Aquarius younger by billions of years

Stars in the Milky way

Astronomers have identified a massive swarm of stars within the Milky Way, now known as the Aquarius Stream, that seem to be the remains of a smaller, external galaxy that was destroyed by the Milky Way's gravitational pull.

AN INTERNATIONAL TEAM of astronomers has discovered a new stream of stars in our Milky Way, thanks to data collected at the ANU Siding Spring Observatory.

The research, led by Dr Mary Williams from the Astrophysical Institute Potsdam (AIP), is part of the Radial Velocity Experiment (RAVE) and used data from Siding Spring to measure the velocities of 250,000 stars.

The new ‘Aquarius Stream’ is named after the constellation of Aquarius in which it resides. The stream of stars is a remnant of a smaller galaxy in our cosmic neighbourhood, which was pulled apart by the gravitational pull of the Milky Way about 700 million years ago.

Dr Mary Williams, a former graduate student of the Research School of Astronomy and Astrophysics at ANU, said the Aquarius Stream was particularly hard to find, located deep within the Milky Way where it was indistinguishable from the huge quantity of stars blocking our view of it.

Aquarius Stream map

Astronomers have identified a massive swarm of stars within the Milky Way, now known as the Aquarius Stream, that seem to be the remains of a smaller, external galaxy that was destroyed by the Milky Way's gravitational pull.

“It was right on our doorstep, but we just couldn’t see it,” said Dr Williams.

Dr Williams used the RAVE data to draw conclusions about the formation of the Milky Way.  She said that by astronomical standards, the 700-million-year-old Aquarius stream is exceptionally young. Other known streams of stars located on the outskirts of our galaxy are billions of years old.

Professor Matthias Steinmetz, project leader of the multinational RAVE collaboration at AIP said he is optimistic the method used by Dr Williams and her team will lead to many more discoveries of this kind.

“We want to understand the formation history of our Milky Way,” he said. “We want to find out how frequently constellations have merged with neighbouring galaxies in the past, and how many we are to expect in the future.”

While much about the galaxy surrounding our planet Earth remains unknown, astronomers are certain about one thing—the Milky Way’s next huge collision will be with the Andromeda galaxy. This cosmic collision is predicted to take place in about three billion years—unless one of the dwarf galaxies discovered over the past few years beats Andromeda to it.

This video shows a highly speeded up computer simulation of the collision between the Milky Way and Andromeda. See what happens to the shape of the Milky Way following the collision:

RAVE is a multinational project, involving scientists from Australia, Germany, France, UK, Italy, Canada, the Netherlands, Switzerland, Slovenia and the USA.

Adapted from information issued by ANU. Images courtesy ANU and Hubble Heritage Team (AURA / STScI / NASA / ESA).

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  1. Anne says:

    Hello Jonathan

    When the Moon is in the Seventh House
    And Jupiter aligns with Mars ——–

    Could this be the coming of the Age of Aquarius?
    (As the song says??)

    Congrats to researchers at ANU Siding Spring.