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Largest meteor seen hitting the Moon so far captured on film

The flash would have been visible from Earth, and as bright as the brightest stars.

The above video shows the largest meteor strike on the Moon’s surface ever caught on film. It’s not as spectacular as the Chelyabinsk meteor that exploded over Russia in February 2013, but it’s still quite the sight. The Moon’s craters form an uneroded, unweathered record every impact since the Solar System formed - this is a rare chance to see one of those impacts as it happened.

This impact on 11 September was seen by a team of astronomers led by José M Madiedo at the Spanish universities of Huelva and Sevilla and the Institute of Astrophysics of Andalusia, as part of the Moon Impacts Detection and Analysis System, or Midas. The glow of the impact was as bright as some of the brightest stars in the night sky, and lasted for at least eight seconds until fading. “At that moment I realised that I had seen a very rare and extraordinary event,” Madiedo said.

There’s a really good reason to monitor the Moon for impacts: it’s a lot easier than keeping track of impacts on Earth. Most of the stuff that hits us in space is tiny, no more than a few centimetres across at most, but there are always larger objects that could threaten us. Ideally, scientists would like to know how many large rocks there are relative to the small ones - but if the smaller ones burn up in the atmosphere before hitting the ground, that kind of survey is made difficult.

However, the Moon has no atmosphere, and so the impacts of even the smallest objects on its surface are visible to telescopes down on Earth. The Moon therefore makes a useful sampling tool - relative to the size of the Solar System, it’s right next door to Earth, and that makes the things that hit it indicative of what will also, on average, hit us.

In a paper published in the Monthly Notices of the Royal Astronomical Society, Mediedo and his team estimate the object - which was between 60cm and 1.4m wide - was travelling faster than 60,000km/h. Despite its tiny size, it left a crater 40m wide, and the explosive energy was the equivalent of more than 15 tonnes of TNT. The press release accompanying this paper describes the 400kg object as having “the mass of a small car”, but that’s a bit misleading - most cars weigh more than a tonne. A more accurate mental image, considering its height and mass, would be of three average-sized adult American men holding each other in a circle. Only, you know, made of rock.

It also reached an apparent magnitude of 2.9. Apparent magnitude is a somewhat strange measurement, as things get brighter the lower the value. The Sun is the brightest object in the sky, and has an apparent magnitude of -26.7, while Mars might get as bright as -2.8; the dimmest stars visible to the eye, though, are of magnitude 6, while the dimmest objects seen by Hubble have magnitudes around 30. This meteor's 2.9 makes it brighter than two 3 magnitude flashes seen during the Leonid meteor shower in 1999, and the light burst also lasted much longer, not fading away until eight seconds after impact. That's because dust and tiny bits of rock get vapourised in the collision, and take a few seconds to cool down again.

There's no danger to humans from meteorites of this size, however - anything around a metre in size would almost entirely burn up while falling. There are, however, some "implications" for the assessing meteor strike risk on Earth, the scientists write in the paper. Across their study, they can average that the Moon should received an average of 126 events per years with an energy release of more than 15 tonnes of TNT - and, scaled up to the Earth, that should give 1680 such hits per year. That's a much higher estimate than some other studies have given.

They write: "This event exemplifies that Earth impact hazard estimations were not well constrained... Thus, a systematic monitoring of moon impact flashes but also of fireballs in the Earth’s atmosphere would provide a more reliable impact frequency, especially if the luminous efficiency is well calibrated."

Ian Steadman is a staff science and technology writer at the New Statesman. He is on Twitter as @iansteadman.

Photo: Getty Images
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What do Labour's lost voters make of the Labour leadership candidates?

What does Newsnight's focus group make of the Labour leadership candidates?

Tonight on Newsnight, an IpsosMori focus group of former Labour voters talks about the four Labour leadership candidates. What did they make of the four candidates?

On Andy Burnham:

“He’s the old guard, with Yvette Cooper”

“It’s the same message they were trying to portray right up to the election”​

“I thought that he acknowledged the fact that they didn’t say sorry during the time of the election, and how can you expect people to vote for you when you’re not actually acknowledging that you were part of the problem”​

“Strongish leader, and at least he’s acknowledging and saying let’s move on from here as opposed to wishy washy”

“I was surprised how long he’d been in politics if he was talking about Tony Blair years – he doesn’t look old enough”

On Jeremy Corbyn:

"“He’s the older guy with the grey hair who’s got all the policies straight out of the sixties and is a bit of a hippy as well is what he comes across as” 

“I agree with most of what he said, I must admit, but I don’t think as a country we can afford his principles”

“He was just going to be the opposite of Conservatives, but there might be policies on the Conservative side that, y’know, might be good policies”

“I’ve heard in the paper he’s the favourite to win the Labour leadership. Well, if that was him, then I won’t be voting for Labour, put it that way”

“I think he’s a very good politician but he’s unelectable as a Prime Minister”

On Yvette Cooper

“She sounds quite positive doesn’t she – for families and their everyday issues”

“Bedroom tax, working tax credits, mainly mum things as well”

“We had Margaret Thatcher obviously years ago, and then I’ve always thought about it being a man, I wanted a man, thinking they were stronger…  she was very strong and decisive as well”

“She was very clear – more so than the other guy [Burnham]”

“I think she’s trying to play down her economics background to sort of distance herself from her husband… I think she’s dumbing herself down”

On Liz Kendall

“None of it came from the heart”

“She just sounds like someone’s told her to say something, it’s not coming from the heart, she needs passion”

“Rather than saying what she’s going to do, she’s attacking”

“She reminded me of a headteacher when she was standing there, and she was quite boring. She just didn’t seem to have any sort of personality, and you can’t imagine her being a leader of a party”

“With Liz Kendall and Andy Burnham there’s a lot of rhetoric but there doesn’t seem to be a lot of direction behind what they’re saying. There seems to be a lot of words but no action.”

And, finally, a piece of advice for all four candidates, should they win the leadership election:

“Get down on your hands and knees and start praying”

Stephen Bush is editor of the Staggers, the New Statesman’s political blog.