Since we announced, via this blog and via a paper we submitted to the Astrophysical Journal and released on the arXiv, there’s been a lot of talk about our wonderful seven planet system. If you remember, amongst the other discoveries we claimed to add a seventh planet to the six already known in a system going by the name of KOI-351.
One of the responses was by a team of astronomers in Europe, who released a paper on the same system, which they nicely describe as ‘a compact analogue to the Solar System’. In that paper, they claim to discover four of the seven planets in the system, including the same one that the Planet Hunters had identified. To make things more complicated, in news from the Kepler science conference yesterday, the Kepler team announced that they’d assigned the system the name ‘Kepler-90’.
In total, we announce the discovery of 14 planet candidates, all of which were identified by volunteers through the Planet Hunters Talk page. Of these, eight reside in their host star’s habitable zone, but none of them approach Earth or super-Earth size. Additionally, five of these new candidates met the requirements to have been detected by the Kepler team’s automated Transit Planet Search algorithm, but were undetected, including KOI-351.07, the newly discovered seventh candidate.
This post is by Tabby Boyajian, one of the Planet Hunters science team at Yale
As you all know, planethunter volunteers use archive data taken with the Kepler space telescope to classify lightcurves and identify transiting planets. Since the launch of the Planethunters citizen science program, we have contributed five scientific publications reporting on the discovery of dozens of candidate and confirmed exoplanetary systems – otherwise undiscovered by the Kepler team.
The design of the project is expanding with the opportunity for Planethunter volunteers to support astronomers interested in using Kepler data for scientific research unrelated to the main exoplanet goals of the Kepler mission. We have dubbed this as our own ‘Guest Scientist’ program. The idea is that guest scientists participate in Planethunters Talk forum and make requests for the public to collect particular light curves, such as signatures of moons or rings, pulsators, variable stars, flare stars, cataclysmic variables, or microlensing events.
We are delighted to announce that the first paper presenting results associated with the Planethunters Guest Scientist program has been accepted for publication in the Astrophysical Journal! In this paper, the lead scientists Doug Gies and Zhao Guo from Georgia State University and Steve Howell and Martin Still from NASA AMES follow up on a mysterious object in the Kepler field identified by Planethunters, later confirming it to be an unusual type of cataclysmic variable. They perform an in-depth analysis on the Kepler lightcurve as well as observations made at the Kitt Peak National Observatory 4-m Mayall telescope and RC spectrograph. The result is a newly published paper, so take a momtent to read ‘KIC 9406652: An Unusual Cataclysmic Variable in the Kepler Field of View’ or to check out the planethunters talk thread where the object was first discovered and discussed:
Thanks you all for your enthusiasm and contributions to the scientific community. We have several other projects underway so keep an eye out for updates in the future!
Astronomers at Keck have it easy – whereas I used to slog up to the summit of Mauna Kea*, dealing with the lack of oxygen up there in harsh conditions**, Meg is observing from a sumptuous sea-level facility. Before her night started, she decided to take us on a tour :
* – Someone drove me up the road in a perfectly comfortable car.
** – The scenery was beautiful but due to the altitude it was really difficult to make good tea.
I’m an astronomer partly because of the power of science fiction to inspire the imagination. While I still read plenty today, there were a few years where I did nothing but devour novel after novel, and series after series. My favorite pieces, then and now, are those which take an unfamiliar situation – an Earth with an extra Moon, a Universe in which pi varies – and follow the logic through remorselessly I was talking at dinner last night about a particularly chilling example, the unforgettable noirish Rogue Moon, but there are uncountable examples.
One perhaps more familiar than most to planet hunters is Asimov’s story Nightfall, a dramatic evocation of what happens on a planet with six suns when night eventually falls, something that happens only once every 2049 years. (I wonder why he chose 2049?). This story inevitably comes up whenever I mention our very our four-star world Planet Hunters 1b, although it would have a more normal setting; two of the stars are distant enough, I reckon, for it to still be ‘night’ when only they are above the horizon and the planet’s circumbinary orbit also would seem more normal. I’m mentioning it now because it’s been slowly dawning on me that, while Planet Hunters 1b is only an approximation to the planet in Nightfall, thanks to the work of planet hunters everywhere science fiction authors now have a wide variety of real worlds to choose from – real planets on which to set their stories.
On the other hand, we seem to get a kick out of discovering worlds we’ve already imagined (many of the press reports for our habitable worlds paper suggested that an Avatar-like moon might exist, for example). This theme is taken up by Oxford’s Ruth Angus in a public talk she gave a few weeks ago – the video’s worth a watch.
Today brought some incredibly sad news to planet hunters everywhere. The Kepler satellite, which has provided all the data which has fed our site since the beginning, has probably reached the end of its useful life, at least as far as hunting for planets goes.
Facts first. As reported elsewhere, Kepler’s fourth reaction wheel seems to have failed. The reaction wheels are what the spacecraft uses to point accurately, and with this failure Kepler’s down to only two, not the three needed to point precisely at its targets. Without three functioning reaction wheels, Kepler won’t be able to hold its gaze on the part of the sky that hold the stars that we’ve all become so familiar with over the last few years. There are still things to be tried – most of them variants on the tried and trusted ‘turn off and turn back on again’ methods – but the participants in today’s press conference didn’t seem very confident. The likely best case scenario involves Kepler being placed into a stable mode while those of us left on Earth spend the next few months contemplating what else it might be used for (budgets notwithstanding).
So where does this leave Planet Hunters? Bill Borucki – Kepler’s indefatigable principal investigator – was at pains during the press conference to stress that there is plenty of science left in the data that the spacecraft has already sent to Earth. He believes (and who are we to doubt) that Kepler already has enough information on hand to satisfy the critical science goal of determining what the odds of an Earth-sized planet are. There is a year or so of data that hasn’t been seriously reviewed by anyone, and much less than half of the data supplied has ever been viewed by Planet Hunters. In the long run, there are other data sets (the European COROT mission might be worth a look) and future missions (NASA’s TESS will follow where Kepler led, but looking for nearby planets).
Those discussions are for the days to come, though. For now, I want to pay tribute to the people behind the spacecraft. There’s a temptation at times like this to anthropomorize, to feel sorry for our plucky little planet hunter way up in space. Yet the truth is a mission like Kepler is what it is because of the blood, sweat and tears of hundreds of people, many of whom have dedicated literally years of their lives. I don’t know Bill Borucki well, but I first met him when I interviewed him for the BBC’s Sky at Night program. What struck me then, apart from his relaxed humility, was the tale he spun of year after year pitching what was to become Kepler only to be told that his ideas were unrealistic. Most people would have given up, but Bill and his team pressed on and as a result of that dedication were in the right place at the right time when the time came for an exoplanet mission to be picked.
The Kepler team are scattered across the US, and indeed across the world this evening. I hope many of them will be raising a glass to (what seems to be) the end of a job well done. Before we join them, the least we can do is go and look at some of their data they collected – after all, we still don’t know what’s lurking in the Kepler data displayed at Planet Hunters.
One of the many varied things I get to do with my time is act as an advisor to the Oxford Sparks project. As part of our mission to inform the world about the wonderful science this place is involved in, we get to produce animations like this :
The eagle-eyed will have spotted that there’s a world in there familiar to Planet Hunters volunteers, as our slightly intrepid hero is whizzed past PH1. There’s another interesting link, I think, between the two projects; both planet hunters and the animation take us to the cutting (some would say bleeding edge) of science.
Pretty much everything in the animation is open to question (and you can read more background over on the main Sparks site) – we have only weak evidence that there was a fifth giant planet in the Solar System, and many question the portrayal of the sudden bombardment of the Moon as shown here – it’s difficult to tell whether the evidence we have points to a true sudden bombardment or the mere end of a longer period of increased impact probability. On the broader questions too, there is disagreement – what sort of world would really be suitable for life? Do Earth-like planets such as the one we end up with really exist out there? (Probably – but we’re not sure yet).
All of this is ok. My aim – our aim – was to present science with the ink still wet rather than wait for the final draft. After all, it’s most inspiring when we can still make discoveries, and hopefully the video will make people think – and maybe even make a few discoveries of their own on Planet Hunters.
Today we’re pleased to announce the discovery of the first confirmed planet discovered by Planet Hunters, and it’s a fabulous and unusual world. Labelled ‘Planet Hunters 1’ (or PH1) in a paper released today and submitted to the Astrophysical Journal, it is the first planet in a four-star system. It is a circumbinary planet – one which orbits a double star – and our follow-up observations indicate that there is a second pair of stars approximately 90 billion miles (1000 Astronomical Units) away which are gravitationally bound to the system.
This is much closer than the nearest stars are to the Sun, so anyone viewing the sky from PH1 would have a spectacular view of all four stars. More importantly, this amazing system will help us understand how and where planets can form – producing a stable planet in a system where four different stars are moving about can’t be easy. This is the seventh circumbinary planet, and the first to be in a quadruple system.
The planet itself has a radius a little more than 6 times that of Earth, making it a little bigger than Neptune. It’s mass is harder to pin down (and being in such a complicated system didn’t help), but we have a definite limit that means it must be no more than half that of Jupiter – so this is definitely a planet.
A huge amount of work went into this discovery (as well as a fair bit of observing time on the Keck and other telescopes), but a lot of the credit should be pointed at the Planet Hunters who made the discovery. It was Kian Jek and Robert Gagliano, working together on Talk that made the initial discovery; there’s a post from them on exactly what happened up already. The paper also credits Hans Martin Schwengeler, Dr. Johann Sejpka, and Arvin Joseﬀ Tan all of whom flagged one or more of the transits before the paper was published! This is great news for us and we’re sure there are more planets hiding in data, both at the main interface and over on Talk. For today, though, we can celebrate the arrival of Planet Hunters 1!
PS We’ve announced discoveries before, of course – as well as being the first four-star planetary system, this is the first where we’ve been able to obtain not only transit information but follow up with radial velocity measurements, detecting the wobbles of the parent stars as well as the dips in light seen when the planet moves in front of them. This is the gold standard for planet discovery, and so this is officially a planet, not just a planet candidate.
PPS The paper, of course, still has to be refereed. We’ll keep you updated here as that process goes on, but as Meg is presenting the details of the system at the annual Division of Planetary Sciences meeting right now we thought you’d want to know the news as soon as possible. There will be more posts about exactly how PH1 was tracked down later in the week, so watch this space. In the meantime, you might prefer version of the paper, which has been annotated with the ScienceWISE tool in order to help explain some of the more technical language.
PlanetHunters has inspired all sorts of activity, and all sorts of people, but I think one of the most creative responses yet is in a new song by the Regaae/rock/much else besides band Echo Movement.
There’s a track on their new album that contains sounds generated from the light-curves of KIC4665989 and KIC10291683, an eclipsing binary they (and some colleagues at Georgia Tech) found in the Planet Hunters data. You can read more about their efforts in these articles.
The band aren’t the only ones looking at turning light curves into sound – there are some excellent efforts on this talk thread too.
PS The Echo Movement song is on iTunes here (track 8!), but I hope they’ll put up a music video we can link to before too long. Perhaps illustrated with Planet Hunters data…
PPS If you have spotify’s desktop client installed, you can listen to Echo Movement’s track just by clicking here :
A recent paper announcing 16 new candidates from Kepler data by Princeton astronomers Xu Huang, Gaspar Bakos and Joel Hartman has got some attention on Talk, as one of the candidates they report is the one we identified back during our mad rush through Stargazing Live. While that’s been clearly identified on talk for a while, we didn’t rush to write a paper on it, and a few people have asked why not given that the glory of first in print has now gone to the Princeton team.
The main reason is that for this candidate in particular, we wanted to wait until we could get plenty of follow-up data. Tom Barclay, in the last post on the blog talked through the various scenarios that lead to false positives, even when the transits themselves are real, and the only way to be sure you’re looking at a real planet is to go observing. We’ve been doing that for a selection of Planet Hunters candidates, including this one, and hope to report good news soon. In the meantime, for this candidate, we chose not to write up a separate paper until we had better evidence – there’s some circumstantial evidence that there might be some interference from a background source and we wanted to be careful. (We weren’t helped by the fact that the Kepler field is best seen in the summer…)
In such a new field as planet hunting, it’s not at all clear what we should make public early and what we should hang on to. This was one call it seems we got wrong, but we’re still looking forward to analysing our observations and seeing what’s really going on with this star. One thing we know we can do better is be faster to find interesting candidates, and if you want to help us with that you could do a lot worse than head over to a new part of the site where we’ve asking your help to review our best candidates.