Galaxy seen blasting its neighbor
Jan 04,2008 00:00 by Bend_Weekly_News_Sources

In a never-before seen event, a pow­er­ful jet from a gal­ax­y’s gi­ant, cen­tral black hole is pum­mel­ing a near­by gal­axy, ac­cord­ing to as­tro­no­mers. The beam may pro­foundly dis­turb plan­ets in its path and lat­er trig­ger a burst of star forma­t­ion, they said. 

A com­pos­ite im­age from sev­er­al ob­ser­va­to­ries shows what as­tro­no­mers say is a jet from a black hole at the cen­ter of a gal­axy, strik­ing an­oth­er gal­axy. The beam is dif­fi­cult to see in the ar­ea where it emerges, from the bright zone in the mid­dle of the large gal­axy at low­er left. It be­comes more ap­par­ent where as­tro­no­mers say it is strik­ing the sec­ond gal­axy, to the up­per right of the first one. There, it cre­ates what ap­pears as a blue spot in on the low­er right of the smaller gal­axy. Con­tin­u­ing on­ward to the up­per right of the pic­ture, the rem­nants of a beam ap­pear dis­rupted and de­flect­ed, re­sem­bling a vast wisp of smoke. This is si­m­i­lar to the way a stream of wa­ter from a hose will splay out af­ter hit­ting a wall at an an­gle, re­search­ers ex­plain. In the im­age, da­ta from sev­er­al wave­lengths of light have been com­bined: X-rays from Chan­dra (col­ored pur­ple); op­ti­cal and ul­tra­vio­let da­ta from the Hub­ble Space Te­le­scope (red and or­ange); and ra­dio emis­sion from the Very Large Ar­ray (VLA) and MER­LIN (blue) te­le­scopes. (Im­age cred­it: X-ray: NA­SA/CX­C/C­fA/D.E­ et al.; Op­ti­cal/UV: NA­SA/STScI; Ra­di­o: NS­F/VLA/C­fA/D.Evans et al., STFC/JBO/MER­LIN)

NASA’s Chan­dra X-ray Ob­serv­a­to­ry, the re­search­ers ex­plained, has re­vealed that both ga­lax­ies—or­bit­ing each oth­er in a sys­tem called 3C321—have cen­tral “su­per mas­sive” black holes. The smaller gal­axy, as­tro­no­mers said, seems to have swung in­to the path of a beam com­ing from the black hole of the larg­er gal­axy.

“We’ve seen many je­ts pro­duced by black holes, but this is the first time we’ve seen one punch in­to anoth­er gal­axy,” said Dan Ev­ans, a sci­ent­ist at the Har­vard-Smith­son­ian Cen­ter for As­t­ro­phys­ics in Cam­bridge, Mass. and lead­er of the stu­dy. “This je­t could be caus­ing all sorts of prob­lems for the smaller gal­axy.”

Black holes are ob­jects so dense that their gravita­t­ion sucks in an­y­thing that comes too close, in­clud­ing light. But some near­by ma­te­ri­al does­n’t fall in­side the black hole, and in­stead gets ejected in beams, a phe­nom­e­non be­lieved to re­sult from mag­net­ic fields.

The larg­est black holes are thought to lurk at the cen­ters of ga­lax­ies. Jets from these are found to pro­duce co­pi­ous radia­t­ion, es­pe­cially pow­er­ful X-rays and gamma-rays, which can be deadly in large quan­ti­ties. The com­bined ef­fects of this radia­t­ion and par­t­i­cles trav­el­ing at near-light speed in the beam could se­verely dam­age plan­e­tary at­mo­spheres in the je­t’s path, as­tro­no­mers say; for in­stance, pro­tec­tive lay­ers of ozone in the up­per at­mo­spheres could be de­stroyed.

Su­per ­mas­sive black hole je­ts car­ry tor­rents of en­er­gy far from their or­i­gin, and un­der­stand­ing them is a key goal for as­t­ro­phys­i­cists. “We see je­ts all over the un­iverse, but we’re still strug­gling to un­der­stand some of their bas­ic prop­er­ties,” said co-in­vest­iga­tor Mar­tin Hard­cas­tle of the Un­ivers­ity of Hert­ford­shire in the U.K. The new find­ing “gives us a chance to learn how they’re af­fect­ed when they slam in­to some­thing like a gal­axy and what they do af­ter that.”

The ef­fect of the je­t on the com­pan­ion gal­axy is probably sub­s­tan­tial, re­search­ers said, be­cause the ga­lax­ies are very close by as­tronomical stan­dards—a­bout 20,000 light years apart. A light-year is the dis­tance light trav­els in a year. They lie about the same dis­tance apart as Earth is from the cen­ter of our gal­axy.

The so-called “death star” gal­axy in 3C321 was disco­vered us­ing both space and ground-based tele­scopes, re­search­ers said. A bright spot in ra­di­o tel­e­scope im­ages, they re­marked, shows where the je­t has struck the side of the gal­axy.

A un­ique as­pect of the find­ing, they added, is how short-lived the event is in cos­mic terms: they es­ti­mate the je­t be­gan hit­ting the gal­axy a mil­lion years ago, a small frac­tion of the sys­tem’s life­time. This would sug­gest the align­ment is rare in the near­by uni­verse. But the event may not be all bad news for the vic­tim­ized gal­axy, they added: the huge in­flux of en­er­gy and radia­t­ion could prompt many stars and plan­ets to form in the de­struc­tion’s wake. The find­ings are to ap­pear in the re­search pub­lica­t­ion As­t­ro­phys­i­cal Jour­nal.

Courtesy of World-Science