Dark Matter Could be Way More Complicated Than Scientists Thought

Sacramento, California (Sputnik) – Despite the fact that dark matter makes up approximately 80% of the universe, we know astonishingly little about the mass. We’ve never even seen it; its existence is only hypothesized by our observations of dark matter’s effects on gravity.

“We are confident that it’s there, that is has mass, and that it tugs on itself and on other things via gravity,” James Bullock, a professor of physics and astronomy at the University of California, Irvine, told Quanta Magazine.

“That’s about it.”

Much of our ignorance stems from the fact that the studies of universe typically depend on our observation of light. Distant planets, for instance, are only observed when they pass between the observer and its host star.

Studying dark matter, which neither absorbs nor reflects light, becomes exponentially more difficult. Which isn’t to say scientists don’t have some ideas.

“First-guess models for what it is suggests that it is one particle that doesn’t really interact with much of anything,” Bullock said. “Another possibility is this 80% of the universe is also complex. Maybe there’s something interesting going on in what’s called the dark sector.”

Researchers are beginning to probe these dark sectors – located primarily in the centers of galaxies – to observe dark matter’s effects on gravity. Observations are then compared with computer models to see which best fit the existing universe.

But the problem is: neither explanation entirely matches.

“At first it was thought maybe we’re interpreting the data wrong,” Bullock said. “And now the question comes down to: Does galaxy formation eject dark matter somehow, or do we need to modify our understanding of dark matter?”

“Could it be,” he added, “that these little discrepancies we’ve been seeing in the observational data are actually a clue that there’s something interesting and fun going on in the dark sector that we weren’t thinking about before?”

Bullock and his team have been running comparative models for years, and they’re still nowhere close to a concrete answer. That’s partly because dark matter’s nature makes it a bit of a cosmological chameleon.

“There’s all of this other annoying normal stuff that we have to think about, too,” Bullock said. “Gas that can turn into stars – and some of those stars are going to be so massive that they blow up as supernovae. When they blow up as supernovae, they are effectively jostling the gravitational field around them, and this jostling can potentially move the dark matter around.”

Bullock plans to continue his research, but his money is on the complex theory.

Image Source: NASA Goddard Space Flight Center. Flickr, Creative Commons Mapping the Invisible - Hubble Yields Clues to Galaxy Cluster Growth NASA image release November 12, 2010 Hubble's Dark Matter Map: Detailed Dark Matter Map Yields Clues to Galaxy Cluster Growth This NASA Hubble Space Telescope image shows the distribution of dark matter in the center of the giant galaxy cluster Abell 1689, containing about 1,000 galaxies and trillions of stars. Dark matter is an invisible form of matter that accounts for most of the universe's mass. Hubble cannot see the dark matter directly. Astronomers inferred its location by analyzing the effect of gravitational lensing, where light from galaxies behind Abell 1689 is distorted by intervening matter within the cluster. Researchers used the observed positions of 135 lensed images of 42 background galaxies to calculate the location and amount of dark matter in the cluster. They superimposed a map of these inferred dark matter concentrations, tinted blue, on an image of the cluster taken by Hubble's Advanced Camera for Surveys. If the cluster's gravity came only from the visible galaxies, the lensing distortions would be much weaker. The map reveals that the densest concentration of dark matter is in the cluster's core. Abell 1689 resides 2.2 billion light-years from Earth. The image was taken in June 2002. Read more about this image here: www.nasa.gov/mission_pages/hubble/science/dark-matter-map... Image credit: NASA, ESA, D. Coe (NASA Jet Propulsion Laboratory/California Institute of Technology, and Space Telescope Science Institute), N. Benitez (Institute of Astrophysics of Andalusia, Spain), T. Broadhurst (University of the Basque Country, Spain), and H. Ford (Johns Hopkins University)

Image Source: NASA Goddard Space Flight Center. Flickr, Creative Commons
Mapping the Invisible – Hubble Yields Clues to Galaxy Cluster Growth
NASA image release November 12, 2010
Hubble’s Dark Matter Map: Detailed Dark Matter Map Yields Clues to Galaxy Cluster Growth
This NASA Hubble Space Telescope image shows the distribution of dark matter in the center of the giant galaxy cluster Abell 1689, containing about 1,000 galaxies and trillions of stars.
Dark matter is an invisible form of matter that accounts for most of the universe’s mass. Hubble cannot see the dark matter directly. Astronomers inferred its location by analyzing the effect of gravitational lensing, where light from galaxies behind Abell 1689 is distorted by intervening matter within the cluster.
Researchers used the observed positions of 135 lensed images of 42 background galaxies to calculate the location and amount of dark matter in the cluster. They superimposed a map of these inferred dark matter concentrations, tinted blue, on an image of the cluster taken by Hubble’s Advanced Camera for Surveys. If the cluster’s gravity came only from the visible galaxies, the lensing distortions would be much weaker. The map reveals that the densest concentration of dark matter is in the cluster’s core.
Abell 1689 resides 2.2 billion light-years from Earth. The image was taken in June 2002.
Read more about this image here: www.nasa.gov/mission_pages/hubble/science/dark-matter-map…
Image credit: NASA, ESA, D. Coe (NASA Jet Propulsion Laboratory/California Institute of Technology, and Space Telescope Science Institute), N. Benitez (Institute of Astrophysics of Andalusia, Spain), T. Broadhurst (University of the Basque Country, Spain), and H. Ford (Johns Hopkins University)

This report was prepared by Sputnik