A dwarf galaxy named Sagittarius loaded with dark matter has careened twice through our much larger home galaxy in the past two billion years, according to telescope data and detailed simulations, and is poised to strike the southern face of the Milky Way disk in another 10 million years or so.
Many astronomers believe that the large galaxies seen today were formed from smaller "dwarf" galaxies, which formed first after the Big Bang. Many of these dwarfs either clumped together to form larger galaxies or were gradually swallowed up by larger galaxies that continued to grow by "cannibalizing" smaller ones.
It's the weighty dark matter from Sagittarius that provided the initial push, the researchers said.
"It's kind of like putting a fist into a bathtub of water as opposed to your little finger," said James Bullock, a theoretical cosmologist who studies galaxy formation.
I find it very helpful to read George Gamow our sun a star when confronted with words like 'dark matter;' his book makes it clear back in 1965 when science was a lot clearer for all of us, that extreme heat would separate the atom into free electrons and nucleus, and then if these were exposed to pressure it would be theoretically possible for a nuclear fluid to be the result of this compression. One imagines a neutron star.
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