sciencetech-blog

comments

Striking differences have been found between our galaxy, the Milky Way, and its near-twin neighbour, Andromeda.

Both are spiral collections of stars with similar structures and look almost identical, despite Andromeda being about twice as large as the Milky Way.

But appearances can be deceptive. A new study into the motion of stars has found Andromeda has a history of violence, in contrast to the relatively peaceful Milky Way.

A new study into the motion of stars has found Andromeda (left) has a history of violence, in contrast to the relatively peaceful Milky Way (artists's impression right)

Andromeda's stars are more disordered than those of our galaxy, probably as a result of clashes and mergers with smaller galaxies.

Such violent histories are thought to be common for large spiral galaxies, with 70 per cent experiencing at least one interaction in the last 10,000 years.

The apparent orderliness of the Milky Way marks it out as unusual.

Professor Puragra Guhathakurta, from the University of California at Santa Cruz, who led the research using observation data from the Keck Observatory in Hawaii, said: 'In this context, the motion of the stars in Andromeda's disk is more normal, and the Milky Way may simply be an outlier with an unusually quiescent accretion history.'

Click on the image to zoom in on Andromeda 

Although 'neighbours' the Milky Way and Andromeda are separated by a distance of 2.5 million light years.

The two are the largest members of the Local Group, a collection of 30 galaxies.

The scientists found that the youngest stars in Andromeda moved in a relatively ordered way around its centre while older stars displayed much more disordered motion.

Previous studies have found evidence of galactic mergers in tidal streams of stars in Andromeda's extended halo. They appear to be the remnants of cannibalised dwarf galaxies.

STUNNING SIMULATION REVEAL THE FATE OF OUR GALAXY

It's widely accepted than in five billion years our Milky Way will collide with the nearby Andromeda galaxy - but what will happen when it does?

In a new simulation revealed in September, scientists showed the intricate process that will take place, with the two central supermassive black holes merging into one. And the newly formed super-galaxy, dubbed 'Milkomeda', will also ultimately spell disaster for Earth as our planet is flung out into interstellar space.

The simulation was created by a number of institutions led by the International Centre for Radio Astronomy Research (Icrar) in Western Australia. In the simulation it can be seen how the two galaxies will interact as they approach each other.

First, in a tentative meeting, they will 'swoop' past each other, possibly disrupting some of the orbits of stars in the arms of each spiral galaxy. Then, after separating, the two galaxies will accelerate towards each other again.

As Andromeda is larger than the Milky Way, with one trillion stars in the former compared to about 300 billion in the latter, it will technically be the one 'eating' our galaxy.

The Milky Way is also expected to 'eat' two nearby dwarf galaxies, the Large and Small Magellanic Clouds, at some point in the future. 

What happens when Andromeda and the Milky Way collide

The findings were presented at the winter meeting of the American Astronomical Association in Seattle

Earlier this week the sharpest and largest image ever taken of the Andromeda Galaxy - the nearest spiral galaxy to our Milky Way - has been revealed by astronomers.

It shows more than 100 million stars and thousands of star clusters embedded in a section of the galaxy's pancake-shaped disc stretching across over 40,000 light-years.

The sweeping view, which reveals one third of our galactic neighbour, also suggests that the galaxy may have been battered by a collision with another galaxy two billion years ago. 

Benjamin Williams of the University of Washington in Seattle told Nature that the image hints at an older wave of starbirth that had previously only been spotted in one area of Andromeda.

'No one would have guessed it was galaxy-wide', he said, suggesting there may have been a major collision in the galaxy's history. 

Although 'neighbours' the Milky Way (pictured) and Andromeda are separated by 2.5 million light years