Thousands of citizen scientists got to work on Kepler data in 2017 when Exoplanet Explorers launched. Exoplanet Explorers is hosted on Zooniverse, an online platform for crowdsourcing research. But it was a feature on the ABC Australia television series Stargazing Live that ultimately yielded the most new data from citizens.
"People anywhere can log on and learn what real signals from exoplanets look like, and then look through actual data collected from the Kepler telescope to vote on whether or not to classify a given signal as a transit, or just noise", says Christiansen. "We have each potential transit signal looked at by a minimum of 10 people, and each needs a minimum of 90 per cent of "yes" votes to be considered for further [study]". In the first 48 hours after the project was introduced, Exoplanet Explorers received over 2 million classifications from more than 10,000 users.
The system has been named K2-138, after the second phase of the Kepler mission. No professional astronomer had yet looked through this dataset, called C12.
These planets are mostly located between 1,000 and 4,000 light-years away from Earth. "So, we chose to look for a multi-planet system because it's very hard to get an accidental false signal of several planets".
After this decision, Barentsen left to get a cup of tea. If there was a dip in the intensity, it could indicate a possible transit across the star's face by a planet or some other object.
The paper, which also mentions the possibility of a sixth exoplanet in K2-138, is titled "The K2-138 system: A Near-Resonant Chain of Five Sub-Neptune Planets Discovered by Citizen Scientists".
Using a statistical analysis, the team found two surprising patterns - that exoplanets tend to be the same sizes as their neighbours. They statistically validated the set of planet signals as being "extremely likely", according to Christiansen, to be signals from true planets. The planets were also found orbiting in an interesting mathematical configuration called "resonance" in which, each planet takes 50 percent longer to complete its orbit than the planet further in.
A study describing the system has been accepted for publication in The Astronomical Journal. The hope is that this will not only provide a better understanding of system formation, but the ability to predict the presence of potentially life-bearing planets. "Orbital commensurabilities among planets are fundamentally fragile, so the present-day configuration of the K2-138 planets clearly points to a rather gentle and laminar formation environment of these distant worlds".
"It is exciting, because we are getting the public excited about science, and it is really leveraging the power of the human cloud", Crossfield said.
Abundant evidence in the solar system suggests that Jupiter and Saturn disrupted our systems early structure, resulting in the four widely-spaced terrestrial planets we have today, researchers said. "However, these theories are unlikely to result in such a closely packed, orderly system as K2-138", Christiansen said in a statement.