One notable aspect of research into extra-solar planets is that both the media and the wider public are very interested. The first press release that I ever wrote, on the discovery of the first planets by our Wide Angle Search for Planets collaboration, back in 2007, ended up in TIME magazine as number 6 in their “Top 10 Scientific Discoveries” of the year. But the days of easy publicity for merely discovering a planet have passed. With astronomers worldwide having now found over 1000 exoplanets, it is getting harder to find a new angle when writing a press release.
Our WASP project uses arrays of cameras to monitor millions of stars in order to look for tiny dips in their light caused by a planet orbiting in front of them. This requires a huge data-processing operation and the need for sophisticated search algorithms to look for the transit events.
The big problem is that the data, being obtained looking through Earth’s atmosphere, are hugely noisy. In the end, we need a human to help out the computer algorithms and make a judgement about what is likely to be an actual transit event. And that requires looking at lots and lots of light-curves of lots and lots of stars.
When I got an email from a 15-yr-old schoolboy — Tom Wagg — saying that he was keen on science and asking if he could join my research group for a week of work-experience, I figured that a bright 15-yr-old would be as good at that sort of pattern-recognition task as the best computer algorithms. So, I trained him up by showing him all the planet-transit dips that we’d already found, and set him the task of finding more of the same in our extensive data archive.
Among the dips Tom came to show me was this one:
It’s not much to look at, but that slight dip in the middle of the plot, at phase zero, is caused by a planet. Each black dot is one observation of a star’s brightness, plotted against the phase of the planet’s orbit, while the blue curve (shifted upwards) is the same data binned a bit to reduce the noise level.
The problem is that most such dips are not planets, they’re just noise. For example this one, which looks as good, is just an errantly low section of light-curve:
False-alarm dips greatly outnumber real dips, and thus we have to check a whole load of things to convince ourselves that a dip feature really is a good transit candidate. Tom applied himself to that task, and by the end of the week we were convinced that Tom’s dip really could be a planet.
However, many other astrophysical phenomena can cause dips in a stars’ light, mimicking a planet transit, and so we first needed to get more data. I sent Tom’s candidate to the University of Liège team who operate the TRAPPIST telescope, which often observes WASP candidates, getting far better photometry than obtainable with the small, wide-field WASP cameras.
The TRAPPIST data showed that Tom’s dip was real, that it did recur with the period of the possible planet’s orbit, and that the dip had exactly the characteristic shape of a planetary transit. When you see a light-curve like this one you immediately think “planet!”.
The dip is about 1% deep. One can estimate the size of the star from knowing what type of star it is, which enables you to deduce the size of the planet from the depth of the dip. The TRAPPIST data showed that it was just right to be a Jupiter-size planet.
But we still had to prove that the orbiting body had the right mass to be a planet, and to do that one has to measure the Doppler shift of the star’s spectrum, which reveals the gravitational tug of the planet on the star. Observations with the CORALIE spectrograph on the Euler telescope, operated by the University of Geneva, showed that the orbiting body also had a Jupiter-like mass.
Thus, two years after Tom’s work-experience week, we now had proof that his find was indeed a Jupiter-like planet, though it was in a much shorter orbit than our Jupiter, orbiting its star in only two days. The find was labelled WASP-142b, the 142nd planet found by WASP (the “b” denotes the second body in the system, after the star itself).
The planet is actually a fairly routine “hot Jupiter”, of which we have found over a hundred. But Tom’s involvement meant there was an opportunity for some good publicity. After all, he was likely the youngest human ever to have found a new planet!
“15-yr-old work-experience schoolboy discovers a new planet” sounded like a good start to the press release. I’d been keeping in touch with Tom over the progress of the follow-up observations, and, since a press release needs quotes, a quick phone call elicited: “I’m hugely excited to have found a new planet, and I’m very impressed that we can find them so far away”.
Any good press release also needs visual images, and one problem with exoplanet research is that they’re so far away that we can’t actually get images of the planets. The media and public, used to spectacular images of our own Solar System planets from NASA and ESA probes, are not going to be impressed by plots like those above.
Fortunately, this being a human-interest story helped there also, and a trip to Keele Observatory (to provide an astronomy-themed background), coupled with me trying my hand at portrait photography, produced some photos of Tom.
The time-honoured way of getting round the lack of images of exoplanets is to opt for artists’ impressions. There are many on the web, but it seemed appropriate to dignify Tom’s planet with its very own artist’s impression, so I commissioned David A. Hardy of astroart.org to produce an image to the specifications of WASP-142b, as seen from an adjacent (and entirely hypothetical!) moon.
Of course the first thing that everyone would ask Tom is what he was going to call the planet. Until recently, exoplanets were not given names, just catalogue numbers, but the naming body, the International Astronomical Union, are now asking the world’s public to get involved and have started an open competition for suggestions. Thus Tom’s planet will end up with a name eventually, though there are a few hundred others to name first. Tom wants to call his Zeus.
By that point we had all the ingredients of the press release, hoping that it was a compelling combination of trendy science topic and human-interest story.
It worked. The online press release was read 30,000 times. The BBC came to film Tom, both at his school and at Keele Observatory, broadcasting a 5-min segment on prime-time TV that evening, which was followed by Tom being interviewed live on BBC Breakfast and Sky News.
Seven UK national newspapers carried the story, while we did six interviews for BBC radio stations. Emails and phone-calls came from as far afield as the US, Canada, Europe, Australia and China, all wanting to talk to Tom.
Ten days later, the story has spread to over 650 news websites worldwide, from about 40 different countries and in 20 different languages, and has also appeared in many of the printed counterparts of those websites. That must make my press release on Tom’s discovery my most-distributed and most-read piece of writing by miles.