bhanditz / open_exoplanet_catalogue

The Open Exoplanet Catalogue

Open Exoplanet Catalogue

Status update

As you might have noticed the Open Exoplanet Catalogue has been in a a dormant state for a few months, recieving only a few updates. This is mainly due to a lack of contributors. In the fall, we plan to have about 100 undegraduates in computer science work on the OEC. Their main goal will be to implement an automated way to gather data from various sources on the internet. We will keep the data fully referenced so that it is easy to find out where the data is coming from. We will also allow for manual edits of the accumulated data (as it has been in the past). All of these things together should make the OEC the most complete and most up-to-date exoplanet catalogue out there. In the meantime, please keep your pull request coming! -- Hanno Rein -- June 2016.

About the Open Exoplanet Catalogue

The Open Exoplanet Catalogue is a database of all discovered extra-solar planets. New planets are usually added within 24 hours of their announcement.

The database is licensed under an MIT license (see below), which basically says you can do everything with it. If you use it for a scientific publication, please include a reference to the Open Exoplanet Catalogue on github or to this arXiv paper.

The catalogue is a community project. Please send corrections and additions via pull request or email. If you have questions or comments about git or the database, please do not hesitate to contact of the contributors directly.

If you are looking for a simple comma/tab separated table, you might want to check out this repository.

How to access the catalogue using Python

It is very easy to access the Open Exoplanet Catalogue using python. Here is a short snippet to print out some basic planet data. No download, no installation and no external libraries are required.

# python 2.x
import xml.etree.ElementTree as ET, urllib, gzip, io
url = "https://github.com/OpenExoplanetCatalogue/oec_gzip/raw/master/systems.xml.gz"
oec = ET.parse(gzip.GzipFile(fileobj=io.BytesIO(urllib.urlopen(url).read())))
 
# Output mass and radius of all planets 
for planet in oec.findall(".//planet"):
    print [planet.findtext("mass"), planet.findtext("radius")]
 
# Find all circumbinary planets 
for planet in oec.findall(".//binary/planet"):
    print planet.findtext("name")
 
# Output distance to planetary system (in pc, if known) and number of planets in system
for system in oec.findall(".//system"):
    print system.findtext("distance"), len(system.findall(".//planet"))

If you are using python 3, replace the first three lines by

import xml.etree.ElementTree as ET, urllib.request, gzip, io
url = "https://github.com/OpenExoplanetCatalogue/oec_gzip/raw/master/systems.xml.gz"
oec = ET.parse(gzip.GzipFile(fileobj=io.BytesIO(urllib.request.urlopen(url).read())))

Data Structure

The following table shows all the possible tags in the Open Exoplanet Catalogue.

Tag	Can be child of	Description	Unit
system		This is the root container for an entire planetary system
planet	system, binary, star	This is the container for a single planet. The planet is a free floating (orphan) planet if this tag is a child of system.
star	system, binary	This is the container for a single star. A star can be host to one or more planets (circum-stellar planets).
binary	system, binary	A binary consists of either two stars, one star and one binary or two binaries. In addition a binary can be host to one or more planets (circum-binary planets).
declination	system	Declination	+/- dd mm ss
rightascension	system	Right ascension	hh mm ss
distance	system	Distance from the Sun	parsec
name	system, binary, star, planet	Name of this object. This tag can be used multiple times if the object has multiple Names.
semimajoraxis	binary, planet	Semi-major axis of a planet (heliocentric coordinates) if child of planet. Semi-major axis of the binary if child of binary.	AU
separation	binary, planet	Projected separation of planet from its host, or if child of binary the projected separation from one component to the other. This tag can occur multiple times with different units. It is different from the tag semimajoraxis as it does not imply a specific orbital configuration.	AU, arcsec
positionangle	binary	Position angle	degree
eccentricity	binary, planet	Eccentricity
periastron	binary, planet	Longitude of periastron	degree
longitude	binary, planet	Mean longitude at a given Epoch (same for all planets in one system)	degree
meananomaly	binary, planet	Mean anomaly at a given Epoch (same for all planets in one system)	degree
ascendingnode	binary, planet	Longitude of the ascending node	degree
inclination	binary, planet	Inclination of the orbit	degree
impactparameter	planet	Impact parameter of transit
epoch	system	Epoch for the orbital elements	BJD
period	binary, planet	Orbital period	day
transittime	binary, planet	Time of the center of a transit	BJD
periastrontime	binary, planet	Time of periastron	BJD
maximumrvtime	binary, planet	Time of maximum radial velocity	BJD
mass	planet, star	Mass (or m sin(i) for radial velocity planets)	Jupiter masses (planet), Solar masses (star)
radius	planet, star	Physical radius	Jupiter radii (planet), Solar radii (star)
temperature	planet, star	Temperature (surface or equilibrium)	Kelvin
age	planet, star	Age	Gyr
metallicity	star	Stellar metallicity	log, relative to solar
spectraltype	star, planet	Spectral type
magB	binary, star, planet	B magnitude
magV	binary, star, planet	Visual magnitude
magR	binary, star, planet	R magnitude
magI	binary, star, planet	I magnitude
magJ	binary, star, planet	J magnitude
magH	binary, star, planet	H magnitude
magK	binary, star, planet	K magnitude
discoverymethod	planet	Discovery method of the planet. For example: timing, RV, transit, imaging.
istransiting	planet	Whether the planet is transiting (1) or not (0).
description	planet	Short description of the planet
discoveryyear	planet	Year of the planet's discovery	yyyy
lastupdate	planet	Date of the last (non-trivial) update	yy/mm/dd
spinorbitalignment	planet	Rossiter-McLaughlin Effect.	degree

Errors

Uncertainties can be added to values using the following attributes of the tag. We assume that these uncertainties represent the standard error of the measurement (68.2% confidence level). However, keep in mind that it is often not possible to collapse an entire posterior distribution to a single number.

The syntax for error bars is: <mass errorminus="0.1" errorplus="0.1">1.0</mass>

The syntax for upper/lower limits is: <mass upperlimit="1.0" />

Constants

The Open Exoplanet Catalogue stores information using a few basis units. For stars, mass and radius units are derived from our star, Sol (the Sun). For exoplanets, mass and radius units are derived from the planet Jupiter.

The mass of Jupiter, the Sun, and even Earth are so huge that it is more meaningful to simply reference their mass in relation to each other, rather than common SI units. These values are approximate.

Ratio	Value
Sol/Jupiter mass	1047.566
Jupiter/Earth mass	317.8284
Sol/Earth mass	332,946.1

In many publications, radius measurements are quoted based on Earth’s or Jupiter’s equatorial radius, so we list here the relevant IAU recommended nominal constants.

Constant Name	Value
Solar radius	695,700 km
Jupiter equatorial radius	71,492 km
Earth equatorial radius	6378.1 km

There are a few more units and standards used: degrees, days, billions of years (gigayears or Gyr), AU, parsecs, sexagesimal degrees (declination), and sexagesimal hour angle (Right Ascension). These are all much more well defined than the mass and radius units above, so we will not produce them here. Please note that the Open Exoplanet Catalogue makes no accommodation for different celestial reference frames.

Plots

To create custom plots please visit this repository for example scripts.

Download ASCII tables

A few words of caution: Many planetary systems are part of binary star systems. The architecture of these systems is correctly represented in the original XML files of the Open Exoplanet Catalogue. In fact, it is to my knowledge the only catalogue that can do that. However, you might prefer to work with a simpler comma or tab separated table instead of the hierarchical XML file format. During the conversion process, some information is inevitably lost. Most importantly, the architecture of the star system. One cannot easily represent an arbitrary binary/triple/quadruple system in a simple table. Additionally, if planets have multiple identifiers only the first identifier is outputted. Using the original XML file format and git, you can use the git blame functionality to find references to scientific publications for every numeric value in the database. This functionality is also lost in the conversion process.

In a separate repository, you will find a comma separated and a tab separated ASCII table of the Open Exoplanet Catalogue.

Documentation

This file describes the philosophy and data-format of the catalogue. However, everything should be rather self-explanatory. The actual data is in the systems directory. Each XML file corresponds to one planetary system.

If you are editing the file with vim, have a look at the xmledit plugin. I found it very helpful.

How to include references to publications

It seems that the most elegant place to put references to publications is the commit message. This allows one to trace back each individual value in the database to the source using git blame. Furthermore it does not add any additional clutter to the text files themselves. So, when committing any changes, please create one commit per publication and include the reference in the commit message from now on.

Derived products

The following list contains links to other catalogues, websites and apps that are derived from or make use of the Open Exoplanet Catalogue.

• oec_web: A suite of HTML pages acting as a front-end of the Open Exoplanet Catalogue. It includes visualizations of orbits, planet sizes and habitable zones. It also includes a plotting tool to generate correlation diagrams. The website is hosted at openexoplanetcatalogue.com.
• oec_plots: Plots and example scripts that make use of the Open Exoplanet Catalogue.
• oec_outreach: A clone of the main repository with images and tags that are mainly used for outreach purposes.
• oec_iphone: Compressed files, references to refereed publications, resized images and legacy support for various versions of the mobile version are in the repository.
• ExoData: A Python module for loading the catalogue into python for use with applications along with many exoplanet related equations and tools.
• iPhone Exoplanet App: Popular iOS application with many visualizations of the entire catalogue. Version 9.1 and later will fully support planets in multiple star systems.

License

Copyright (C) 2012 Hanno Rein

Permission is hereby granted, free of charge, to any person obtaining a copy of this database and associated scripts (the "Database"), to deal in the Database without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Database, and to permit persons to whom the Database is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Database. A reference to the Database shall be included in all scientific publications that make use of the Database.

THE DATABASE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE DATABASE OR THE USE OR OTHER DEALINGS IN THE DATABASE.