Featured Research

from universities, journals, and other organizations

New Evidence For Dark Dwarf Galaxies Supports Dark Matter Theory

Date:
May 21, 2002
Source:
University Of California - San Diego
Summary:
Two scientists have found evidence that galaxies are surrounded by halos containing hundreds of invisible dwarf galaxies. Their discovery, described in a paper in the June 10 issue of The Astrophysical Journal, provides strong support for the theory that most of the matter in the universe is in the form of some undetected type of slowly moving particles called cold dark matter.

Two scientists have found evidence that galaxies are surrounded by halos containing hundreds of invisible dwarf galaxies. Their discovery, described in a paper in the June 10 issue of The Astrophysical Journal, provides strong support for the theory that most of the matter in the universe is in the form of some undetected type of slowly moving particles called cold dark matter.

Related Articles


Astrophysicists Neal Dalal of the University of California, San Diego, and Christopher Kochanek of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA, based their conclusion on an analysis of the gravitational lensing of light from distant galaxies by intervening galaxies. According to Einstein's theory of gravity, large concentrations of matter such as galaxies can warp the surrounding space and bend the light from distant galaxies in much the same way that a glass lens can bend light.

One consequence of gravitational lensing is that the image of a single galaxy can be split into two or more images. The number and appearance of these multiple images depend on the distribution of mass in the lensing galaxies. In particular, if a lensing galaxy is surrounded by many smaller dwarf galaxies, the brightness of one of the lensed images could be significantly enhanced if it were aligned with one of the dwarf galaxies.

Dalal and Kochanek performed a statistical analysis of 7 different lensing galaxies which had each split the light of a background galaxy into 4 images of varying brightness. They found that about 2 percent of the mass of the lensing galaxies must be in the form of dwarf galaxies in order to explain the observed brightness variations among the multiple images of the background galaxies. Their study could help vindicate a model for the formation of galaxies in the eons after the Big Bang. A growing body of evidence indicates that from 80 to 90 percent of the matter in the universe is in the form of an as yet unknown type of elementary particle that contributes to gravity through its mass but otherwise interacts weakly with normal matter composed of protons and neutrons.

The currently favored form of dark matter is cold dark matter, so-called because the particles are assumed to move slowly, making it easier for gravity to pull them together to form galaxies. A firm prediction of this model is that large galaxies such as our Milky Way Galaxy should have numerous small satellite galaxies around them. The failure of astronomers to find the predicted swarms of dwarf galaxies around large galaxies has led a number of scientists to call for the abandonment of the cold dark matter model.

"The lack of observed satellite galaxies around large galaxies has been a major point in the prosecution of the case against cold dark matter," said Dalal. "Our result can be regarded as a major vindication of the model."

One puzzle remains as to why the dark dwarf galaxies contain few or no stars, if 10 to 20 percent of their mass is in the form of normal matter. "It's difficult to hide that much material," said Dalal. "Perhaps most of the gas was stripped from the dwarfs when the galaxy was formed."

Their research was supported by the National Aeronautics and Space Administration, U.S. Department of Energy, Smithsonian Institution and the ARCS Foundation.


Story Source:

The above story is based on materials provided by University Of California - San Diego. Note: Materials may be edited for content and length.


Cite This Page:

University Of California - San Diego. "New Evidence For Dark Dwarf Galaxies Supports Dark Matter Theory." ScienceDaily. ScienceDaily, 21 May 2002. <www.sciencedaily.com/releases/2002/05/020521072151.htm>.
University Of California - San Diego. (2002, May 21). New Evidence For Dark Dwarf Galaxies Supports Dark Matter Theory. ScienceDaily. Retrieved October 25, 2014 from www.sciencedaily.com/releases/2002/05/020521072151.htm
University Of California - San Diego. "New Evidence For Dark Dwarf Galaxies Supports Dark Matter Theory." ScienceDaily. www.sciencedaily.com/releases/2002/05/020521072151.htm (accessed October 25, 2014).

Share This



More Space & Time News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: China Launches Moon Orbiter

Raw: China Launches Moon Orbiter

AP (Oct. 24, 2014) China launched an experimental spacecraft Friday to fly around the moon and back to Earth in preparation for the country's first unmanned return trip to the lunar surface. (Oct. 24) Video provided by AP
Powered by NewsLook.com
China Prepares Unmanned Mission To Lunar Orbit

China Prepares Unmanned Mission To Lunar Orbit

Newsy (Oct. 23, 2014) The mission is China's next step toward automated sample-return missions and eventual manned missions to the moon. Video provided by Newsy
Powered by NewsLook.com
Russian Cosmonauts Kick Off Final Spacewalk of 2014

Russian Cosmonauts Kick Off Final Spacewalk of 2014

Reuters - US Online Video (Oct. 22, 2014) Russian cosmonauts Maxim Suraev and Alexander Samokutyaev step outside the International Space Station to perform work on the exterior of the station's Russian module. Rough Cut (no reporter narration) Video provided by Reuters
Powered by NewsLook.com
Comet Siding Spring Grazes Mars' Atmosphere

Comet Siding Spring Grazes Mars' Atmosphere

Newsy (Oct. 19, 2014) A comet from the farthest reaches of the solar system passed extremely close to Mars this weekend, giving astronomers a rare opportunity to study it. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins