On April 14, NASA, on its official blog, shared an image of galaxy JO204, captured by the NASA/ESA Hubble Space Telescope shows JO204. JO204 is a massive galaxy in the low-mass cluster A957.
This ‘jellyfish galaxy’ got its nickname from the brilliant tendrils of gas that appear to be flowing lazily beneath JO204’s luminous core bulge in this view. The galaxy is located in the constellation Sextans, over 600 million light-years away.
The tendril is, in fact, the result of an intense astronomical process known as ram pressure stripping.
Ram pressure is a specific kind of pressure applied to a body when it is moving in relation to a fluid. An intuitive illustration is a pressure you feel when standing in a strong wind gust; the wind is a moving fluid, and you feel pressure from it. This analogy can be extended to mean that while your body will remain intact and cohesive, the looser components of your appearance, such as your hair and clothes, will flap in the wind. In the same way, jellyfish galaxies exist.
As part of a survey to learn more about star formation in harsh environments, Hubble observed JO204.
They experience ram pressure because of their movement against the intergalactic medium that fills the spaces between galaxies in a galaxy cluster. The galaxies experience intense pressure from that movement, and as a result, their more loosely bound gas is stripped away. This gas is mostly the colder and denser gas in the galaxy – gas which, when stirred and compressed by the ram pressure, collapses and forms new stars in the jellyfish’s beautiful tendrils.