Cosmic cannibalising: Images show one galaxy engulfing another

As cosmic events go, this one is hard to beat. Scientists have built up a dramatic time-lapse picture of one galaxy swallowing up another in a cannabilistic act that takes place over a period of three billion years – about as long as it took for slime-like earthlings to evolve into humans.

Astronomers have been able to witness a feature of galaxy evolution that they have long suspected but have been unable to visualise whereby one swirling mass of stars devours another that happens to have come within its gravitational sphere of influence.

A telescopic study of the Andromeda galaxy some 2.3 million light years away, the nearest spiral galaxy to our own Milky Way that can be seen with the naked eye, has exposed the galaxy’s immense gravitational tides that are eating away at the smaller Triangulum galaxy as it slowly orbits its galactic master.

The images captured by the Andromeda Archaeological Survey team, using the Canada-France-Hawaii Telescope on the summit of Mauna Kea in Hawaii, show for the first time the immense tidal forces and interactions that cause one galaxy to slowly swallow the stars and cosmic gases of another.

The findings, published in the journal Nature, support a central hypothesis in cosmology called the “hierarchical model” which predicts that large galaxies should be surrounded by the relics of smaller galaxies that the larger galaxies have either completely digested or have begun to engulf.

“Galaxies like our own Milky Way were not born in their current state and they grow by cannabilising smaller galaxies in their path – this is exactly the same with Andromeda,” said Mike Irwin of Cambridge University’s Institute of Astronomy, a member of the international research team.

“What these images tell us is that even galaxies that look beautiful and symmetrical when looked at through a telescope have structure and interactions that you don’t see,” Dr Irwin said.

“This is a startlingly visual demonstration of the truly vast scale of galaxies. The survey has produced an unrivalled panorama of galaxy structure which reveals that galaxies are the result of an ongoing process of accretion and interaction with their neighbour,” he said.

The results of the study were made possible because of the huge area of sky surveyed by the telescope’s powerful digital camera. The observations covered an area with a diameter equivalent to a million light years, a panorama of space that the scientists said is the broadest and deepest view of a galaxy ever made.

One of the problems of finding the evidence to support the hierarchical model of galaxy evolution is that the “leftovers” of the galactic dinner are too faint to be seen over an area that is hundreds of times larger than the galaxy’s central disc of bright stars and gas.

“We mapped Andromeda’s unexplored outskirts for the first time and found stars and giant structures that are remnants of smaller galaxies, which have been incorporated into Andromeda as part of its ongoing growth,” said Professor Geraint Lewis of the University of Sydney.

“The big surprise in the data was finding that Andromeda is interacting with its neighbour, the Triangulum galaxy, a galaxy which is also visible in the northern hemisphere using a small telescope. Millions of Triangulum’s stars have been pulled in by Andromeda as part of the encounter,” Professor Lewis said.

It takes about 3 billion years for the two galaxies to complete one round of their cosmic dance but eventually they are expected to merge into one entity. Some of the stars in Andromeda are so far from the galactic core that they could only have formed in another galaxy that had long-since been swallowed up.

Another surprise for the survey team is finding the immense scale of a galaxy’s influence. “We’ve found coherent structures and star formations over the entire survey area, showing that galaxies are much bigger than we originally thought. Andromeda is considered by astronomers to be a typical galaxy, so it’s surprising to see how vast it really is,” Professor Lewis said.

“We found loosely bound stars at distances up to a hundred times the radius of the large galaxy’s central disc,” he said.

Start your day with The Independent, sign up for daily news emails
Ed Miliband and David Cameron are neck and neck in the polls
election 2015Armando Iannucci: on how British politics is broken
Life and Style
Great minds like Einstein don't think alike
Missing: 'Mail' columnist Peter Hitchens
election 2015
Arts and Entertainment
Billie Piper as Brona in Penny Dreadful
tvReview: It’s business as usual in Victorian London. Let’s hope that changes as we get further into the new series spoiler alert
Life and Style
A nurse tends to a recovering patient on a general ward at The Queen Elizabeth Hospital in Birmingham
ebooksA celebration of British elections
Arts and Entertainment
No Offence
tvReview: No Offence has characters who are larger than life and yet somehow completely true to life at the same time spoiler alert
Chuck Norris pictured in 1996
Arts and Entertainment
Sarah Lucas, I SCREAM DADDIO, Installation View, British Pavilion 2015
artWhy Sarah Lucas is the perfect choice to represent British art at the Venice Biennale
A voter placing a ballot paper in the box at a polling station
  • Get to the point
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Ashdown Group: IT Support Engineer - Leeds

£22000 - £25000 per annum: Ashdown Group: IT Support Engineer - Leeds This i...

SThree: Trainee Recruitment Consultant - Bristol

£18000 - £23000 per annum + Uncapped OTE: SThree: SThree Trainee Recruitment C...

SThree: Trainee Recruitment Consultant - Birmingham

£18000 - £23000 per annum + Uncapped OTE: SThree: SThree Trainee Recruitment C...

SThree: Trainee Recruitment Consultant - Dublin

£13676.46 - £16411.61 per annum + OTE: SThree: SThree Trainee Recruitment Cons...

Day In a Page

General Election 2015: Ed Miliband's unlikely journey from hapless geek to heart-throb

Miliband's unlikely journey from hapless geek to heart-throb

He was meant to be Labour's biggest handicap - but has become almost an asset
General Election 2015: A guide to the smaller parties, from the the National Health Action Party to the Church of the Militant Elvis Party

On the margins

From Militant Elvis to Women's Equality: a guide to the underdogs standing in the election
Amr Darrag: Ex-Muslim Brotherhood minister in exile still believes Egypt's military regime can be replaced with 'moderate' Islamic rule

'This is the battle of young Egypt for the future of our country'

Ex-Muslim Brotherhood minister Amr Darrag still believes the opposition can rid Egypt of its military regime and replace it with 'moderate' Islamic rule, he tells Robert Fisk
Why patients must rely less on doctors: Improving our own health is the 'blockbuster drug of the century'

Why patients must rely less on doctors

Improving our own health is the 'blockbuster drug of the century'
Sarah Lucas is the perfect artist to represent Britain at the Venice Biennale

Flesh in Venice

Sarah Lucas has filled the British pavilion at the Venice Biennale with slinky cats and casts of her female friends' private parts. It makes you proud to be a woman, says Karen Wright
11 best anti-ageing day creams

11 best anti-ageing day creams

Slow down the ageing process with one of these high-performance, hardworking anti-agers
Juventus 2 Real Madrid 1: Five things we learnt, including Iker Casillas is past it and Carlos Tevez remains effective

Juventus vs Real Madrid

Five things we learnt from the Italian's Champions League first leg win over the Spanish giants
Ashes 2015: Test series looks a lost cause for England... whoever takes over as ECB director of cricket

Ashes series looks a lost cause for England...

Whoever takes over as ECB director of cricket, says Stephen Brenkley
Fishing for votes with Nigel Farage: The Ukip leader shows how he can work an audience as he casts his line to the disaffected of Grimsby

Fishing is on Nigel Farage's mind

Ukip leader casts a line to the disaffected
Who is bombing whom in the Middle East? It's amazing they don't all hit each other

Who is bombing whom in the Middle East?

Robert Fisk untangles the countries and factions
China's influence on fashion: At the top of the game both creatively and commercially

China's influence on fashion

At the top of the game both creatively and commercially
Lord O’Donnell: Former cabinet secretary on the election and life away from the levers of power

The man known as GOD has a reputation for getting the job done

Lord O'Donnell's three principles of rule
Rainbow shades: It's all bright on the night

Rainbow shades

It's all bright on the night
'It was first time I had ever tasted chocolate. I kept a piece, and when Amsterdam was liberated, I gave it to the first Allied soldier I saw'

Bread from heaven

Dutch survivors thank RAF for World War II drop that saved millions
Britain will be 'run for the wealthy and powerful' if Tories retain power - Labour

How 'the Axe' helped Labour

UK will be 'run for the wealthy and powerful' if Tories retain power