Featured Research

from universities, journals, and other organizations

University Of Toronto Team Maps Halos Around Galaxies

Date:
August 4, 2003
Source:
University Of Toronto
Summary:
Two University of Toronto astronomers and a U.S. colleague have made the first-ever measurements of the size and shape of massive dark matter halos that surround galaxies.

Two University of Toronto astronomers and a U.S. colleague have made the first-ever measurements of the size and shape of massive dark matter halos that surround galaxies.

Related Articles


"Our findings give us the clearest picture yet of a very mysterious part of our universe," says principal investigator Henk Hoekstra, a post-doctoral fellow at U of T's Canadian Institute for Theoretical Astrophysics. "Using relatively simple physics, we can get our first direct glimpse of the size and shape of these halos which are more than fifty times more massive than the light-producing part of galaxies that we can see." He and his team presented their findings July 25 at the 25th general assembly of the International Astronomical Union in Sydney, Australia.

Their research indicates that dark matter halos extend more than five times further than the visible stars in a galaxy, says Hoekstra. In the case of our Milky Way galaxy, he says, the halo extends to more than 500,000 light-years away and weighs approximately 880 billion times more than the sun. The findings also provide strong support for the popular "cold dark matter" model of the universe.

Dark matter emits no light and, therefore, cannot be seen directly, Hoekstra explains. The only evidence for its existence comes from its gravitational pull on stars, gas and light rays. Dark matter is believed to account for approximately 25 per cent of the total mass in the universe, with the rest of the universe composed of normal matter (five per cent) and dark energy (70 per cent).

To date, most information about dark matter has come from measurements of the motion of gas and stars in the inner regions of galaxies. Other important data have come from computer simulations of the formation of the universe's structure. However, scientists can explain their findings about dark matter only if it is true that galaxies are surrounded by massive, three-dimensional halos.

The majority of astronomers believe in the so-called cold dark matter theory of the universe, which suggests these halos are slightly flattened. Hoekstra's findings corroborate this. Using the relatively new technique of weak gravitational lensing which allows astronomers to study the size and shape of dark matter, the team measured the shapes of more than 1.5 million distant galaxies using the Canada-France-Hawaii Telescope in Hawaii. "The small changes in the shapes of the galaxies offered a strong indication to us that the halos are flattened, like a rubber ball compressed to half its size," Hoekstra says.

Their findings can also be applied to a larger scientific debate about the nature of the universe. Some scientists have developed theories about the universe using the assumption that dark matter does not exist and, as a result, they have proposed changes to the law of gravity. However, Hoekstra is confident that his team's findings will refute these theories.

The research was conducted with Professor Howard Yee of U of T's Department of Astronomy and Astrophysics and Michael Gladders, a former U of T graduate student now at the Observatories of the Carnegie Institution of Washington in Pasadena, Calif. It was funded by the Natural Sciences and Engineering Research Council of Canada and U of T.


Story Source:

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


Cite This Page:

University Of Toronto. "University Of Toronto Team Maps Halos Around Galaxies." ScienceDaily. ScienceDaily, 4 August 2003. <www.sciencedaily.com/releases/2003/07/030725081053.htm>.
University Of Toronto. (2003, August 4). University Of Toronto Team Maps Halos Around Galaxies. ScienceDaily. Retrieved March 28, 2015 from www.sciencedaily.com/releases/2003/07/030725081053.htm
University Of Toronto. "University Of Toronto Team Maps Halos Around Galaxies." ScienceDaily. www.sciencedaily.com/releases/2003/07/030725081053.htm (accessed March 28, 2015).

Share This


More From ScienceDaily



More Space & Time News

Saturday, March 28, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Why So Many People Think NASA's Asteroid Mission Is A Waste

Why So Many People Think NASA's Asteroid Mission Is A Waste

Newsy (Mar. 27, 2015) — The Asteroid Retrieval Mission announced this week bears little resemblance to its grand beginnings. Even NASA scientists are asking, "Why bother?" Video provided by Newsy
Powered by NewsLook.com
Robot Returns from International Space Station and Sets Two Guinness World Records

Robot Returns from International Space Station and Sets Two Guinness World Records

Reuters - Light News Video Online (Mar. 27, 2015) — The companion robot "Kirobo" returns to earth from the International Space Station and sets two Guinness World Records. Sharon Reich reports. Video provided by Reuters
Powered by NewsLook.com
Supermassive Blackhole Detector Ready for Business

Supermassive Blackhole Detector Ready for Business

Reuters - Innovations Video Online (Mar. 25, 2015) — Construction of the world&apos;s largest and most powerful observatory designed to detect and analyze gamma rays has been completed in Mexico. Gamma ray particles are considered the most energetic in the universe and scientists hope to use the observatory to learn more about the supernovas and black holes that produce them. Ben Gruber reports. Video provided by Reuters
Powered by NewsLook.com
Rocket Blasts Off Carrying U.S. Air Force GPS Satellite

Rocket Blasts Off Carrying U.S. Air Force GPS Satellite

Reuters - News Video Online (Mar. 25, 2015) — A U.S. Air Force GPS IIF-9 satellite launches aboard a United Launch Alliance Delta IV rocket into semi-synchronous orbit. Rough Cut (no reporter narration). Video provided by Reuters
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