Astrochemistry#
Introduction
Much of this chemistry occurs in “dense” interstellar clouds and protostellar disks surrounding forming stars because these environments have higher relative densities and more benign radiation fields than in stellar ejectae or the diffuse interstellar medium.
In this section we will focus on the chemistry within Molecular clouds.
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Updated: 15/02/2023
Introduction#
The ISM has always been considered too hostile of an environment for the formation of molecules.
Intrerstellar Radiation Field (ISRF) that have UV wavelength < 200 nm dissociates any molecules that may have formed (atom density also very low in the ISM).
However ISM is not homogeneous and it’s physical and chemical composition can vary widely.
Note
Should I include ISM environments here
Think so
ISM#
Note
include
Most of the molecules discovered have been observed within molecular clouds - coldest densest regions of the ISM.
Dust grains shield those clouds from ISRF. Hence molecules within the clouds are not dissociated
Basic Chemistry in Cold Cores#
‣ Gas-phase chemistry #
‣ Grain-surface chemistry #
From Cold core to PPD#
How much of the initial material is processed
Fig. 21 Taken from [Herbst and Dishoeck, 2009]#
Photoprocessing#
[Mason et al., 2006]: VUV spectroscopy, morphology of various molecular ices
Pre-biotique molecules in space#
Prebiotic molecules are defined as molecules that are thought to be involved in the processesleading to the origin of life.
Below are a few of them:
Glycoaldehyde
Glycolonitrile
Aminoacetonitrile
Formamide
Of the interstellar prebiotic molecules, many were first detected toward Sgr B
Nucleobase synthesis#
in interstellar ices
[Oba et al., 2019] (❌ to read)
Reactivity#
Surface reaction#
[Henning and Krasnokutski, 2019] (❌ to read)