Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/jwst/science/sodrm/highlightDwarfPlanets.pdf Дата изменения: Unknown Дата индексирования: Tue Feb 5 06:51:03 2013 Кодировка: Поисковые слова: http astrokuban.info astrokuban

NASA's James Webb Space Telescope:

Obser vations of Dwarf Planets

There are 4 dwarf planets (Pluto, Eris, Makemake and Sedna) beyond the orbit of Neptune that have significant inventories of volatile ices on their surfaces. These ices give rise to organic molecules via UV photolysis and radiolysis by galactic cosmic rays. Haumea is also a dwarf p la n e t , b u t is n ot cur re n t l y k n ow n t o possess any volatile ices. The physical state of the ices and the composition of the organics on these objects are of significant interest because these bodies are large enough to have retained nearly the entire inventory of material from which they accreted. The volatile ices are mobile, moving in response to seasonal variations in insolation, and the ices also support the vapor-pressure atmospheres around these bodies. An important goal for JWST will be to make detailed studies of the composition of each object to determine what molecules are present on their surfaces (and in their atmospheres), measure isotopic compositions on each, and map the distribution of the constituents vs. longitude. JWST may also allow for the first detection of the low-temperature phase of solid N2 on one or more of these objects, for the first time, and determine whether N2 is present at all on Eris (where there is only indirect evidence for it). These NIRSpec and MIRI capabilities will also be exploited to characterize smaller transneptunian objects (e.g., Kuiper Belt Objects). JWST will be able to determine diameters and albedos for a large sample of transneptunian objects; search for evidence of collisionally­induced changes in albedo; make near­simultaneous measurements to mitigate rotational ambiguity; and obser ve a large enough sample to search for differences in different classes of objects. Studies of asteroids, comets and icy moons are similarly enabled. The thermal state of the surfaces for each of these objects is also of interest, so MIRI 25µm photometry will be done to measure the thermal light-curves for the brighter objects (for comparison with Spitzer and Herschel light-curve data, and to measure secular changes related to seasonal cycles), and to measure the mid-IR thermal emission for the first time for the fainter objects.
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23.68 micron

F24 flux (mJy)

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Lollouch et al. (2011)

Pluto/Charon

The figure at left shows a Spitzer/MIPS thermal light curve. Similar data will be obtained for other dwarf planets using JWST/MIRI.

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East Longitude


Fixed Slit (Giant KBOs: Volatile Ice Absorptions FS) mode of NIRSpec
Appropriate for Pluto, Triton, Eris, Sedna, 2005 FY9

Stansberry et al. (2012)

The figure above shows some of the features that can potentially be obser ved using the Fixed Slit ( FS) mode of NIRSpec

N2, CH4, CO fundamentals > 3um

Near-Infrared Spectrograph (NIRSpec) Micro-Shutter Assembly (MSA) 4 separate quadrants 365 x 171 user configurable shutters per quadrant Fixed slits (FS) Always open, no overlap with MSA on detectors Four narrow slits and one 1.6" square for high throughput Integral Field Unit (IFU ) 3" x 3" FOV in 30 slices, each 0.1" (dispersion) x 3" (spatial)

Mid-Infrared Instrument (MIRI) Direct Imaging nine photometric bands from 5 to 28 µm Coronagraphic Imaging three four-quadrant phase masks (4QPMs) at 10.65, 11.4,& 15.5 µm, Lyot coronagraph at 23 µm Low-Resolution Spectroscopy (LRS) 5-14 µm, /-100 at 7.5 µm, 0.6" x 5.5" slit LRS Slitless Spectroscopy for exoplanet studies Medium Resolution Spectrometer (MRS) · / ~ 2200 ­ 3500 4.9 to 28.8 µm, enabled by four IFUs 3.7" to 7.7" field-of-views (wavelength-dependent)

See more at ht tp: // w w w.s t sci.edu / jws t and jwst.nasa.gov and do your own E TC calculations at jwstetc.stsci.edu/etc

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Images cour tesy of N ASA