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Research Fellows Directory

Graham Smith

Dr Graham Smith

Research Fellow


University of Birmingham

Research summary

Galaxy clusters are the most massive objects in the universe, containing

approximately 1000 galaxies that orbit around each other in the same region

of space. Clusters also contain dark matter and hot (roughly 100 million

degrees Centigrade) gas. Dark matter is invisible because it doesn't

interact with the "ordinary" matter from which you and I are made. We still

don't know what dark matter is, so by studying it within galaxy clusters, I

aim to help narrow down the options on what dark matter is.

Dark matter is detectable in galaxy clusters via gravitational lensing -

the deflection of light by mass. The path of light from galaxies that lie

behind galaxy clusters is bent by the huge concentration of dark matter in

clusters. Sometimes this bending is so strong that you can see several

images of the same galaxy! I use the Hubble Space Telescope to measure the

bending of light by dark matter in clusters. I then use these measurements

to calculate how much dark matter there is in galaxy clusters, and how it

is organized - the mass and structure of clusters.

Accurate measurements of galaxy cluster masses help astronomers to measure

the properties of the other dark component of the universe - dark energy -

in the coming years. Dark energy is the mysterious "negative gravity" that

is causing the expansion of the universe to accelerate. One way to choose

between alternative dark energy theories is to count galaxy clusters. It's

not enough to simply count clusters - we also need to know how massive they

are, because the accelerating expansion should influence how quickly

clusters can grow to a given mass. My mass measurements are therefore vital

to the huge effort across the astronomical community to measure the

properties of dark energy. One exciting possibility is that we might prove

that Einstein's theory of general relativity is wrong in some way!

Interests and expertise (Subject groups)

Grants awarded

Evolution of Cosmic Structures Revealed by Gravitational Lensing

Scheme: University Research Fellowship

Dates: Oct 2010 - Sep 2014

Value: £327,118.54

Evolution of Cosmic Structures Revealed by Gravitational Lensing

Scheme: University Research Fellowship

Dates: Nov 2005 - Sep 2010

Value: £241,981.29

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