A dark matter halo (yellow) forms around the galaxy
Ralph Koehler/SLAC National Accelerator Laboratory
When you think of the Milky Way, “delicate” may not be the first word that comes to mind. But when Mariangela Lisanti started tinkering with the recipe for Our Galaxy, she found it surprisingly fragile.
Lisanti, a particle physicist at Princeton University, wonders what would happen if dark matter, a mysterious substance thought to make up more than 80 percent of all matter in the universe, was more exotic than researchers usually assumed. She was simulating something like that. She replaced a small portion of standard dark matter with something more complex. “We thought we could just add 5% and everything would be fine,” she says. “And we destroyed the galaxy.”
There are good reasons for such interference. Since the 1980s, astronomical signs have shown that dark matter is a single type of slow-moving particle that does not interact with itself. Particle physicists have spent a great deal of effort searching for that particle. But decades later, it remains a no-show. Perhaps because dark matter is not what we tend to imagine.
Recently, a series of galactic anomalies have sparked a scramble to find alternatives. This “complex” dark matter can be as simple as subatomic particles bouncing off each other, or as complex as dark particles forming dark atoms, stars, and even galaxies. There are a number of mind-boggling possibilities.
But now observations of anomalies in our galaxy promise to finally help narrow down the options. and…
Source: www.newscientist.com
