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This is the laboratory notebook of the PHL, a preprint and technical blog space of ideas and progress reports that could be later incorporated into peer-review research. Its content is mostly oriented to scientists, specially to those involved in our projects. However, many of the entries contain links to images and software that could be of interest to the general scientific community, educators, and public. You can subscribe to it via RSS.
  • Radio Emissions from Red Dwarf Stars with Planets: The GJ 436 Campaign Abel Méndez, PHL @ UPR Arecibo ( Zuluaga, Institute of Physics / FCEN - Universidad de Antioquia ( activity of red dwarf stars, such ...
    Posted Jun 23, 2017, 6:25 PM by Abel Mendez
  • 25 Years of Exoplanet Discoveries Image Credit: NASA/JPL-Caltech January 9, 2017 is the 25th anniversary of the announcement of the first confirmed exoplanets. The planets were discovered around the pulsar PSR 1257 ...
    Posted Dec 30, 2016, 12:35 PM by Abel Mendez
  • Research Opportunities for Undergraduates 2017 Photo: Students from a REU @ Arecibo ObservatoryThese are research opportunity related to astrobiology and astronomy for undergraduate students in 2017, including some targeted at underrepresented students.National OpportunitiesBanneker ...
    Posted Jan 15, 2017, 1:21 PM by Abel Mendez
  • Exoplanet Habitability and Biosignatures @ AbSciCon 2017 The PHL @ UPR Arecibo has an exoplanets session on Connecting Habitability and Biosignature Observations as part of the AbSciCon 2017, April 24-28, 2017 in Mesa, Arizona. The session is ...
    Posted Oct 28, 2016, 10:19 AM by Abel Mendez
  • The 2nd Earth-like Worlds Workshop Details will be available here soon.
    Posted Oct 23, 2016, 5:02 PM by Abel Mendez
  • Charla sobre Planetas Habitables Lugar: Anfiteatro de Éxito Estudiantil, UIPR de AreciboFecha: 25 de octubre de 2016 @ 2:30pm
    Posted Oct 10, 2016, 10:15 AM by Abel Mendez
  • Noche de Observación en el Observatorio de Arecibo
    Posted Aug 11, 2016, 1:48 PM by Abel Mendez
  • Exoplanet Density vs Stellar Flux This plot shows the density-flux distribution for exoplanets less than 20 Earth masses. Size of the planets are to scale. The inside of the planets are color coded by ...
    Posted Jun 22, 2016, 9:42 PM by Abel Mendez
  • Book: Searching for Habitable Worlds An illustrated introduction to the search for habitable worldsWhat does it take to consider a planet potentially habitable? If a planet is suitable for life, could life be present ...
    Posted Aug 26, 2016, 11:50 AM by Abel Mendez
  • An Alien Message was Decrypted This is the list of 66 successful crackers (teams or individuals) of the SETI Decrypt Challenge, which ran from 26 April to 3 June 2016. The solutions to the six ...
    Posted Jun 3, 2016, 8:09 AM by Abel Mendez
  • The Compositional Diversity of Exoplanets This plot shows exoplanets less than 20 Earth masses with known mass and radius, including error bars (light grey lines). Most of these are too hot for life. Only K2 ...
    Posted Jun 2, 2016, 10:51 AM by Abel Mendez
  • Proyectos de Computación e Investigación en el PHL El PHL está buscando estudiantes subgraduados para varios proyectos de computación e investigación durante el año académico 2016-2017. Los requisitos para participar de estos proyectos es ser un estudiante ...
    Posted Jun 22, 2016, 5:57 AM by Abel Mendez
  • Projects for University Students at the Arecibo Observatory The Arecibo Observatory is inviting university students from Puerto Rico to contribute to different research and engineering projects for fall 2016 and early 2017. These projects can be completed as ...
    Posted May 9, 2016, 9:27 AM by Abel Mendez
  • Can you decrypt this alien message? This is a call for a fun scientific challenge by Dr. René Heller.Suppose a telescope on Earth receives a series of pulses from a fixed, unresolved source beyond the ...
    Posted May 4, 2016, 3:10 PM by Abel Mendez
  • A Planet Around Proxima Centauri This is a computer simulation of a hypothetical planet around the nearest star Proxima Centauri. The animation also shows how the star moves due to the gravitational interaction with the ...
    Posted Jan 17, 2016, 7:25 PM by Abel Mendez
  • New Science at the Arecibo Observatory These scientists met yesterday to plan new research endeavors at the Arecibo Observatory. From left to right: Abel Méndez (PHL @ UPR Arecibo), Alex Wolszczan (CEHW @ Penn State), Andrew Seymour (Arecibo ...
    Posted Jan 15, 2016, 6:16 AM by Abel Mendez
  • The Minority Science Writers Internship Program Spend a summer at Science The Minority Science Writers Internship Program 2016 application is now available onlinePlease share this opportunity with your studentsThe AAAS Pitts Family Foundation Minority ...
    Posted Dec 14, 2015, 10:24 PM by Abel Mendez
  • Minority Institution Research Support Program Astrobiology Research Experiences for Faculty from Minority Serving InstitutionsThe Minority Institution Research Support (MIRS) Program was initiated in 2002 to provide opportunities for faculty from Minority Serving Institutions (MSIs ...
    Posted Feb 22, 2016, 12:45 AM by Abel Mendez
  • Charla Magistral: El Comienzo Cuántico del Universo
    Posted Dec 1, 2015, 8:15 AM by Abel Mendez
  • Curso de Astrobiología General El próximo primer semestre (1er Semestre 2016-17) se estará ofreciendo el curso Astrobiología General (ASTR 3010) en la UPR de Arecibo. Esta es la primera vez que se ofrece ...
    Posted Dec 1, 2015, 3:26 AM by Abel Mendez
  • Measurement Errors of Exoplanets These plots show the measurement errors associated with some planetary and stellar properties of confirmed exoplanets. The mean error values are only valid for the given range and not the ...
    Posted May 30, 2015, 7:27 PM by Abel Mendez
  • The First 32 Exoplanets to be Named Here is a table of the first 32 exoplanets that will be named by the general public as part of the ExoWorlds Naming Contest of the International Astronomical Union (IAU ...
    Posted Mar 30, 2015, 1:04 PM by Abel Mendez
  • The Diversity of Worlds: Comparative Planetology and Habitability A session on the Habitability of Exoplanets at the Astrobiology Science Conference 2015 Organizers: Tyler Robinson, NASA Ames Research Center (   Abel Méndez, University of Puerto ...
    Posted Feb 25, 2015, 12:10 PM by Abel Mendez
  • Another Visualization of the Protoplanetary Disk Around HL Tau Here we show a test of a simple IDL code to analyze and visualize the dust structure of protoplanetary disks. We used the impressive image of HL Tau (Figure 1 ...
    Posted Nov 6, 2014, 8:20 AM by Abel Mendez
  • False Starts: Potentially Habitable Exoplanets Here is a list of the first claims of potentially habitable exoplanets that later were found to be incorrect. Now we know that Gliese 581 c is too hot, Gliese ...
    Posted Oct 28, 2014, 10:59 PM by Abel Mendez
  • The Map to the Stars "There will certainly be no lack of human pioneers when we have mastered the art of flight ...In the meantime, we shall prepare, for the brave sky-travellers, maps of ...
    Posted Oct 6, 2014, 3:23 PM by Abel Mendez
  • We should prepare the map for the future space explorers Map of the constellations around Cygnus published on 1825, the first NASA Kepler Field of View. Credit: LoC.Here are two translations from a passage of an open letter from ...
    Posted Oct 6, 2014, 3:21 PM by Abel Mendez
  • Astrobiology @ AGU Fall Meeting The deadline for abstract submissions is fast approaching for sessions at the American Geophysical Union's (AGU) 47th annual Fall Meeting in San Francisco. Below are some sessions that might ...
    Posted Jul 30, 2014, 2:10 PM by Abel Mendez
  • What is habitability and how is it measured? Three very distinct habitable environments. Puerto Rico's El Yunque Rain Forest and Guánica Dry Forest, and Chile's Atacama Desert. Credit: PHL @ UPR AreciboNot everywhere on Earth is ...
    Posted Jan 9, 2015, 7:30 AM by Abel Mendez
  • Beer with BMSIS: Habitability Metrics for Astrobiology Copyright (2007) Scott Adams, Inc. Used with educational license. Original Source. Quantifying the Unquantifiable!Join the Blue Marble Space Institute of Science (BMSIS) for the next "Beer with BMSIS" seminar ...
    Posted Apr 22, 2016, 10:35 AM by Abel Mendez
  • 4D-Exoplanets: A summary of known exoplanets in four dimensions. This plot summarizes all confirmed exoplanets known today (~1,800) as a function of distance from the Sun (light years), their stellar flux (i.e. the energy that they receive ...
    Posted Jun 29, 2014, 11:28 PM by Abel Mendez
  • Exoplanets: From Exhilarating to Exasperating Here are the abstracts of the exoplanets press-conference of the AAS 224 on Monday, 2 June, 2:15 pm EDT. All findings are embargoed until the time of presentation ...
    Posted Jun 2, 2014, 9:06 AM by Abel Mendez
  • Not all habitable planets are equally ‘habitable’ So far we know many potentially habitable planets around other stars out of nearly 2,000 planets that have been detected and confirmed. We expect to find many more in ...
    Posted Mar 27, 2015, 9:41 AM by Abel Mendez
  • Surface Temperature of Planets The mean global surface temperature of a planet in a circular orbit is given by (adapted from Qiu et al., 2003): (1) where Ts = mean global surface temperature (K ...
    Posted Jan 7, 2014, 6:22 AM by Abel Mendez
  • A New Large Batch of Earth-like Worlds Candidates The NASA Kepler added 1,089 new objects of interest from the Q1-16 release to its KOI database. All are objects of interest pending further verification (not dispositioned) to ...
    Posted Jan 4, 2014, 7:10 AM by Abel Mendez
  • Spatial and Temporal Averages for Elliptical Orbits Mean orbital values for distance, stellar flux, and equilibrium temperature can be computed with respect to spatial or temporal coordinates. Spatial averages are usually calculated with respect to the mean ...
    Posted Jan 4, 2014, 8:50 AM by Abel Mendez
  • SER: First Look at Pluto The Scientific Exoplanets Renderer (SER) is our core software to generate photorealistic-looking images of planets such as the ones for the Visible Paleo-Earth and the Habitable Exoplanets Catalog ...
    Posted Nov 13, 2013, 10:02 AM by Abel Mendez
  • Occurrence of Earth-like planets around GKM Stars Here we combine and interpret results from Kopparapu (2013) and Petigura et al. (2013) on the occurrence of Earth-like planets around red-dwarf (type M) and Sun-like (type ...
    Posted Nov 5, 2013, 8:47 AM by Abel Mendez
  • New Kepler Potential Planet Transit Signals The NASA Kepler team released a revised global list of 16,285 potential planet transit signals (formally known as Threshold-Crossing Events or TCE) from quarters one to sixteen, the ...
    Posted Nov 4, 2013, 8:03 AM by Abel Mendez
  • 50th Anniversary of the Arecibo Observatory The Arecibo Observatory (AO) was inaugurated November 1, 1963. To recognize its 50th year of service to the scientific community, the AO is having a science symposium, “50 Years of ...
    Posted Oct 27, 2013, 7:20 PM by Abel Mendez
  • A Binomial Nomenclature for Common Names of Exoplanets When naming exoplanets create common names for both the stellar system and the exoplanetsThere are nearly one thousand exoplanets already confirmed and many more waiting for confirmation. The general ...
    Posted Sep 27, 2013, 12:20 AM by Abel Mendez
  • About 40 potentially habitable worlds by the end of 2015? We started with just two planets in our Habitable Exoplanets Catalog almost two years ago on December 2011. At that time having a catalog for just two planets was overkill ...
    Posted Sep 20, 2013, 3:12 AM by Abel Mendez
  • One-AU Exoplanets Most known exoplanets are within one astronomical unit (AU) from their stars, a bias of our detection methods. Here are graphical representations of 417 stellar systems with planets within one ...
    Posted Aug 12, 2013, 1:01 PM by Abel Mendez
  • Earth from Near and Deep Space The Cassini spacecraft on Saturn and the Messenger spacecraft on Mercury are taking images of Earth in July 19, 2013. From their vantage point Earth will be just a few ...
    Posted Jul 23, 2013, 3:07 AM by Abel Mendez
  • Statistics of Nearby Earth-like Planets Around M-dwarfs Stars Here is an analysis on the frequency, number, distance, and probability of Earth-like planets (Earth-size within the habitable zone) around M-dwarf stars within 10 parsecs (~33 light ...
    Posted Apr 8, 2013, 1:20 AM by Abel Mendez
  • Transits of Earth-like Exoplanets and Exomoons Here are a few transit simulations of Earth-like planets with and without moons (Figures 1-3) including Avatar's Pandora (Figure 4). All simulations assume long cadence observations (every ...
    Posted Apr 29, 2013, 12:31 AM by Abel Mendez
  • Summary of the Limits of the New Habitable Zone The new habitable zone (Kopparapu et al., 2013) has a narrow and wide definition (Figure 1). The narrower 'conservative habitable zone' is bounded by the 'moist greenhouse' and 'maximum greenhouse ...
    Posted Apr 8, 2013, 12:39 AM by Abel Mendez
  • Conferencia en el IITF El Prof. Abel Méndez ofrecerá una conferencia sobre planetas habitables en el Instituto Internacional de Dasonomía Tropical el jueves, 21 de marzo de 2013 a las 2:30 PM. Para ...
    Posted Mar 19, 2013, 1:20 AM by Abel Mendez
  • Limits of the New Habitable Zone Here are some limits of the new habitable zone (HZ) for main sequence stars (Table 1) from Kopparapu et al. (2013) for six parameters: distance from star (Table 2), stellar ...
    Posted Mar 17, 2013, 9:59 PM by Abel Mendez
  • TCE01: Terrestrial Climatology and Ecology Initial test of reading, plotting, and estimate of NPP. These files are part of a study of terrestrial climatology and ecology and are only intended for the scientisits working on ...
    Posted Mar 17, 2013, 3:01 PM by Abel Mendez
  • KOI-172.02: An excellent candidate for a “Venus-twin” (Reposted from It seems that we have our latest "Earth twin candidate." This time, the planet is in orbit around a star very similar to our Sun. It ...
    Posted Jan 14, 2013, 7:56 PM by Abel Mendez
  • The New Potential Habitable Exoplanets Candidates of NASA Kepler We evaluated the new release of 2740 NASA Kepler Candidates and identified 10 new candidates for potential habitable exoplanets from the previous batch. We also noticed that nine of the ...
    Posted Jan 11, 2013, 4:19 PM by Abel Mendez
  • Current NASA Kepler Confirmed Planets This is a list of 132 confirmed planets by the NASA Kepler mission. The list combines both the Kepler Team and the general scientific community detections. All Kepler stars systems ...
    Posted Jan 10, 2013, 3:30 PM by Abel Mendez
  • Exoplanets @ AAS 221 Here are the presentations program and press information for the 221st American Astronomical Society Meeting (AAS 221) from January 6 to 10, 2013. Below are three press conferences related to ...
    Posted Jan 4, 2013, 2:48 PM by Abel Mendez
  • HEC Dump Files for Confirmed Planets, Kepler Candidates, and TCE Here are the HEC Dump Files with the basic statistics as of Jan 3rd, 2013 for Confirmed Exoplanets, NASA Kepler Candidates, and NASA Kepler TCE. They are used as a ...
    Posted Jan 4, 2013, 7:52 AM by Abel Mendez
  • Science Definition Team for the 2020 Mars Science Rover Call for Letters of Application for Membership on the Science Definition Team for the 2020 Mars Science Rover  Solicitation Number: Posted Date:FedBizOpps Posted Date:Recovery and Reinvestment Act Action ...
    Posted Dec 23, 2012, 9:54 AM by Abel Mendez
  • Planetary Habitability @ AGU 2012 Here is a list of the sessions related to planetary habitability that will be presented in the AGU Fall meeting 2012, from December 3 to 7, 2012 in San Francisco ...
    Posted Nov 30, 2012, 10:06 AM by Abel Mendez
  • Annual Arecibo Observatory Scientific Conference Image Credit: Arecibo ObservatoryIMPORTANT: THIS ACTIVITY HAS BEEN POSTPONEDDecember 27 & 28, 2012 Arecibo Observatory, Arecibo, Puerto Rico Overview We cordially invite Puerto Rican astronomers with interests in astronomy ...
    Posted Dec 20, 2012, 7:59 AM by Abel Mendez
  • Exoplanets at the DPS Annual Meeting Here are the exoplanet oral and poster presentations at the 44th annual meeting of the Division for Planetary Sciences (DPS) of the American Astronomical Society (AAS) in Reno, Nevada, 14 ...
    Posted Oct 14, 2012, 7:32 PM by Abel Mendez
  • Exoplanets and Astrobiology at EPSC These are the presentations related to exoplanets and astrobiology at the European Planetary Science Congress 2012, IFEMA-Feria de Madrid, 23–28 September 2012, Madrid, Spain.Oral Program EX1Observations ...
    Posted Sep 25, 2012, 8:22 AM by Abel Mendez
  • AGU Fall Meeting 2012 Here are most of the proposed sessions related to astrobiology, in no particular order, as part of the next AGU Fall Meeting from December 3-7, 2012 on San Francisco ...
    Posted Jul 8, 2012, 12:15 PM by Abel Mendez
  • 84 New Kepler Exoplanet Candidates Ofir and Dreizler (2012) did an independent analysis to 64 stellar systems from the NASA Kepler dataset. They found 84 new exoplanets candidates in these systems increasing the number of ...
    Posted Aug 7, 2012, 7:10 PM by Abel Mendez
  • Exoplanet Presentations at AAS 220th Here is a list of various sessions with exoplanet presentations on the 220th Meeting of the American Astronomical Society from June 10-14, 2012 in Anchorage, Alaska. Check the ...
    Posted Oct 21, 2012, 2:44 PM by Abel Mendez
  • Reference and Color Calibration for the Visible Daily-Earth This is test image that we are using as landmasses reference and color calibration for the Visible Daily-Earth. It shows computer generated global views of Earth as seen from ...
    Posted Jun 4, 2012, 8:37 PM by Abel Mendez
  • Eclipse of May 20-21, 2012 Here is the shadow over Earth near the maximum during the Annular Solar Eclipse of May 20-21, 2012. This image was generated during a color test of our Visible ...
    Posted Jun 4, 2012, 8:38 PM by Abel Mendez
  • Visible Daily-Earth: May 16, 2012 This is a test of the code for our new Visible Daily-Earth project where we will have a true-color global picture of Earth generated daily from geostationary satellites ...
    Posted Jun 4, 2012, 8:39 PM by Abel Mendez
  • Earth Live We are working in a project to put online current daily global satellite images of Earth in true-color (colors as seen by the human eye). Unfortunately, satellites that have ...
    Posted Jun 4, 2012, 8:40 PM by Abel Mendez
  • Three Hot Subterran Exoplanets around KOI-961 Here are some quick stellar and planetary properties (Tables 1 and 2) for the three exoplanets system KOI-961 plus the basic habitability assessment with the Habitable Zone Distance (HZD ...
    Posted Jun 30, 2012, 11:10 AM by Abel Mendez
  • AAS 219 Press Conference: Extraordinary Exoplanets Here are the abstracts of the presentations related to the AAS 219 press conference Extraordinary Exoplanets schedule on Wednesday, January 11, 2012 at 1:00 PM CST (3:00 PM ...
    Posted Jan 11, 2012, 10:15 AM by Abel Mendez
  • Exoplanets with the Most Earth-like Interiors This is a list of exoplanets with the most Earth-like interiors ranked by the Interior Earth Similarity Index (iESI), a measure of how an exoplanet size and bulk density ...
    Posted Aug 11, 2012, 1:56 PM by Abel Mendez
  • Habitability Assessments using Habitable-Space Metrics One of the main problems of measuring habitability, the suitability of an environment to support life, is how to connect the dependency of many environmental variables with life. The best ...
    Posted Jun 30, 2012, 11:16 AM by Abel Mendez
  • Habitable Zone Atmosphere (HZA): A habitability metric for exoplanets The Habitable Zone Atmosphere (HZA) is a measure of the potential of an exoplanet to hold a habitable atmosphere. Most life forms requires some basic atmospheric ingredients like carbon dioxide ...
    Posted Jun 30, 2012, 11:49 AM by Abel Mendez
  • Habitable Zone Composition (HZC): A habitability metric for exoplanets The Habitable Zone Composition (HZC) measures how compatible for life is the bulk composition of an exoplanet within the habitable zone. Life requires a variety of elements from volatiles to ...
    Posted Jul 1, 2012, 11:24 AM by Abel Mendez
  • Standard Mass-Radius Relation for Exoplanets We are trying to develop a standard mass-radius relationship for exoplanets to predict the most likely value from the other. There are very high uncertainties in predicting radius from ...
    Posted Jun 30, 2012, 11:54 AM by Abel Mendez
  • Updates on Kepler-22 b during the First Kepler Science Conference Dec05: The recent confirmation of Kepler-22 b (KOI-087) does not qualify as a potential habitable exoplanet in the Habitable Exoplanets Catalog. It is in the habitable zone of ...
    Posted Jun 30, 2012, 11:56 AM by Abel Mendez
  • Data Comparison of Confirmed Exoplanets with Kepler Candidates Here we show a simple statistical comparison of data for confirmed exoplanets ( and Kepler candidates (Borucki et al., 2011). This analysis was done as a quality test of ...
    Posted Oct 29, 2011, 6:22 AM by Abel Mendez
  • Exoplanets Continuously Within the Habitable Zone There are 83 exoplanets in the habitable zone (HZ) in the currently known 694 exoplanets, but many exhibit wide elliptical orbits that take them just inside or outside the edges ...
    Posted Jun 30, 2012, 12:02 PM by Abel Mendez
  • The Night Sky of Exoplanets We are developing software code to generate photorealistic visualizations of star fields. The code uses information from the stars to generate their visual appearance from any vantage point including relative ...
    Posted Jun 30, 2012, 12:06 PM by Abel Mendez
  • The Periodic Table of Exoplanets This table summarizes in eighteen thermal-mass categories most of the current known exoplanets (as of October 2011). Planets are divided in six mass classes as mercurians, subterrans, terrans, superterrans ...
    Posted Jun 30, 2012, 12:08 PM by Abel Mendez
  • The Apparent Brightness and Size of Exoplanets and their Stars One thing that we are trying to reproduce for the Habitable Exoplanets Catalog is the visual appearance of exoplanets and stars. This includes the color, brightness, and size of the ...
    Posted Jun 30, 2012, 12:10 PM by Abel Mendez
  • Location and Relative Size of Exoplanets on the Night Sky This is a visualization of the location and relative size of current 690 confirmed exoplanet on the night sky, using equatorial coordinates with a rectangular projection. The constellation outlines are ...
    Posted Jun 30, 2012, 12:12 PM by Abel Mendez
  • A Stellar System Map for Exoplanets Here we created a stellar map of 564 exoplanets systems from the latest database of confirmed exoplanets from the Extrasolar Planets Encyclopaedia. The map helps to visualize the relative distance ...
    Posted Jun 30, 2012, 12:19 PM by Abel Mendez
  • Latest List of Potential Habitable Exoplanets and Exomoons We finally identified potential habitable exoplanets and exomoons from three catalogs. This was the first step in the construction of our Habitable Exoplanets Catalog (HEC). No exomoons have been detected ...
    Posted Oct 1, 2011, 8:32 PM by Abel Mendez
  • Earth Around a Red Star The current potential habitable exoplanets, HD 85512 b and Gliese 581 d, orbit red stars. HD 85512 is a K5V and Gliese 581 is a M3V type star, both dimmer ...
    Posted Sep 26, 2011, 1:18 PM by Abel Mendez
  • Earth "Real" Blues Our vision is not only limited by the energy range on the visible spectrum but also by its sensitivity to particular colors. The eyes are more adapted to see green ...
    Posted Sep 26, 2011, 7:29 AM by Abel Mendez
  • Current Number of Habitable Exoplanets: 16 There are now two potential habitable exoplanets out of the confirmed 687, and 14 out of the published 1235 Kepler candidates. The original Kepler paper by Borucki et al. (2011 ...
    Posted Sep 24, 2011, 7:46 PM by Abel Mendez
  • Only 39 Kepler Planet Candidates in the Habitable Zone Last April 2011 the Kepler Mission Team published a paper describing 1235 new planet candidates (Borucki et al., 2011). They argue that 56 of those where in the habitable zone ...
    Posted Sep 22, 2011, 6:36 AM by Abel Mendez
  • The Exoplanet's Stars We are developing a code to automatically generate updated diagrams and visualizations from various exoplanets catalogs for the Habitable Exoplanet Catalog. Here is a test showing the mass, temperature, and ...
    Posted Sep 18, 2011, 10:11 PM by Abel Mendez
  • The Habitability of "Tatooine" Kepler-16 (AB) b Kepler-16 (AB) b, an exoplanet with a Saturn-like mass, Venus-like orbit, and Mars-like temperatures.Kepler-16 (AB) b, aka "Tatooine," is the first exoplanet detected around ...
    Posted Sep 17, 2011, 12:39 PM by Abel Mendez
  • Habitability Metrics and Classifications for Exoplanets Various habitability metrics can be used to assess and compare the potential for life, as we know it, of exoplanets. The main idea behind these metrics is to simplify the ...
    Posted Sep 6, 2011, 6:50 AM by Abel Mendez
  • The Surface Pressure of Earth-like Exoplanets Earth's atmospheric mass is about 5.3 x 1018 kg, that is close to one part per million (ppm) of its total mass. The atmosphere mass fraction of ...
    Posted Jan 24, 2016, 2:13 PM by Abel Mendez
  • A Mass Classification for both Solar and Extrasolar Planets We will need a simple way to communicate results as part of the Habitable Exoplanets Catalog. Our Habitable Exoplanet Classification focus only on habitable planets and a broader classification will ...
    Posted Oct 2, 2011, 11:18 AM by Abel Mendez
  • The Mass and Radius of Potential Exomoons We barely have the capability to detect Earth-size exoplanets, less moons around them. Small exomoons will be atmosphere-less bodies, like our own Moon that shares with Earth the ...
    Posted Sep 30, 2011, 10:35 AM by Abel Mendez
  • Habitable Zone Distance (HZD): A habitability metric for exoplanets The search for life in the universe requires methods to identify and characterize habitable planets in other stars. The concept of habitable zones (HZ) around stars provides the easiest procedure ...
    Posted Jul 30, 2012, 2:17 PM by Abel Mendez
  • A Thermal Planetary Habitability Classification for Exoplanets Current and future observations by ground and orbital missions will be able to identify habitable exoplanets. As a first assessment, the surface temperature of Earth-like exoplanets is used as ...
    Posted Aug 9, 2011, 10:06 AM by Abel Mendez
  • Vegetation, Ice and Deserts of the Paleo-Earth In our previous post we discussed the distribution of landmasses of the Paleo-Earth. Here we used the Visible Paleo-Earth (VPE) datasets to estimate the global surface coverage of ...
    Posted Jul 29, 2011, 3:46 AM by Abel Mendez
  • Habitability of the Paleo-Earth as a Model for Earth-like Exoplanets The Phanerozoic is the last Eon of Earth history, from 542 million years ago to today. This was the period when large and complex life started to populate the ocean ...
    Posted Aug 6, 2011, 3:05 AM by Abel Mendez
  • Distribution of landmasses of the Paleo-Earth Our planet shows different features as it rotates along its axis, sometimes dominated by land and others by ocean. Land areas are distributed predominantly in the Northern Hemisphere (68%) relative ...
    Posted Jul 8, 2011, 6:53 AM by Abel Mendez
  • The Distribution of Complex Life in the Last 540 Million Years Following our previous post for the paleo-distribution of life, here we show two animations of the distribution of complex life in the last 540 million years based on the ...
    Posted Jul 1, 2012, 7:19 PM by Abel Mendez
  • The Global Paleo-Distribution of Life 120 Ma We will be doing a simple habitability analysis of Earth in the last 750 million years as part of the Visible Paleo-Earth (VPE) project. We are using the fossil ...
    Posted May 30, 2011, 3:26 AM by Abel Mendez
Showing posts 1 - 100 of 108. View more »

Radio Emissions from Red Dwarf Stars with Planets: The GJ 436 Campaign

posted Apr 6, 2017, 8:07 PM by Abel Mendez   [ updated Jun 23, 2017, 6:25 PM ]

Abel Méndez, PHL @ UPR Arecibo (
Jorge Zuluaga, Institute of Physics / FCEN - Universidad de Antioquia (

The activity of red dwarf stars, such as Proxima Centauri and TRAPPIST-1, are of special interest due to their potential to support habitable planets around them. Planets around these stars could experience tidal locking, strong stellar magnetic fields, strong flares and high UV and X-ray fluxes, all factors that might affect their habitability. Red dwarf stars are also known emitters of radio-flaring emissions near 5 GHz that are not always correlated with other spectral emissions. We hypothesize that periodic interaction of close-in planets with the magnetosphere of the star might produce small but detectable effects on the occurrence or shape of their radio emissions. Here we used the Arecibo Observatory to observed at 4 to 5 GHz (C-band) the red dwarf star Gliese 436. This star is not a known emitter of radio flares but has a close-in hot-neptune planet in an elliptical orbit. Our goal was to characterize its radio emissions and search for any potential correlations between its activity and the presence of its planet. For comparisons, we observed the six known flare stars Ross 128, Wolf 359, HD 95735, BD +202465, and V* RY Sex. We also observed K2-18, a red dwarf star with an Earth-sized planet in the habitable zone. Radio flux calibration was done with the quasar 3C263.1 (B1140+223). We are currently analyzing over 200 Gb of data from these observations.

GJ 436 b Summary

Observation Schedule

A31232929Apr201720:4523:00Abel MendezJorge Zuluaga
A312366May201720:1522:30Abel MendezJorge Zuluaga
A31231212May201720:0022:00Abel MendezJorge Zuluaga
A31232020May201719:3021:30Abel MendezJorge Zuluaga

Stellar Data

Visual Reference Images

25 Years of Exoplanet Discoveries

posted Dec 30, 2016, 12:33 PM by Abel Mendez   [ updated Dec 30, 2016, 12:35 PM ]

January 9, 2017 is the 25th anniversary of the announcement of the first confirmed exoplanets. The planets were discovered around the pulsar PSR 1257+12 from the Arecibo Observatory by Alex Wolszczan and Dale Frail.

Note from the Discoverer

The pulsar planets have been detected orbiting PSR B1257+12, the 6.2-millisecond pulsar discovered in February 1990, during a survey of the radio sky with the 305-m Arecibo radio telescope. The two outer planets, announced in January 1992, have masses of about 4 times the mass of our Earth, and the inner one, detected in 1994, is only twice as massive as the Moon. The corresponding orbital periods of the three planets are 98, 65 and 25 days. The whole system is compact enough to fit inside the orbit of Mercury.

The pulsar planet discovery has been made using the highly precise pulse timing technique. It was possible because the orbiting planets make the pulsar wobble in space, and that motion translates into easily measurable, millisecond variations in the pulse arrival times at the telescope. The same technique was used to confirm the existence of the pulsar planets by detecting subtle changes in the orbits of the two larger planets caused by their proximity to the 3:2 orbital resonance.

A planetary system orbiting PSR B1257+12 represents the first confirmed planets beyond the Sun. It is also the first extrasolar planetary system, in which an orbital resonance has been measured, and it is the first example of a “tightly packed”, super-Earth mass system, which is the kind of orbital configuration now commonly detected by the Kepler telescope and the most sensitive radial velocity surveys. From the very start, the existence of such a system carried with it a prediction that planets around other stars must be common, and that they may exist in a wide variety of architectures, which would be impossible to anticipate on the basis of our knowledge of the Solar System alone.

- Alex Wolszczan


Research Opportunities for Undergraduates 2017

posted Nov 19, 2016, 10:26 AM by Abel Mendez   [ updated Jan 15, 2017, 1:21 PM ]

Photo: Students from a REU @ Arecibo Observatory

These are research opportunity related to astrobiology and astronomy for undergraduate students in 2017, including some targeted at underrepresented students.

National Opportunities
        Search for more opportunities in Pathways to Science.

Local Opportunities

Exoplanet Habitability and Biosignatures @ AbSciCon 2017

posted Oct 28, 2016, 9:52 AM by Abel Mendez   [ updated Oct 28, 2016, 10:19 AM ]

The PHL @ UPR Arecibo has an exoplanets session on Connecting Habitability and Biosignature Observations as part of the AbSciCon 2017, April 24-28, 2017 in Mesa, Arizona. The session is organized by Abel Méndez (PHL @ UPR Arecibo), Dirk Schulze-Makuch (Washington State University), and Edgard Rivera-Valentin (Arecibo Observatory/USRA). Here are the abstract submission instructions (Deadline: January 18, 2017). There is also a related workshop on quantitative measures of habitability on February 2017 in Puerto Rico.

Theme: Exoplanets
Session: Biosignatures
Topic: Connecting Habitability and Biosignature Observations

Organizers: Abel Mendez (PHL @ UPR Arecibo),; Dirk Schulze-Makuch (Washington State University),; and Edgard Rivera-Valentin (Arecibo Observatory/USRA),

Summary: On Earth, habitability is generally correlated with the presence of life, but this will not necessarily be the case for all habitable planets. For instance, a biosignature on a non-habitable planet by terrestrial standards could be interpreted as a false-positive or caused by very different biological process, among other explanations. Therefore, it is necessary to include quantitative measures of habitability to properly assess the significance of any biosignature detections. This session is requesting presentations about potential correlations between habitability and biosignature observations based on theoretical or empirical models, including those for complex or exotic life forms. The models presented as part of this session might consider any spatial and temporal scale, and extend from microbial to complex life, but should address how these models might scale-up and produce together both detectable global habitable conditions and biosignatures from afar.

The 2nd Earth-like Worlds Workshop

posted Oct 23, 2016, 4:59 PM by Abel Mendez   [ updated Oct 23, 2016, 5:02 PM ]

Details will be available here soon.

Charla sobre Planetas Habitables

posted Oct 10, 2016, 10:14 AM by Abel Mendez   [ updated Oct 10, 2016, 10:15 AM ]

Lugar: Anfiteatro de Éxito Estudiantil, UIPR de Arecibo
Fecha: 25 de octubre de 2016 @ 2:30pm

Noche de Observación en el Observatorio de Arecibo

posted Aug 11, 2016, 1:47 PM by Abel Mendez   [ updated Aug 11, 2016, 1:48 PM ]

Exoplanet Density vs Stellar Flux

posted Jun 22, 2016, 9:41 PM by Abel Mendez   [ updated Jun 22, 2016, 9:42 PM ]

This plot shows the density-flux distribution for exoplanets less than 20 Earth masses. Size of the planets are to scale. The inside of the planets are color coded by composition. The color of their outside borders correspond to the parent star spectral type. Mercury, Venus, Earth, and Mars are included for comparison. Data is from the NASA Exoplanet Archive. This is large plot intended for viewing at high resolutions, click to enlarge. Credit: PHL @ UPR Arecibo. 

Book: Searching for Habitable Worlds

posted Jun 19, 2016, 7:36 AM by Abel Mendez   [ updated Aug 26, 2016, 11:50 AM ]

An illustrated introduction to the search for habitable worlds

What does it take to consider a planet potentially habitable? If a planet is suitable for life, could life be present? Is life on other planets inevitable? Searching for Habitable Worlds answers these questions and provides both the general public and astronomy enthusiasts with a richly illustrated discussion of the most current knowledge regarding the search for extrasolar planets. Nearly everyone wants to know if we are alone in the universe. This book might not have the answers, but shows where we should look.

This book is a fun and accessible book for everyone from middle schoolers to amateur astronomers of all ages. The use of non-technical language and abundant illustrations make this a quick read to inform everyone about the latest movement in the search for other planets that we might be able to inhabit. After a brief discussion on why humans are hard-wired to be curious, and to explore the unknown, the book describes what extrasolar planets are, how to detect them, and how to pin down potential targets. In addition, a data-driven list of the best candidates for habitability is profiled and the next generation of exoplanet-hunting scientific instruments and probes are identified.

ISBN: 9781681744001 | PDF ISBN: 9781681744018
Copyright © 2016 | 78 Pages | Publication Date: June, 2016

Get the book from:

Amazon Kindle

About the Authors

Abel Mendez is an Associate Professor of Physics and Director of the Planetary Habitability Laboratory, Department of Physics and Chemistry, University of Puerto Rico at Arecibo, Puerto Rico. He does research about planetary habitability, exoplanets, and astrobiology in general. He is also the creator of the Habitable Exoplanets Catalog.

Wilson Gonzalez-Espada is an Associate Professor of Physics and Science Education, Department of Mathematics and Physics, Morehead State University, Morehead, Kentucky. His scholarly interests include science communication, the public understanding of science, and physics education research. He is also one of the editors of the book Ciencia Boricua.

An Alien Message was Decrypted

posted Jun 3, 2016, 7:58 AM by Abel Mendez   [ updated Jun 3, 2016, 8:09 AM ]

This is the list of 66 successful crackers (teams or individuals) of the SETI Decrypt Challenge, which ran from 26 April to 3 June 2016. The solutions to the six test questions Dr. Rene Heller asked are:
  1. What is the typical body height of our interstellar counterparts? 2.45 m
  2. What is their typical lifetime? 180 yr
  3. What is the scale of the devices they used to submit their message? 100 km
  4. Since when have they been communicating interstellar? 10,000 yr
  5. What kind of object do they live on? This one is tricky because I don't know the answer myself, making this part of the experiment a blind-blind test. The spatial information translates into 0.26 AU (100 times the Earth-Moon distance, if anyone recognized). The corresponding picture shows four planets or moons, one of which seems to be inhabited by our alien friends. So they might live on the 4th planet (or on one of three moons orbiting a giant planet) in the habitable zone around a low-mass star.
  6. How old is their stellar system? 6 Gyr
Dr. Heller have been asked whether they could not have used the period of the radio signal as a yardstick for the temporal dimension to make the message more universally readable - and not only by us. Obviously, the fact that they used the 50 yr as a yardstick means that they deliberately sent the message to us. Yes, the wave period could also be used. But the fact that they used their distance to us as a yardstick tells us that they know that we exist. They found us first. It's like they winked at us with this yardstick.

In total, Dr. Heller received about 500 e-mails relating to the SETI Decrypt Challenge and sent out about 200. More background information including a full description on how to interpret the message will be given in a journal article.

Thanks for your participation also to those about 30 individuals who sent Dr. Heller their not fully correct solutions. The successful crackers are sorted by date of their submission below. Their twitter user names are in braces if provided and cleared for publication.

01. Andy Stewart (@k4patzer)                                                     27 April 2016
02. Daniel Angerhausen (@dan_anger)                                              28 April 2016
03. Puiyan & Jason (@xeph_yr & @perfinion)                                       04 May   2016
04. reddit /r/askscience moderators (@RedditAskSci)                              04 May   2016
05. Mark Collins                                                                 05 May   2016
06. John Graham-Cumming (@jgrahamc)                                              06 May   2016
07. Robert Danorth                                                               06 May   2016
08. Frederick John Milens III (@FrederickMilens)                                 06 May   2016
09. Ching                                                                        06 May   2016
10. Shawn Beard (@DrShawnBeard)                                                 07 May   2016
11. Carlos Garcia Rodriguez                                                     07 May   2016
12. Hector Sanchez Iranzo (hesai88)                                             07 May   2016
13. Erick Vermot (@erickvermot1)                                                07 May   2016
14. Team Bip/Blop (@securityliaison & @alistairheath & @LondonCoal)             07 May   2016
15. Leon Hostetler                                                              07 May   2016
16. Gonzalo Bernabe Pacheco Covili (@gonn)                                      07 May   2016
17. Ian Baudains                                                                07 May   2016
18. Paulo Barreto (@pbarreto)                                                   07 May   2016
19. Xavi R. Pinteno (@frikjan)                                                  07 May   2016
20. Robert Boone (@BigRobVT)                                                    08 May   2016
21. Antoni Burguera (@tburguera)                                                08 May   2016
22. Daniel Nava (@dap_19)                                                       08 May   2016
23. Vladimir Kovoltelov (@Vokdal)                                               08 May   2016
24. Marco Lopez                                                                 08 May   2016
25. Patrik Hedstroem (@pathe915)                                                08 May   2016
26. Kurt Forsberg                                                               08 May   2016
27. Carlos Domingo (@Choli)                                                     08 May   2016
28. Ben Pearce (@AstroBio_Ben)                                                  08 May   2016
30. Griffin Smith (@PossiblyAWizard)                                            08 May   2016
31. Mike Matessa (@mmatessa)                                                    09 May   2016
32. Panupong V (@praew_proud)                                                   09 May   2016
33. Sergio Machado (@SergioM_71)                                                09 May   2016
34. Jeff Fountain (@jeff_fountain)                                              10 May   2016
35. Kevin Ducrocq                                                               10 May   2016
36. Matti Timonen (@timonenma)                                                  10 May   2016
37. Marcin Romaszewicz (@marcin_roma)                                           10 May   2016
38. Rafael Rubio (@rafa78bcn)                                                   10 May   2016
39. Orencio Robaina & Orencio Robaina & Vincent Cohen                           10 May   2016
40. David Bardini (@DBarTweet)                                                  11 May   2016
41. Pedro Igrejas                                                               11 May   2016
42. Anton Sudnikov                                                              12 May   2016
43. Sieg du Preez (@SiegDuPreez)                                                12 May   2016
44. Marius Utheim (@MariusUt)                                                   12 May   2016
45. Rodrigo Bascunan Barnert (@barnert)                                         12 May   2016
46. Juanma de los Santos                                                        12 May   2016
47. Davide Silvestri (@silvestridavide) & Gilles Mariotti (@GillesMariotti)     12 May   2016
48. Oliver Read (@ollie_read)                                                   12 May   2016
49. ISIR team - R. O. Chavez-Garcia & T. Goncalvez                              13 May   2016
50. Michael Luciani (@mikeluciani)                                              13 May   2016
51. Cedric Rousseau (@cedrouTwitting)                                           13 May   2016
52. Robert Pfender (@pfenderrg)                                                 13 May   2016
53. Borja Paz Rodriguez (@borjapazr)                                            14 May   2016
54. Jeff Landgraf (@jml985)                                                     14 May   2016
55. Rob van den Tillaart (@robtillaart)                                         16 May   2016
56. Carlos Laborde                                                              18 May   2016
57. Brian Irick                                                                 18 May   2016
58. Felipe Alejandro Salazar Vazquez (@Eofreond)                                19 May   2016
59. Fernando Daniel Leon                                                        19 May   2016
60. Luke Arpino & Rosie Leaman                                                  19 May   2016
61. Adrian D (@racanu)                                                          20 May   2016
62. Carlos Pena (@Wopper) & Alberto Cid (@Acido)                                21 May   2016
63. Nick Cranch (@2minds1)                                                      25 May   2016
64. Cedric Bassem & Yannick Jadoul                                              03 June  2016
65. Brian Hayzlett & Benj Zagorski & Ksenia Kriksunov & Matt Dubin              03 June  2016
66. Daniel Reardon (@Daniel_Reardon) & Ross Turner (@rossjturner)               03 June  2016

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