A new NASA initiative is embracing a team approach to the quest for life on planets around other stars. The new Nexus for Exoplanet System Science initiative (NExSS) is a virtual institute that will benefit from the expertise of several dozen team leaders across the NASA science community in an effort to find clues to life on faraway worlds. Two Penn State University astronomers are among the first 16 leaders on the NExSS team.
By bringing together the “best and brightest,” NASA expects the NExSS team to produce a better understanding of the various components of an exoplanet, as well as of how the parent stars and neighbor planets interact to support life.
One of the two NExSS teams at Penn State is led by Professor of Astronomy and Astrophysics Eric Ford. His team will apply advanced statistical models to observations of planets by NASA’s Kepler mission to infer the relationships between the orbit, radius, mass, and composition of small planets, focusing on planetary systems with multiple, closely-spaced planets. This team will further the understanding of planetary formation by investigating the properties of small transiting planets and the implications for their formation.
Another of the two NExSS teams at Penn State has Jason Wright as its principal investigator. This team will study the atmospheres of giant planets that are transiting hot Jupiters. The team will use a novel technique (diffuser-assisted photometry) to enable high-precision measurements from ground-based observatories. This research aims to make possible more detailed characterization of the temperatures, pressures, composition, and variability of exoplanet atmospheres, and to aid the characterization of smaller planets with the future generation of extremely large telescopes.
The study of exoplanets — planets around other stars — is a relatively new field, with the first discovery in 1995. Since the launch of NASA’s Kepler space telescope six years ago, more than 1,800 exoplanets are known, with thousands of additional candidates waiting to be confirmed. Some of these worlds are potentially habitable, so now scientists are developing ways to confirm the habitability of these worlds and to search them for signs of life. Key to this effort is to understand how biology interacts with the atmosphere, geology, oceans, and interior of a planet, and how these interactions are affected by the host star. This “system science” approach is what NExSS will use to better understand how we can look for life on exoplanets. NExSS is tapping into the collective expertise from each of the divisions in NASA’s Science Mission Directorate:
- Earth scientists develop a systems science approach by studying our home planet.
- Planetary scientists apply systems science to a wide variety of worlds within our solar system.
- Heliophysicists add another layer to this systems science approach, by looking in detail at how the Sun interacts with orbiting planets.
- Astrophysicists provide data on the exoplanets and host stars for the application of this systems science framework.
These different research communities, often unaware of work outside of their own discipline, are being brought together by NExSS to share their perspectives, research results, and approaches. This unprecedented collaboration will help to classify the diversity of worlds being discovered, to understand the potential habitability of these worlds, and to inform the development of tools and technologies needed in the search for life beyond Earth. Through this work, NExSS is expected to play a key role in the pursuit of one of humanity’s deepest questions: Are we alone?
The NExSS initiative is led by scientists from the NASA Ames Research Center, the NASA Exoplanet Science Institute at the California Institute of Technology, and the NASA Goddard Institute for Space Studies. It includes team members from 10 different universities, three NASA centers, and two research institutes. These teams were selected from proposals by scientists from across NASA’s Science Mission Directorate.
More information about the 16 NExSS science teams
- A Penn State University team, led by Eric Ford, will further our understanding of planetary formation by investigating the bulk properties of small transiting planets and implications for their formation.
- A second Penn State group, with Jason Wright as team leader, proposes a ground-based study of the atmospheres of transiting hot Jupiters with a novel, high-precision technique called diffuser-assisted photometry.
- The Berkeley/Stanford University team is led by James Graham. This “Exoplanets Unveiled” group will focus on the following question: “What are the properties of exoplanetary systems, particularly as they relate to their formation, evolution, and potential to harbor life?”
- Daniel Apai leads the “Earths in Other Solar Systems” team from the University of Arizona. The EOS team will combine astronomical observations of exoplanets and forming planetary systems with powerful computer simulations and cutting-edge microscopic studies of meteorites from the early solar system to understand how Earth-like planets form and how biocritical ingredients – C, H, N, O-containing molecules – are delivered to these worlds.
- The Arizona State University team takes a similar approach. Led by Steven Desch, this research group will also place planetary habitability in a chemical context, with the goal of producing a “periodic table of planets”.
- Researchers from Hampton University are exploring the sources and sinks for volatiles on habitable worlds. The “Living, Breathing Planet Team,” led by William B. Moore, will study how the loss of hydrogen and other atmospheric compounds to space has profoundly changed the chemistry and surface conditions of planets in the solar system and beyond. This research will help determine the past and present habitability of Mars and even Venus, and will form the basis for identifying habitable and eventually living planets around other stars.
- The team based at NASA’s Goddard Institute for Space Studies will investigate habitability on a more local scale. Led by Tony Del Genio, it will examine the habitability of solar system rocky planets through time, and will use that foundation to inform the detection and characterization of habitable exoplanets in the future.
- The NASA Astrobiology Institute’s Virtual Planetary Laboratory was founded in 2001 and is a heritage team of the NExSS network. This research group combines expertise from Earth observing, Earth system science, planetary science, and astronomy to explore factors likely to affect the habitability of exoplanets, as well as the remote detectability of global signs of habitability and life.
- A group led by Neal Turner at the Jet Propulsion Laboratory, California Institute of Technology, will work to understand why so many exoplanets orbit close to their stars. Were they born where we find them, or did they form farther out and spiral in? The team will investigate how the gas and dust close to young stars interact with planets, using computer modeling to go beyond what can be imaged with today’s telescopes on the ground and in space.
- A team at the University of Wyoming, headed by Hannah Jang-Condell, will explore the evolution of planet formation, modeling disks around young stars that are in the process of forming their planets. Of particular interest are “transitional” disks, which are protostellar disks that appear to have inner ‘holes’ or regions partially cleared of gas and dust. These inner holes may be caused in part by planets inside or near the holes.
- A University of Maryland and NASA’s Goddard Space Flight Center team, with Wade Henning at the helm, will study tidal dynamics and orbital evolution of terrestrial class exoplanets. This effort will explore how intense tidal heating, such as the temporary creation of magma oceans, can actually save Earth-sized planets from being ejected during the orbital chaos of early solar systems.
- Another University of Maryland project, led by Drake Deming, will leverage a statistical analysis of Kepler data to extract the maximum amount of information concerning the atmospheres of Kepler’s planets. The group led by Hiroshi Imanaka from the SETI Institute will be studying laboratory investigation of plausible photochemical haze particles in hot exoplanetary atmospheres.
- The Yale University team, headed by Debra Fischer, is constructing new spectrometers with the stability to reach Earth-detecting precision for nearby stars. The team has also designed Planet Hunters a web interface that allows citizen scientists to search for transiting planets in the NASA Kepler public archive data. Citizen scientists have found more than 100 planets not previously detected; many of these planets are in the habitable zones of host stars.
- A group led by Adam Jensen at the University of Nebraska-Kearney is exploring the existence and evolution of ‘exospheres’ around exoplanets, the outer, ‘unbound’ portion of a planet’s atmospheres. This team previously made the first visible light detection of hydrogen absorption from an exoplanet’s exosphere, indicating a source of hot, excited hydrogen around the planet. The existence of such hydrogen can potentially tell us about the long-term evolution of a planet’s atmosphere, including the effects and interactions of stellar winds and planetary magnetic fields.
- From the University of California, Santa Cruz, Jonathan Fortney’s team will explore how novel statistical methods can be used to extract information from the light emitted and reflected by planetary atmospheres, in order to understand their atmospheric temperatures and the abundance of molecules.
Featured Image: The search for life beyond our solar system requires unprecedented cooperation across scientific disciplines. NASA’s NExSS collaboration includes those who study Earth as a life-bearing planet (lower right), those researching the diversity of solar system planets (left), and those on the new frontier, discovering worlds orbiting other stars in the galaxy (upper right). Image: NASA
Provided by: Penn State University