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Journal articles on the topic 'Protoplanetary nebula'

Author: Grafiati

Published: 4 June 2021

Last updated: 8 February 2022

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1

Howe, D. A., T. J. Millar, and D. A. Williams. "Chemistry in a protoplanetary nebula." Monthly Notices of the Royal Astronomical Society 255, no. 2 (March 15, 1992): 217–26. http://dx.doi.org/10.1093/mnras/255.2.217.

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2

Weiss, Benjamin P., Xue-Ning Bai, and Roger R. Fu. "History of the solar nebula from meteorite paleomagnetism." Science Advances 7, no. 1 (January 2021): eaba5967. http://dx.doi.org/10.1126/sciadv.aba5967.

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We review recent advances in our understanding of magnetism in the solar nebula and protoplanetary disks (PPDs). We discuss the implications of theory, meteorite measurements, and astronomical observations for planetary formation and nebular evolution. Paleomagnetic measurements indicate the presence of fields of 0.54 ± 0.21 G at ~1 to 3 astronomical units (AU) from the Sun and ≳0.06 G at 3 to 7 AU until >1.22 and >2.51 million years (Ma) after solar system formation, respectively. These intensities are consistent with those predicted to enable typical astronomically observed protostellar accretion rates of ~10−8M⊙year−1, suggesting that magnetism played a central role in mass transport in PPDs. Paleomagnetic studies also indicate fields <0.006 G and <0.003 G in the inner and outer solar system by 3.94 and 4.89 Ma, respectively, consistent with the nebular gas having dispersed by this time. This is similar to the observed lifetimes of extrasolar protoplanetary disks.

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3

Fang, Xuan, Martín Guerrero, Ana Castro, Jesús Toalá, Bruce Balick, and Angels Riera. "UV Monochromatic Imaging of the Protoplanetary Nebula Hen 3-1475 Using HST STIS." Galaxies 6, no. 4 (December 14, 2018): 141. http://dx.doi.org/10.3390/galaxies6040141.

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Collimated outflows and jets play a critical role in shaping planetary nebulae (PNe), especially in the brief transition from a spherical AGB envelope to an aspherical PN, which is called the protoplanetary nebula (pPN) phase. We present UV observations of Hen 3-1475, a bipolar pPN with fast, highly collimated jets, obtained with STIS on board the Hubble Space Telescope (HST). The deep, low-dispersion spectroscopy enabled monochromatic imaging of Hen 3-1475 in different UV nebular emission lines; this is the first of such attempt ever conducted for a pPN. The northwest inner knot (NW1) is resolved into four components in Mg ii λ 2800. Through comparison analysis with the HST optical narrowband images obtained 6 yr earlier, we found that these components of NW1 hardly move, despite of a negative gradient of high radial velocities, from −1550 km s - 1 on the innermost component to ∼−300 km s - 1 on the outermost. These NW1 knot components might thus be quasi-stationary shocks near the tip of the conical outflow of Hen 3-1475.

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Cox, Pierre, Jean-Pierre Maillard, P. J. Huggins, T. Forveille, R. Bachiller, S. Guilloteau, and A. Omont. "K’-Band Spectro-imagery of AFGL 2688 and NGC 7027." International Astronomical Union Colloquium 149 (1995): 332–35. http://dx.doi.org/10.1017/s0252921100023265.

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5

Podolak, M., and Y. Mekler. "Dirty ice grains in the protoplanetary nebula." Planetary and Space Science 45, no. 11 (November 1997): 1401–6. http://dx.doi.org/10.1016/s0032-0633(97)00143-8.

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6

Davis, Sanford S. "Condensation Front Migration in a Protoplanetary Nebula." Astrophysical Journal 620, no. 2 (February 20, 2005): 994–1001. http://dx.doi.org/10.1086/427073.

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7

Dubrulle, B., G. Morfill, and M. Sterzik. "The Dust Subdisk in the Protoplanetary Nebula." Icarus 114, no. 2 (April 1995): 237–46. http://dx.doi.org/10.1006/icar.1995.1058.

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8

Klochkova, V. G., V. E. Panchuk, M. V. Yushkin, and A. S. Miroshnichenko. "Polarimetry of the protoplanetary nebula AFGL 2688." Astronomy Reports 48, no. 4 (April 2004): 288–300. http://dx.doi.org/10.1134/1.1704674.

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9

Russell, Sara S., Enrica Bonato, Helena Bates, Ashley J. King, Natasha V. Almeida, and Paul F. Schofield. "Carbonaceous chondrite meteorites as a record of protoplanetary disk conditions." Proceedings of the International Astronomical Union 15, S350 (April 2019): 135–38. http://dx.doi.org/10.1017/s1743921319009177.

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AbstractChondritic meteorites, and especially the most volatile-rich chondrites, the carbonaceous chondrites, preserve a record of the solar protoplanetary disk dust component and how it has been changed both in the disk environment itself and in its asteroidal parent body. Here we review some of the key features of carbonaceous chondrites and report some new data on their organics component. These show that the nebula reached temperature of >10000C, but only very locally, to produce chondrules. Most meteoritic material underwent thermal and/or aqueous processing, but some retain delicate nebular components such as complex organic molecules and amorphous silicates.

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10

Howe, D. A., T. J. Millar, and D. A. Williams. "Chemistry in Protoplanetary Nebulae." Symposium - International Astronomical Union 150 (1992): 363–64. http://dx.doi.org/10.1017/s0074180900090392.

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We have investigated gas-phase chemistry in a remnant red giant wind, during transition to a planetary nebula, using the interacting stellar winds model. Rapid destruction by UV of most existing molecules is predicted, within ~ 100 yrs of the core star heating up, suggesting that the large molecules in CRL 618 may be destroyed within decades. However, significant abundances of some hydrogenated molecules and ions (eg. CH+, CH2+, CH3+, CH, CH2, NH) may form behind the shock predicted by the interacting stellar winds model. Also, survival and/or formation of observable amounts of some molecules (eg. HCN, CN, HC3N) may occur in dense clumps which survive transition, and may explain the existence eg. of HCN in NGC 7027.

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11

Lin, Min-Kai, and Andrew N. Youdin. "Vertical Shear Instability in the Solar Nebula." Proceedings of the International Astronomical Union 10, S314 (November 2015): 195–96. http://dx.doi.org/10.1017/s174392131500589x.

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12

Markwick, A. J., and S. B. Charnley. "Disk Chemistry and Cometary Composition." Highlights of Astronomy 13 (2005): 518–21. http://dx.doi.org/10.1017/s1539299600016488.

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AbstractWe describe a theoretical study of protoplanetary disk chemistry. By considering physical conditions similar to that of the protosolar nebula, we attempt to assess the contribution made by material from the cooler nebular regions to cometesimal composition. Calculations are presented which determine the spatial and temporal chemistry of the gas and dust within the 5-40 AU comet-forming region of the nebula. We show that there is little radial variation in the solid-state distribution of some molecules which could potentially be parents of the carbon-chain species observed in comets. We conclude that the apparent variation in abundance of C2 and C3 between long- and short-period comets is the result of chemical processing during their lifetimes and not differences in composition at the time of formation.

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13

Ciesla, Fred J. "Outward Transport of High-Temperature Materials Around the Midplane of the Solar Nebula." Science 318, no. 5850 (October 26, 2007): 613–15. http://dx.doi.org/10.1126/science.1147273.

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The Stardust samples collected from Comet 81P/Wild 2 indicate that large-scale mixing occurred in the solar nebula, carrying materials from the hot inner regions to cooler environments far from the Sun. Similar transport has been inferred from telescopic observations of protoplanetary disks around young stars. Models for protoplanetary disks, however, have difficulty explaining the observed levels of transport. Here I report the results of a new two-dimensional model that shows that outward transport of high-temperature materials in protoplanetary disks is a natural outcome of disk formation and evolution. This outward transport occurs around the midplane of the disk.

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14

Mekler, Y., and M. Podolak. "Formation of amorphous ice in the protoplanetary nebula." Planetary and Space Science 42, no. 10 (October 1994): 865–70. http://dx.doi.org/10.1016/0032-0633(94)90067-1.

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15

Davis, Sanford S. "A Simplified Model for an Evolving Protoplanetary Nebula." Astrophysical Journal 592, no. 2 (August 2003): 1193–200. http://dx.doi.org/10.1086/375730.

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16

Morfill, G. E., C. K. Goertz, and O. Havnes. "Thermal cycling and fluctuations in the protoplanetary nebula." Icarus 76, no. 3 (December 1988): 391–403. http://dx.doi.org/10.1016/0019-1035(88)90012-7.

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17

Desmurs, Jean-François, C. Sánchez Contreras, Valentín Bujarrabal, Francisco Colomer, and Javier Alcolea. "Detection of an inner torus in the protoplanetary nebulae OH231.8+4.2." Symposium - International Astronomical Union 206 (2002): 344–47. http://dx.doi.org/10.1017/s0074180900222687.

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We performed the first VLBI observations of the SiO v = 1 and v = 2 J = 1-0 masers in a Proto Planetary Nebula OH 231.8+4.2 (also known as the Rotten Egg nebula), at milliarcsecond resolution. Only the v=2 maser transition was detected. We detect several maser spots lying along a line which is almost perpendicular to the axis of symmetry of the Nebula. We find that all the emission is concentrated in an area of ∼ 10 mas, indicating that the SiO masers are originated very close to the surface of the star. One of the two emission areas presents an elongated structure with a clear velocity gradient. The detected emission is consistent with a torus, or disk, in rotation with a velocity of ∼ 6 km/s and with an infall velocity of ∼ 10 km/s.

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18

Ciesla, Fred J. "Chemical evolution of planetary materials in a dynamic solar nebula." Proceedings of the International Astronomical Union 15, S350 (April 2019): 152–57. http://dx.doi.org/10.1017/s1743921319009499.

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AbstractAs observational facilities improve, providing new insights into the chemistry occurring in protoplanetary disks, it is important to develop more complete pictures of the processes that shapes the chemical evolution of materials during this stage of planet formation. Here we describe how primitive meteorites in our own Solar System can provide insights into the processes that shaped planetary materials early in their evolution around the Sun. In particular, we show how this leads us to expect protoplanetary disks to be very dynamic objects and what modeling and laboratory studies are needed to provide a more complete picture for the early chemical evolution that occurs for planetary systems.

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19

D’Angelo, M., S. Cazaux, I. Kamp, W. F. Thi, and P. Woitke. "Water delivery in the inner solar nebula." Astronomy & Astrophysics 622 (February 2019): A208. http://dx.doi.org/10.1051/0004-6361/201833715.

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Context. Endogenous or exogenous, dry or wet, various scenarios have been depicted for the origin of water on the rocky bodies in our solar system. Hydrated silicates found in meteorites and in interplanetary dust particles, together with observations of abundant water reservoirs in the habitable zone of protoplanetary disks, are evidence that support aqueous alteration of silicate dust grains by water vapor condensation in a nebular setting. Aims. We investigate the thermodynamics (temperature and pressure dependencies) and kinetics (adsorption rates and energies, surface diffusion and cluster formation) of water adsorption on surfaces of forsterite grains, constraining the location in the solar nebula where aqueous alteration of silicates by water vapor adsorption can occur efficiently and leads to the formation of phyllosilicates. We analyze the astrophysical conditions favorable for such hydration mechanism and the implications for water on solid bodies. Methods. The protoplanetary disk model (ProDiMo) code is tuned to simulate the thermochemical disk structure of the early solar nebula at three evolutionary stages. Pressure, temperature, and water vapor abundance within 1 au of the protosun were extracted and used as input for a Monte Carlo code to model water associative adsorption using adsorption energies that resemble the forsterite [1 0 0] crystal lattice. Results. Hydration of forsterite surfaces by water vapor adsorption could have occurred within the nebula lifetime already at a density of 108 cm−3, with increasing surface coverage for higher water vapor densities. Full surface coverage is attained for temperatures lower than 500 K, while for hotter grain surfaces water cluster formation plays a crucial role. Between 0.5 and 10 Earth oceans can arise from the agglomeration of hydrated 0.1 μm grains into an Earth-sized planet. However, if grain growth occurs dry and water vapor processes the grains afterward, this value can decrease by two orders of magnitude. Conclusions. This work shows that water cluster formation enhances the water surface coverage and enables a stable water layer to form at high temperature and low water vapor density conditions. Finally, surface diffusion of physisorbed water molecules shortens the timescale for reaching steady state, enabling phyllosilicate formation within the solar nebula timescale.

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20

Choi, Y. K., A. Brunthaler, K. M. Menten, and M. J. Reid. "Trigonometric Parallax of the Protoplanetary Nebula OH 231.8+4.2." Proceedings of the International Astronomical Union 8, S287 (January 2012): 407–10. http://dx.doi.org/10.1017/s1743921312007387.

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AbstractWe report a trigonometric parallax measurement for the H2O masers around the protoplanetary nebula OH 231.8+4.2 carried out with the Very Long Baseline Array (VLBA). Based on astrometric monitoring for 1 year, we measured a parallax of 0.65 ± 0.01 mas, corresponding to a distance of 1.54 +0.02−0.01 kpc. The spatial distribution of H2O masers is consistent with that found in the previous studies. After removing the average proper motion of 1.4 mas yr−1, corresponding to 10 km s−1, the internal motions of the H2O maser spots indicate a bipolar outflow.

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21

Waelkens, C. L., and L. B. F. M. Waters. "How unique is the protoplanetary nebula star HR 4049?" Symposium - International Astronomical Union 122 (1987): 509–10. http://dx.doi.org/10.1017/s0074180900157201.

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The late B-supergiant HR 4049 is peculiar in different respects: (1) It is located far from the galactic plane (b = 23°); (2) It is a variable with a large amplitude and on a long time scale (Waelkens and Rufener, 1983); (3) It has a spectacular infrared excess (Lamers et al., 1986). Two models were proposed: (i) HR 4049 is a runaway hypergiant embedded in a dust cloud, or (ii) HR 4049 is a low-mass star in a post-AGB stage of evolution. In this paper we present evidence that favours the second hypothesis. This evidence consists of new observational data on HR 4049 itself and of the discovery of a second very similar object, that is located still farther from the galactic plane.

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22

Choi, Yoon Kyung, Andreas Brunthaler, Karl M. Menten, and Mark J. Reid. "Trigonometric parallax of the protoplanetary nebula OH 231.8+4.2." Proceedings of the International Astronomical Union 7, S283 (July 2011): 330–31. http://dx.doi.org/10.1017/s1743921312011271.

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AbstractWe report trigonometric parallx measurements for H2O masers around the protoplanetary nebula OH 231.8+4.2 carried out with the Very Long Baseline Array. Based on astrometric monitoring for 1 year, we measured a trigonometric parallax of 0.89 ± 0.04 mas, corresponding to a distance of 1.12+0.05−0.05 kpc. This is the most accurate distance to OH 231.8+4.2, and the first one based on an annual parallax measurement. The distribution and internal motions of the H2O masers are consistent with the bipolar outflow suggested in literatures.

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23

Zhang, Yong, and Sun Kwok. "DETECTION OF C60IN THE PROTOPLANETARY NEBULA IRAS 01005+7910." Astrophysical Journal 730, no. 2 (March 14, 2011): 126. http://dx.doi.org/10.1088/0004-637x/730/2/126.

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24

Scarrott, R. M. J., S. M. Scarrott, and R. D. Wolstencroft. "H imaging polarimetry of the protoplanetary nebula M2-9." Monthly Notices of the Royal Astronomical Society 264, no. 3 (October 1, 1993): 740–48. http://dx.doi.org/10.1093/mnras/264.3.740.

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25

Sheehan, D. "Rossby Wave Propagation and Generation in the Protoplanetary Nebula." Icarus 142, no. 1 (November 1999): 238–48. http://dx.doi.org/10.1006/icar.1999.6200.

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26

Arkhipova, V. P., N. P. Ikonnikova, R. I. Noskova, and G. V. Komissarova. "Photometric variability of the protoplanetary nebula LSIV-12°111." Astronomy Letters 28, no. 4 (April 2002): 257–60. http://dx.doi.org/10.1134/1.1467261.

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27

Cuzzi, Jeffrey N., Robert C. Hogan, and Karim Shariff. "Toward Planetesimals: Dense Chondrule Clumps in the Protoplanetary Nebula." Astrophysical Journal 687, no. 2 (November 10, 2008): 1432–47. http://dx.doi.org/10.1086/591239.

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28

Scally, A., and C. Clarke. "Destruction of protoplanetary discs in the Orion Nebula Cluster." Monthly Notices of the Royal Astronomical Society 325, no. 2 (August 1, 2001): 449–56. http://dx.doi.org/10.1046/j.1365-8711.2001.04274.x.

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29

Sánchez Contreras, C., V. Bujarrabal, J. Alcolea, Luis F. Miranda, and J. Zweigle. "OH 231.8+4.2: its energetic bipolar outflow and rich chemistry." Symposium - International Astronomical Union 191 (1999): 347–52. http://dx.doi.org/10.1017/s0074180900203264.

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We report results from observations taken at different wavelengths (optical, radio and NIR) of the bipolar Protoplanetary Nebula OH 231.8+4.2. Radio interferometry with high spatial resolution has been particularly revealing. We study the complex structure and dynamics of this object as well as its rich chemistry.

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30

Kress, Monika E. "New Developments in Inner Solar Nebula Chemistry." Symposium - International Astronomical Union 197 (2000): 537–47. http://dx.doi.org/10.1017/s007418090016509x.

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The molecular cloud material which became the asteroids, meteorites and inner planets was extensively processed in the inner solar nebula. The chemical complexity of the most ancient meteorites attests to the highly nonequilibrium nature of the chemistry in this region, particularly regarding the volatile elements. Theoretical models describing the time evolution of the temperature and density profiles of protoplanetary accretion disks have recently become available. Such models provide a realistic framework within which to study, for instance, the effects of lightning and surface-catalyzed (gas-grain) reactions in the inner nebula. Here, we show that the latter would have been most efficient during the meteorite-forming epoch of the nebula, at the present position of the asteroid belt.

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31

Deguchi, Shuji, and Jun-ichi Nakashima. "Molecular Line Observations of the Protoplanetary Nebula, IRAS 19312+1950." Symposium - International Astronomical Union 209 (2003): 259–62. http://dx.doi.org/10.1017/s007418090020867x.

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We give a summary of radio molecular-line and infrared imaging observations of the newly found O-rich protoplanetary nebula, IRAS 19312+1950. This object exhibits a bipolar nebulosity of size ~ 30″ on the near-IR (JHK) images. A ring-like structure with a diameter of about 10″ is seen surrounding the central star. Toward this object, we detected thermal lines of CO, HCO+, SO, and SiO (O-bearing) molecules and CN, CS, HNC, NH3, N2H+, and HC3N (C- and N-bearing) molecules, as well as H2O and SiO masers lines. The line profiles of 12CO, HCN, SO, and HCO+ are composed of broad (Δv ~ 30–40 km s-1) and narrow (Δv < 5 km s-1) components. The SiO profile (J = 2—1 v = 0 thermal line) has only broad component, and the line profiles of non-O-bearing molecules (except HCN) have only a narrow component. Both components are spatially strongly peaked in intensity at the center of this object within a ~ 15″ telescope beam. We infer that both components originate from cool material surrounding the central star. This object is most likely an O-rich protoplanetary nebula with high mass loss rate and envelope chemistry similar to that of OH 231.8+0.4.

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32

de la Fuente Marcos, Carlos. "Dynamics and Growth of Dust Grains in the Protoplanetary Nebula." Publications of the Astronomical Society of the Pacific 114, no. 792 (February 2002): 259. http://dx.doi.org/10.1086/338857.

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33

Garaud, P., L. Barriere‐Fouchet, and D. N. C. Lin. "Individual and Average Behavior of Particles in a Protoplanetary Nebula." Astrophysical Journal 603, no. 1 (March 2004): 292–306. http://dx.doi.org/10.1086/381385.

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34

ZaČs, L., V. G. Klochkova, V. E. Panchuk, and R. Spēlmanis. "The chemical composition of the protoplanetary nebula candidate HD 179821." Monthly Notices of the Royal Astronomical Society 282, no. 4 (October 1996): 1171–82. http://dx.doi.org/10.1093/mnras/282.4.1171.

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35

Quinn, D. E., T. J. T. Moore, R. G. Smith, C. H. Smith, and T. Fujiyoshi. "10- m imaging of the bipolar protoplanetary nebula Mz-3." Monthly Notices of the Royal Astronomical Society 283, no. 4 (December 11, 1996): 1379–82. http://dx.doi.org/10.1093/mnras/283.4.1379.

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36

Schwarzschild, Bertram. "New Hubble Camera Finds Many Protoplanetary Disks in Orion Nebula." Physics Today 47, no. 8 (August 1994): 20–21. http://dx.doi.org/10.1063/1.2808596.

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37

Cuzzi, Jeffrey N., Anthony R. Dobrovolskis, and Joelle M. Champney. "Particle-Gas Dynamics in the Midplane of a Protoplanetary Nebula." Icarus 106, no. 1 (November 1993): 102–34. http://dx.doi.org/10.1006/icar.1993.1161.

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38

Semenov, D., and D. Wiebe. "CHEMICAL EVOLUTION OF TURBULENT PROTOPLANETARY DISKS AND THE SOLAR NEBULA." Astrophysical Journal Supplement Series 196, no. 2 (October 1, 2011): 25. http://dx.doi.org/10.1088/0067-0049/196/2/25.

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39

Cataldo, Franco, and Yeghis Keheyan. "Heavy petroleum fractions as possible analogues of carriers of the unidentified infrared bands." International Journal of Astrobiology 2, no. 1 (January 2003): 41–50. http://dx.doi.org/10.1017/s1473550403001381.

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The Fourier-transform infrared spectra and the electronic spectra of a series of petroleum fractions of different composition and origins have been studied. Furthermore, these fractions have been modified through the Scholl reaction, a reaction that causes an increase in the aromatic content of the fractions by causing the formation of polycyclic aromatic hydrocarbons (PAHs) or larger PAHs if they were already present in the pristine samples. It is shown that some heavily aromatic petroleum fractions are able to match the emission spectra of the protoplanetary nebula IRAS 22272+5435. Additionally, it is shown that the modified petroleum fractions are able to match the infrared spectrum of anthracite, a high-rank type of coal that has been proposed as the material responsible for the emission of the unidentified infrared bands (UIBs), but which can also be thought of as a model of the kerogen found in meteorites or assumed to be present in cometary nuclei. It is shown that the petroleum fractions considered in this work can be considered even better candidates than coal as a model for the matter present in protoplanetary nebulae and the carrier of the UIBs.

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40

Nakagawa, Yoshitsugu. "Possible in situ Formation of Close Giant Planets in a Passive Quiescent Nebula." Symposium - International Astronomical Union 202 (2004): 285–90. http://dx.doi.org/10.1017/s007418090021807x.

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Formation of giant planets along the standard model is considered in the innermost region of protoplanetary nebulae where turbulence has already decayed. Preference of quiescent nebulae is discussed. It is shown that if dust material enough to form a core with about ten times Earth mass and the corresponding amount of gas exist in the innermost region, a giant planet with mass somewhat larger than our Jupiter can form there.

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41

Sirono, Sin-iti. "THE SINTERING REGION OF ICY DUST AGGREGATES IN A PROTOPLANETARY NEBULA." Astrophysical Journal 735, no. 2 (June 24, 2011): 131. http://dx.doi.org/10.1088/0004-637x/735/2/131.

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42

Boss, Alan P. "Evolution of the Solar Nebula. III. Protoplanetary Disks Undergoing Mass Accretion." Astrophysical Journal 478, no. 2 (April 1997): 828. http://dx.doi.org/10.1086/303838.

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43

Fang, Xuan, Ana I. Gómez de Castro, Jesús A. Toalá, and Angels Riera. "HST STIS UV Spectroscopic Observations of the Protoplanetary Nebula Hen3-1475." Astrophysical Journal 865, no. 2 (October 1, 2018): L23. http://dx.doi.org/10.3847/2041-8213/aae20c.

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44

Champney, Joëlle M., Anthony R. Dobrovolskis, and Jeffrey N. Cuzzi. "A numerical turbulence model for multiphase flows in the protoplanetary nebula." Physics of Fluids 7, no. 7 (July 1995): 1703–11. http://dx.doi.org/10.1063/1.868486.

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45

Velázquez, Pablo F., Angels Riera, Alejandro C. Raga, and Juan C. Toledo-Roy. "AN ASYMMETRIC JET-LAUNCHING MODEL FOR THE PROTOPLANETARY NEBULA CRL 618." Astrophysical Journal 794, no. 2 (October 1, 2014): 128. http://dx.doi.org/10.1088/0004-637x/794/2/128.

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46

Boss, Alan P. "Evolution of the Solar Nebula. III. Protoplanetary Disks Undergoing Mass Accretion." Astrophysical Journal 469 (October 1996): 906. http://dx.doi.org/10.1086/177838.

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47

Alcolea, J., and V. Bujarrabal. "Imaging the two wind post-AGB interaction in M 1-92." Symposium - International Astronomical Union 191 (1999): 419–24. http://dx.doi.org/10.1017/s0074180900203355.

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M 1-92, Minkowski's Footprint, is a well studied protoplanetary nebula (PPN). Here we present high resolution observations of this object in atomic and molecular lines, as well as in the continuum, at optical and radio wavelengths. From these observations we conclude that the present bipolar nebula is the old AGB shell, strongly modified by the interaction with some powerful post-AGB bipolar ejections, which started suddenly about 900 years ago. The nature of these post-AGB ejections as well as its comparison with the present bipolar fast flow are discussed. We conclude that a mechanism different from photon pressure must be invoked in order to explain the morphology and dynamics of M 1-92 and other similar objects.

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Baessgen, M., W. Hopfensitz, and J. Zweigle. "Spectroscopy of the Proto-Planetary Nebula CRL 618." Symposium - International Astronomical Union 180 (1997): 343. http://dx.doi.org/10.1017/s0074180900131201.

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We present spectroscopic observations of the protoplanetary nebula CRL 618. The spectra in the range from 370 to 800 nm were taken at the 3.5m telescope on Calar Alto (Spain). The slit of the spectrograph covered both the brighter E-lobe and the fainter W-lobe. Using the balmer line we found an extinction of about c= 1.6 for both lobes. The emission lines show a velocity difference between the two blobs. The difference of the forbidden lines is found to be bigger than the v-difference of the permitted recombination lines in agreement with Carsenty and Solf (1982). Exceptions are the OII 732.0nm and 733.0nm and the NII 575.5nm lines. It also seems that the spatial separations of the peak emis-sivities of the forbidden lines are bigger than the separation of the recombination lines. This might be a result of the geometry and structure of the object. The permitted lines are emitted from the central source and reflected towards the observer at the inner edges of the blobs while the forbidden lines are emitted from the lobes themselves. Kelly et al. (1992) found a different I(NII 658.4nm + NII 654.8nm)/I(NII 575.5nm) ratio for the bright E-lobe than the older observations from Schmidt and Cohen (1981). This indicates an increased temperature of the bright lobe. We found now a similar temperature enhancement for the faint W-lobe. This may be caused by a shock reaching the inner edges of the blobs. This may also be the reason that the N II 575.5 nm line seems to originate at the inner blob edges, showing a smaller spatial separation. There is another indication for an increased temperature, we found some evidence for the S III 631.2nm, the He II 468.6nm and the O III 500.7 nm lines. The protoplanetary nebula CRL 618 is one of the few objects in this transition stage where dynamical processes can directly be observed.

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Guilera, Octavio M., Adrián Brunini, and Omar G. Benvenuto. "Simultaneous formation of Jupiter and Saturn." Proceedings of the International Astronomical Union 6, S276 (October 2010): 428–29. http://dx.doi.org/10.1017/s1743921311020655.

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AbstractWe calculate the simultaneous in situ formation of Jupiter and Saturn by the core instability mechanism considering the oligarchic growth regime for the accretion of planetesimals. We consider a density distribution for the size of planetesimals and planetesimals migration. The planets are immersed in a realistic protoplanetary disk that evolves with time. We find that, within the classical model of solar nebula, the isolated formation of Jupiter and Saturn undergoes significant change when it occurs simultaneously.

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Mann, Rita K., and Jonathan P. Williams. "A SUBMILLIMETER ARRAY SURVEY OF PROTOPLANETARY DISKS IN THE ORION NEBULA CLUSTER." Astrophysical Journal 725, no. 1 (November 18, 2010): 430–42. http://dx.doi.org/10.1088/0004-637x/725/1/430.

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