Abstract
Most stars in the Universe that leave the main sequence in a Hubble time will end their lives evolving through the Planetary Nebula (PN) evolutionary phase. The heavy mass loss which occurs during the preceding Asymptotic Giant Branch (AGB) phase is important across astrophysics, dramatically changing the course of stellar evolution, contributing to the dust content of the interstellar medium, and influencing its chemical composition. The evolution from the AGB phase to the PN phases remains poorly understood, especially the dramatic transformation that occurs in the morphology of the mass-ejecta as AGB stars enter the post-AGB phase and their round circumstellar envelopes evolve into pre-PNe (PPNe) and then to PNe. The majority of PPNe and PNe deviate strongly from spherical symmetry. Strong binary interactions most likely play a fundamental role in influencing this evolutionary phase, but the details of these interactions remain shrouded in mystery. Thus, understanding the formation and evolution of these objects is of wide astrophysical importance. PNe have long been known to emit across a very large span of wavelengths, from the radio to X-rays. Extensive use of space-based observatories at X-ray (Chandra/ XMM-Newton), optical (HST) and mid- to far-infrared (Spitzer, Herschel) wavelengths in recent years has produced significant new advances in our knowledge of these objects. Given the expected advent of the James Webb Space Telescope (JWST) in the near future, we focus on future high-angular-resolution, high-sensitivity observations at near and mid-IR wavelengths with JWST that can help in addressing the major unsolved problems in the study of PNe and their progenitors.
Highlights
The Extraordinary Deaths of Ordinary StarsThe late evolution and deaths of a very significant percentage (âŒ60â80%) of stars in the Universe are likely to be fundamentally affected by strong binary interactions1
R = 150 at 1.4 ÎŒm over the entire field of view, using one or both of a pair of identical grisms and a selection of blocking filters to isolate specific wavelength intervals between 0.8â2.2 ÎŒm6, (ii) single object slitless spectroscopy (SOSS) with a cross-dispersed grism with R = 700 at 1.4 ÎŒm that is designed to deliver broad wavelength coverage and spectro-photometric stability, optimized for time-series observations (TSOs), (iii) aperture masking interferometry (AMI) through specific filters that is enabled by a mask with seven sub-apertures, and (iv) standard imaging, that can be done in 7 wide- and 5 medium-band filters that are closely matched to the NIRCam filter set between
Working Angle [IWA] of 0.00 4 â 0.00 81, and (ii) a bar for observations at 2â3.7 ÎŒm, with an IWA of mid-infrared instrument (MIRI), using (i) a Lyot stop for observations at 23 ÎŒm, with an IWA of 2.00 16 and a 3000 Ă 3000 field of view (FOV), and (ii) a 4-quadrant phase mask (4QPM) and filters at 10.65, 11.4, 15.5 ÎŒm, with an IWA of NIRISS, which admits light through seven holes or sub-apertures in an otherwise opaque pupil mask that interferes to produce an interferogram on the detector in the AMI, effectively making the full aperture of James Webb Space Telescope (JWST) into an interferometric array
Summary
The late evolution and deaths of a very significant percentage (âŒ60â80%) of stars in the Universe are likely to be fundamentally affected by strong binary interactions. Giant Branch (AGB) starsâlose almost all of their stellar envelopes via extensive mass-loss (with rates as high as ⌠10â4 M yrâ1 ) This is followed by the formation of pre-PNe (PPNe) and PNe. If we include interactions with giant planets (âhot Jupitersâ) (e.g., [1]), this percentage becomes much higher. All PPNe and the majority (i.e., âŒ80%) of PNe, unlike the generally roughly round circumstellar envelopes around most AGB stars , display a spectacular array of morphologies and geometrical complexities These include elliptical, bipolar and multipolar shapes, nested geometrical structures (e.g., hourglass within hourglass structures), equatorial density enhancements (including rotating disks, torii), low-latitude jets, and central stars offset from the geometrical centers of the nebulae (e.g., [7] (ST98), [8,9]), etc. The mid-infrared instrument (MIRI: see below) will work at a temperature of 7 K using a cryocooler system
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