|
By Tara Sharpe
This computer simulation sketches a possible orbit of the Triangulum galaxy around Andromeda, suggesting the former will eventually be devoured by its massive neighbour.
Image: Pan-Andromeda Archaeological Survey (PAndAS)
What do you see when you look up at night? For three University of Victoria researchers, what’s up there is a better show than anything science fiction film directors can come up with. Now thanks to them and an international team of astronomers led by Dr. Alan McConnachie—an astrophysicist with the National Research Council of Canada’s Herzberg Institute of Astrophysics—we too can imagine exactly what the outermost edges of our nearest large galaxy look like.
Andromeda, more than 2.5 million light years from our Milky Way, is the closest large galaxy visible to the naked eye. You are likely to see it this month from the sky’s northern hemisphere; it is usually best spotted in October and November and resembles a blurry star.
The UVic researchers are members of the Pan-Andromeda Archeological Survey (PAndAS), which has been staring at Andromeda from the Canada-France-Hawaii Telescope at the top of Mauna Kea, Hawaii. PAndAS has now charted a panoramic image of the galaxy’s unexplored outskirts.
“This study—notably accomplished in the International Year of Astronomy—marks another phenomenal step forward in understanding what is out there in space,” says Dr. Arif Babul, UVic Distinguished Professor of Physics and Astronomy and one of the three UVic astronomers involved in the study. “We have been able to acquire the deepest ever image of our nearest neighbouring galaxy. And what is truly amazing is that we are actually seeing stellar wisps that are the leftovers of smaller galaxies swallowed up by Andromeda during its formation.”
The Milky Way and its two nearest star systems, Andromeda and Triangulum, are spiral galaxies occupying an infinitesimally small region of space. There are tens of billions of other galaxies spread through the universe, and current cosmological theory suggests the larger ones are busy (in the snail-like galactic sense of industry) devouring smaller galaxies and essentially feeding off their weaker counterparts in a cannibalistic outer-space version of Darwinian survival.
The PAndAS panoramic image will help to chart the continuing formation of Andromeda—an evolution that has so far spanned approximately 13 billion years—and lend further substance to the cannibalization theory.
“By exploring the end of a galaxy and its remnants, astronomers hope to recreate earlier steps in galactic evolution and shed more light on the dark of space,” says UVic’s Dr. Julio Navarro, Fellow of the Canadian Institute for Advanced Research and a co-author of the panoramic study.
Fellow co-author Dr. Kimberly Venn, UVic’s Canada Research Chair in Observational Astrophysics, adds, “This is big science, vast space and near-unimaginable stretches of time. Although we talk about the cannibalization of smaller galaxies as if it is a short galactic snack, even one ‘bite’ would encompass about one billion years.”
The team’s findings were published last month in the international weekly science journal Nature and online at www.nature.com. Further details about the Pan-Andromeda Archaeological Survey: www.nrc-cnrc.gc.ca/eng/ibp/hia.html or www.astrosci.ca/users/alan/PANDAS
|
