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The Cosmos: A Beginner's GuideIt's a huge universe - get a primer with The Cosmos: A Beginner's Guide.
On my first morning back from teaching at geology residential school, I find an urgent email requesting material for the BBC News website. It seems they are (quite rightly) excited by the new Open University TV series The Cosmos: a beginner’s guide (7.30 pm, every Tuesday for six weeks beginning 7 August) and would like a news feature about the ‘latest developments in planet hunting’. This means finding planets round other stars, by the way (sometimes called ‘exoplanets’), rather than new planets in our own Solar System.
I worked on this series as an academic consultant, which means suggesting ideas, and ensuring that the science stays essentially correct even if it has to be simplified. It was made easier because the lead presenter, Adam Hart-Davis, has a good knowledge of science, and the co-presenters, my Open University colleague Janet Sumner and Astrium’s Maggie Aderin, have current research reputations in the fields of planetary science and telescope engineering respectively.
It took about six months to make the series, during which time the presenters were sent to various exotic locations, and I got to go as far afield as Leeds (to view the rough cuts of the first two programmes) and Leicester (to be filmed as a contributor, talking about unmanned space exploration and the BepiColombo mission to Mercury).
My personal goal during the planning of the series (which did not acquire the name ‘Cosmos’ until quite late) was to ensure that planetary matters got a fair share of the treatment, rather than being overshadowed by things cosmological like the Big Bang and black holes. I mean, I chair the Open University's planetary science courses, so that's my job, right? Whether or not I succeeded, you’ll have to judge for yourself.
Anyway, to get back to the BBC News website request, it turns out that I’m the only member of the team free to today, so it falls to me to write the ‘news’ story, Hunting for another Earth-like planet, which has by now appeared online.
The trouble is that, for reasons unnecessary to dwell on, the BBC News website was unable to include the ‘planet hunting’ clips from the series that I had persuaded people to sort out for them. "Waste not, want not,” says I, so here you are:
The first clip shows Adam visiting the ‘Super Wide Angle Search for Planets’ (SuperWASP) telescopes on La Palma. This is particularly interesting for me, because colleagues from the Open University Department of Physics and Astronomy are heavily involved in the project.
SuperWASP Video
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Adam
WASP stands for Wide Angle Search for Planets, and Super WASP here has actually found other worlds orbiting not our sun but other stars. The more planets it finds the higher our chances are of finding another earth, and maybe life in the Cosmos. Dr Don Pollacco, from Queen’s university Belfast, is the astronomer who led the team which designed and built Super WASP.
Is this it, I thought it was a powerful thing you looked at planets with?
Don
It is extremely powerful.
Adam
But it’s tiny
Don
It’s tiny for a good reason.
Adam
Go on, what’s the good reason?
Don
The reason is that if you want to cover large bits of sky you need very short focal lens so we use these paparazzi lenses, to cover huge bits of sky.
Adam
Oh I see, so actually this is what, 8 digital cameras?
Don
8 digital cameras. We have very simply a camera lens and a digital camera at the end. High quality, science grade digital camera, but a digital camera nonetheless.
Adam
Tell me, how does Super WASP work?
Don
Super WASP is very very straight forward in principle. All it does is take pictures of the sky and we measure the brightnesses of those stars; if a planet is going around one of those stars and it happens to pass across the face of that star we see the star get a little bit fainter.The SuperWASP array is great for scanning the sky and keeping track of thousands of stars on the off-chance of seeing a dip in the light from one of them when a planet gets in the way. The second clip shows Adam being shown the much bigger William Herschel Telescope that can make more detailed measurements after SuperWASP has done the vital job of initial discovery.
William Herschel Video
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Adam
Back in La Palma, planet-hunter Don Pollacco has invited me to take a look around a much larger telescope down the road; in fact it’s the largest one in Europe.
It’s a vital part of Don’s quest to discover worlds outside our solar system.
So this is the William Herschel telescope, is it?
Don
Yes
Adam
How big is it?
Don
The mirror itself is 4.2 metres, in diameter
Adam
4.2, wow. When Don finds an Exoplanet with SuperWASP he uses a powerful telescope like the William Herschel to confirm his results. Both telescopes take a series of measurements known as a light curve, but the William Herschel is able to home-in on a particular star and get more detail. It’s this measurement that confirms the existence of the planet, and can tell Don some interesting facts about its character.
So this is real information, this is WASP I?
Don
This data came from these images.
Adam
Wow, ok
Don
And so each one of these points is about 3 seconds period, and so this is the start of the decline, this is when the planet is moving onto the disk of the star, this is when it’s fully on, this is it moving across the star’s face, this is when it starts to come off.
Adam
Wow, now it doesn’t go as quick as that in real time does it?
Don
No, this takes several hours
Adam
Several hours ok. Now why is it a diagonal line here, why doesn’t it just go jonk?
Don
Because the planet has a certain size, and this actually shows you the length of time it takes for the planet to move fully onto the disc of the star, so in other words that can actually tell us something about the size of the planet.
Adam
That is fantastic, so that if you like is the fingerprint of WASP I?
Don
That’s right, that is the transit shape of WASP I
Adam
Teams across the world have found over 200 Exoplanets. And with each discovery comes the hope that one day astronomers will find a small rocky planet like earth.In the third clip, we see Janet visiting the ‘Virtual Planetary Laboratory’ in Los Angeles, where the conditions on planets around other stars are investigated, and demonstrating ‘just right’ conditions in the so-called ‘habitable zone’ around a star.
Virtual Planetary Laboratory Video
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Janet
A leafy suburb of Los Angeles is the last place you’d expect to find a planet-making factory, but the California Institute of Technology is home to a very special think-tank, the Virtual Planetary Laboratory. I’ve come to meet Astro-biologist Dr Vikky Meadows to find out more.
What exactly does the Virtual Planetary Laboratory do?
Vikky
Well the Virtual Planetary Laboratory is a group of about 40 scientists who work together to create computer models of what extra solar planets might look like, so that we can understand when we look at distant planets whether they have life on them.
Janet
In her virtual universe Vikky and her team take the earth, a planet we know and love, and they place it around another star.
Vikky
And then we let the computer models that describe the environment of the planet interact with the star and with each other until they finally came to an agreement and said, well you know, we’re all in balance now, and so this is our final environment for the planet, and at that point we say that the planet is made.
Janet
So how long does it take to kind of gestate one of these little planetary babies?
Vikky
Well you know, it depends on the complexity of the planet, but typically it probably takes about a week.
Janet
And this week’s virtual baby was produced by putting the earth next to the star AD Leonis, smaller and cooler than our sun and this is what Vikky gets, a graph that indicates the atmospheric content of the real earth alongside data for the newly created virtual planet.
Vikky
Now the black line is earth for comparison and what we ended up with is this orange line and the big difference here was that we got a lot more methane and we also got a lot less ozone.
Janet
That’s interesting that you’ve pointed out the differences, but what I’m seeing is how incredibly similar those two lines look.
Vikky
Yes, and if I was to get a spectrum like that back from a planet around another star we’d be incredibly excited because it looks very, very similar to the earth.
Janet
By monitoring the effect of different stars on earth-like environments the Virtual Planetary Laboratory can identify stars that stand the best chance of parenting planets like ours. It could help to narrow down the future search for other earths and ultimately help scientists define life in the Cosmos. To get the most useful result, Vikky needs to give her virtual planets the best start in life; she places them in an orbit where life can thrive; the so-called ‘habitable zone’.
It’s all to do with the distance of a planet from its sun; now if this lamp is a sun and this soft ball is a planet, the closer to the sun it is the less likely it is to have liquid water because the heat of the sun will have evaporated it all away. The further away it is the colder it gets, water freezes and again chances of life are reduced, but here in the habitable zone, conditions are just right. Now that sounds pretty simple, but stars vary in size and brightness so the position of the habitable zone changes.
There is a further clip on YouTube, in which Janet struts her stuff at the very same observatory once used by Edwin Hubble.
About the author
Dave Rothery is a volcanologist and planetary scientist at the Open University. His current research includes studying volcanic eruptions on the Earth and characterising planetary surfaces.
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