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Goldilocks Zones
– a Fine-Grained Exoplanet Taxonomy
Patrick J. Talbot (Presenter)
Dennis R. Ellis (Analysis)
Introduction and Summary
Situation: Since the 1990's, over 5,000
exoplanets have been identified* and the rate of
discovery 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
https://github.com/OpenExoplanetCatalogue/open_exop
Need: a robust, extensible organization scheme
for 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.
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* http://exoplanets.org/, as of 1 September 2015.
Objective
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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
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Perform Trades
Mission
Functional
Discretize
● Rules
Filter Attributes
● Birthday Problem
Compute Signatures
Yes
Verify
Uniqueness
No
Unique?
Reduce
#States
Increase
#States
No
Yes
Minimal?
Done
Tag
Planet
Star
Binary
Declination
Rightascension
Distance
Name
Semimajoraxis
Separation
Positionangle
Eccentricity
Periastron
Longitude
Meananomaly
Ascendingnode
InclinatioN
Epoch
Period
Transittime
Periastrontime
Mass
Radius
Temperature
Age
Metallicity
Spectraltype
MagB
MagV
MagR
MagI
MagJ
MagH
MagK
Discoverymethod
Istransiting
Description
Discoveryyear
Lastupdate
Spinorbitalignment
Data Structures, MIT Open Exoplanet Catalog
Description
a single planet. May be a free floating (orphan) planet
A single star. A star can be host to one or more planets
two stars, star/binary or two binaries.
Declination
Right ascension
Distance from the Sun
Used multiple times for objects with multiple names.
Semi-major axis of a planet (heliocentric coordinates)
Projected separation of planet from its host
Position angle
Eccentricity
Longitude of periastron
Mean longitude at a given Epoch (all planets in a system)
Mean anomaly at a given Epoch (all planets in one system)
Longitude of the ascending node
Inclination of the orbit
Epoch for the orbital elements
Orbital period
Time of the center of a transit
Time of periastron
Mass (or m sin(i) for radial velocity planets)
Physical radius
Temperature (surface or equilibrium)
Age
Stellar metallicity
Spectral type
B magnitude
Visual magnitude
R magnitude
I magnitude
J magnitude
H magnitude
K magnitude
Discovery method : timing, RV, transit, imaging.
Whether the planet is transiting (1) or not (0).
Short description of the planet
Year of the planet's discovery
Date of the last (non-trivial) update
Rossiter-McLaughlin Effect.
Mission Trade Study
Functional Trade Study
Node Composite Score
Sample Rules
Probability of Duplicates vs Catalog Size
Exoplanet Characteristics Hierarchy
Exoplanet
Name
Input
Header Only
Elements
Period
Exoplanets
Header Only
Physical
Header Only
Host star
Inclination
Metallicity
Distance
Binary
Eccentricity
Spectral
Type
Mass
Semi-major axis
Radius
Separation
Age
Temperature
Exoplanet Signature
Separation
(Moderate)
Distance
(Far)
Eccentricity
(Nearly Circular)
Mass
(Small)
Spectral type
(Hottest)
Age
(Ancient)
Temperature
(Hot)
H H 2 M LS L N L O LA
Binary
(2 stars)
Period
(Long)
Inclination
(Low)
Semi-major Axis
(Large)
Physical Radius
(Large)
Exoplanet Kiviat Diagram
Physical
Orbital
Composition
[FeHg]
Inclination
Mass
Period
Size
Goldilocks
Zone
Kepler 423c
Habitability
Index = .3
Host Variability
Host Age
Host Spectral Type
Environmental
Influential
Coming in the Full Paper
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Percent of Duplicate Signatures
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Sensitivity of Duplicates to Attribute States
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Optimum Set of Attributes and # States
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Weka Rule Induction to Identify Patterns
Summary
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Characteristics of an exoplanet taxonomy were
identified
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Trade studies ranked attributes
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Rules discretized attributes
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Taxonomy was sized (Birthday Problem)
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A fine-grained taxonomy was portrayed:
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Taxonomy Hierarchy
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Taxonomy Signature
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Taxonomy Kiviat
Backup:Example Histograms