SciTech

Experiment of the Week: Dark matter brought to new light by Cambridge scientists

Scientists have been plagued with the problem of proving the facts that explain theory for many centuries. Until recently, one of the key issues in astronomy, the existence of dark matter, has been greatly debated. This great debate has been due to a lack of evidence supporting dark matter theory.

Dark matter, as implied by the name, refers to particles of unknown composition that can’t be visibly seen or analytically detected due to their lack of electromagnetic radiation emission or light reflection. Then why, one might ask, is there reason to believe this dark matter really exists? The answer is simple — although dark matter cannot be detected directly, its presence can be deduced from the otherwise unexplainable gravitational effects of stars and galaxies in space.

This hypothetical explanation was first conjured up by Swiss astrophysicist Fritz Zwicky in 1933, and has been debated ever since. The presence of this material can only be inferred from inconsistencies with gravitational effects of galaxy orbits. The way that galaxies rotate, for example, defies Einstein’s general theory of relativity. Stars move so fast that they should, if they stick to relativity laws, fly far apart. Instead, what is observed seems to indicate the existance of extra, unseen mass that creates adequate gravitational attraction for the stars to remain intact in orbit. For more information on dark matter and dark energy, read our previous article, “How Things Work: Dark energy”.

Although some scientists disagree on the range, many believe that dark matter would make up approximately 80 to 90 percent of the matter in the universe. Many scientists agree that dark matter is the best explanation for inconsistencies with gravitational-mass problems; however, there has been no take-home proof of these particles until now.

Recently, a group of scientists from the University of Cambridge published a statement saying that they were able, for the first time, to analyze some of the physical properties of the mysterious dark matter. This team, led by professor Gerry Gilmore, has been working on the dark matter problem since 2003. The Cambridge team did much of their research using the Very Large Telescope facility, located in Chile. This facility contains a system of four of the largest optical telescopes in the world. Using these facilities, the group was able to observe and analyze a number of small galaxies that lie just outside our very own Milky Way galaxy.

Through the Cambridge team’s observations, they were able to create various maps of these galaxies and calculate the movement of their stars. The intricate part of their research was the creation of thousands of these 3-D galaxy maps. With these maps, it was possible for them to outline the existence of dark matter in galaxies. Eventually, after taking more than 7000 separate measurements, the team was able to calculate the mass of the mystery matter. The mass determined, referred to by Gilmore as having a “magic volume,” corresponds to an amount that is 30 million times the mass of the sun. From this information, the group was able to determine the speed of the particles to be 9 km/s and the temperature to be somewhere around 10,000° C — much hotter than the sun’s surface!

Gilmore regards his team’s research as an ongoing search into the truth of our universe.  “The most interesting aspect of this research is not what we have measured — rather, I find it remarkable, and humbling, that we are able to identify and study the reality which is the universe, even though that reality is so very different from that which we see every day,” said Gilmore. The Cambridge team hopes to submit their results to an astrophysics journal sometime soon.

These research findings, if reproducable, will have an enormous effect on how astronomers view the universe. The existence of dark matter will allow for a more complete and accurate depiction of galaxy structure and composition. Dark matter may literally change our universe.