Knowra Molecular cloud Molecular cloud A cold, dense interstellar cloud containing abundant molecules, especially molecular hydrogen. Its dense regions shield molecules from radiation and can collapse to form stars.
Molecular hydrogen : The simplest molecule, consisting of two hydrogen atoms; it is the most abundant molecule in molecular clouds. Its rotational emission reveals molecular gas, though the molecule itself is difficult to observe directly.
Interstellar medium : The matter and radiation occupying the space between stars in a galaxy. Molecular clouds are its cold, dense component.
Star formation : The process by which dense regions of gas and dust collapse to form stars. Molecular clouds are the principal sites of star formation in galaxies.
Orion Molecular Cloud : A nearby complex of molecular clouds in Orion that contains active star-forming regions. Its proximity makes it a major laboratory for studying massive and low-mass star formation.
Interstellar dust : Tiny solid particles dispersed between stars, composed mainly of silicates, carbon compounds, and ices. Dust absorbs ultraviolet light, helping shield molecules inside the cloud.
Hydrogen : The lightest chemical element, with one proton in its nucleus. Hydrogen dominates cloud mass and occurs in both atomic and molecular forms.
Protostar : A young stellar object still gaining mass from its collapsing envelope and not yet powered by sustained hydrogen fusion. Protostars emerge from collapsing cores within molecular clouds.
Taurus Molecular Cloud : A nearby, relatively quiet molecular cloud complex containing many low-mass young stars. It shows how isolated, low-mass stars form in a comparatively calm environment.
Jeans instability : The gravitational instability that causes a gas region to collapse when its mass exceeds a threshold set by pressure and temperature. It describes when a dense cloud region can overcome pressure and begin gravitational collapse.
Carbon monoxide : A molecule of one carbon atom and one oxygen atom, commonly used to trace molecular gas in space. Its emission lines provide a practical tracer of molecular cloud structure.
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