Bipolar nebula

Protostars and Pre-main-sequence Objects (including disks, jets, HH objects, bipolar nebulae, T Tauri stars, and Ae and Be stars)... 

Fig. 2. VLA detection of 3He+ in the PN J 320. We have modeled the radio continuum and line emission using the radiative transfer code NEBULA [1], assuming an expanding shell of ionized gas. The dashed line is the model including the H171 7 and 3He+ transitions. The solid line shows the observed spectrum and only includes the 3He+ transition. The model fits the data reasonably well even though the morphology is bipolar as indicated by the HST image [6]...

At the centre of the cloud is the young stellar object destined to become the Sun. It accounts for approximately 99.9 per cent of the mass of the nebula and there are various examples of this in the heavens, including the classic pre-main sequence T-Tauri star. The star continues to evolve, blowing off bipolar jets (see Figure 4.5) and beginning a solar wind of particles. Of course, the star does not reach its full luminous intensity and the best theories suggest that the Sun was some 30 per cent less luminous when the Earth began to form. 

With current instruments it is possible to make spatial maps of the emission from different species in the Red Rectangle. These maps might provide valuable clues to the origin of different spectroscopic features. For example, in the spectrum of the Red Rectangle, the emission features which correspond to the diffuse interstellar bands are concentrated in what appears to be two hollow cones oriented perpendicular to the plane of this bipolar system (Schmidt Witt 1991). This hollow cone is similar to that proposed by Jura Kroto (1990) to explain the observed (Nguyen-Q-Rieu et al. 1986) HC,N emission (see around AFGL 2688, the Egg Nebula ), a very well studied carbon-rich object that appears to be in transition from a red giant to a planetary nebula. 

Protostellar phases class —I, 0, 1, II, III objects. 04.2.2.2 Ubiquity of bipolar outflows from earliest phases ASTROPHYSICAL ANALOGUES FOR THE SOLAR NEBULA... 

If an X-wind is responsible for driving bipolar outflows, then there are possibly important implications for the thermal processing of solids and the production of short-lived radioisotopes (Shu et al., 1996, 2001). The basic idea is that some of the solids that spiral inward and approach the boundary layer between the solar nebula and the protosun will be lifted upward by the same magnetically driven wind that powers bipolar outflows. While close to the protosun, these solids will be subject to heating by the solar radiation... 

Figure 6 The X-wind model for meteoritical processing involves subjecting solids to high temperatures and fluxes of energetic particles from the early Sun during and after being lifted from the midplane of the solar nebula in a bipolar wind, and afterward falling back onto the nebula at greater distances (Shu et al., 2001) (reproduced by permission of University of Chicago Press and American Astronomical Society from Astrophys. J., 2001, 548, 1029-1050).

Two types of jet or outflow models have been proposed. Liffman and Brown (1996) suggested that chondrules formed in a bipolar outflow by ablation of planetesimals and were then injected into the asteroid belt. The observed correlation between rim thickness and chondrule size may have arisen when chondrules reentered the dusty nebula at hypersonic speeds (Liffman and Toscano, 2000). 

A second consequence is that the outflow which occurs due to a star hitting the 12-limit, is predicted to be highly bipolar. This is illustrated by a hydrodynamical simulation of the giant eruption of r] Car by Langer el al. (1999). The fact that virtually all LBV nebulae are highly bipolar supports the idea that the D-limit is actually involved in the LBV instability. 

Abstract. We resolved dust shells at 10.5 and 12.5 pm around the post asynq>totic pant branch stars HD 161796 and AFGL 2343, two oxygen-ridi proto-planetary nebulae with very cold IRAS colors. The shell of AFGL 2343 appears as a drculax ring with 4" — 5" diameter, while HD 161796 appears bipolar with 2" diameter, bmer shell radii indicate that both stars left the asymptotic giant brand about 200 years ago. 

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