Scientists find evidence of interstellar collision

The Andromeda galaxy is more than just the closest large spiral to the Milky Way as it appears through the naked eye, Wits University’s professor David Block said on Wednesday.

“There is new evidence that Andromeda was involved in a violent head-on collision with the neighbouring dwarf galaxy Messier 32 (M32) more than 200-million years ago.”

He addressed a group of students, lecturers and members of the media at the university’s Senate House.

“Astronomers have found a never-before-seen dust ring deep within the Andromeda galaxy. When combined with a previously observed outer ring, the presence of both dust rings suggest a long-ago disturbance whose effects are still expanding outward through Andromeda.”

Block described the dust rings as “ripples in a pond”.

“Plop a stone into water and you get an expanding series of rings or waves. Let a small galaxy collide nearly head-on with a larger one and you will see waves or rings of gas and dust, which propagate outwards, caused as a result of the violent gravitational interaction.”

The discovery was made using the Infrared Array Camera (Irac) on the National Aeronautics and Space and Administration’s (Nasa) Spitzer space telescope.

The camera was designed by renowned space pioneer Dr Giovanni Fazio from Havard University, who was also present during the presentation.

“Spitzer has the ability to understand galaxies.
It enables scientists to get clear pictures of galaxies and to be able to separate different stars in the galaxy,” said Fazio.

Previously scientists were only able to see dust, but the camera enables them to penetrate the dust and isolate particles, hence the new discovery.

One of Block’s doctoral students, Robert Groess, used sophisticated image processing techniques to extract crucial data from the Spitzer space telescope images and also had to electronically remove foreground stars in the Milky Way. Other astronomers involved in the project were Frederic Bournaud and Francoise Combes, who are based in Paris.

Block and Fazio are expected to hold a public lecture at the Wits university theatre at 7pm on Thursday. - Sapa

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