ﻻ يوجد ملخص باللغة العربية
Cometary studies suggest that the organic composition of the early Solar Nebula was rich in complex nitrile species such a CH$_3$CN. Recent ALMA detections in protoplanetary disks suggest that these species may be common during planet and comet formation, but connecting gas phase measurements to cometary abundances first requires constraints on formation chemistry and distributions of these species. We present here the detection of seven spatially resolved transitions of CH$_3$CN in the protoplanetary disk around the T-Tauri star TW Hya. Using a rotational diagram analysis we find a disk-averaged column density of N$_T$=1.45$^{+0.19}_{-0.15}times10^{12}$ cm$^{-2}$ and a rotational temperature of T$_{rot}$=32.7$^{+3.9}_{-3.4}$ K. A radially resolved rotational diagram shows the rotational temperature to be constant across the disk, suggesting that the CH$_3$CN emission originates from a layer at z/r$sim$0.3. Through comparison of the observations with predictions from a disk chemistry model, we find that grain-surface reactions likely dominate CH$_3$CN formation and that in situ disk chemistry is sufficient to explain the observed CH$_3$CN column density profile without invoking inheritance from the protostellar phase. However, the same model fails to reproduce a Solar System cometary abundance of CH$_3$CN relative to H$_2$O in the midplane, suggesting that either vigorous vertical mixing or some degree of inheritance from interstellar ices occurred in the Solar Nebula.
The precursors to larger, biologically-relevant molecules are detected throughout interstellar space, but determining the presence and properties of these molecules during planet formation requires observations of protoplanetary disks at high angular
Planets form in the disks around young stars. Their formation efficiency and composition are intimately linked to the protoplanetary disk locations of snow lines of abundant volatiles. We present chemical imaging of the CO snow line in the disk aroun
Previous investigations have employed more than 100 close observations of Titan by the Cassini orbiter to elucidate connections between the production and distribution of Titans vast, organic-rich chemical inventory and its atmospheric dynamics. Howe
We review recent advances in our understanding of magnetism in the solar nebular and protoplanetary disks (PPDs). We discuss the implications of theory, meteorite measurements, and astronomical observations for planetary formation and nebular evoluti
If we want to understand planetesimal formation, the only data set we have is our own Solar System. It is particularly interesting as it is so far the only planetary system we know of that developed life. Understanding the conditions under which the