Ellison with students
An international team led by a University of Victoria astronomer has discovered tantalizing new clues to the origins of life in the universe.
Dr. Sara Ellison, UVic graduate student Brian York, and researchers from British and Australian universities have discovered evidence that a galaxy 5.7 billion light years away from Earth contains the carbon-based molecules that could form the basic building blocks of life.
Ellison, who is the Canada Research Chair in Observational Cosmology, studies the chemical evolution of galaxies. Using powerful telescopes, she searches the far reaches of the universe and analyses the light from distant points of intense light (known as quasars) as it passes through galaxies on its way to Earth.
“Some of the light will interact with the gases in a galaxy,” she explains. “When that happens, an analysis of the light spectrum using spectrography tells us what elements and molecules are present.
“We’re not actually observing the galaxy itself. Instead, we know it’s there because of the spectroscopic fingerprint in the quasar’s light. It’s a bit like knowing that someone is in a room by seeing their shadow.”
It’s the distant galaxies that hold special interest for Ellison. “Light from these galaxies was transmitted millions or billions of years ago,” she says. “As we look further and further away, it’s like taking slices through the history of the universe.”
In this study, the team’s observations were made with a spectrograph at the Very Large Telescope in Chile. They were searching for patterns of light known as diffuse interstellar bands, or DIBs—the telltale spectrographic signature of complex carbon-based molecules.
Ellison wants to know if DIBs can be used as a tool for studying the chemistry of distant galaxies.
“DIBs are common in our own Milky Way galaxy and we figured that if other galaxies had similar quantities, they should be easy to detect,” she says. “It turns out that the distant galaxies we studied are very poor in DIBs compared to the Milky Way.”
She believes this may be because the distant galaxies aren’t as evolved chemically, unlike the rich “chemical smorgasbord” in the Milky Way.
The team also found that the presence of DIBs seems to be linked to the amount of dust in a galaxy. This will help in future searches, says Ellison. One of the goals of this work is to determine when the ingredients for life first existed in the universe.
“Galaxies that are rich in heavy elements and dust seem to be good signposts for finding DIBs. Knowing this, we can target our searches to determine when these organic molecules were first abundant in the universe.”
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