Where in heaven’s name are all the dwarfs? Astronomers have been wondering! According to the best theoretical models scientists can come up with, there should be many more small galaxies with relatively low populations of stars: “dwarf galaxies” in other words. Wait, before you send me that flaming e-mail: “Dwarf” is a not a derogatory term when you're talking about an astronomical object: A galaxy… or a star… or a planet. It just means little. And with dwarf galaxies, the astrophysicists are the ones who have come up short. 20 years of measurements using the best telescopes in space and on the ground have found only a few of these small galaxies in our cosmic backyard; each one about a thousand times less massive than our Milky Way spiral It's like we live in a large galactic city, but there are very few small towns anywhere nearby. And those that exist are ghost towns. Computer simulations clearly show that many, many more dwarfs should have formed within what’s called the “Cosmic Web,” the filigree of galaxies and empty bubble between them, which form the 3D Map of Everything. And the lack of little communities of stars has head scientists scratching their heads. Now, a group of researchers calling themselves the CLUES collaboration think they have a clue as to what happened. Their new simulations show that dwarf galaxies on the outskirts of our Local Group of galaxies are whipped around so fast by gravity that their gas matter is stripped away. With much less gas to work from many fewer stars form; and particularly not massive bright ones. So the dwarfs may actually be there, but very dim and extra small in stature. This so-called “Cosmic Web Stripping” mechanism is driven by the filamentary structure of the Universe itself. And it lets astronomers keep their current grand model of a Cosmos composed of 75% Dark Energy; 20% Dark Matter; and 5% ordinary matter like stars and planets and you and me. For SPACE.com, I'm Dave Brody
For 20 years, computer models have been telling astrophysicists there should be many more dwarf galaxies. New research shows the dwarfs are whipped around so fast by gravity that their gas matter is stripped off and they shrink away.
Credit: SPACE.com / Alejandro Benítez Llambay / Leibniz Institute for Astrophysics Potsdam