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Kelly Lepo (kellylepo@astrodon.social)'s status on Tuesday, 07-May-2024 20:08:08 UTC Kelly Lepo

Baby stars are messy eaters. This diagram from a review article illustrates the complex interplay between protostars, magnetic fields, and the surrounding gas on large and small scales.
Stars form in cold, dusty clouds of mostly hydrogen gas. As they grow, stars pull in more mass from disks, permeated with magnetic fields. The fields twist around the star, channeling some gas into the star and some into jets above and below the disk.
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📷 Frank et al. 2014
https://ui.adsabs.harvard.edu/abs/2014prpl.conf..451F/abstract
In conversation about 7 months ago from astrodon.social permalink
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1. Three panel illustration showing the disk scale area around a forming T Tauri star at 0.01 astronomical units, 0.05 astronomical units, and 5 astronomical units. The 0.01 astronomical unit panel shows a closeup of the star with three rope-like accretion columns flowing into the surface. The point where the column meets the star is labeled "accretion hot spot". There are dark star spots on the surface of the star. Arrows show stellar winds blowing off of the star. The 0.05 astronomical unit panel is a more zoomed out view, with the star and the innermost portion of the accretion disk visible. The star is at the center and the disk fills the outer third of the frame. There is a gap between the star and the disk. Connecting the two are the accretion columns of magnetized gas, which form a sideways figure 8 pattern with the star at the center of the eight. Arrows show stellar winds blowing off of the star and a MHD wind blowing off of the disk. The center of the disk is a horizontal dark band. A lighter area flares up from the disk, creating a wedge shape. The 5 astronomical unit panel shows the flared accretion disk and jet. The star is now too small to see. The disk extends horizontally and flares up vertically, making a wedge shape. On the left edge of the frame, at the upper edge of the disk is a small dot labeled "secondary star". A jet rises up above and below the disk. Arrows show the gas moving up vertically and magnetic fields twisting around the column-like structure.
  https://cdn.masto.host/astrodonsocial/media_attachments/files/112/396/705/274/290/729/original/c1495e842afea922.png
2. A two-panel illustration showing the envelope scale area around a forming star at 100 astronomical units and 500 astronomical units. The 100 astronomical unit panel shows the area around a clump in the jet. A line traces a backwards C shape that fills most of the panel. The line is labeled "bow shock". To the left are a series of x and o shapes representing the pileup of gas. The o shapes are labeled "forbidden lines" the x shapes are labeled "H alpha emitting layer". Wavy lines show UV light traveling away from the shock. The 500 AU panel shows a wider view of the disk, jet, and cavity carved by the variable-velocity, clumpy, precessing jet. The flared disk extends horizontally and flares up vertically, creating a wedge shape. The edge of the disk is labeled "cavity wall". Clumps of material extend above and below the disk in a line at its center. The clumps are slightly misaligned from each other horizontally. An area at the edge of one clump is labeled "spur shock" the area at the edge of the topmost clump is labeled "bow shock"
  https://cdn.masto.host/astrodonsocial/media_attachments/files/112/396/705/496/370/450/original/df9a0f45f07c09f7.png
3. An illustration showing the 1 parsec scale area in a molecular cloud forming many new stars. There are two darker areas. The one at the bottom right is labeled “core” and has three hourglass-shaped cavities carved out by new stars. The dark area at upper right is labeled "cluster". It has four hourglass-shaped cavities. They are labeled "active outflows". Two larger hourglass-shaped light areas are at the top of the frame. They are labeled "fossil outflow cavities". The lighter areas at the outer edge of the frame are filled with abstract, wavey lines. They are labeled "turbulence on large and small scales." Solid wavy lines with arrows are labeled “Alven waves driven by turbulence”
  https://cdn.masto.host/astrodonsocial/media_attachments/files/112/396/705/819/073/183/original/bc9ff1cb2068d117.png
4. Jets and Outflows from Star to Cloud: Observations Confront Theory
  
  from Raga, A.
  
  In this review we focus on the role jets and outflows play in the star- and planet-formation process. Our essential question can be posed as follows: Are jets/outflows merely an epiphenomenon associated with star formation, or do they play an important role in mediating the physics of assembling stars both individually and globally? We address this question by reviewing the current state of observations and their key points of contact with theory. Our review of jet/outflow phenomena is organized into three length-scale domains: (1) source and disk scales (0.1-102 AU) where the connection with protostellar and disk evolution theories is paramount; (2) envelope scales (102-105 AU) where the chemistry and propagation shed further light on the jet launching process, its variability and its impact on the infalling envelope; and (3) parent cloud scales (105-106 AU) where global momentum injection into cluster/cloud environments become relevant. Issues of feedback are of particular importance on the smallest scales, where planet formation regions in a disk may be impacted by the presence of disk winds, irradiation by jet shocks, or shielding by the winds. Feedback on envelope scales may determine the final stellar mass (core-to-star efficiency) and envelope dissipation. Feedback also plays an important role on the larger scales with outflows contributing to turbulent support within clusters, including alteration of cluster star-formation efficiencies (SFEs) (feedback on larger scales currently appears unlikely). In describing these observations we also look to the future and consider the questions that new facilities such as the Atacama Large Millimeter/submillimeter Array (ALMA) and the Jansky Array can address. A particularly novel dimension of our review is that we consider results on jet dynamics from the emerging field of high-energy-density laboratory astrophysics (HEDLA), which is now providing direct insights into the three-dimesional dynamics of fully magnetized, hypersonic, radiative outflows.

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