Scientists trying to solve the mystery of the birth of some of the brightest galaxies ever to exist in the universe have turned to supercomputers to help come up with answers.

Known as submillimeter galaxies for the far-infrared wavelengths of light the astronomers used to detect them more than 10 years ago, they are the most luminous galaxies in the universe.

Interstellar dust absorbs most of the incredible amounts of visible light they emit, so they were only discovered when astronomers began to survey the skies at wavelengths outside those of visible light, researchers explain.

If we could see them without the effect of the dust, their brightness would be incredible, they say.

"They have luminosities maybe hundreds to thousands of times that of the Milky Way," says Desika Narayanan, an astrophysicist at Haverford College in Pennsylvania and lead author of a study appearing in Nature.

These galaxies, which we see today as they existed around three billion years ago, come from a time when some galaxies were forming stars at incredible rates, a thousand times greater than what our Milky Way galaxy is doing today.

Even the brightest of galaxies existing today would pale in comparison, the researchers say, but no submillimeter galaxies are observed in the cosmos today.

There has been debate as to how they formed, with some scientists suggesting collisions between gas-rich galaxies could create new ones with spectacular rates of formation but which existed only briefly in the cosmic scale of time, just 100 million years.

Others suggest they formed slowly, by accruing mass gradually over a period of a billion years.

To help settle the question, the researchers turned to a supercomputer at the Texas Advance Computing Center to churn through sophisticated simulations of one submillimeter galaxy.

The necessary calculations were so complex, it required thousands of computers to be networked together and run for a month just to do part of the simulation, they explained.

The final computer model showed that the slow-growth scenario could create such galaxies, without the need of a possible rare, violent cosmic collision, and that they could remain super bright for the full billion years of their life spans.

"Our model is showing that what's powering submillimeter emission of these galaxies is constant bombardment by smaller galaxies and lots of gas that they are eating from their surroundings," says study co-author Dusan Keres, an astrophysicist at the University of California, San Diego.

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