But new research shows that there are galaxies out there which are almost completely comprised of dark matter. They’re called dwarf spheroidals, and they only contain a few stars and almost no gas. Instead, they’ve got an overwhelming amount of dark matter, whose gravity compacts what few stars it has into a roughly spherical shape. And because they don’t have many stars, they’re hard to see, even when they’re nearby.
An international team of researchers has developed a simulation to explain how galaxies like this could form. They used supercomputers to calculate how galaxies interact. When a smaller galaxy collides with a much larger galaxy, friction causes the gas to slow down and be stripped out a galaxy, while the stars and dark matter continue on.
Without this gas, the galaxy can’t continue making stars. It’s only got the stars that had formed before the collision. A massive galaxy can also strip away stars and material through a process called “tidal shocking”. Between these two effects, you can end up with a galaxy devoid of regular matter – all that’s left is dark matter.
Original Source: Stanford News Release
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