By Jose M. Madiedo
On 11 September 2013, an unusually long and bright impact flash was observed on the Moon. Its peak luminosity was equivalent to a stellar magnitude of around 2.9.
What happened? A meteorite with a mass of around 400 kg hit the lunar surface at a speed of over 61,000 kilometres per hour.
Rocks often collide with the lunar surface at high speed (tens of thousands of kilometres per hour) and are instantaneously vaporised at the impact site. This gives rise to a thermal glow that can be detected by telescopes from Earth as short duration flashes. These flashes, in general, last just a fraction of a second.
The extraordinary flash in September was recorded from Spain by two telescopes operating in the framework of the Moon Impacts Detection and Analysis System (MIDAS). These devices were aimed to the same area in the night side of the Moon. With a duration of over eight seconds, this is the brightest and longest confirmed impact flash ever recorded on the Moon.
Click here to view the embedded video.
Our calculations show that the impact, which took place at 20:07 GMT, created a new crater with a diameter of around 40 meters in Mare Nubium. This rock had a size raging between 0.6 and 1.4 metres. The impact energy was equivalent to over 15 tons of TNT under the assumption of a luminous efficiency of 0.002 (the fraction of kinetic energy converted into visible radiation as a consequence of the hypervelocity impact).
The detection of impact flashes is one of the techniques suitable to analyze the flux of incoming bodies to the Earth. One of the characteristics of the lunar impacts monitoring technique is that it is not possible to unambiguously associate an impact flash with a given meteoroid stream. Nevertheless, our analysis shows that the most likely scenario is that the impactor had a sporadic origin (i.e., was not associated to any known meteoroid stream). From the analysis of this event we have learnt that that one metre-sized objects may strike our planet about ten times as often as previously thought.
Dr. Jose Maria Madiedo is a professor at Universidad de Huelva. He is the author of “A large lunar impact blast on 2013 September 11” in the most recent issue of the Monthly Notices of the Royal Astronomical Society.
Monthly Notices of the Royal Astronomical Society is one of the world’s leading primary research journals in astronomy and astrophysics, as well as one of the longest established. It publishes the results of original research in astronomy and astrophysics, both observational and theoretical.
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I realize I’m privileged to have access to some of the world’s cutting edge science, but last week was particularly special with a visit to University College London to hear a mixture of astrophysicists and astrobiologists talk to journalists about their cutting edge work,organized by the ABSW, the Association of British Science Writers, of which I’m a member.
Now we all know scientists can sometimes waffle, but this brave half-dozen weren’t allowed that luxury. The format for the talks was a pecha kucha – born in Japan, you have 20 slides, each lasting for exactly 20 seconds, to get your point across. That’s 6 minutes, 40 seconds (and not a second more) to say who you are, what you do and pitch for a place in the science columns of Britain’s newspapers.
First up, Giovanna Tinetti asked what exoplanets are actually made of. For those out of the loop, exoplanets are those orbiting other stars, far beyond out own solar system. We weren’t sure such things even existed until the 1990s, but nowadays there are more than 700 confirmed cases, with hundreds more candidates awaiting confirmation. recently some astronomers have gone so far as to sayy that every star in our galaxy must have planets orbiting.The most productive way to search for these faraway worlds is by using the Kepler Space Telescope. Looking back along a populous spiral arm of the Milky Way, this other Hubble is a study in concentration, staring fixedly at a single window on the stars, watching for the most minute variation in their light. And by analying this light – the chemical clues hidden within the spectra, scientists like Giovanna can tell what planets hundreds of light years away are made from. She’s looking for those that are habitable. Soon, New Earth need not be a thing of science fiction stories, especially if Giovanna’s plans for ECHO, the Exoplanet Characterisation Observatory, are approved by ESA (the European Space Agency).
Ofer Lahav, Professor of Astronomy at UCL, chose to talk about dark energy, the mysterious entity that apparently makes up three quarters of out universe, but which we didn’t even know was there until 1998. For me the most incredible, unexpected discovery of the last fifty years has been that the rate of expansion of the universe is increasing. No one expected this. Everyone wants to know why, but Ofer was impressively agnostic in his views. Either an entity we call dark energy permeates space itself, acting as Einsteins cosmological constant, or the best theories we have are very wrong. Once upon a time our best theory was Newton’s, but it couldn’t explain why Mercury orbited the Sun the way it did. Along came Einstein, General Relativity and a revolution in science. With the dark energy anomaly, are we on the cusp of another such paradigm shift?
Richard Dawkins is the bestselling author of The Selfish Gene and The God Delusion. He’s also a pre-eminent scientist, the first holder of the Charles Simonyi Chair of the Public Understanding of Science at Oxford, and is a fellow of New College, Oxford. His most recent book is The Oxford Guide to Modern Science Writing, a collection of the best science writing in the last century.
This is the fourth in our series of podcasts. Dawkins has talked about a wide range of scientists before, and now he introduces us to Fred Hoyle, one of the astronomers who originally proposed the steady state theory of the universe. The steady state theory may have been disproved, but Hoyle’s contributions to science–and science fiction–still remain.
Transcript after the jump.
DORIAN DEVINS: Outside of the realm of biology, you have a lot of physicists and mathematicians as well, and it struck me that you have Fred Hoyle in here—a lot of people may not be familiar with Fred Hoyle.
RICHARD DAWKINS: Yes, Fred Hoyle was an English astronomer, astrophysicist. He was one of the three physicists who proposed the steady state theory of the universe, which is now out of fashion. Indeed, it’s almost certainly wrong, disproved by the evidence. But it was a very, very interesting theory. According to the steady state theory, there never was a beginning to the universe. The universe has always been in existence; and the expanding universe, the galaxies pulling apart, that is true, but the gaps between the galaxies get filled with spontaneously created new matter, so there are new galaxies being created in the gaps that are left as the other, older galaxies pull apart. Now, that theory is wrong, but it was never obviously silly. You might think “Well how on Earth can matter just spontaneously be created?” And Hoyle’s point was well that’s no more odd than the idea that it should be spontaneously created in the first place, at the time of the Big Bang. So it was an interesting theory; its now been disproved. He had another great claim to fame, which was that he worked out how the elements, the chemical elements, are formed in the interior of stars. We now know that in this case, Hoyle was absolutely right, that all the elements apart for hydrogen and helium I think, are made in the interior of stars. And we’re all made of star stuff, that was the poetic phrase that Carl Sagan used to quote. I think maybe he got it from Joni Mitchell or the other way around. But anyway, that all comes from Fred Hoyle. He was also a science fiction writer. His first science fiction book, The Black Cloud, is a wonderful story. I mean it’s just a feast, it’s just a riveting science fiction story marred by the fact that its hero is such a deeply unpleasant character. And all the heroes of Fred Hoyle’s science fiction books are the same deeply unpleasant character, you can’t help wondering where that unpleasant character came from.