Galaxies are ravenous eaters. In addition to occasionally cannibalizing each other, galaxies are constantly feeding on gases strewn across the vast spaces that separate them.
These gases spill into the intergalactic medium when stars explode into supernovae, and are subsequently recycled when they are sucked back into galaxies to fuel the formation of new stars.
On Wednesday, NASA released a mesmerizing new visualization of this dynamic process playing out over the course of billions of years. The simulation was generated by the Pleiades supercomputer at NASA’s Ames Research Center in Silicon Valley, based on observations of galaxies and the rare glimpses scientists sometimes get of gas surrounding them.
The team that collected the data and ran the supercomputer models is called Figuring Out Gas and Galaxies in Enzo (FOGGIE). The FOGGIE acronym refers to the term “cosmic fog” which describes intergalactic gases that are illuminated by nearby galaxies. These spectral gases look something like “fog rolling in from the dark ‘oceans’ between galaxies," according to a NASA statement.
Molly Peeples, an associate research scientist at Johns Hopkins University who leads the FOGGIE project, presented the simulation at the supercomputing conference SC19, which is being held this week in Denver, Colorado.
The visualization is color-coded, with yellow representing regions with high densities of gas, such as the core of the simulated galaxy, while purples show where gas is more sparse. Reds and blues illustrate the temperature gradient, from hot to cold. Sudden bursts of red show how hot energetic supernovae explosions create superwinds which blow gas into intergalactic space, where it cools into blue cosmic fog.
Gases expelled in supernovae tend to be drawn back into the galaxy along so-called “large-scale structures,” which scientists think connect galaxies in a cosmic web of filaments and knots made of gas and dark matter.
In the early life of a galaxy, the process of sneezing out gases in supernovae winds, then slurping them back in to make more stars, is much wilder and more turbulent. As galaxies mature, they tend to calm down, though this quiescence is easily interrupted by collisions between galaxies. This type of crash is fated to happen to the Milky Way when it collides with the nearby Andromeda galaxy in about five billion years.
Because the gas in between galaxies does not emit much light, it’s tough to reconstruct the bigger picture of gas exchange between galaxies and the intergalactic medium. As shown by FOGGIE and NASA in this new video, supercomputers can help to fill in the gaps, while also producing stunning visualizations of the epic cycle of star death and rebirth that drives so much of galactic evolution.