Research

My Research Interests

  • solar system and planet  formation
  • small bodies in the Solar System
  • seasonal processes on Mars
  • extrasolar planets
  • applying citizen science to mine large datasets for Solar System science

Current

Planet Hunters-Searching for Exoplanets with Citizen Science

When an extrasolar planet (exoplanet) moves in front of it’s parent star, a portion of the star’s light is blocked out by the planet as it crosses the face of it’s star. This causes the star to dim.  These characteristic dips in light are known as transits and can signal the presence of an orbiting planet. A Jupiter size planet transiting a Sun-like star will cause a 1% drop in star light.

NASA’s Kepler spacecraft is staring at over 160,000 stars looking for the signs of a transits to further understand the frequency of planets in the Milky Way.  Kepler is capable of detecting the ~0.01% decrease caused by small rocky planets and potentially Earth-like planets. The Kepler team has found over 2,000 planet candidates in their search to date.But the Kepler light curves are complex, many exhibiting short-lived brightness variations that may make difficult to characterize. Despite the impressive success of automated period finding search algorithms and data validation pipelines may miss transits dominated by the star’s natural variability.

The human brain excels at pattern recognition and. Though impossible for a single person to review each of the ~150,000 Kepler light curves, with the Internet we can gather multiple independent assessments of the data set. With Planet Hunters (http://www.planethunters.org), one of the many  Zooniverse citizen science projects, we enlist the general public to inspect the publicly released Kepler data via the World Wide Web. For each star, ~5-10 volunteers review 30 days worth of observations marking possible transits by drawing boxes directly on the presented light curve in the web interface.

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Planet Hunters web interface

Planet Hunters is a collaboration between Yale University, University of Oxford, and Adler Planetarium with Yale Professor Debra Fischer serving as PI of the project. We have demonstrated the success of utilizing citizen science, with the discovery of four unknown planet candidates not previously identified by the Kepler team. I am presently studying the abundance of single planetary systems with Planet Hunters classifications for >2 Earth radii planets on less than 15-day orbits. With Planet Hunters I aim complete a census of the exoplanet population and provide an independent assessment of the Kepler exoplanet inventory. Comparing the two, we can determine the true frequency of planetary systems.

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Light curve of the first identified planet candidate by Planet Hunters

In October 2012, we announced the discovery of our first confirmed planet, PH1 b. PH1 b is a circumbinary planet, orbiting two stars in a stellar binary, in a four star system. Learn more about PH1 b here. In January 2013, we announced the disocovery of our 2nd confirmed planet, PH2 b a Jupiter-sized planet orbiting in the habitable zone of a Sun-like star. You can learn more the science and discoveries coming from the project on the Planet Hunters’ blog.

 Transiting family portrait of the PH1 system. Image credit: Haven Giguere/Yale
Transiting family portrait of the PH1 system. Image credit: Haven Giguere/Yale

To date nearly 300,000 people have joined in world wide to search for planets.  Fancy giving  Planet Hunters a try?

Follow the project on Twitter @planethunters

Planet Four – Studying the Martian Climate by Mapping Seasonal Fans on the South Pole of Mars

Launched in January 2013, Planet Four is a  Zooniverse citizen science project enlisting members of the general public to help study dark blotches and fans that appear on top of the Martian South Pole’s thawing carbon dioxide ice sheet during the Southern Spring and Summer. I am a member of the Planet Four science team led by PI Candy Hansen (PSI).

Planet Four web interface
Planet Four web interface

Using data from the High Resolution Imaging Science Experiment (HiRISE) camera on Mars Reconnaissance Orbiter (MRO), citizen scientists are examining images of Mars’ South Pole mapping the size and directions of seasonal fans. These dark fans develop on the top of the polar carbon dioxide ice sheet, as it thaws over the spring and summer months. The Sun heats the base of the semi-translucent ice sheet producing carbon dioxide gas trapped below the remaining ice. The gas breaks through to the surface exploiting weaknesses and cracks in the ice forming geysers or jets. The geysers loft dust through the cracks in the ice sheet to the surface where it is believed surface winds subsequently sculpted the material into the dark fans observed from orbit. If no wind is present, then instead a elliptical blotch is thought to be produced. This process is completely alien with no analog on our own Earth.

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Seasonal fans spotted on the South Pole of Mars by the HiRISE camera Image Credit:NASA/HiRISE/U. of Arizona

Mapping the distribution and length of the fans is unable to be automated by computers. Planet Four volunteers will produce the largest dataset of fan directions and sizes, providing crucial information for studying the seasonal processes of the Martian South pole.

Seasonal fans spotted on the South Pole of Mars by the HiRISE camera Image Credit:NASA/HiRISE/U. of Arizona
Seasonal fans spotted on the South Pole of Mars by the HiRISE camera Image Credit:NASA/HiRISE/U. of Arizona

To date over 100,000 volunteers world wide have contributed to Planet Four. Map the blotches and fans in HiRISE images and help scientists explore the climate and wind patterns of Mars today at planetfour.org.

Follow the project on Twitter @planet_four

Previous

Searching for Dwarf Planets in the Southern Skies

The last decade has seen an explosion in our understanding of the solar system with the discovery of the largest Kuiper belt objects (KBOs) of comparable and even larger size than Pluto. Each one of these objects; including Makemake, Pluto, Eris, Haumea, Sedna, Quaoar, and Orcus, is bright enough for detailed study. The physical and dynamical properties of these large icy planetoids add another puzzle piece to our understanding of the formation and evolution of the solar system. Each object has a different history and tells its own unique story. For more information on the known dwarf planets  in the Kuiper belt check out my thesis advisor Mike Brown’s dwarf planet website.

Studying these dwarf planets has led to a revolution in our understanding of the Kuiper belt. These objects are the lighthouses of the population; bright enough to be studied with large ground-based and space-based telescopes. With photometric and spectroscopic observations, we have been able to learn about the surface properties and the physical processes acting on these large planetoids. From the discovery of moons around these icy bodies, the internal composition, mass, density, and internal structure of these dwarf planets has been revealed. Satellite formation and orbits of these large KBOs shed light on their dynamical and collisional history. These bright bodies provide a window into the early environment of the outer solar system and planet formation processes.

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Dwarf planet Eris moving in three images taken by the QUEST camera in La Silla, Chile. A passing asteroid appears above Eris in the first image.

I  have helped search the southern skies for the largest and brightest members of the Kuiper belt, including a few undiscovered dwarf planets. The known dwarf planets have all been found from the northern hemisphere.  Yale University had  robotized the 1.0-m Schmidt telescope at the European Southern Observatory (ESO) at La Silla, Chile. The telescope has been equipped with the refurbished Quasar Equatorial Survey Team (QUEST) large-area CCD camera the automation of the 1.0-m Schmidt telescope has provided the unique opportunity to conduct a three-year survey led by  David  Rabinowitz  to search the entire sky south of the ecliptic. We didn’t find any new dwarf planets, but we found many new Kuiper belt objects and a low perihelion, high inclination Centaur 2010 WG9.

Searching for Sednas

The discovery of Sedna on a highly eccentric orbit beyond Neptune  suggests a perplexing new population of icy bodies residing far outside the Kuiper Belt. Sedna is relegated to a no-man’s land between the Kuiper Belt and the Oort Cloud (the source of long period comets). With a perihelion of 76 AU (more than twice that of Neptune), Sedna is well beyond the reach of the gas giants and unlike other Kuiper Belt Objects, could not be scattered into its highly eccentric orbit from gravitational interactions with Neptune alone. Its aphelion of ~1000 AU, is too far from the edge of the solar system to feel the perturbing effects of passing stars or galactic tides. Sedna’s origin challenges our understanding of the solar system.

Some other mechanism no longer active in the solar system today is required to emplace Sedna on its orbit. Several formation mechanisms have been proposed to explain Sedna’s extreme orbit, including interactions with planet-sized bodies, stellar encounters, multiple stellar fly-bys in a stellar birth cluster, interstellar capture, and perturbations from a wide-binary solar companion. A population of icy bodies residing beyond the Kuiper belt is formed in each model. Each of the proposed formation scenarios for Sedna leaves a distinctive imprint on the members of this class of distant objects and has profound consequences for our understanding of the solar system’s origin and evolution. The orbits of these distant planetoids are likely dynamically frozen in place providing a fossilized record of their formation.

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Image Credit: NASA/JPL-Caltech/R. Hurt (SSC-Caltech)

The main focus of my thesis is to explore the outer solar system beyond Neptune to find more objects on orbits like Sedna and what they can tell us about the formation and evolution of the solar system. I have been working on two surveys using the 48-inch Palomar Oschin Telescope at Palomar Observatory and 8.2-m Subaru telescope telescope on Mauna Kea to search for the most distant objects in the solar system. My thesis focuses on the Kuiper belt and the objects in the Sedna region.

For more information on Sedna and other dwarf planets check out Mike Brown’s dwarf planet website.

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