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Reflection nebula IRAS 10082-5647 observed by the Hubble Space Telescope. These interstellar clouds possess a velocity higher than can be explained by the rotation of the Milky Way. [5] By definition, these clouds must have a v lsr greater than 90 km s −1, where v lsr is the local standard rest velocity.
They can change visibly over timescales of a few years as they move rapidly away from their parent star into the gas clouds of interstellar space (the interstellar medium or ISM). Hubble Space Telescope observations have revealed the complex evolution of HH objects over the period of a few years, as parts of the nebula fade while others ...
The interstellar medium (ISM) is the matter and radiation that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space.
In the low-density (H atoms per ) diffuse interstellar medium, dust particles up to micron size couple with gas clouds within a frictional scale of less than 1 pc. Within the denser, colder interstellar medium found in molecular clouds ( n H = 10 8 − 10 12 m − 3 {\displaystyle {10^{8}-10^{12}m^{-3}}} ), the growth of grains occurs through ...
NASA released the first complete set of images from the James Webb Space Telescope, including stars in their infancy and their final gasps.
[f] [154] [155] Filling the space between the stars is a disk of gas and dust called the interstellar medium. This disk has at least a comparable extent in radius to the stars, [156] whereas the thickness of the gas layer ranges from hundreds of light-years for the colder gas to thousands of light-years for warmer gas. [157] [158]
Molecular clouds typically have interstellar medium densities of 10 to 30 cm-3, and constitute approximately 50% of the total interstellar gas in a galaxy. [11] Most of the gas is found in a molecular state. The visual boundaries of a molecular cloud is not where the cloud effectively ends, but where molecular gas changes to atomic gas in a ...
The extremely low density of the interstellar medium is not conducive to the formation of molecules, making conventional gas-phase reactions between neutral species (atoms or molecules) inefficient. Many regions also have very low temperatures (typically 10 kelvin inside a molecular cloud), further reducing the reaction rates, or high ...