Galaxies are often found in clusters, with many "red and dead" neighbors that stopped forming stars in the distant past. Now an international team of astronomers, led by Andra Stroe of Leiden Observatory and David Sobral of Leiden and the University of Lisbon, have discovered that these comatose galaxies can sometimes come back to life. If clusters of galaxies merge, a huge shock wave can drive the birth of a new generation of stars - the sleeping galaxies get a new lease of life. The scientists publish their work in the journal Monthly Notices of the Royal Astronomical Society.

A radio image highlighting the shock wave (seen here as the bright arc running from bottom left to top right) in the "Sausage" merging cluster, made using the Giant Metrewave Radio Telescope. The shock wave was generated 1 billion years ago, when the two original clusters collided, and is moving at a very high speed of 9 million kilometers per hour.


Galaxy clusters are like cities, where thousands of galaxies can be packed together, at least in comparison to the sparsely-populated space around them. Over billions of years, they build up structure in the universe - merging with adjacent clusters, like growing cities absorb nearby towns. When this happens, there is a huge release of energy as the clusters collide. The resulting shock wave travels through the cluster like a tsunami, but until now there was no evidence that the galaxies themselves were affected very much.

Stroe and Sobral observed the merging galaxy cluster CIZA J2242.8+5301, nicknamed the "Sausage", located 2.3 billion light years away in the direction of the constellation of Lacerta, in the northern hemisphere of the sky. They used the Isaac Newton and William Herschel Telescopes on La Palma, and the Subaru, CFHT and Keck Telescopes on Hawaii, and found that far from "watching from the back" the cluster galaxies were transformed by the shock wave, triggering a new wave of star formation.

Stroe comments: "We assumed that the galaxies would be on the sidelines for this act, but it turns out they have a leading role. The comatose galaxies in the Sausage cluster are coming back to life, with stars forming at a tremendous rate. When we first saw this in the data, we simply couldn't believe what it was telling us."

A composite image of the "Sausage" merging cluster CIZA J2242.8+5310, made using data from the Subaru and Canada France Hawaii Telescopes (CFHT). The white circles indicate galaxies outside of the cluster, while yellow circles are cluster galaxies, where accelerated star formation is taking place. Green marks regions of radio emission, tracing out shock waves and purple marks the hot gas between the galaxies that emits X-rays. The cluster is one of the most massive in the Universe.
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Credit: Andra Stroe.

The new work implies that the merger of galaxy clusters has a major impact on the formation of stars. "Much like a teaspoon stirring a mug of coffee, the shocks lead to turbulence in the galactic gas. These then trigger an avalanche-like collapse, which eventually leads to the formation of very dense, cold gas clouds, which are vital for the formation of new stars", says Stroe.

Sobral adds: "But star formation at this rate leads to a lot of massive, short-lived stars coming into being, which explode as supernovae a few million years later. The explosions drive huge amounts of gas out of the galaxies and with most of the rest consumed in star formation, the galaxies soon run out of fuel. If you wait long enough, the cluster mergers make the galaxies even more red and dead - they slip back into a coma and have little prospect of a second resurrection."

Every cluster of galaxies in the nearby Universe has experienced a series of mergers during its lifetime, so they should all have passed through a period of extremely vigorous production of stars. Given that the shocks will only however lead to a brief (in astronomical terms) increase in star formation, astronomers have to be very lucky to catch the cluster at a time in its evolution when the galaxies are still being "lit up" by the shock.

The next step is to see if the Sausage cluster is unique and that these bursts of star formation need very particular conditions. By studying a much bigger sample of galaxies, the team hope to find out exactly how they happen.

Contacts and sources:
Andra Stroe
Leiden Observatory

Dr David Sobral
IA University of Lisbon and Leiden Observatory

Dr Robert Massey
Royal Astronomical Society

The research is published in two papers:
A. Stroe et al., "The rise and fall of star formation in z 0.2 merging galaxy clusters", Monthly Notices of the Royal Astronomical Society, vol. 450, pp. 646-665, 2015, published by Oxford University Press. A preprint of the paper is available on the arXiv server.
D. Sobral et al., "MC2: boosted AGN and star formation activity in CIZA J2242.8+5301, a massive post-merger cluster at z = 0.19", Monthly Notices of the Royal Astronomical Society, vol. 450, pp. 630-645, 2015, published by Oxford University Press. A preprint of the paper is available on the arXiv server.

Cool.

I thought of trying to locate the Sausage; I mean we need a frame of reference; like distance from earth to understand what this tsunami means, if anything to us on earth; figure out risks like if solar flares could impact electrical grids; could cluster collisions?
There are experts for this kind of stuff but here is what commonsense seems to say:



So lets take this 2.3 billion LY as the magic figure.

Wiki says Milky Way is 100,000 LY in it's disc diameter

Let's say 100,000 LY = 1 Red Dia.

Our Magic Figure 2.3 billion LY = 2,300 million LY = 23,000 Red Dia

Now locating Milky Way, where is it?
Inside Virgo sub-cluster which is inside...Lania (Laniakea)



So as per grid lines on this picture where 1 grid cell = 2 RD (approx)
& marking the right edge of the picture as the end of Lania
Then distance from Milky Way to right edge = 80 RD = 8 million LY
Clearly our Magic Number '23,000 Red Dia' is way outside of Lania

Then where is Lania's closest neighbour?



Perseus - Pisces?
Now by scaling; Outer edge of Lania to outer of Perseus - Pisces is 200RD,
20 Million Light Years.

So magic number 2.3 Billion Light Years is 10 times this distance (L to P).

So far, ok.
The interesting point is both super clusters Lania & P_Pisces are moving
away; i.e., moving with expanding space with P_Pisces leading.

So the Sausage is not in this expansion vector (reasonable assumption)

Then we look inwards, towards the super clusters which are contracting
I understand that a 'great attractor' is pulling these clusters in a
shrinking spiral orbit.

But there is a large gap between the outer most 'spiraling-in' cluster
and our Lania. An ocean of a gap, say 2000 RD.(which is our magic number.
2.3Billion Light Years)

In other words, the sausage is within the grip of the great Attractor
and with the shrinking spiral; clusters are bound to collide & more.


Fortunately, Lania is being guided away (by Divine Hand?)

---

Now I Google Andra Stroe and she is a 27 year young researcher and
Dr. Sobral is the guru on "star formation, death & second resurrections"

but the least these people could have done is give the position of the
Sausage w.r.t earth.

Why? Because any cluster collision is mini version of the B Bang
bigger than any solar flare bringing down the grid.


Stirring a mug of dense clouds of radio-active debris will coalesce to form
stars? Some people are getting a lot of the Hawaii sun; and getting paid for that.

Or am I missing something?

Trying to get the images up, let's see.

Image 1



Image 2


Sorry this picture of Lania was missed. Tried to get a grid
placed on the picture to get us distances in terms of dia of red disc.
Had to give up; so just the plain picture.



Well, this is the Lania with P_Pisces - double super cluster

Now if you've the patience to toggle between the thread & the previous post
may it will all start making some sense.

not sure where you're going with this...

so i wonder what this "tsunami" is made from? is there that many particles to support it?

Hey moe
Pretty heavy reading here for me...
Sorry...i have to say it...that first picture made me think of a dividing protozoa...

actually, it does... lots of things in the universe have some resemblances to different nature aspects...

what would you guess this is?

Yeah...that is true...we are all a series of microscopic repetitions of patterns reflecting a macrocosm....

Looks like brain cells to me...

Thinking the "tsunami" is a collision...maybe from all the negative energy of the 2 dying galaxies colliding or imploding...? ...like what jaigi said...an intergalactic big bang...?

yes, lots of people say that same thing, but the pic is actually what the "known" universe looks like in the strings that bind it together... the dots are galaxies, not stars...

i don't believe in the BBT myself, but i agree something like this could be what confused the scientists into believing there was one...

Makes sense why the "known" universe looks like interconnected neurons....

The complexities of the brain-mind dichotomy might reflect the complexities of the science-faith dichotomy as well...

You are missing how the delicate balance of gravity is upset causing a chain reaction of dust and gas to form new stars.

For example, the Oort cloud about our Solar System orbits in a delicate balance. The unbalanced objects fell inwards long ago. It takes very little motion to make a stable orbit that far from the Sun.

Along comes a rogue star, planet, black hole, planetoids, or even large puff of gas and the balance is disturbed. Comets start to slowly fall towards the Sun and nudge others as they pass by or even bump into a few (they are very far apart). Many years later a new wave of objects is falling towards the Sun by the above action. There is a theory that the Earth gets hits on a regular basis due to to this effect.

A supernova sends a shockwave of gas and dust outwards from it's explosion. The shockwave disturbs the delicate balance of gas clouds in exactly the same manner and the cloud falls together and forms new stars.

It doesn't take much.

not to mention the fact there's enough energy to make it travel for millions of light years, it would be able to "stir" things up in local solar systems/galaxies...

The original post was as a member mentioned . Problem was as there was no other post then, read it
a second time & OMG, it all started rocking.
Actually Moe, to understand the article better, I started looking at the
numbers and here's what I got from the OP: The A + B:

A.


B.

Therefore A + B = Galaxy shaking Tsunami - 2.3billion light years away

You know the rest of the story; my trying to figure out how far
2.3billion light years is.

Then Metal came up with the Oort Cloud model & now the distances
would have to be refined (or so I thought).

Not quite,if we review the distances:

Point of Start:
The Milky Way has a stellar disk dia of 100,000ly - source Wiki

But Metal's model on Oort Cloud proves Wiki's number as wrong
Oort cloud radius = 10^5 AU, = so dia 20^5 AU = 200,000ly
encompassing our solar system alone (my interpretation).

On the other hand NASA's measure of Milky Way is also 100,000 light years
(30 kpc) across.

So in the Oort Cloud model, we would have to relocate the solar system
somewhere way off center, nearer the boundary Sagittarius. Anyway, where the sun lies does not matter, since it is the Milky Way that's our unit of measure.

If we check back on the picture of Laniakea, the Milky Way is shown
as a Red Disk.

It was a matter of pasting the picture on Excel's grid lines
and then taking the distance from Milky Way's edge (in the direction of the
'Great Accelerator' )- worked out as around 80 Red Disk





Alright, we got the picture in with the grid lines,
so now we can count out the cells 30 x 1.5 times

End of story:
80 Red Disk gives 100,000ly x 45 = 4.5 million ly; and
this is nowhere close to 2.3 billion light years where the 'sausage of clusters of galaxies' is located.

In addition to all of above, when we bear in mind that the photo on
'sausage of clusters' is data that is 2.3billion years old; this
discussion tends to be inconclusive - as commented earlier
'something seemed to be missing'

Of course as space scientists Andre Stroe and Dr Sobral don't have
to contribute anything just their observations: "We see that the male
rhinos are edging closer to the females, looks like the mating season
begins". Probably, their pictures will come out in the next edition
of National Geography. It will be interesting what interpretations
the editors give.

Moving forward on Metal Wings clarifications on how stars are
formed from dust & clouds; that's amazing.

I'm just not able to get over the fact that dust & gas can be so compressed
as to light up nuclear fission. If that's so, it's a whole new
source of energy Or where have I been?

The question now would be what's the magnitude of this gravitational force.

A huge mass of cloud dust, say approximating mass of sun 2 x 10^27 tons
(333,000 times the mass of earth) condensing to the point all matter
begins to loose it's electronic identity - condensing further to fissionable Uranium; all from inexorable gravity at work..,
(thinking aloud: Wasn't this the favorite model of alchemists?)

Extending this logic, particles could very well fuse in the CERN Lab instead of splitting. So the question, what magnitude of gravitational forces are required for fusion - appears to be valid & possibly the
CERN guys have the numbers & are not telling.

i'm sure there is a reason to spend over 10 billion dollars building this thing...everything is "hush hush" nowadays...