This confusion is exacerbated by the tendency for airburst energies to be expressed in terms of nuclear weapon yields, as when the Tunguska airburst is given a rating in megatons of TNT. The use of the term explosion is somewhat loose in this context, and can be confusing. Larger or more solid meteorites may explode instead in a meteor airburst. Ram pressure and the very high temperatures it causes are the reasons few meteors make it all the way to the ground and most simply burn up or are ablated into tiny fragments. This is not due to friction, rather it is simply a consequence of many molecules and atoms being made to occupy a smaller space than formerly. As the air in front of the meteoroid is compressed its temperature quickly rises. The meteoroid then experiences what is known as ram pressure. Despite moving through the rarified upper reaches of Earth's atmosphere the immense speed at which a meteor travels nevertheless rapidly compresses the air in its path, creating a shock wave. Meteoroids enter Earth's atmosphere from outer space traveling at hypersonic speeds of at least 11 km/s (7 mi/s) and often much faster. Ram pressure and atmospheric entry/re-entry In meteoroids
This is an attractive mechanism to explain not only the presence of isolated dwarf galaxies away from galaxy clusters with particularly low hydrogen abundance to stellar mass ratio, but also the compression of gas in the centre of a dwarf galaxy and the subsequent reignition of star formation. Although the typical overdensity within the cosmic web is significantly lower than that found in the environment of galaxy clusters, the high relative speed between a dwarf and the cosmic web renders ram pressure efficient. More recently, it has been shown that ram pressure can also lead to the removal of gas in isolated dwarf galaxies that plunge through the cosmic web (the so-called cosmic web stripping process). Increased Hα emission, a sign of star formation, corresponds to the compressed CO region, suggesting that star formation may be accelerated, at least temporarily, while ram pressure stripping of neutral hydrogen is ongoing. Recent radio observation of carbon monoxide (CO) emission from three galaxies ( NGC 4330, NGC 4402, and NGC 4522) in the Virgo cluster point to the molecular gas not being stripped but instead being compressed by the ram pressure. Spiral galaxies that have fallen at least to the core of both the Virgo and Coma clusters have had their gas (neutral hydrogen) depleted in this way and simulations suggest that this process can happen relatively quickly, with 100% depletion occurring in 100 million years to a more gradual few billion years. As galaxies fall toward the center of a cluster, more and more of their gas is stripped out, including the cool, denser gas that is the source of continued star formation.
Ram pressure stripping is thought to have profound effects on the evolution of galaxies. These ram pressure stripped galaxies will often have a large trailing tail and because of this they are commonly called "Jellyfish galaxies."
Evidence of this ram pressure stripping can be seen in the image of NGC 4402. This pressure can strip gas out of the galaxy where, essentially, the gas is gravitationally bound to the galaxy less strongly than the force from the intracluster medium 'wind' due to the ram pressure. P ram = ρ u i u j the speed of the galaxy relative to the medium. It causes a drag force to be exerted on the body. Ram pressure is a pressure exerted on a body moving through a fluid medium, caused by relative bulk motion of the fluid rather than random thermal motion. Note the dust (brown) trailing behind (toward upper right) the galaxy, versus the dust-free (blue-white) leading edge. Ram pressure stripping in NGC 4402 as it falls towards the Virgo Supercluster (off image, toward bottom left).
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