NASA Announces the First Multi-Planet System Discovered Entirely Through Crowdsourcing

Posted: January 12, 2018 by oldbrew in Astronomy, exploration
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K2-138 could even have more than five planets. [image credit: NASA/JPL-Caltech]

And it’s a good one. The abstract says: ‘The periods of the five planets are 2.35, 3.56, 5.40, 8.26, and 12.76 days, forming an unbroken chain of near 3:2 resonances.’

The Exoplanet Explorers project has led to the first discovery of a multi-planet system solely through crowdsourcing efforts, as Futurism reports.

Through a project called Exoplanet Explorers, a band of citizen scientists has discovered K2-138, a far-off planetary system that houses least five exoplanets.

This is the first time that a multi-planet system has been discovered entirely through crowdsourcing.

UC Santa Cruz astronomer Ian Crossfield and Caltech staff scientist Jessie Christiansen launched the Exoplanet Explorers project on the online platform Zooniverse in 2017. The project gives volunteers the ability to sift through data from NASA’s Kepler space telescope for signs of exoplanets.

“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,” said Christiansen in a Caltech news release.

“We have each potential transit signal looked at by a minimum of 10 people, and each needs a minimum of 90 percent of ‘yes’ votes to be considered for further characterization,” she added.

In April 2017, the Exoplanet Explorers project was featured on the Australia Broadcasting Corporation (ABC) program Stargazing Live. On the final night of the three-day event, citizen scientists uncovered K2-138.

Originally thought to be a four-planet system, it has since been upgraded to a five-planet system. Eventually, more planets could be discovered orbiting the system’s star.

Continued here.
– – –
Cosmos: Music of the spheres: chain of planets rotates at “perfect fifth” intervals

  1. oldbrew says:

    From the Discussion section:

    A further interesting subset of these systems are those demonstrating resonances, or chains of resonances. The five validated planets of K2-138 lie close to a first-order resonant chain. We find period ratios of 1.513, 1.518, 1.528, and 1.544 for the b–c, c–d, d–e, and e–f pairs, respectively, just outside the 3:2 resonance. Fabrycky et al. (2014), examining the large population of multi-transiting planet systems in the Kepler data, showed that pair-wise period ratios pile-up just outside of the first- and second-order resonances.

    What they will find is that the conjunction ratios are also near 3:2, but even nearer than the orbit ratios are. This is generally the case (i.e. conjunctions better than orbits for resonance), e.g. for Jupiter’s four Galilean moons, and Trappist-1 exoplanets.

    Note: conjunction means two planets in line with their star.

    RE ‘pair-wise period ratios pile-up’ – see ‘Planets around other stars are like peas in a pod’:

  2. oldbrew says:

    Planets d,e and f orbit in 5.40, 8.26, and 12.76 days respectively.

    26 d = 140.40 days
    17 e = 140.42 days
    11 f = 140.36 days

    26 – 17 = 9 d-e conjunctions
    17 – 11 = 6 e-f conjunctions

    9 d-e = 6 e-f
    9:6 = 3:2

    Also 26 – 11 = 15 d-f conjunctions
    15:9:6 = 5:3:2 (Fibonacci numbers)

    ‘K2-138 is the only system with an unbroken chain of four period ratios near 3:2’

    Update: the ratio of e-f to b-c (innermost and outermost conjunctions) is 2³:3³ or 8:27

  3. oldbrew says:

    ‘We find period ratios of 1.513, 1.518, 1.528, and 1.544 for the b–c, c–d, d–e, and e–f pairs, respectively, just outside the 3:2 resonance.’

    Using the data from the above pdf, the % match to 3:2 conjunction ratio is:
    b-c:c-d > 99.854%
    c-d:d-e > 99.918%
    d-e:e-f > 99.98%

    Using the best of the orbit ratios (1.513) the match is 99.14%, reducing to 97.15% for the worst.
    That confirms the conjunctions ‘fit’ much better than the orbits, as expected.