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Featured I New Kepler results (8th planet around Kepler-90)

  1. Dec 9, 2017 #1

    mfb

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    Announcement
    Vanderburg works on various stuff, with a focus on more recent data (K2 mission).
    Jessie Dotson works on K2 data and seems to be a contact person for external users working with Kepler data.
    Christopher Shallue uses deep learning to find exoplanets.
    Based on the panel, I have no idea what they are planning to announce. Yet another system with planets in the habitable zone would be boring. There is no expert from a different observatory, so it is probably not based on spectroscopy. Machine learning has to play a big role.

    Transit timing variations? A double planet or a moon? A planet in a complex orbit in a multiple star system?
     
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  3. Dec 9, 2017 #2

    Drakkith

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    I hope it's a moon!
     
  4. Dec 11, 2017 #3
  5. Dec 12, 2017 #4

    Ygggdrasil

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    Initial exoplanet discoveries were large gas giants that were easy to find because of their large size. More recent discoveries have been of smaller, Earth-like rocky planets in the habitable zone of stars. However, many of these planets have been around red dwarf stars as their short revolutions allow astronomers to observe many revolutions of the planet around the star to more easily find them. Unfortunately, these "habitable" planets are very close to their stars (which would lead to high levels of ionizing radiation on the surface of the planet) and likely tidally locked, making it questionable how habitable the planets would actually be. So far, only one exoplanet has been confirmed to be in the habitable zone of a sun-like star.

    My guess would be the discovery of (perhaps many) more exoplanets in the habitable zones of sun-like stars, which would be quite an exciting discovery.
     
  6. Dec 12, 2017 #5

    mfb

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    The K2 mission is limited to short orbital periods as Kepler doesn't look long enough at one region in the sky to find orbital periods of the order of one year.
     
  7. Dec 12, 2017 #6
    Is there a plan to do a bigger survey similar to that which Kepler now is doing?.
     
  8. Dec 12, 2017 #7

    mfb

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    Bigger, better, more, ...

    TESS (NASA, first half of 2018) will study about 500,000 stars, three times the number Kepler studied, and most of them brighter and closer (which means follow-up measurements are easier). The mission duration is just 2 years, however, Earth-like planets will mostly escape detection unless the mission gets extended.
    CHEOPS (ESA, late 2018) will study only about 500 known systems, but these with a much better precision.
    PLATO (ESA, 2026) will study up to one million stars - with a similar precision as CHEOPS, and with a focus on bright/nearby stars as well. Its mission duration is planned for 4-8 years. It will dwarf all the previous missions.
     
  9. Dec 14, 2017 #8

    mfb

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    6 pm UTC if I got the time zone correct, or in 8.5 hours.


    We might get the NASA press conference, the first successful Electron rocket launch and the Falcon 9 launch with reused booster and reused capsule, all within 24 hours if everything works.
     
  10. Dec 14, 2017 #9
    What do you guys think they found, I hope its a habitable planet, but I doubt that. By the way I have not looked at almost any articles and such on it. So I do not know much about what happened, so I am gonna look at that when I get a chance
     
  11. Dec 14, 2017 #10

    mfb

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    „In the habitable zone“ is all Kepler can do. And we had that already, one more wouldn’t be that interesting.

    The press conference starts now.

    Edit: An 8th planet around Kepler-90. The size of that system matches our solar system now. Nice... but a simple press release would have done the job as well.
     
    Last edited: Dec 14, 2017
  12. Dec 14, 2017 #11

    Ygggdrasil

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    Here's the press release:

    Artificial Intelligence, NASA Data Used to Discover Eighth Planet Circling Distant Star
    https://www.nasa.gov/press-release/...-discover-eighth-planet-circling-distant-star

    The research is accepted for publication in the Astronomical Journal: https://www.cfa.harvard.edu/~avanderb/kepler90i.pdf
     
  13. Dec 14, 2017 #12
    Unfortunately, new discovery of Earth-like planets around G-dwarfs by transit photometry would probably not be made until the end of 2020s. TESS is designed to survey all-sky within 2 years. In order to complete this task, it will only monitor each sky patch for less than a month (27.4 days specifically) and then move on to the next one. The year-long stable survey will be limited to the region around the ecliptic, which will make the discovery of Earth-like planets around G-dwarfs statistically unlikely (extended mission lifetime would not help), but it will be sensitive to the planets with periods less than 10-20 days, including those habitable-zone planets around late- and mid-M-dwarfs.
    CHEOPS is designed to study those known systems (especially the planets detected by radial velocity method) rather than to discover. Because radial velocity method can constrain the mass, and transit photometry (like CHEOPS) can determine the radius, with better precision of CHEOPS, it will improve our understanding of structures and formations of exoplanets
    PLATO will probably just change our understanding of planets around G-dwarfs, 3 years of continuous monitoring over one patch of sky, with much better precision and larger sky coverage, but it will not be launched until 2026 or later. Considering the mission duration, long orbital periods, and the time to validate, the first discovery (of Earth-like planet) would likely be announced 2 years after the launch year(2028 or later).
    While ten years is sure a long wait, a new radial velocity instrument ESPRESSO was just being installed on Very Large Telescope, and it just targeted Tau Ceti for testing a week ago. It will be open to the science community by early 2018. The precision of ESPRESSO is 10 times better than HARPS which discovered Proxima Centauri b last summer. It has the capability of detecting planets down to Earth-mass in the habitable-zone of nearby quiet late-G-dwarfs with precision under 10cm/s. Its precursor HARPS is limited at 100cm/s which is barely enough to detect Earth-mass planets in the habitable-zone of nearby active mid-M-dwarfs. Project Blue is also aiming to directly detect (transit photometry and radial velocity are both indirect methods) habitable-zone planets around Alpha Centauri systems (the two stars are nearly identical to our own) by imaging them with a 40-cm space telescope sometime before 2025, and the scientists would be able to study the atmosphere and surface environment (thus fully assessing the habitability) based on the image.
     
    Last edited: Dec 14, 2017
  14. Dec 14, 2017 #13
    So before AI (machine learning), some smart people write a computer program to search a data set for planets. Isn't AI just a computer "program" now being used to search a data set for planets? Is there a simple way to explain what AI (machine learning) adds to the search?

    Just curious, what is the data, I assume it is more then just numbers of photons collected from some very small patch of sky per unit time from individual pixels?

    Thanks!
     
  15. Dec 14, 2017 #14

    mfb

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    Kepler can't count individual photons, but it is basically that. The brightness of the star seen by the telescope, every 15 minutes, for a few years. For 150,000 stars.

    Machine learning means the way to look for the planets is determined by a computer. Traditionally you would write a program that takes in all data and then looks for x measurements in a row that have an average of y% below the points around them or something like that, where you put x and y into the program. The machine learning approach is a program that you can tell "here are simulated datasets without planets, here are some simulated datasets with planet, learn how to distinguish between them" and then that program is used to search for planets in the data.
     
  16. Dec 14, 2017 #15

    Dale

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    I wonder if we could apply machine learning to predict the content of press conferences and press releases.
     
  17. Dec 15, 2017 #16

    BillTre

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    There probably are ways to predict the direction of a press conference in times of stress, given some knowledge of personal tendencies.
    Redirecting in some way is popular.
    Or the non-press conference.
     
  18. Dec 15, 2017 #17
    A nice "force multiplier". I've participated in a few of the "zoo" projects, and such datasets should be handy for training machine learning programs.

    As mentioned in the press conference both the data set and the source code is open, which is nice. Since the training dataset is so small, training only takes a couple of hours on a desktop computer.
     
  19. Dec 15, 2017 #18

    Ygggdrasil

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    It definitely seems like finding Earth-like planets around sun-like stars is a difficult, resource intensive task. How will the researchers choose which region of the sky to examine? Are there other data available that can give us an idea of which G-type stars might harbor habitable planets?
     
  20. Dec 15, 2017 #19
    Take Kepler's field of view as an example, Cygnus was intentionally chosen to be the target of Kepler mission because of high density of stars. The goal of Kepler mission was to understand the occurrence rate of Earth-like planets (define as similar insolation and size). While many Earth-like planets have been discovered (thus high occurrence rate), their host stars are so faint that follow-up study is impossible in the near future. For example, the apparent magnitudes (mv) of Kepler-186 and Kepler-452 are 15 and 14 respectively. Radial velocity method is used to constrain the mass of planets, but it only applies to the stars that are brighter than mv 12. Any further update on those planets is unlikely in the short-term. (Original: We probably can never determine the habitability of most habitable-zone planets in Kepler's field of view).
    PLATO will be on a whole new level. It will only search the planets around stars with 4 ≤ mv ≤ 11, which the follow-up asteroseismology and radial velocity method will be applicable (accurate determination of age, density, composition, stellar activity, formation, evolution, and possible surface environment and atmosphere). While too many stars would cause light contamination, to maximize the target numbers, PLATO's field of view will be pointing to Lyra/Hercules and Pictor.
    The last question, can we infer whether the star harbors a habitable planet based on just the star's properties along? It is possible. Scientists have been using the composition of stars as a proxy of protoplanetary disk. Protoplanetary disk is where planets form. Because the planets and the star both emerge in the same disk, the stellar composition might be reflected in the planets too. Stars that show high metallicity usually mean a high density disk, which planetary embryos grow quickly and accrete much gas forming mini-Neptunes (Dawson et al., 2015). Stars with low metallicity imply a low density disk, and embryos grow slowly forming terrestrial planets (Dawson et al., 2015). Some other elements ratios in the stars might tell us whether the rocky planets have higher chance or lower chance of driving plate tectonics (Unterborn et al., 2017). Stellar activities are important factors too. Active stars (especially M-dwarf to mid-K-dwarf) are dangerous to habitable planets because of high frequency of flares and coronal mass ejections and strong stellar winds, radiation, and magnetic field. Our sun is relatively quiet even among G-dwarfs.
     
    Last edited: Dec 15, 2017
  21. Dec 15, 2017 #20

    mfb

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    Don't say never.

    ELT will be able to collect as much light from mag 15 stars as a 4 meter telescope from a mag 10 star. And who knows what we can build in 50, 100 or 200 years.
     
  22. Dec 15, 2017 #21
    True, but I think the goal of fully characterizing planets would shift to image the nearby terrestrial planets in the next few decades. The Kepler habitable-zone planets are so far away that imaging their separation angles is impossible to achieve in the next 30 years. Perhaps transmission spectroscopy is possible with next-generation ground-based telescope or JWST, but nothing can be better than directly studying the spectroscopy of the planets. I think in the future even we have the capability of studing those planets, we would not spend much time on them.
     
    Last edited: Dec 15, 2017
  23. Dec 15, 2017 #22

    mfb

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    Sure, spectroscopy of a direct image of a nearby exoplanet is a much better use of ELT time.
     
  24. Dec 18, 2017 #23

    Buzz Bloom

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    I tried to find the 8 orbital radii, or periods, by searching the Internet, but my skills were inadequate. I am curious about whether the 8 planets have orbital radii that satisfy something related to the Titus-Bode law.
     
  25. Dec 18, 2017 #24

    mfb

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    The Wikipedia article has at least the periods. You can calculate the radii with Keplers’s law.
     
  26. Dec 19, 2017 #25

    mfb

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    • The stellar mass is known with 10% uncertainty.
    • It doesn't matter if you are only interested in relative values. The Titus-Bode law doesn't care about absolute values.
    The absolute orbital periods are known with basically zero uncertainty, the relative orbital radii can be derived from that with essentially no uncertainty as well.

    Edit: This was an answer to a post that got deleted.
     
    Last edited: Dec 19, 2017
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