Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/jwst/doc-archive/flyers/JWST-GiantPlanets.pdf Дата изменения: Unknown Дата индексирования: Mon Apr 11 04:28:34 2016 Кодировка: Поисковые слова: volcano pele

NASA's James Webb Space Telescope:
The James Webb Space Telescope (JWST) offers unprecedented observing opportunities in the near- and mid-infrared for the planets Jupiter, Saturn, Uranus, and Neptune. Potential groundbreaking investigations of these planets include such studies as mapping H 3+ emission to study auroral processes, tracking atmospheric dynamics in the af termath of impact events, and more. Additional fields of investigation are showcased here.

Obser vations of the Giant Planets
J. N o r w o o d ( N M S U ), J. M o s e s (S SI), L . F l e t c h e r ( U. o f Ox ford), G. Or ton (JPL), P. Ir win (U. of Ox ford), S. Atreya (U. Michigan), K. Rages (SE TI Institute), A . SАnchez-L avega (U. del PaМs Vasco), R. Hueso (U. del PaМs Vasco), T. CavaliИ (MPS), N. Chanover (NMSU)

Reflected and thermally emit ted light from the four giant planets is at tenuated by methane to a degree that varie s gre atly acros s the ne ar-IR spe c trum. JWST obser vations can take advantage of this to probe to dif ferent depths in these atmospheres and engage in such investigations as the following: · M a p p i n g t h e v e r ti c a l a n d h o ri z o n t a l c l o u d structures (including major storm systems) and their evolution, with finer detail than previously possible. · High-resolution mapping of the latitudinal variation in the methane abundance on Uranus and N eptune to ex plore it s implic ations for glob al circulation. · Comparing near-simultaneous reflected-light and t h e r m a l im a g e r y t o s t u d y t h e t h e r m o - c h e m i c a l processes behind dif ferent features. ever y six months. All four Spec (R =2700) and MIRI to the brightness of these to decrease the minimum these ver y bright objects

JWST will provide spatial resolution comparable to the largest ground-based telescopes, with ~600 resolution elements across the Jovian disk at 2 m (~300 at 5 m), and at wavelengths accessible only from space. Near-infrared view of Jupiter from UK IRT, cour tesy of P. Ir win. Red: Fe II (1.644 m) Green: Bracket t (2.17 m) Blue: 2.27 m.

Obser vabilit y windows for the giant planets span ~50 days and occur approximately giant planets can be obser ved using the highest spectral-resolution modes of NIR (2000 < R < 3700), delivering ver y high signal-to-noise data in shor t exposures. Due targets, sub-array readout pat terns are being implemented for all JWST instruments exposure time and raise the saturation limits. This will enable obser vations of even over much of the JWST spectral range, as shown below.
S p e c t r a of J u p i te r, S a t u r n, U r anus, and N e pt une c ompared to saturation limit s of N I R C a m f i l te r s, a s s u m i n g 640 X 640 sub-array imaging. S p e c t r a c o mp o si te d f r o m C l ar k and M c C o r d ( 19 79 ), K a r k o s ch k a ( 19 9 4 ), E n cre naz (1997 ), Fink and Larson (1979), and Burgdor f (2008).

Jupiter S a t ur n Uranus Neptune


Ephemeral phenomena are fairly common in the atmospheres of the giant planets. These and other time variable ef fects driven (e.g.) by seasonal changes, will provide a rich environment for maximizing the impact of JWST's combined spatial resolution and its spectral grasp and resolution, on studies of these dynamic and complex atmospheres. Events such as the large storm system that developed on Saturn hot stratospheric "beacon" (shown here) that developed af ter the tion, provide unique oppor tunities to deepen our understanding of giant planet atmospheres. 2011 V LT image of Saturn at 12 m (e cour tesy of L. Fletcher. in 2010 and the storm's dissipaprocesses in the thane emission),

S pe c t ra of J upiter, S at ur n, U ranus, and Neptune compared to saturation limits of MIRI filters ( F560W not shown), assuming 64 x 64 sub-array imaging with minimum integration time. Jupiter/Saturn spectra are from Cassini/CIRS. Uranus/ Neptune spectra are from Spitzer/ IRS cour tesy of G. Or ton.
Jupiter S a t ur n Uranus Neptune

The mid-infrared is replete with emission features from photochemically produced hydrocarbons such as ethane and acetylene. JWST will enable mapping of this emission across the disks of Uranus and Neptune for the first time, providing insight into the thermodynamics, chemistr y, and global circulation within these t wo atmospheres. Other stratospheric investigations on these planets include · Detection of (or improving the upper limits for) new hydrocarbons on these planets. Ethylene and the CH3 radical have been detected on Neptune, but not on Uranus. Benzene may be detectable on Neptune. · Time-domain studies to clarif y the obser ved temporal variation in stratospheric emission, and investigation of whether such changes are consequences of local weather, or tied to solar activit y or the seasonal cycle. · Mapping the distrib CO2, CO, and H2O of ex ternal ox ygen. par ticles, dust from impacts. utions of ox ygen-bearing species such as to constrain the influx rates and sources Such sources may include infalling ring satellites, Kuiper Belt objects, or cometar y
The MIRI Medium-Resolution Spectrometer IF Us will ef ficiently produce spectral maps, even at the highest spectral resolution possible (R =3000). Here the fields of view of the four IFU bands (centered at 6.4, 9.2, 14.5, and 22.5 m) are compared to the angular size of Uranus. Pseudo-color Uranus image (1.26, 1.62, and 2.1 m) cour tesy of L. Sromovsky.
AC SP E TELESCOPE SCIENCE INSTITUTE

See more at ht t p: // w w w.s t sci.edu / jws t /science /s olar-sys tem and ht tp: //w w w.stsci.edu / jwst /doc-archive

Operated for NASA by AURA