Lost for words: Astronomers discover 'outrageous' galaxies as bright as 100 trillion suns

Galaxies are typically grouped into categories depending on their brightness, the Daily Mail reports. 

Ultra-luminous galaxies are 1 trillion times brighter than the sun, while hyper-luminous galaxies glow at 10 trillion solar luminosities.

But now eight galaxies have been found that are so bright they do not fit into these categories.

Astronomers believe they may be as bright as 100 trillion suns and they appear to be forming new stars every hour.

For comparison, the Milky Way produces a few solar masses of stars every year.

'We've taken to calling them 'outrageously luminous' among ourselves, because there is no scientific term to apply,' said undergraduate student and lead author Kevin Harrington, at the University of Massachusetts Amherst.

When grouping luminous sources, astronomers call an infrared galaxy 'ultra-luminous' when it has a rating of about 1 trillion solar luminosities, and that rises to about 10 trillion solar luminosities at the 'hyper-luminous' level, according to Mr Harrington.

Beyond that, for the 100 trillion solar luminosities range of the new objects, 'we don't even have a name,' he said.

Professor Min Yun, leader of Harrington's astronomy research group, said 'the galaxies we found were not predicted by theory to exist; they're too big and too bright, so no-one really looked for them before.'

Discovering them will help astronomers understand more about the early universe.

The researchers estimate that the newly observed galaxies they identified are about 10 billion years old and were formed only 4 billion years after the Big Bang.

'Knowing that they really do exist and how much they have grown in the first 4 billion years since the Big Bang helps us estimate how much material was there for them to work with,' said Mr Harrington.

'Their existence teaches us about the process of collecting matter and of galaxy formation. They suggest that this process is more complex than many people thought.'

The newly observed galaxies are not as large as they appear, the researchers pointed out.

Further studies have suggested the galaxies' extreme brightness came from a phenomenon called gravitational lensing.

Gravitational lensing means that the gravity of nearby massive object magnifies light as it passes. This was predicted by Einstein's theory of  general relativity.

As a result, from Earth they look about 10 times brighter than they really are.

Even so, they are impressive, Professor Yun said.

Gravitational lensing of a distant galaxy by another galaxy is rare, because it requires the galaxies to be lined up perfectly when viewing from Earth.

Finding as many as eight potential lensed objects as part of this investigation 'is another potentially important discovery,' Professor Yun said.

The researchers conducted analysis to show that the galaxies' brightness is most likely due solely to their amazingly high rate of star formation.

'The Milky Way produces a few solar masses of stars per year, and these objects look like they forming one star every hour,' Professor Yun said.

Mr Harrington added 'we still don't know how many tens to hundreds of solar masses of gas can be converted into stars so efficiently in these objects, and studying these objects might help us to find out.'

The research group used the 164ft (50 metre) diameter Large Millimeter Telescope (LMT), in Mexico.

The LMT is the largest, most sensitive single-aperture instrument in the world for studying star formation.

The telescope is located on the summit of Sierra Negra, a 15,000ft extinct volcano in the central state of Puebla, a companion peak to Mexico's highest mountain.