Astronomers at Yale University have discovered seven new galaxies 20 million light years away from our own, “the blink of an eye in cosmological terms,” according to lead researcher Professor van Dokkum.
They discovered them using a new type of telescope, made by stitching together telephoto lenses, while probing a nearby spiral galaxy called M101. They had never discovered them before because they are “diffuse galaxies”: ones that are so dim and spread out that normal telescopes, which focus on a compact area, are unable to pick them up.
Called the Dragonfly Telephoto Array, the telescope uses eight telephoto lenses with special coatings that suppress internally scattered light. This makes it uniquely adept at detecting very low surface brightness.
“Because the light is so spread out in diffuse galaxies, it makes them very hard to see: it's as though you are looking through them. This telescope allowed us to spot things that normal telescopes, which study compact areas, could not pick up on,” says van Dokkum, who designed the robotic telescope.
“Many people were saying that the galaxies ought to be there, while others said they probably wouldn't be. The great thing is that the universe is so full of surprises, and in this case we have found that they do exist.”
He adds that although they are 20m light years away, this is really nothing in terms of cosmological events: “The galaxies probably look much the same now as they did then.”
The key question will be whether they are orbiting the already discovered M101 galaxy or not: if they are associated with the galaxy, then it is the first time that researchers can study how small “dwarf” galaxies such as these interact with a larger galaxy.
However, if they are found to be in front of or behind M101, it means that they are completely new objects to study. “This would be very exciting,” says van Dokkum. “Studying these galaxies could help us to understand the formation and evolution of our own galaxy, and to understand if it is like these other galaxies: we never know if our own situation is normal. It's a new domain. We're exploring a region of parameter space that had not been explored before."
The galaxies could also help scientists to understand dark matter: the universe's mysterious areas of blackness which no one fully understands. As its name suggests, dark matter cannot be seen and so cannot be studied easily, but these galaxies are made up of it to a large extent, with stars scattered sparsely within them.
Could there be life contained within the dwarf galaxies? Van Dokkum doesn't think so; if they are anything like the dwarf galaxies already known about, it means that even if there was life it would have to be significantly different to life on Earth.
“Dwarf galaxies tend to be composed of a lot of Hydrogen and Helium but very little Carbon or Iron: the elements that have been fundamental to creating life on Earth,” he said.