New Statesman. She tweets at @stephanieboland