Nebula Orion

Fig. 1. Li EW (left panel) and abundances (right panel) of NGC 6530 stars compared to those of the coeval Orion Nebula cluster, using the same growth curves. Most of our targets show very strong Li lines increasing at lower temperatures. The results are not corrected for NLTE and veiling effects, as in Orion in [3]. Absolute values are overestimated but, relative values do not suffer from systematic errors.

Figure 3.11 The microwave spectrum of the Orion nebula. Reproduced by permission of Geoffrey...

Astronomical observations are complicated by the presence of many molecules in the field of view so that the measured spectrum is a complicated mixture of allowed rotational transitions such as in the Orion nebula (Figure 3.11). Identifying molecules is then a matter of experience based on knowledge of absolute transition frequencies and how the lines form rotational progressions. There are many things to consider in assigning the spectrum ... 

Calculate the transition wavelengths of the first four terms and the convergence wavelength for the Balmer series and identify the red transition responsible for the colour of the Orion nebula. 

Giant molecular clouds the GMCs have a lifetime of order 106—10s years and are the regions of new star formation. The Orion nebula (Orion molecular cloud, OMC) is some 50 ly in diameter and 1500 ly from Earth. The temperature within the cloud is of order 10 K and the atomic density is 106 cm-3. The chemical composition is diverse and contains small diatomic molecules, large polyatomic molecules and dust particles covered with a thick ice mantle. 

Fig. 5. Spectra in the 3200 to 2700 cm-1 range taken in a 5 arcsecond beam at three locations near the ionization ridge in the Orion Nebula. Position 4 is on the ridge between the ionized gas (HII region) and neutral molecular cloud while the positions 10 and 20 arcseconds south are within the molecular cloud. The dotted lines indicate the broad component, the dashed line the presumed continuum. Wavelengths, in microns, of the features are indicated in the top panel (Figure is from Reference [46])...

Fig. 11. Spectra between 900 to 770 cm-1 from 10 arcseconds north to 20 arcseconds south of position four on the ionization ridge in the Orion Nebula. Positions 4,10S and 20S are the same as the positions for the spectra shown in Fig. 5 (Figure from Ref. [53])...

Figure 5.5 The constellations of Orion and Canis Major. Note the location of Sirius, the Orion Nebula, and Betelgeuse, which are discussed throughout this book. [From Hubert Reeves, Atoms of Silence (Cambridge, Massachusetts MIT Press, 1984), 127, fig. 41, after Vesalius.]...

Kant was essentially correct, Bob says. In the last years of the twentieth century, the Hubble Space Telescope (HST) revealed several dozen disks at visible wavelengths in the Orion Nebula, a giant stellar nursery about 1,600 light years away. We call them proplyds, a contraction of the term protoplanetary disks. The Orion proplyds are larger than the Sun s solar system and contain enough gas and dust to provide the raw material for future planetary systems (figure 6.1). 

Figure 6.1 Attack of the proplyds A Hubble Space Telescope close-up of the Orion Nebula reveals disks of dust and gas surrounding newly formed stars. These fuzzy blobs, called proplyds, may be infant solar systems in the process of formation. This chunk of the sky spans about 0.14 light-years. (Image courtesy of Charles Robert O Dell of Vanderbilt University and NASA.)...

Bob leans back in the Naugahyde chariot seat. Stellar evolution refers to what happens to stars as they get older. We can use the H-R diagrams I already told you about to visualize this. In our twenty-first century, stars were born all the time in huge clouds of gas and dust called nebulae. Think of these clouds as stellar nurseries. One of the most famous is the Orion Nebula (figure 5.5). 

In 2000, researchers conducted a deep infrared photometric survey in the Orion nebula when they found that 30 percent of their 500 infrared sources were brown dwarfs. [For more information, see Linda Rowan, Free-floating planets in Orion, Science 288(5467) 773 (May 5,2000).]... 

Figure 10.40. N = 1 — - 0 rotational emission lines of CN observed from the Orion nebula [114]. The two lines correspond to the two transitions marked with asterisks in figure 10.41.

The microwave rotational spectrum of the CN radical has been elusive in the laboratory, and the first observations were made by astronomers in 1970 [113], with more extensive studies four years later [114, 115]. Figure 10.40 shows two emission lines observed from the Orion nebula, the initial assignment being based upon constants obtained from the electronic spectrum. Three years later the first observations of the... 

The fundamental initial parameters of protoplanetary disk evolution are the masses and sizes of the disks. Optical silhouettes of disks in the Orion Nebula Cluster (McCaughrean O Dell 1996), scattered light imagery (e.g. Grady et al. 1999), interferometric maps in millimeter continuum or line emission (e.g. Rodmann et al. 2006 Dutrey et al. 2007), and disk spectral energy distributions... 

Fig. 14. Energy levels of the free radical CN showing the observed optical and radio transition. The violet band is observed against Ophiuchi (Thaddeus and Clauser, 1966) and the radio frequency transitions are measured in the Orion nebula (Jefferts et al., 1970). In the interstellar optical spectra quadrupole hyperfine and spin-doubling structure are entirely unresolved and therefore the rotational levels can be approximated as though the electronic states were However, these splittings are partly resolved in the radio frequency region but we note that only one component of the spin doublet has been observed...

There exists some circumstantial evidence linking interstellar molecules to protostars. The more complex interstellar molecules tend to occur only in regions of very high density ( 10 H /cm ), e.g. the infrared nebula in Orion. Star formation proceeds at a rapid rate in such clouds, and thus solar nebulae may have formed and dissipated. The lifetime of our solar nebula seems to have been rather short 10 to 10 yr, or 1-2 orders of magnitude less than the age of a typical cloud, e.g. the Orion Nebula, or lifetimes of molecules against UV photolysis (Gammon, 1978). 

One feature suggestive of the FTT reaction is the variable abimdance of the two structural isomers, CH3OCH3 and CjHjOH, which dominate in the Orion Nebula and Sagittarius B2, respectively (Zuckerman et al., 1975). A similar variation was... 

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