Strange rings and arcs revealed among universe's brightest galaxies

The universe's brightest galaxies have been seen in unprecedented detail thanks to alignment with a gravitational lens, one of the universe's naturally occurring cosmic magnifying glasses. As well as the oddly shaped galaxies, 'exotic' shapes have been spotted among them.

Gravitational lenses happen around extremely massive entities such as galaxy clusters. Their intense gravitational pull bends the spacetime around it. This also bends the path of light passing through it, in the same way a magnifying glass bends light to make objects appear larger.

When a galaxy or even a supernova happens to be on the other side of a gravitational lens from Earth, it can be magnified to appear much larger than it is. This can reveal these entities in exquisite detail.

This is exactly what happened with the brightest known galaxies in the universe, which shine about 10,000 times brighter than our own galaxy, the Milky Way. Scientists used Nasa's Hubble Telescope to take close-ups of these 'starburst' galaxies that shine most intensely in the infra-red part of the spectrum.

"We have hit the jackpot of gravitational lenses," said James Lowenthal of Smith College who presented the findings American Astronomical Society meeting in Austin, Texas.

"These ultra-luminous, massive, starburst galaxies are very rare. Gravitational lensing magnifies them so that you can see small details that otherwise are unimaginable.

"We can see features as small as about 100 light-years or less across. We want to understand what's powering these monsters, and gravitational lensing allows us to study them in greater detail."

The objects shown by the lens have very peculiar shapes. As well as unusually shaped galaxies, it revealed a series of rings and arcs.

This could be for two reasons. First, the gravity lens distorts the image of the objects behind it. Second, giant cosmic collisions have ripped the galaxies and intergalactic space objects in these strange shapes.

Disentangling what effects are due to the foreground magnifying galaxies and which are actually real phenomena in the background galaxies that are being magnified is a tricky job.

"We need to understand the nature and scale of those lensing effects to interpret properly what we're seeing in the distant, early universe," Lowenthal said. "This applies not only to these brightest infrared galaxies, but probably to most or maybe even all distant galaxies."

Next, the researchers plan to tackle this problem using the Hubble Telescope and the Gemini Observatory in Hawaii to take a closer look at the galaxies through the gravitational lens.