page_title: Ram pressure
section_title: Galactic ram pressure stripping
hierarchical_section_title: Ram pressure / Astrophysical examples of ram pressure / Galactic ram pressure stripping
caption_attribution_description: English: This striking image combines data gathered with the Advanced Camera for Surveys, installed on the NASA/ESA Hubble Space Telescope and data from the Subaru Telescope in Hawaii. It shows just a part of the spectacular tail emerging from a spiral galaxy nicknamed D100. Tails such as these are created by a process known as ram-pressure stripping. Despite appearances, the space between galaxies in a cluster is far from empty; it is actually filled with superheated gas and plasma, which drags and pulls at galaxies as they move through it, a little like the resistance one experiences when wading through deep water. This can be strong enough to tear galaxies apart, and often results in objects with peculiar, bizarre shapes and features — as seen here. D100’s eye-catching tail of gas, which stretches far beyond this image to the left, is a particularly striking example of this phenomenon. The galaxy is a member of the huge Coma cluster. The pressure from the cluster’s hot constituent plasma (known as the intracluster medium) has stripped gas from D100 and torn it away from the galaxy’s main body, and drawing it out into the plume pictured here. Densely populated clusters such as Coma are home to thousands of galaxies. They are thus the perfect laboratories in which to study the intriguing phenomenon of ram-pressure stripping, which, as well as producing beautiful images such as this, can have a profound effect on how galaxies evolve and form new generations of stars.
context_page_description: In physics, 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. It causes a drag force to be exerted on the body. Ram pressure is given in tensor form as
  ,
  where is the density of the fluid; this is the momentum flux per second in the direction through a surface with normal in the direction. are the components of the fluid velocity in these directions. The total Cauchy stress tensor is the sum of this ram pressure and the isotropic thermal pressure.
  In the simple case when the relative velocity is normal to the surface, and momentum is fully transferred to the object, the ram pressure becomes
  .
context_section_description: Within astronomy and astrophysics, James E. Gunn and J. Richard Gott first suggested that galaxies in a galaxy cluster moving through a hot intracluster medium would experience a pressure of
  where  is the ram pressure,  the intracluster gas density, and  the speed of the galaxy relative to the medium. 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. Evidence of this ram pressure stripping can be seen in the image of NGC 4402.
  Ram pressure stripping is thought to have profound effects on the evolution of galaxies.  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.  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.
  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.  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.
caption: Tails in spiral galaxy D100, found in the Coma Cluster, are created by ram-pressure stripping.[2][3]
exif: {"Image ImageDescription": "This striking image combines data gathered with the Advanced Camera for Surveys, installed on the NASA/ESA Hubble Space Telescope and data from the Subaru Telescope in Hawaii. It shows just a part of the spectacular tail emerging from a spiral galaxy nicknamed D100. Tails such as these are created by a process known as ram-pressure stripping. Despite appearances, the space between galaxies in a cluster is far from empty; it is actually filled with superheated gas and plasma, which drags and pulls at galaxies as they move through it, a little like the resistance one experiences when wading through deep water. This can be strong enough to tear galaxies apart, and often results in objects with peculiar, bizarre shapes and features \u2014 as seen here. D100\u2019s eye-catching tail of gas, which stretches far beyond this image to the left, is a particularly striking example of this phenomenon. The galaxy is a member of the huge Coma cluster. The pressure from the cluster\u2019s hot constituent plasma (known as the intracluster medium) has stripped gas from D100 and torn it away from the galaxy\u2019s main body, and drawing it out into the plume pictured here. Densely populated clusters such as Coma are home to thousands of galaxies. They are thus the perfect laboratories in which to study the intriguing phenomenon of ram-pressure stripping, which, as well as producing beautiful images such as this, can have a profound effect on how galaxies evolve and form new generations of stars. Links  Hubblesite release", "Image Software": "Adobe Photoshop CC (Macintosh)", "Image DateTime": "2018:05:02 21:06:53"}