Astronomers have discover a new kind of galaxy - dubbed "super spirals" - that trumps our own spiral galaxy, the Milky Way, and possesses a size and brightness that is close to that of the largest galaxies in the universe.
The new study used archived NASA data to reveal that these super spirals, which went undetected until now due to their similar appearance to standard spiral galaxies, are massive versions of regular spirals. Scientists are now focusing on discovering how these giant galaxies came to be.
"We have found a previously unrecognized class of spiral galaxies that are as luminous and massive as the biggest, brightest galaxies we know of," said Patrick Ogle, lead author of the paper. "It's as if we have just discovered a new land animal stomping around that is the size of an elephant but had shockingly gone unnoticed by zoologists."
The team discovered the super spirals by accident in their search for galaxies with high luminosity and mass using the NASA/IPAC Extragalactic Database (NED), an online database that contains information on over 100 million galaxies.
"Remarkably, the finding of super spiral galaxies came out of purely analyzing the contents of the NASA/IPAC Extragalactic Database, thus reaping the benefits of the careful, systematic merging of data from many sources on the same galaxies," said George Helou, one of the co-authors of the study. "NED is surely holding many more such nuggets of information, and it is up to us scientists to ask the right questions to bring them out."
While the team was expecting to find ellipticals - massive, mature galaxies - in their search, they instead found that of the 800,000 galaxies 3.5 billion light-years or closer to Earth, 53 of the brightest ones had spiral shapes. Further examination led to the discovery of the new spiral galaxies and revealed that they are anywhere from eight to 14 times as bright as the Milky Way and up to 10 times as heavy.
Ogle and his team hope to discover the origins of these galaxies and currently believe that they likely stem from a unique merger between two gas-rich spiral galaxies whose pooled gases eventually settle into a super spiral.
"Super spirals could fundamentally change our understanding of the formation and evolution of the most massive galaxies," said Ogle. "We have much to learn from these newly identified, galactic leviathans."
The findings will be published in the March 20 issue of The Astrophysical Journal.
