Goldilocks Zones

– a Fine-Grained Exoplanet Taxonomy

Patrick J. Talbot (Presenter)

Dennis R. Ellis (Analysis)

Introduction and Summary

https://github.com/OpenExoplanetCatalogue/open_exoplanet_catalogue

* http://exoplanets.org/, as of 1 September 2015.

Situation: Since the 1990's, over 5,000exoplanets have been identified* and the rate ofdiscovery is accelerating:

1,569 Planets with good orbits + 24 Microlensing and imaged planets = 1,593 Total confirmed planets + 3,751 Unconfirmed Kepler candidates = 5,344 Total exoplanets + Kelper Candidates

Need: a robust, extensible organization schemefor understanding, processing, and pattern discovery

Approach:● A classic trade study to rank and score candidate attributes● A critic, a sequential optimizer, and software tests● Iteration to find a minimum spanning taxonomy

●Result:● A minimum spanning taxonomy provides a uniques set of characteristics for each exoplanet.● To the extent practical, each exoplanet has a unique set of characteristics, or signature.

Objective● Organize information about exoplanets● Input exoplanets characteristics into a hierarchical,

frame-based ontology, like Protege● Identify the minimum set of characteristics that span

the problem space, so that each exoplanet has, to the extent practical, a unique signature.

● Input the knowledge base into data analytics tools, such as Weka Rule Induction, to automatically discover interesting pattterns.

● Quantify missing and conflicting data as sources of uncertainty to drive further refinement

Approach

Compute Signatures

Unique?

Reduce #States

Increase #States

Yes

Minimal?

No

VerifyUniqueness

Done

Yes

Perform Trades● Mission● Functional Filter Attributes

● Birthday ProblemDiscretize● Rules

No

Tag Description UnitPlanet a single planet. May be a free floating (orphan) planetStar A single star. A star can be host to one or more planetsBinary two stars, star/binary or two binaries.Declination Declination +/- dd mm ssRightascension Right ascension hh mm ssDistance Distance from the Sun parsecName Used multiple times for objects with multiple names.Semimajoraxis Semi-major axis of a planet (heliocentric coordinates) AUSeparation Projected separation of planet from its host AU, arcsecPositionangle Position angle degreeEccentricity EccentricityPeriastron Longitude of periastron degreeLongitude Mean longitude at a given Epoch (all planets in a system) degreeMeananomaly Mean anomaly at a given Epoch (all planets in one system) degreeAscendingnode Longitude of the ascending node degreeInclinatioN Inclination of the orbit degreeEpoch Epoch for the orbital elements BJDPeriod Orbital period dayTransittime Time of the center of a transit BJDPeriastrontime Time of periastron BJDMass Mass (or m sin(i) for radial velocity planets) Jupiter/SolarRadius Physical radius Jupiter/SolarTemperature Temperature (surface or equilibrium) KelvinAge Age GyrMetallicity Stellar metallicity log, rel/ solarSpectraltype Spectral typeMagB B magnitudeMagV Visual magnitudeMagR R magnitudeMagI I magnitudeMagJ J magnitudeMagH H magnitudeMagK K magnitudeDiscoverymethod Discovery method : timing, RV, transit, imaging.Istransiting Whether the planet is transiting (1) or not (0).Description Short description of the planetDiscoveryyear Year of the planet's discovery yyyyLastupdate Date of the last (non-trivial) update yy/mm/ddSpinorbitalignment Rossiter-McLaughlin Effect. degree

Data Structures, MIT Open Exoplanet Catalog

Mission Trade Study

Functional Trade Study

Node Composite Score

Sample Rules

Probability of Duplicates vs Catalog Size

Exoplanet Characteristics HierarchyExoplanets

Elements Physical Host star

Period

Binary

Metallicity

Semi-major axis

SpectralType

Mass

Age

RadiusSeparation

Eccentricity

Inclination

Temperature

Distance

ExoplanetName

Input

Header Only Header Only Header Only

H H 2 M L S L N L O L A

Temperature(Hot)

Distance(Far)

Separation(Moderate)

Binary(2 stars)

Semi-major Axis(Large)

Mass(Small)

Inclination(Low)

Eccentricity(Nearly Circular)

Period(Long)

Spectral type(Hottest)

Physical Radius(Large)

Age(Ancient)

Exoplanet Signature

Physical Orbital

InfluentialEnvironmental

Size

Mass

Composition[FeHg]

Period

Inclination

Host Spectral TypeHost Age

Host Variability

Kepler 423cHabitabilityIndex = .3

GoldilocksZone

Exoplanet Kiviat Diagram

Coming in the Full Paper

● Percent of Duplicate Signatures

● Sensitivity of Duplicates to Attribute States

● Optimum Set of Attributes and # States

● Weka Rule Induction to Identify Patterns

Summary● Characteristics of an exoplanet taxonomy were

identified● Trade studies ranked attributes● Rules discretized attributes● Taxonomy was sized (Birthday Problem)● A fine-grained taxonomy was portrayed:

● Taxonomy Hierarchy● Taxonomy Signature● Taxonomy Kiviat

Backup:Example Histograms