Way Beyond Astrophysics!

What is it?

This study area bridges the divide between astronomy and chemistry to show how molecules' formation, destruction, and excitation in astronomical environments shape the structure, dynamics, and development of celestial bodies.

The field focuses on various scientific endeavours, from studying and explaining ideas like star formation to identifying distinct chemical species unknown to a laboratory chemist.

Why is the chemistry of outer space so unique and pivotal?

The outer space environment is very different from what we have on Earth in many ways.

Significant decrease and augmentation of gravitational Force
Temperatures as low as 2.7 K to be High as 1013 K
Densities as low as one atom per cubic centimetre to hundreds of million tons per cubic centimetre.

These reasons distinguish the chemistry of celestial bodies and space from laboratory chemistry. Space chemistry can be broken down into subfields like ice-phase, dust-phase, and gas-phase chemistry. Insight into the new reaction routes for a particle chemical reaction and a foundation for many astronomical phenomena may be gained from theoretical knowledge based on the chemical reactions under these conditions.

This article kicks off a series that will explore various aspects of chemistry as it adapts to the extreme circumstances of space, with a particular emphasis on the first step towards this goal: identifying the many chemical entities involved.

Identification of different chemical entities

To date, more than 160 molecular species have been identified in interstellar, circumstellar, and cometary clouds. This provides a wide range of molecules, including neutrals, cations, and anions, containing up to 7, 8,13, 17 and even 19 atoms- in addition to detecting C60 and C70. Among the extraordinarily intriguing and atypically produced molecules are the following:

Molecule	Designation	Description
PO	Phosphorus Monoxide	Unstable radical inorganic compound. Detected in the circumstellar shell of VY Canis Majoris (RHG OR RSG) located in the slightly southern constellation of Canis Major.
HeH+	Helium Hydride Ion	Lightest Heteronuclear Ion and the very first compound formed after the big bang. Detected in ISM using SOFIA Telescope
HN+2	Diazenylium	Inorganic Cation. One of the first ions to be observed in Interstellar clouds
HC3N	Cyanoacetylene	The simplest cyano polyyne. Detected in interstellar clouds, in the coma of comet Hale–Bopp and in the atmosphere of Saturn's moon Titan where it sometimes forms expansive fog-like clouds.

These molecules are just the tip of the iceberg of the far-fetched compounds discovered. Several astronomical spectroscopic techniques, detailed below, can identify the presence of such improbable molecules and other simple and generally stable molecules like Ammonia, Water, Oxides, etc.

Infrared Spectroscopy

This technique is used to detect the presence of molecules in the gas phase. It detects the absorption of infrared radiation by the molecules (emitted as a result of molecular vibrations) and provides information about the chemical composition and temperature of the gas.

Ultraviolet Spectroscopy

This technique detects the presence of molecules in the gas phase and in solid or icy grains. It detects the absorption of ultraviolet radiation by the molecules and provides information about the chemical composition and temperature of the gas or grains. This method utilizes the electronic transitions between a molecule's electronic energy levels.

Microwave Spectroscopy

This technique is used to detect the presence of molecules in the gas phase. It sees the rotational transitions of the molecules in the microwave region of the electromagnetic spectrum and provides information about the molecular structure and abundance.

Millimeter/Submillimeter Spectroscopy

This technique is used to detect the presence of molecules in the gas phase. It sees the rotational transitions of the molecules in the millimetre and submillimeter region of the electromagnetic spectrum and provides information about the molecular structure and abundance.

Mass Spectroscopy

This technique detects the presence of molecules in the gas phase and in solid or icy grains. It sees the mass-to-charge ratio of the molecules and provides information about the chemical composition and isotopic ratios of the gas or grains.

These techniques are combined to comprehensively understand the chemical composition and physical conditions of interstellar, circumstellar, and cometary clouds.

In conclusion, developing new technologies and methods for detecting and analyzing molecules in space has led to a deeper understanding of the chemical reactions that occur under extreme conditions, which can inform the development of new materials and chemical processes on Earth. Overall, the study of Astrochemistry provides exciting opportunities for exploration and discovery, offering a window into the mysteries of the universe and the fundamental processes that govern it.

Acronyms:

ISM - Interstellar Medium

SOFIA - Stratospheric Observatory for Infrared Astronomy

RHG - Red Hypergiant

RSG - Red Supergiant

References:

https://www.nist.gov/pml/sensor-science/optical-radiation/large-amplitude-motion

https://upload.wikimedia.org/wikipedia/commons/thumb/8/8f/Star-stuff.png/525px-Star-stuff.png

https://en.wikipedia.org/wiki/Helium_hydride_ion

https://www.astro.princeton.edu/events/spitzer_lecture_series/Lecture1.pdf

https://en.wikipedia.org/wiki/Phosphorus_monoxide

https://en.wikipedia.org/wiki/List_of_interstellar_and_circumstellar_molecules