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Issue 12 - October 2013
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Genius Granted |
Program Update |
Director's Update |
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Update from |
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In May 2013, the Kepler spacecraft suffered its second failure of a momentum wheel. Kepler uses momentum wheels to point itself accurately and stably to obtain the extremely precise brightness measurements of stars that have allowed the spacecraft to detect small planets around the target stars in its exoplanet survey. Kepler started its mission with four operational momentum wheels and requires three operational wheels to maintain stable pointing. With the failure of a second wheel on Kepler, the existing pointing-system software can no longer control the spacecraft as before, thus ending the ability to search for Earth-size planets orbiting Sun-like stars. For now, science data collection has stopped and the Kepler spacecraft has been placed in a fuel-efficient safe mode while we decide what to do next. Read More...
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In May 2013, NASA chartered two Science and Technology Definition Teams (STDTs) to develop probe-scale mission concepts for direct detection and spectroscopy of exoplanets. Karl Stapelfeldt's team is studying a mission based on a telescope with an internal coronagraph; Sara Seager's team is looking at blocking out the interfering starlight using an external occulter (starshade) that flies in formation with a telescope.
The teams are now well into their studies, and have met in person twice so far, opting to hold meetings at the team leaders' home institutions -- at GSFC on July 1-2, and at MIT on September 11-12. At the first meeting, the teams were introduced to the Design Team, staffed through the Exoplanet Exploration Program's Study Office and led by Keith Warfield (JPL). The program presented an overview of the task ahead, which culminates in early 2015 with the delivery of Concept Study Reports (one from each team) to NASA HQ. To be fully responsive to the STDT charter, a mission concept must have certain attributes -- most notably a cost target. These reports will become a key part of the Astrophysics Division's presentation to the NRC Committee on Astronomy and Astrophysics, which is chartered to review NASA's progress in implementing the recommendations of the 2010 Astronomy and Astrophysics Decadal Survey. Read More...
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On Tuesday, August 27, the Discovery Channel filmed the initial deployments of the world's first prototype deployable Starshade, a huge deployable structure for the direct imaging of extrasolar planets, or exoplanets. The video sequences, filmed by a crew from Pioneer TV of the UK, are for an exoplanet-themed segment of "How the Universe Works," scheduled to air in 2014.
The starshade concept is comprised of an external occulter, or Starshade, flown in formation with a companion telescope, capable of launching jointly on a single launch vehicle. The Starshade is compactly stowed for launch and deploys to a very large structure of approximately 34 meters in diameter. Resembling a sunflower in shape, the Starshade consists of an opaque inner disk with flower-like petals around the circumference, shaped to control the diffraction of starlight. Read More...
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Many exoplanets are different from the planets in our solar system: they often orbit their host stars at very close distances, with a full orbit lasting only a couple of days. The atmospheres of such planets are strongly heated by the stellar irradiation, and we can observe those atmospheres through transits of the planet in front of the stellar disk. In my work as a Sagan Fellow, I use x-ray observations to study the outermost layers of exoplanetary atmospheres. These observations are challenging because stars are much fainter in x-rays than they are in optical light. However, the combined signal from several x-ray transits allows us to peek into atmosphere layers that cannot be observed at other wavelengths. My goal is to use these observations to understand how the atmospheres of exoplanets evolve over time. To learn more, please visit http://hea-www.harvard.edu/~kpoppen/.
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Thanks to Kepler, today we know that small stars commonly host Earth-size planets. Approximately half of all stars are low-mass M dwarfs, and at least half of these may have an Earth-size companion, making it likely that there are Earth-like planets within just a few parsecs of the Sun. Given the cool temperature, low mass, and feeble luminosity of an M dwarf, the Doppler signal induced by an Earth-mass companion in the Habitable Zone (HZ) is significantly larger than the Sun's wobble caused by Earth. The hunt for these nearby planets is on.
As a Nancy Grace Roman Fellow, I am developing an instrument to conduct a census of planets in the HZs of our nearest stellar neighbors. The Small Red Spectrometer (SRS) is a Doppler spectrometer designed specifically for telescopes of modest aperture. A small telescope permits the use of a compact instrument that is stable, inexpensive, and easy to replicate. SRS is optimized for red optical wavelengths, where modern CCDs are very sensitive and an M dwarf is near peak brightness. SRS will be adaptable for observations from new platforms, such as high-altitude balloons, and new observing modes, including a "Beowulf Telescope" mode in which it accepts light from several telescopes simultaneously.
Designed exclusively for precise Doppler measurements of the brightest low-mass stars, SRS can play a key role in the discovery and characterization of the nearest Earth-like planets to the Sun and provide crucial follow-up observations of planet candidates from the upcoming Transiting Exoplanet Survey Satellite (TESS) mission.
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Following an icing accident in April 2013, the right-side adaptive optics (AO) secondary was replaced by a spare unit that has now been mounted and tested at the telescope. The spare AO secondary unit is currently undergoing calibrations on the sky in order to be operational when observing resumes, following the monsoon season summer shutdown. During the shutdown, the Large Binocular Telescope Interferometer (LBTI) team (P.I. Phil Hinz, University of Arizona) has been busy characterizing the instrument's photometric sensitivity and implementing sequencer software, which has greatly improved the observing efficiency. NASA commissioning nights that could not be used in spring 2013 due to the adaptive secondary failure have been rescheduled to fall 2013, and commissioning is now expected to be completed during three observing runs of two nights each in October, November, and December 2013.
On a related note, the LMIRCam 3-5 micron high-contrast imager (funded by NSF but also housed by the LBTI instrument) had a very productive spring 2013 observing season for the LBTI Exozodi-Exoplanet Common Hunt (LEECH) project (P.I. Andrew Skemer, University of Arizona): 36 objects were observed during 14 nights (all non-NASA thus far). No new exoplanets have been discovered yet, but a number of very interesting discoveries on a variety of topics (e.g., brown-dwarf companions and debris disks) have been made along the way, and the observations have served to validate the instrument's capabilities for direct detection and spectroscopic characterization of Jupiter-mass exoplanets as close to their parent star as 0.75 arcsec.
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The "snow line" is an almost poetical term that tells us where it gets cold enough in a protoplanetary disk for gas molecules to freeze out as "snow." In a recent Atacama Large Millimeter/submillimeter Array (ALMA) observation, the snow line for CO was found by the indirect trick of imaging N2H+, and noticing that in the frozen phase of CO the N2H+ remains as a gas, whereas in the gas phase of CO there is very little N2H+ because the species react, depleting the latter. Thus, the observed ring of N2H+ is a marker for frozen CO. See http://www.sciencemag.org/content/341/6146/630.full.pdf for the paper by Qi et al. Read More...
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Exoplanet technology is in a period of transition right now. Back in May, Paul Hertz received the go-ahead from the NASA Administrator to continue studying how the Astrophysics Focused Telescope Assets (AFTA) 2.4-meter telescope could be used to implement Wide-Field Infrared Survey Telescope (WFIRST) science. With that approval, the AFTA coronagraph went from being a "proxy for an instrument" to an integral part of the ongoing study plans. However, for a coronagraph to be part of AFTA, it must demonstrate that it is ready -- and convincingly so by January 2015. That is when NASA Astrophysics will decide on its future path and begin pre-formulation activities for its next big mission. Read More...
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The NASA Exoplanet Science Institute (NExSCI) solicits applications for Sagan Postdoctoral Fellowships to begin in the fall of 2014. The deadline for applications and letters of reference and endorsement is Thursday, November 7, 2013 at 4 pm PST.
The Sagan Fellowships support outstanding recent postdoctoral scientists to conduct independent research that is broadly related to the science goals of NASA's Exoplanet Exploration program. The primary goal of missions within this program is to discover and characterize planetary systems and Earth-like planets around nearby stars.
Jared Males will work at the University of Arizona, Tucson, to investigate exoplanetary habitability by perfecting instrumentation to image Jupiter- and Saturn-sized planets in the liquid water habitable zone of nearby stars.
More information: http://nexsci.caltech.edu/sagan/fellowship.shtml
Questions: saganfellowship@ipac.caltech.edu
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The ExEP Program's new "Eyes on Exoplanets" visualization tool provides a visually stunning, fully rendered 3D universe of the 900-plus "exoplanet" discoveries in our galactic neighborhood. With the click of a mouse, users can now visit all types of newly discovered worlds, including gas giants, terrestrials, super-Earths, and more.
Powered by NASA's Exoplanet Archive and available at http://eyes.jpl.nasa.gov/exoplanets/index.html, "Eyes" is JPL's most advanced interactive visualization product to date, according to Kevin Hussey, manager of visualization technology at JPL. "This program turns raw numbers and statistical data into a stunning, immersive environment, and is able to keep pace with the onslaught of new discoveries," Hussey said.
Visitors to "Eyes on Exoplanets" can instantly find out the time it would take to travel to each planetary system by car, jet plane, bullet train, or starship; use an overlay to compare the orbits of planets in our solar system with those around other stars; view the night sky and see visible stars where exoplanets have been discovered; and access a variety of other interactive features.
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