Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Dwarf galaxies need dark matter too

26.10.2007
Stars in dwarf spheroidal galaxies behave in a way that suggests the galaxies are utterly dominated by dark matter, University of Michigan astronomers have found.

Astronomy professor Mario Mateo and post-doctoral researcher Matthew Walker measured the velocity of 6,804 stars in seven dwarf satellite galaxies of the Milky Way: Carina, Draco, Fornax, Leo I, Leo II, Sculptor and Sextans. They found that, contrary to what Newton's law of gravity predicts, stars in these galaxies do not move slower the farther they are from their galaxy's core.

"These galaxies show a problem right from the center," Mateo said. "The velocity doesn't get smaller. It just stays the same, which is eerie."

Astronomers already know stars in spiral galaxies behave in a similar way. This research dramatically increases the available information about smaller galaxies, making it possible to confirm that the distribution of light and stars in them is not the same as the distribution of mass.

"We have more than doubled the amount of data having to do with these galaxies, and that allows us to study them in an unprecedented manner. Our research shows that dwarf galaxies are utterly dominated by dark matter, so long as Newtonian gravity adequately describes these systems," Walker said. Walker received his doctorate from U-M earlier this year and currently has a post-doctoral position at the University of Cambridge in the United Kingdom.

Dark matter is a substance astronomers have not directly observed, but they deduce it exists because they detect its gravitational effects on visible matter. Based on these measurements, the prevailing theory in astronomy and cosmology is that the visible parts of the universe make up only a fraction of its total matter and energy.

The planet Neptune was once "dark matter," Mateo said. Before the term was even coined, astronomers predicted its existence based on an anomaly in the orbit of Neptune's neighbor Uranus. They knew just where to look for Neptune.

For the past quarter century, astronomers have been looking for the Neptune of the universe, so to speak. Dark matter could take the form of dwarf stars and planets, elementary particles including neutrinos, or hypothetical and as-yet undetected particles that don't interact with visible light or other parts of the electromagnetic spectrum.

Dark matter is believed to hold galaxies together. The gravitational force of the visible matter is not considered strong enough to prevent stars from escaping. Other theories exist to explain these discrepancies, though. For example, Modified Newtonian Dynamics, Mateo said, proposes that gravitational forces become stronger when accelerations are very weak. While their results align with current dark matter models, Mateo and Walker say they also bolster this less-popular explanation.

"These dwarf galaxies are not much to look at," Mateo continued, "but they may really alter our fundamental views on the nature of dark matter and, perhaps, even gravity."

Walker will present a paper on these findings on Oct. 30 at the Magellan Science Meeting in Cambridge, Mass. The paper he will present is Velocity Dispersion Profiles of Seven Dwarf Spheroidal Galaxies. It was published in the Sept. 20 edition of Astrophysical Journal Letters.

Nicole Casal Moore | EurekAlert!
Further information:
http://www.umich.edu

More articles from Physics and Astronomy:

nachricht Further Improvement of Qubit Lifetime for Quantum Computers
09.12.2016 | Forschungszentrum Jülich

nachricht Electron highway inside crystal
09.12.2016 | Julius-Maximilians-Universität Würzburg

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: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

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

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>