Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


MOND predicts dwarf galaxy feature prior to observations

Also indicates gravity fields vary where dark matter presumes uniformity

A modified law of gravity correctly predicted, in advance of the observations, the velocity dispersion -- the average speed of stars within a galaxy relative to each other -- in 10 dwarf satellite galaxies of the Milky Way's giant neighbor Andromeda.

The relatively large velocity dispersions observed in these types of dwarf galaxies is usually attributed to dark matter. Yet predictions made using the alternative hypothesis Modified Newtonian Dynamics (MOND) succeeded in anticipating the observations.

Stacy McGaugh, professor of astronomy at Case Western Reserve, and Mordehai Milgrom, the father of MOND and professor of physics at Weizmann Institute in Israel, report their findings, which have been accepted for publication by the Astrophysical Journal, in a preprint online:

The researchers tested MOND on quasi-spherical, very low-surface brightness galaxies that are satellites of Andromeda. In the cosmic scale, they are among the smallest galaxies, containing only a few hundred thousand stars. But with conventional gravity, they are inferred to contain huge amounts of dark matter.

"Most scientists are more comfortable with the dark matter interpretation," McGaugh said. "But we need to understand why MOND succeeds with these predictions. We don't even know how to make this prediction with dark matter."

While this study is very specific, it's part of a broader effort to understand how the universe, the Milky Way and Earth formed and what it's all made of. This informs human understanding of our place in the universe, McGaugh said. Such issues have been of such importance that they've changed religion and philosophy over the centuries, sometimes sending people to be burnt at the stake.

"At stake now is whether the universe is predominantly made of an invisible substance that persistently eludes detection in the laboratory, or whether we are obliged to modify one of our most fundamental theories, the law of gravity," McGaugh continued.

The MOND hypothesis says that Newton's force law must be tweaked at low acceleration -- 11 orders of magnitude lower than what we feel on the surface of the Earth. Acceleration above that threshold is linearly proportional to the force of gravity -- as Newton's law says -- but below the threshold, no. At these tiny accelerations, the modified force law resolves the mass discrepancy.

The paper's calculations using MOND also reveal subtle differences in the gravity fields of dwarfs near and far from the host galaxy Andromeda. The gravity fields of dwarfs far from the host appear to be dominated by stars within the dwarf, while the gravity fields of dwarfs close to the host appear to be dominated by the host. No such distinction is expected with dark matter.

"The influence of the host galaxy may provide a test to distinguish between dark matter and MOND," McGaugh says. "Dark matter provides a cocoon for the dwarfs, protecting the stars from tidal influence by the host galaxy. With MOND, the influence of the host is more pronounced."

In a comparison of the predictions calculated using MOND with observations of pairs of similar dwarfs, "the data appears to show MOND's prediction for the influence of the host, but it's fairly subtle," McGaugh said. MOND's predictions of the velocity dispersion were less subtle. These predictions were "really bang on," McGaugh said.

The finding bolsters the case McGaugh and Milgrom made for MOND's effectiveness in predicting properties in dwarf galaxies in a paper published earlier this year. In that paper, they successfully predicted the velocity dispersion in 17 of the galaxies.

Kevin Mayhood | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht OU-led team discovers rare, newborn tri-star system using ALMA
27.10.2016 | University of Oklahoma

nachricht First results of NSTX-U research operations
26.10.2016 | DOE/Princeton Plasma Physics Laboratory

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

How nanoscience will improve our health and lives in the coming years

27.10.2016 | Materials Sciences

OU-led team discovers rare, newborn tri-star system using ALMA

27.10.2016 | Physics and Astronomy

'Neighbor maps' reveal the genome's 3-D shape

27.10.2016 | Life Sciences

More VideoLinks >>>