What happens when cosmic giants meet galactic dwarfs?

July 12, 2015, International Centre for Radio Astronomy Research
An image using galaxy images from the Hubble Space Telescope to show what happens when galaxies of different sizes collide. Credit: The International Centre for Radio Astronomy Research

When two different sized galaxies smash together, the larger galaxy stops the smaller one making new stars, according to a study of more than 20,000 merging galaxies.

The research, published today, also found that when two galaxies of the same size collide, both galaxies produce at a much faster rate.

Astrophysicist Luke Davies, from The University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR), says our nearest major galactic neighbour, Andromeda, is hurtling on a collision course with the Milky Way at about 400,000 kilometres per hour.

"Don't panic yet, the two won't smash into each other for another four billion years or so," he says.

"But investigating such cosmic collisions lets us better understand how galaxies grow and evolve."

Previously, astronomers thought that when two galaxies smash into each other their gas clouds—where stars are born—get churned up and seed the birth of new stars much faster than if they remained separate.

However Dr Davies' research, using the Galaxy and Mass Assembly (GAMA) survey observed using the Anglo-Australian Telescope in regional New South Wales, suggests this idea is too simplistic.

He says whether a galaxy forms stars more rapidly in a collision, or forms any new stars at all, depends on if it is the big guy or the little guy in this galactic car crash.

"When two of similar mass collide, they both increase their stellar birth rate," Dr Davies says.

A short, one minute entertaining and engaging animation showing what happens when big galaxies meet little galaxies. Credit: The International Centre for Radio Astronomy Research
"However when one galaxy significantly outweighs the other, we have found that star formation rates are affected for both, just in different ways.

"The more massive galaxy begins rapidly forming , whereas the smaller galaxy suddenly struggles to make any at all.

"This might be because the bigger galaxy strips away its smaller companion's gas, leaving it without star-forming fuel or because it stops the smaller galaxy obtaining the new gas required to form more stars."

An image using galaxy images from the Hubble Space Telescope to show what happens when galaxies of different sizes collide. Credit: The International Centre for Radio Astronomy Research

The study was released today in the journal Monthly Notices of the Royal Astronomical Society, published by Oxford University Press.

So what will happen in four billion years to the Milky Way and Andromeda?

Dr Davies says the pair are like "cosmic tanks"—both relatively large and with similar mass.

"As they get closer together they will begin to affect each other's star formation, and will continue to do so until they eventually merge to become a new galaxy, which some call 'Milkdromeda'," he says.

Explore further: How do galaxies die?

More information: 'Galaxy and Mass Assembly (GAMA): the effect of close interactions on star formation in galaxies' in the Monthly Notices of the Royal Astronomical Society. Published online on 13/7/2015 at: mnras.oxfordjournals.org/looku … 0.1093/mnras/stv1241

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antialias_physorg
5 / 5 (1) Jul 13, 2015
which some call 'Milkdromeda'

I prefer 'Andyway'.
docile
Jul 13, 2015
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docile
Jul 13, 2015
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Psilly_T
1 / 5 (1) Jul 13, 2015
This effect is visible for example http://i.space.com/images/i/000/012/930/i02/arp-148-galaxy-collision.jpg?1319725711, when the older (yellow) galaxy quenches the stars inside the younger one (blue).

not sure i see this.... "quenching" you are talking about.... and are you assuming that dark matter calms stars? So stars are more unstable and less "lazy" without the presence of dark matter in your paradigm? What do you even mean by "lazy cold stars" red/old/dwarf? I don't know man i don't think im buying what your selling. interesting theory tho amigo.
Bigbangcon
1 / 5 (2) Jul 13, 2015
"So what will happen in four billion years to the Milky Way and Andromeda?"

Nobody knows! "Milkdromeda: and what Dr. Davies and fellow travellers are saying are all idle speculation and mysticism, to create awe and reverence not only about the cosmos, but also about the people (i.e., themselves) who are in the "know" of all these mysteries!

Nothing in the world (from the macrocosm to the microcosm) is deterministic, except short term classical mechanics and everyday life experience. Things in the world are mediated not by causality and determinism, but by dialectical chance and necessity

Halton Arp was the only early astronomer who took interest in the odd interacting and peculiar galaxies, https://en.wikipe...laxies., neglected by others; who were only interested in the majestic and beautiful spiral and elliptical galaxies. No mention of Arp in this narrative!

And Arp never subscribed to Big Bang or GR!
jonesdave
3 / 5 (4) Jul 13, 2015
And Arp never subscribed to Big Bang or GR!


And Arp is essentially treated as a crank. What with his "discordant redshifts" and the like. Nobody of any note takes that seriously any more. Try somebody with a bit more gravity.
vidyunmaya
1 / 5 (2) Jul 14, 2015
Sub; Mislead and mess-up or taken for a ride
Astronomers need to catch-up with Cosmology studies
Andromeda at 2.5 M LY while Milkyway is nearby-with 100,000 lY wide.
How can they mess-up without indexing Supernovas around 10 MLY?
NGC 188 is an open cluster in the constellation Cepheus-5400 LY
NGC 6946 is a rather nearby spiral galaxy, which at one time was suspected to be an outlying member of the Local Group (Hubble 1936). It is highly
obscured by interstellar matter of the Milky Way galaxy, as it is quite close to the galactic plane.
Nine supernovae have been detected in NGC 6946 as of this writing (March 2009) at 10 MLY distance is very bright.
search heart of the universe-Cosmology vedas interlinks-vidyardhi Nanduri
docile
Jul 14, 2015
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docile
Jul 14, 2015
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docile
Jul 14, 2015
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