New supercomputer simulations of galaxy formation show that supernova explosions blasting away gas from nearby galaxies explains the deficit of stars in dwarf galaxies that cannot be explained in the standard cold dark matter theory.

The cold dark matter theory, which holds that around 75 percent of the Universe's matter is made of mysterious, invisible dark matter, has long been used to explain how the initially smooth Universe born 13.7 billion years ago in the big bang has evolved into a galaxy-rich cosmic web, with small structures forming first and evolving into progressively larger structure, but this theory is unable to explain why there are less stars and dark matter in the cores of galaxies than is actually observed. The problem is particularly notable for the most common type of galaxy found in our celestial neighbourhood: dwarf galaxies.

New supercomputer simulations led by the University of Washington have provided a solution to this cosmic conundrum. “Most previous work included only a simple description of how and where stars formed within galaxies, or neglected star formation altogether,” says Fabio Governato, lead author of the paper describing the findings that features in today's edition of the journal Nature. “Instead we performed new computer simulations, run over several national supercomputing facilities, and included a better description of where and how star formation happens in galaxies.”

The simulations demonstrate the importance of considering supernova explosions of the most massive early stars in galaxy formation theories. The blast waves from the explosions generate winds that sweep vast amounts of gas away from centre of what are destined to become dwarf galaxies, preventing star formation there. The knock on effect is that the removed mass means there is less gravitational pull on the dark matter there, and the dark matter drifts away.

“The cold dark matter theory works amazingly well at telling where, when and how many galaxies should form,” adds Governato. “What we did was find a better description of processes that we know happen in the real Universe, resulting in more accurate simulations.”

The results of the new simulations closely match the observed low-density cores seen in dwarf galaxies.

Our latest 132-page Astronomy Now special edition is an extravaganza of astronomy for the year ahead, with a complete 30-page guide to observing the planets, moon, meteor showers, two solar eclipses, and the deep sky in 2010.
 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

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 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

Explore the Universe with these new versions of the award-winning Starry Night Software. Available now from the Astronomy Now Store.
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE

Astronomy Now is pleased to announce the publication of Exploring Mars. The very best images of Mars taken by orbiting spacecraft and NASA's Spirit and Opportunity rovers fill up the 98 glossy pages of this special edition!
 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