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Milky Way found to spin both ways
Thursday Dec 13 09:44 AEDT
Two scientists studying at the Australian National University are part of an international team that has discovered the Milky Way galaxy actually spins in different directions.
In their paper to be published in the journal Nature, the scientists describe how the outer edge of the Milky Way, the halo, is made up of two components that rotate in opposite directions.
The findings prove that the Milky Way halo was not assembled all at once but rather over time, something scientists have suspected for around 30 years.
The lead author of the report, Daniela Carollo, a researcher at Italy's Torino observatory now undertaking her Phd in Canberra, said that they made the discovery by studying the motions and chemical makeup of the halo.
"By examining the motions and chemical makeup of the stars, we can see that the inner and outer halos are quite different beasts and they probably formed in different ways at different times," Ms Carollo said.
The discovery also shows that the different parts of the halo have different chemical makeups with the inner stars containing three times more heavy elements than outer halo stars.
Ms Carollo said that these differences gave a much clearer picture of the formation of the early universe.
"Although it was once considered a single structure, an analysis of the stars shows that the halo is clearly divisible into two, broadly overlapping components. The discovery gives us a much clearer picture of the formation of the first objects in our galaxy and in the entire universe," she said.
This discovery may help to find some of the most primitive stars in the galaxy a quest that another team member ANU Professor John Norris has spent more than two decades on.
"These fossils of the early universe are extremely rare so finding them remains a classic needle in a haystack problem and the discovery of a chemically distinct outer halo, gives us a much better way to search the haystack," he said.
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