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Issue 13 - April 2014
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Congratulations to the 2014 Carl Sagan Postdoctoral Fellows! Visit the NExScI website to learn more. |
Kepler Challenge
Many of you can locate the Kepler field (in the constellation of Cygnus), but can you locate the constellation where Kepler itself appears to be at this time of year? Hint: the spacecraft is in an Earth-trailing heliocentric orbit, about 0.55 astronomical units from Earth, and can currently be found near a first-magnitude star.
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While Kepler has stopped collecting data in support of its primary mission, the telescope continues to capture attention and contribute to the exoplanet discovery story. This edited piece brings together a few of Kepler's recent press releases and includes:
Read the entire edited piece here...
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These are exciting times for the Wide-Field Infrared Survey Telescope-Astrophysics Focused Telescope Assets (WFIRST-AFTA), with significant funding coming from congressional interest in the mission and from NASA. The mission development is preparing for a possible new start in Fiscal Year 2017, but there is a lot of work to do before that in defining the science requirements and advancing needed technologies.
The Science Definition Team (SDT) is completing its first year of studies with an Interim Report due in April 2014. The final report will come out in January 2015.
The capabilities of the current WFIRST-AFTA configuration are impressive. The 2.4-meter telescope provides Hubble-class imaging over larger portions of the sky. The size of the images on the sky is 100 times as large as for Hubble. Also, the microlensing survey and coronagraph instrument will make the next big step in exoplanet understanding following the existing and planned exoplanet missions: Kepler, Transiting Exoplanet Survey Satellite (TESS) and Planetary Transits and Oscillations of stars (the European Space Agency's Plato mission). The SDT is having fun thinking of all the discovery science that the mission can achieve.
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A coronagraph is an optical instrument that suppresses light from bright objects in order to see much fainter ones nearby, whose light would normally be drowned out. It was invented to view the corona of the Sun - hence the name - by French astronomer Bernard Lyot in 1930. A different type of this instrument, called a stellar coronagraph, allows direct imaging of exoplanets around nearby stars. Compared to other methods of exoplanet detection, direct imaging allows us to measure an exoplanet's spectrum, thus providing information about atmospheric composition, which can in turn give us clues about the presence of water and, potentially, life. Circumstellar disks are also coronagraph science targets.
During summer and fall 2013, the Exoplanet Exploration Program (ExEP) and the WFIRST-AFTA Study Office led the assessment of six submitted coronagraph technologies. The recommendation that emerged from this process was to pick a primary coronagraph design called an Occulting Mask Coronagraph that combines two technical approaches, Shaped Pupil and Hybrid Lyot, in one instrument. The Phase-Induced Amplitude Apodization Complex Mask Coronagraph (PIAA-CMC) was selected as the backup design.
For the full story, and a brief description of each technical approach, read more here...
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Water from Radial Velocity. Using spectral cross-correlation of radial-velocity (RV) spectra in the L band, the non-transiting orbit of hot Jupiter tau Boo b was improved and, surprisingly, water vapor detected, by Lockwood et al., see http://iopscience.iop.org/2041-8205/783/2/L29/pdf/apjl_783_2_29.pdf.
Gemini Planet Imager success! The Gemini Planet Imager (GPI) coronagraph was installed at the 8-meter Gemini South telescope in January, and was an instant success on the sky, according to Bruce Macintosh. Near-infrared images of beta Pic b and the disk around HR 4796 A are visual proof, at http://planetimager.org/.
Brown Dwarf maps. Crossfield et al. applied the Doppler imaging technique from stars to a nearby brown dwarf to obtain images of the surface through a full rotation period, with about 10 percent brightness variations. The paper is at http://www.nature.com/nature/journal/v505/n7485/full/nature12955.html and a commentary by Showman is at http://www.nature.com/nature/journal/v505/n7485/full/505625a.html
Read more of this science roundup here...
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The Large Binocular Telescope Interferometer (LBTI, P.I. Phil Hinz, University of Arizona) has been busy with almost monthly commissioning runs for the mid-infrared Nulling mode, and science observations in a variety of areas using the other LBTI modes. In December 2013 we had a big breakthrough in Nulling commissioning, when the phase loop was closed on-sky for the first time. This was the remaining sub-system to be commissioned, and the LBTI is now operating as a fully integrated system, and performing science-quality nulling observations on-sky. However, we still have significant work ahead of us to calibrate the nulls to 0.0075% (1sigma) in order to reach the required exo-zodi sensitivity (3 zodi Level 1 requirement, for nearby Sun-like stars). Improvements are needed both in the phasing algorithm, and in tracking down and eliminating vibrations that appear to originate at the telescopes.
As we work in those areas, we have begun obtaining science verification data on exo-zodi targets (the HOSTS survey) in order to accurately characterize and understand the current performance limitations (null calibration to 0.3%, or 125 zodis on average for the HOSTS target list). These data also provide valuable scientific contributions, as new spatial and sensitivity regimes are being probed, and help identify the best targets for detailed characterization in follow up observations. Five targets have been observed thus far, including the first LBTI detection of a (known) debris disk, around the star eta Corvi. We have one more run this season, in May 2014, before the Summer shutdown due to the Monsoon season. The science team has been busy refining the target list, participating in observing runs, and working with the instrument team in data reduction and developing optimum algorithms for null calibration. Talks and posters were presented at the AAS meeting in Washington, DC (Jan 2014) and the Exoplanets, Biosignatures and Instruments conference in Tucson, AZ (March 2014).
In the meantime, the exoplanet imaging survey (LEECH, P.I. Andy Skemer, University of Arizona) is continuing its observations of nearby stars to search for gas-giant exoplanets. LEECH is reaching unprecedented contrasts at 4 microns, where gas-giant exoplanets emit most of their light, and adaptive optics performance is superb. In the last several months, we have observed a large number of survey targets and also spectro-photometrically characterized known directly-imaged exoplanets from 3-4 microns.
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Even planets around distant stars need an accurate weather forecast. For many of the Jupiter-size exoplanets orbiting close to their host stars, that forecast calls for extreme temperatures and winds approaching, and sometimes exceeding, the local speed of sound. My work as a Sagan Fellow focuses on trying to understand the complex weather patterns (winds, temperature, chemistry, and clouds) that exist in exoplanet atmospheres. To accomplish this goal, I combine information from exoplanet observations with predictions from general circulation models to paint a picture of the global-scale weather patterns present in exoplanet atmospheres. My observational efforts to probe exoplanet weather include monitoring the planet during the entirety of its orbit, so called phase-curve observations, and repeated observations of the planet as it passes behind its host star, so called eclipse-mapping observations, at a variety of infrared and visible wavelengths. These observations provide rough thermal maps that can be compared and contrasted with predictions from my sophisticated three-dimensional atmospheric models to understand the physical processes at work in these alien atmospheres.
Read more about Nikole here...
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On March 5 2014, Professor Sara Seager of MIT, chair of the Exo-S (Exoplanet Starshade) Science and Technology Definition Team (STDT), spoke at the Goddard Memorial Symposium, an event attended by hundreds including NASA leadership and NASA Administrator Charlie Bolden. The title of the talk was "Are We Alone? Seeking Life Among the Nearby Stars." In her talk, Sara spoke not only about the scientific approach to answering this age-old question, but also about the recent work of Exo-S, the Exoplanet Starshade Probe mission, being studied by the STDT. The mission concept consists of a 1.1-meter commercially available telescope and a 34-meter flower-shaped starshade flying in formation at a relative distance of 37,000 km, together in an Earth-leading orbit. The talk featured a 2/3-scale (4-meter) engineering model of a starshade petal recently used in the deployment tests.
The starshade was recently featured in a Space.com which can be found here. In addition, a new video featuring hardware demonstration has been produced by ExEP and can be found here.
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Did you know that you can find many of the presentations from recent exoplanet meetings (including most of those mentioned here) on the ExEP Presentations page at http://exep.jpl.nasa.gov/presentations/?
On this page you can find presentations to the Committee on Astronomy and Astrophysics (CAA) Meeting (March 3-5, 2014), reports from NASA's Astrophysics Program Analysis Groups including: Scott Gaudi's ExoPAG Report from January 2014 223rd AAS Meeting, The Future of NASA's Exoplanet Exploration Program presentation at the Kepler Science Conference, and the complete set of presentations from the American Astronomical Society ExEP Evening Session (January 7, 2014), as well as presentations about the AFTA Coronagraph Architecture Selection.
Some particular presentations of note include: |
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While all of the nearly 1,700 known exoplanets are visualized in NASA's "Eyes on Exoplanets" application, the 900+ confirmed discoveries of the Kepler space telescope now take center spotlight. A newly added Kepler mode, accessible from the top navigation bar, reveals the mission's cone of discoveries extending more than 7,000 light-years from our solar system, including all of the 715 new planets announced in February. Controls within the application allow users to display Kepler's confirmed discoveries, candidate planets, or both at the same time, and users can scroll outward to see the discovery space in the overall context of our Milky Way galaxy. Viewing the Kepler search space from Earth reveals all of the discovered systems in a grid pattern that matches the layout of Kepler's CCD array.
"Eyes" is powered by NASA's Exoplanet Archive and is available at http://eyes.jpl.nasa.gov/exoplanets/index.html. "Eyes on Exoplanets" was developed by the Visualization Technology Applications and Development group at JPL under sponsorship of the Exoplanet Exploration Program.
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