The accompanying image shows gravitational lensing of galaxies (yellow to red) and haloes from clumped dark matter (blue). Image credit: Yale.

Hubble Space Telescope data, analysed by a Yale astronomer using gravitational lensing techniques, has generated a spatial map demonstrating the clumped substructure of dark matter inside clusters of galaxies.

Clusters of galaxies (about a million, million times the mass of our Sun), are typically made up of hundreds of galaxies bound together by gravity. About 90 percent of their mass is dark matter. The rest is ordinary atoms in the form of hot gas and stars.

Although little is known about it, cold dark matter is thought to have structure at all magnitudes. Theoretical models of the clumping properties were derived from detailed, high-resolution simulations of the growth of structure in the universe. Although previous evidence supported the "concordance model" of a universe mostly composed of cold, dark matter, the predicted substructure had never been detected.

In this study, Yale assistant professor of astronomy and physics, Priyamvada Natarajan, and her colleagues demonstrate that, at least in the mass range of typical galaxies in clusters, there is an excellent agreement between the observations and theoretical predictions of the concordance model.

Using gravitational lensing made it possible for the observers to visualise light from distant galaxies as it bent around mass in its way. This allowed the researchers to measure light deflections that indicated structural clumps in the dark matter.

"We used an innovative technique to pick up the effect of precisely the clumps which might otherwise be obscured by the presence of more massive structures," said Natarajan. "When we compared our results with theoretical expectations of the concordance model, we found extremely good agreement, suggesting that the model passes the substructure test for the mass range we are sensitive to with this technique."

"We think the properties of these clumps hold a key to the nature of dark matter — which is presently unknown," said Natarajan. "The question remains whether these predictions and observations agree for smaller mass clumps that are as yet undetected."

Co-author on the study, funded by Yale University, is Volker Springel, MPA, Garching, Germany. Other collaborators include. Jean-Paul Kneib, LAM – OAMP, Marseille, France, Ian Smail, University of Durham, U.K., and Richard Ellis of Caltech.

This special publication features the photography of British astro-imager Nik Szymanek and covers a range of photographic methods from basic to advanced. Beautiful pictures of the night sky can be obtained with a simple camera and tripod before tackling more difficult projects, such as guided astrophotography through the telescope and CCD imaging.
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE

Hubble Reborn
Hubble Reborn takes the reader on a journey through the Universe with spectacular full-colour pictures of galaxies, nebulae, planets and stars as seen through Hubble's eyes, along the way telling the dramatic story of the space telescope, including interviews with key scientists and astronauts.
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE

The Planets
From tiny Mercury to distant Neptune and Pluto, The Planets profiles each of the Solar System's members in depth, featuring the latest imagery from space missions. The tallest mountains, the deepest canyons, the strongest winds, raging atmospheric storms, terrain studded with craters and vast worlds of ice are just some of the sights you'll see on this 100-page tour of the planets.
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE

3D Universe
Witness the most awesome sights of the Universe as they were meant to be seen in this 100-page extravaganza of planets, galaxies and star-scapes, all in 3D!
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE

This new poster features some of the best pictures from NASA's amazing Mars Exploration Rovers Spirit and Opportunity.
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE