Kepler, the planet-hunting space telescope, is dead

3,000 potential exoplanets later, a failed reaction wheel means the end of the Kepler mission.

The Kepler telescope, a one tonne satellite launched in 2009 to scan for planets outside of our solar system, is dead.

Over the four years of its mission, the spacecraft has found over 3,000 stars which might have planets orbiting them, and the earth-based analysis has confirmed 134 planets orbiting 76 of them.

In April, the mission even announced the discovery of two potentially habitable planets. The two were roughly earth sized, and roughly earth temperature as well. Each of them might just lie in the "habitable zone", where liquid water can potentially exist.

Sadly, shortly after that discovery, Kepler ran into problems. The telescope manoeuvres through space with four reaction wheels, which keep it pointing in the right direction using a gyroscope effect. In July 2012, one of the wheels failed, but the mission was designed to only require three to accurately aim. In May this year, however, a second wheel failed. Yesterday, Nasa announced that they had given up trying to fix the wheels. Kepler can no longer be targeted accurately.

But, good news! Rumours of Kepler's death have been greatly exaggerated (by me, in paragraph one. Sorry.), because while the telescope can't be aimed any more, it's still useful. The imaging functionality works fine, and with two remaining reaction wheels and a limited amount of thruster fuel left it's even got a bit of manoeuvrability. NASA has opened it up to the community to work out the best way to make use of what's left working; one proposal, for instance, involves heavily post-processing the images to remove drift caused by the lack of a third wheel.

There's hope for the mission yet, which is great, because as Ars Technica's John Timmer writes, there's a lot more to learn:

A longer mission would identify planets further from their host stars. To identify a candidate, Kepler needs to see it pass between Earth and the star the exoplanet orbits three times. The further out a planet is, the longer one orbit takes, so the longer it will need to do three passes. As such, the existing data is heavily biased toward planets that orbit very close to their host stars; this also means that most of the potentially habitable planets we've spotted are orbiting dwarf stars, which are dim enough that water can remain liquid close in.

In other words, we simply haven't looked long enough to detect planets in a habitable zone around energetic stars. We have a much better picture of the diversity of exoplanets, but it's far from a complete one.

Kepler. Photograph: Wikimedia Commons

Alex Hern is a technology reporter for the Guardian. He was formerly staff writer at the New Statesman. You should follow Alex on Twitter.

Davide Restivo at Wikimedia Commons
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Scientists have finally said it: alcohol causes cancer

Enough of "linked" and "attributable": a new paper concludes that alcohol directly causes seven types of cancer.

I don't blame you if you switch off completely at the words "causes cancer". If you pay attention to certain publications, everything from sunbeds, to fish, to not getting enough sun, can all cause cancer. But this time, it's worth listening.

The journal Addiction has published a paper that makes a simple, yet startling, claim: 

"Evidence can support the judgement that alcohol causes cancer of the oropharynx [part of the throat], larynx, oesophagus, liver, colon, rectum and [female] breast"

So what's especially significant about this? 

First, scientists, unlike journalists, are very wary of the word "causes". It's hard to ever prove that one action directly led to another, rather than that both happened to occur within the same scenario. And yet Jennie Connor, author of the paper and professor in the Preventive and Social Medicine department at the University of Otago, New Zealand, has taken the leap.

Second, alcohol not only causes cancer of one kind – the evidence supports the claim that it causes cancer at seven different sites in our bodies. There was weaker evidence that it may also cause skin, prostate and pancreatic cancer, while the link between mouth cancers and alcohol consumption was the strongest. 

What did we know about alcohol and cancer before?

Many, many studies have "linked" cancer to alcohol, or argued that some cases may be "attributable" to alcohol consumption. 

This paper loooks back over a decade's worth of research into alcohol and cancer, and Connor concludes that all this evidence, taken together, proves that alcohol "increases the incidence of [cancer] in the population".

However, as Connor notes in her paper, "alcohol’s causal role is perceived to be more complex than tobacco's", partly because we still don't know exactly how alcohol causes cancer at these sites. Yet she argues that the evidence alone is enough to prove the cause, even if we don't know exactly how the "biologial mechanisms" work. 

Does this mean that drinking = cancer, then?

No. A causal link doesn't mean one thing always leads to the other. Also, cancer in these seven sites was shown to have what's called a "dose-response" relationship, which means the more you drink, the more you increase your chances of cancer.

On the bright side, scientists have also found that if you stop drinking altogether, you can reduce your chances back down again.

Are moderate drinkers off the hook?

Nope. Rather devastatingly, Connor notes that moderate drinkers bear a "considerable" portion of the cancer risk, and that targeting only heavy drinkers with alcohol risk reduction campaigns would have "limited" impact. 

What does this mean for public health? 

This is the tricky bit. In the paper, Connor points out that, given what we know about lung cancer and tobacco, the general advice is simply not to smoke. Now, a strong link proven over years of research may suggest the same about drinking, an activity society views as a bit risky but generally harmless.

Yet in 2012, it's estimated that alcohol-attributable cancers killed half a million people, which made up 5.8 per cent of cancer deaths worldwide. As we better understand the links between the two, it's possible that this proportion may turn out to be a lot higher. 

As she was doing the research, Connor commented:

"We've grown up with thinking cancer is very mysterious, we don't know what causes it and it's frightening, so to think that something as ordinary as drinking is associated with cancer I think is quite difficult."

What do we do now?

Drink less. The one semi-silver lining in the study is that the quantity of alcohol you consume has a real bearing on your risk of developing these cancers. 

On a wider scale, it looks like we need to recalibrate society's perspective on drinking. Drug campaigners have long pointed out that alcohol, while legal, is one of the most toxic and harmful drugs available  an argument that this study will bolster.

In January, England's chief medical officer Sally Davies introduced some of the strictest guidelines on alcohol consumption in the world, and later shocked a parliamentary hearing by saying that drinking could cause breast cancer.

"I would like people to take their choice knowing the issues," she told the hearing, "And do as I do when I reach for my glass of wine and think... do I want to raise my risk of breast cancer?"

Now, it's beginning to look like she was ahead of the curve. 

Barbara Speed is a technology and digital culture writer at the New Statesman and a staff writer at CityMetric.