Naučnici su konačno rekonstruisali kosmičko „gomilanje“ četiri galaktička jata koje se dešava više od 350 miliona godina. Istraživanje o tome kako je nastao Abell 2744, nazvan Pandorino jato, pružiće značajna saznanja o prirodi tamne materije. Takodje, može da objasni na koji način različite strukture iz univerzuma i različite materije deluju jedna na drugu kada se sudare. U tome su uspeli koristeći teleskope na zemlji i u svemiru.
Abell 2744 je rezultat istovremenih sudara najmanje četiri posebna galaktička jata, a ovaj kompleksan sudar je napravio čudne efekte koji nikada ranije nisu vidjeni.
Kada se ogromna galaktička jata sudare, haos koji nastane postaje dragoceni izvor informacija za astronome. Kao što forenzičari posle avionske nesreće rekonsruišu dogadjaj na osnovu delova koji nadju, tako i naučnici otkrivaju šta se dešavalo u periodu od nekoliko stotina miliona godina.
Ovo jato je dobilo nadimak Pandorino jato zbog toliko različitih i čudnih fenomena koji su oslobodjeni sudarom. Neki od tih fenomena nikada ranije nisu vidjeni.
Medju njima je „metak“ blizu jezgra jata, gde je gas jednog jata u sudaru sa drugim formirao udarni talas. Prolazeći kroz sudar, tamna materija nije osetila nikakav efekat.
U drugom delu jata čini se da postoje galaksije i tamna materija ali ne i vreo gas. Gas je možda nestao tokom sudara ostavljajući za sobom samo bled trag.
Još čudnije pojave leže u spoljnim delovima jata. Jedan deo sadrži dosta tamne materije, ali ne i blistave galaksije ili vreo gas. Izdvaja se jedan sablasni pramen gasa, više kao prethodnica nego ono što sledi tamnu materiju sa kojom je u vezi. Ovaj zbunjujući aranžman možda govori astronomima o tome kako se ponaša tamna materija i kako različiti sastojci univerzuma i tamna materija deluju jedni na druge.
Iako su galaksije svetle, one čine manje od 5 procenata te mase. Ostatak, oko 20 odsto je gas koji je toliko vruć da isijava samo X-zrake, kao i tamna materija, oko 75 procenata, koja je kompletno nevidljiva.
Da bi razumela šta se dešavalo u sudaru, tim je napravio mapu pozicija sva tri tipa materije u Abell 2744.
Tamna materija je posebno nedostižna jer ne emituje, apsorbuje niti reflektuje svetlost. Postaje očigledna samo na osnovu njenog sopstvenog gravitacionog privlačenja.
Da bi tačno odredio lokaciju ove misteriozne supstance, tim je koristio fenomen koji je poznat kao – gravitaciona sočiva. To je krivljenje zraka svetlosti iz udaljenih galaksija dok prolaze kroz gravitaciona polja.
Pažljivo osmatrajući način na koji su dobijene izobličene slike, moguće je prilično precizno odrediti gde se nalazi skrivena masa – a samim tim i tamna materija.
Otkrivanje vrućeg gasa u jatu je daleko jednostavnije. Ova osmatranja nisu samo od neprocenjive važnosti za otkrivanje gasa, već i za otkrivanje uglova i brzine kojom su se različite komponente jata sastale.
Čini se da je kompleksni sudar razdvojio izvesnu količinu vrućeg gasa i tamne materije tako da oni sada egzistiraju medjusobno razdvojeni i van vidljivih galaksija.
Galaktička jata su najveće structure u kosmosu i sadrže bukvalno trilione zvezda. Način na koji se formiraju i razvijaju tokom neprestanih sudara ima izuzetno veliki značaj za naše razumevanje univerzuma.
Crveni delovi su oblaci vrelog gasa; plavi oblaci su delovi u kojima ima dosta tamne materije. Animacija prikazuje kako su se različiti elementi ponašali tokom perioda od nekoliko miliona godina sve do pozicija koje možemo da vidimo danas. / The red regions are clouds of very hot gas; the blue clouds are regions rich in dark matter. It shows how these different components behaved over a period of several million years, leading up to their currently observed positions.
A cosmic “pile-up” between four galaxy clusters that has taken place over 350million years has been pieced together by scientists. The investigation into how Abell 2744 - nicknamed Pandora's Cluster - came to be formed is likely to provide researchers with significant insights into the nature of dark matter. They pieced together the cluster's complex and violent history using telescopes in space and on the ground.
This can reveal how structures form in the Universe, and how different types of matter interact with each other when they are smashed together.
Abell 2744 is the result of a simultaneous collision of at least four separate galaxy clusters and this complex collision has produced strange effects that have never been seen together before.
When huge clusters of galaxies crash together, the resulting mess is a treasure trove of information for astronomers. Like a crash investigator piecing together the cause of an accident, we can use observations of these cosmic pile-ups to reconstruct events that happened over a period of hundreds of millions of years
Pandora's Cluster because unleashed so many different and strange phenomena. Some of these phenomena had never been seen before. Among these is a 'bullet' near the core of the cluster, where the gas of one cluster collided with that of another to create a shock wave. The dark matter passed through the collision unaffected.
In another part of the cluster there seem to be galaxies and dark matter, but no hot gas. The gas may have been stripped away during the collision, leaving behind no more than a faint trail.
Even odder features lie in the outer parts of the cluster. One region contains lots of dark matter, but no luminous galaxies or hot gas. A separate ghostly clump of gas has been ejected, which precedes rather than follows the associated dark matter.
This puzzling arrangement may be telling astronomers something about how dark matter behaves and how the various ingredients of the Universe interact with each other.
Although the galaxies are bright they make up less than 5 per cent of the mass there. The rest, around 20 per cent, is gas, which is so hot that it shines only in X-rays, and dark matter, around 75 per cent, which is completely invisible.
To understand what was going on in the collision the team mapped the positions of all three types of matter in Abell 2744.
Dark matter is particularly elusive as it does not emit, absorb or reflect light, but only makes itself apparent through its gravitational attraction. To pinpoint the location of this mysterious substance the team exploited a phenomenon known as gravitational lensing. This is the bending of light rays from distant galaxies as they pass through the gravitational fields present in the cluster. By carefully plotting the way that these images are distorted, it is possible to map quite accurately where the hidden mass - and therefore the dark matter - actually lies.
Finding the hot gas in the cluster is simpler. These observations are not just crucial to find out where the gas is, but also to show the angles and speeds at which different components of the cluster came together.
It seems that the complex collision has separated out some of the hot gas and dark matter so that they now lie apart from each other, and from the visible galaxies.
Galaxy clusters are the biggest structures in the cosmos, containing literally trillions of stars. The way they form and develop through repeated collisions has profound implications for our understanding of the Universe.
Izvor/Source: Daily Mail