3 research outputs found

    The Surprising Evolution of the Shadow on the TW Hya Disk*

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    We report new total-intensity visible-light high-contrast imaging of the TW Hya disk taken with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope. This represents the first published images of the disk with STIS since 2016, when a moving shadow on the disk surface was reported. We continue to see the shadow moving in a counterclockwise fashion, but in these new images the shadow has evolved into two separate shadows, implying a change in behavior for the occulting structure. Based on radiative-transfer models of optically thick disk structures casting shadows, we infer that a plausible explanation for the change is that there are now two misaligned components of the inner disk. The first of these disks is located between 5 and 6 au with an inclination of 5.5° and position angle (PA) of 170°, and the second between 6 and 7 au with an inclination of 7° and PA of 50°. Finally, we speculate on the implications of the new shadow structure and determine that additional observations are needed to disentangle the nature of TW Hya's inner-disk architecture.</p

    The Mid-infrared Instrument for JWST and Its In-flight Performance

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    The Mid-Infrared Instrument (MIRI) extends the reach of the James Webb Space Telescope (JWST) to 28.5 ÎŒm. It provides subarcsecond-resolution imaging, high sensitivity coronagraphy, and spectroscopy at resolutions of λ/Δλ ∌ 100–3500, with the high-resolution mode employing an integral field unit to provide spatial data cubes. The resulting broad suite of capabilities will enable huge advances in studies over this wavelength range. This overview describes the history of acquiring this capability for JWST. It discusses the basic attributes of the instrument optics, the detector arrays, and the cryocooler that keeps everything at approximately 7 K. It gives a short description of the data pipeline and of the instrument performance demonstrated during JWST commissioning. The bottom line is that the telescope and MIRI are both operating to the standards set by pre-launch predictions, and all of the MIRI capabilities are operating at, or even a bit better than, the level that had been expected. The paper is also designed to act as a roadmap to more detailed papers on different aspects of MIRI.</p
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