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

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Age verification rules won't just affect porn sites – they'll harm our ability to discuss sex

Relying on censorship to avoid talking about sex lets children down.

The British have a long history of censoring sex. In 1580, politician William Lambarde drafted the first bill to ban "licentious" and "hurtful... books, pamphlets, ditties, songs, and other works that promote the art of lascivious ungodly love". Last week, the UK government decided to have another crack at censorship, formally announcing that age verification for all online pornographic content will be mandatory from April 2018.

It is unclear at this point what this mandatory check will entail, but it's expected that you will need to submit your credit card details to a site before being allowed to access adult content (credit cards can’t be issued to under-18s).

The appointed regulator will almost certainly be the British Board of Film Classification who will have the authority to levy fines of up to £250,000 or shut down sites that do not comply. These measures are being directly linked to research conducted by the NSPCC, the Children’s Commissioner and the University of Middlesex in 2016, which surveyed more than 1,000 11 to 16-year-olds about viewing online pornography and found over half had accessed it. 

Digital minister Matt Hancock said age verification "means that while we can enjoy the freedom of the web, the UK will have the most robust internet child protection measures of any country in the world". And who can argue with that? No sane adult would think that it’s a good idea for children to watch hardcore pornography. And because we all agree kids should be watching Peppa Pig rather than The Poonies, the act has been waved through virtually unchallenged.

So, let’s put the issue of hardcore pornography to one side, because surely we are all in agreement. I’m asking you to look at the bigger picture. It’s not just children who will be censored and it’s not just Pornhub and Redtube which will be forced to age check UK viewers. This act will potentially censor any UK site that carries adult content, which is broadly defined by the BBFC as "that it was produced solely or principally for the purposes of sexual arousal".

I am a UK academic and research the history of sexuality. I curate the online research project www.thewhoresofyore.com, where academics, activists, artists and sex workers contribute articles on all aspects of sexuality in the hope of joining up conversations around sex that affect everyone. The site also archives many historical images; from the erotic brothel frescoes of Pompeii to early Victorian daguerreotypes of couples having sex. And yet, I do not consider myself to be a porn baron. These are fascinating and important historical documents that can teach us a great deal about our own attitudes to sex and beauty.

The site clearly signposts the content and asks viewers to click to confirm they are over 18, but under the Digital Economy Act this will not be enough. Although the site is not for profit and educational in purpose, some of the historical artefacts fit the definition of  "pornographic’" and are thereby liable to fall foul of the new laws.

And I’m not the only one; erotic artists, photographers, nude models, writers, sex shops, sex education sites, burlesque sites, BDSM sites, archivists of vintage erotica, and (of course) anyone in the adult industry who markets their business with a website, can all be termed pornographic and forced to buy expensive software to screen their users or risk being shut down or fined. I have contacted the BBFC to ask if my research will be criminalised and blocked, but was told "work in this area has not yet begun and so we are not in a position to advice [sic] you on your website". No one is able to tell me what software will need to be purchased if I am to collect viewers' credit card details, how I would keep them safe, or how much this would all cost. The BBFC suggested I contact my MP for further details. But, she doesn’t know either.

Before we even get into the ethical issues around adults having to enter their credit card details into a government database in order to look at legal content, we need to ask: will this work? Will blocking research projects like mine make children any safer? Well, no. The laws will have no power over social media sites such as Twitter, Snapchat and Periscope which allow users to share pornographic images. Messenger apps will still allow users to sext, as well as stream, send and receiving pornographic images and videos. Any tech savvy teenager knows that Virtual Private Network (VPN) software will circumvent UK age verification restrictions, and the less tech savvy can always steal their parents' credit card details.

The proposed censorship is unworkable and many sites containing nudity will be caught in the crossfire. If we want to keep our children "safe" from online pornography, we need to do something we British aren’t very good at doing; we need to talk openly and honestly about sex and porn. This is a conversation I hope projects like mine can help facilitate. Last year, Pornhub (the biggest porn site in the world) revealed ten years of user data. In 2016, Brits visited Pornhub over 111 million times and 20 per cent of those UK viewers are women. We are watching porn and we need to be open about this. We need to talk to each other and we need to talk to our kids. If you’re relying on government censorship to get you out of that tricky conversation, you are letting your children down.

The NSPCC report into children watching online pornography directly asked the participants about the effectiveness of age verification, and said the children "pointed out its limitations". When asked what intervention would most benefit them, this was the overwhelming response: "Whether provided in the classroom, or digitally, young people wanted to be able to find out about sex and relationships and about pornography in ways that were safe, private and credible." I suggest we listen to the very people we are trying to protect and educate, rather than eliminate. 

Dr Kate Lister researches the history of sexuality at Leeds Trinity University