Skip to comments.Canadian duo step closer to proving existence of mysterious dark matter
Posted on 07/26/2003 12:48:33 PM PDT by LibWhacker
TORONTO (CP) - A pair of Canadian astronomers and an American scientist have for the first time measured the shape and size of dark matter surrounding galaxies and its effect on light emitted from more distant sources - findings that tip the scale in favour of the existence of the mysterious substance.
The existence of dark matter has been hotly debated among astronomers for years. It's believed to comprise about 25 per cent of the total mass of the universe, with the rest consisting of normal matter (five per cent) and dark energy (70 per cent). Dark energy is believed to push particles apart, contributing to the expansion of the universe.
Some astronomers have developed theories based on the assumption that dark matter doesn't exist, and consequently, have suggested changing the law of gravity. The new measurements refute those theories, says Howard Yee, a professor at the University of Toronto who began the research with his colleagues in 1999.
"What we have done is more or less put another nail in the coffin of that kind of theory," Yee said in an interview Thursday.
Yee, along with Henk Hoekstra of the Canadian Institute for Theoretical Astrophysics, and Michael Gladders of the Carnegie Institution of Washington in Pasadena, Calif., are presenting their findings at an international conference of astronomers in Australia on Friday.
Over a four-year period, the team measured the shape of 1.5 million distant galaxies to see how they were distorted by 120,000 closer galaxies. They discovered that dark matter halos extend five to eight times further than the visible stars in a galaxy, causing starlight to bend as it passes by. The team's findings show the shape of the dark matter halo as flattened, resembling the shape of an egg.
"We basically have a somewhat better measurement of the size and we're also, for the first time, able to measure the average shape of the dark matter halo," Yee said.
Dark matter, because it cannot be seen, can only be measured by the gravitational effect it has on light, gas and stars.
In the case of our Milky Way galaxy, the halo extends to more than 500,000 light-years and weighs approximately 880 billion times more than the sun.
"What this shows is that this dark matter, which we know makes up a significant part of the universe, we now know for sure that it's assembled around galaxies," said Michael De Robertis, associate dean of the faculty of pure and applied science at York University in Toronto.
The findings also offer clues as to how galaxies were originally formed, he added.
With the help of a 100-million-pixel digital camera and the powerful Canada-France-Hawaii telescope in Hawaii, the trio photographed a huge chunk of the sky repeatedly for two years. They interpreted the data for another two years before making their findings last year.
Their research is now under review by the Astrophysical Journal, and Yee says it should appear in the North American publication by the end of this year.
Yee said the measurements could not have been done without the sophisticated equipment available to scientists today.
"I have to say, I live in a very lucky age in astronomy because of all the technological advances - and just in the last 10 to 15 years - there has been tremendous progress in what we've learned," Yee said. "So it's really a golden age in astronomy."
We Moderns have now measured the visible universe at 5% of everything.
Atheists and agnostics used to base their "belief/lackofbelief" on the idea that the only thing that counted was the observable universe and that didn't happen to reveal Djin, gods, angels or other supernatural beings.
There's definitely plenty of room for all sorts of metaphysics in the currently defined universe where normal matter is only 5%.
A 100-million pixel digital camera might cost more than my Canon from Fry's. Also, What with the name "Canada-France-Hawaii"? Is Hawaii now to be elevated to the status of a country, such as Canada or France?
OTOH, Hawaii is probably more powerful than either country, and might even be more conservative (just barely).
I didn't even know such a thing existed. Wonder how long it'll take before Canon puts it on the market for under $2,000?
A painter once said
that his struggle to convert
two dimensional canvas
was his metaphor
for the process we
all engage in trying to
deal with "existence"
while we are all bound
in the material world.
Metaphor saves us.