One of the perplexing problems in modern astronomy is the one of trying to determine the composition and location of the “missing galactic mass”. (The missing mass is matter of which can detect gravitational effects, but which we haven’t been able to see. Dark Matter is part of the missing mass, but there are other sorts that can be out there.) Hence the interest in a recent paper published in the journal Science:
“Astronomers studying dwarf galaxies formed from the debris of a collision of larger galaxies found the dwarfs much more massive than expected, and think the additional material is ‘missing mass’ that theorists said should not be present in this kind of dwarf galaxy
…”Dark matter,” which astronomers can detect only by its gravitational effects, comes, they believe, in two basic forms. One form is the familiar kind of matter seen in stars, planets, and humans — called baryonic matter — that does not emit much light or other type of radiation. The other form, called non-baryonic dark matter, comprises nearly a third of the Universe but its nature is unknown.
…What is the dark matter in the dwarfs? The astronomers don’t believe it is the mysterious non-baryonic type, but rather cold Hydrogen molecules that are extremely difficult to detect.
When the astronomers performed computer models of the collision of NGC 5291 to simulate the formation of the system seen today, the models left the resulting recycled dwarfs with almost no dark matter. These computer models had started off with all the dark matter in the galaxy’s larger halo.
“The result of the computer models means that the additional mass we see in the real dwarfs came from the disks, not the haloes, of the larger galaxies that collided,” Bournaud said. That additional mass, the scientists believe, almost certainly is “normal” baryonic matter, probably cold molecular Hydrogen. “
Now the next question, if this observation and explanation is verified, would be to determine how much of the missing mass is normal matter such as this and how much of it is some sort of exotic, non-baryonic matter. No matter what the ratio, there’s going to be a lot of it. Estimates place the amount of missing mass to be between 90 and 99x the total amount of observed matter in the sky.
Read the rest here: ‘Missing Mass’ Found in Recycled Dwarf Galaxies