Molecular hydrogen, also known as dihydrogen, is the simplest and most abundant molecule in the universe. It consists of two hydrogen atoms bonded together and plays a crucial role in the interstellar gas found between stars.
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Molecular hydrogen is the primary constituent of interstellar gas, accounting for approximately 70% of the total mass of the interstellar medium.
Molecular hydrogen is formed through the recombination of atomic hydrogen in cold, dense regions of the interstellar medium, where temperatures are low enough to allow the atoms to stick together.
Molecular hydrogen plays a crucial role in the formation of stars, as it acts as a coolant, allowing gravitational contraction and the collapse of molecular clouds to occur.
The presence of molecular hydrogen in the interstellar medium can be detected through its infrared emission, which is produced when the molecule is excited by the absorption of ultraviolet radiation.
Molecular hydrogen is also an important component of the atmospheres of gas giant planets, such as Jupiter and Saturn, where it makes up a significant portion of the atmospheric composition.
Review Questions
Explain the role of molecular hydrogen in the formation of stars.
Molecular hydrogen is a crucial component in the formation of stars. As gravitational forces cause the collapse of molecular clouds in the interstellar medium, the molecular hydrogen acts as a coolant, allowing the cloud to continue contracting and eventually forming a protostar. The cooling effect of molecular hydrogen is essential for the gravitational forces to overcome the thermal pressure within the cloud, enabling the cloud to condense and eventually give rise to a new star.
Describe how the presence of molecular hydrogen in the interstellar medium can be detected.
The presence of molecular hydrogen in the interstellar medium can be detected through its infrared emission. When molecular hydrogen is excited by the absorption of ultraviolet radiation, it emits characteristic infrared photons as the molecule returns to its ground state. This infrared emission can be observed and analyzed by astronomers to determine the abundance and distribution of molecular hydrogen in the interstellar medium. The detection of this infrared signature is a crucial tool for understanding the composition and structure of the interstellar gas between stars.
Analyze the significance of molecular hydrogen in the overall composition of the interstellar medium.
Molecular hydrogen is the most abundant molecule in the interstellar medium, accounting for approximately 70% of its total mass. This dominance of molecular hydrogen is crucial for understanding the composition and evolution of the interstellar medium. As the primary constituent, molecular hydrogen plays a central role in the formation and evolution of stars, as well as the cycling of matter and energy between stars. The prevalence of molecular hydrogen also has implications for the chemical and physical processes that occur within the interstellar medium, influencing the production of other molecules and the overall structure and dynamics of the galactic ecosystem.
Atomic hydrogen is the simplest atom in the universe, consisting of a single proton and a single electron. It is an important component of interstellar gas.
Ionized hydrogen, or protons, is hydrogen that has lost its electron and exists as a positively charged particle. It is a common component of interstellar plasma.
The interstellar medium is the matter and radiation that exists in the space between stars, including molecular hydrogen, atomic hydrogen, and other gases and dust.