"Long before it's in the papers"
January 28, 2015


Signs of dark matter found?

Nov. 19, 2008
Courtesy Nature
and World Science staff

Tell­tale signs may have turned up of a mys­te­ri­ous sub­stance that per­vades the uni­verse but has nev­er been seen, as­tro­no­mers say.

The “dark mat­ter” is be­lieved to make up five-sixths of the phys­i­cal ma­te­ri­al in the uni­verse, but has re­vealed no sign of its ex­ist­ence oth­er than through its gravita­tional pull. For dec­ades, phys­i­cists have tried to fig­ure out just what the stuff is.

A detector balloon rises into the sky car­ry­ing the ad­vanced thin ion­izati­on cal­o­rim­e­ter. (Credit T. Gre­gory Gu­zik)

Some the­o­ries hold that sig­na­ture signs of dark mat­ter could be de­tected when par­t­i­cles of the stuff meet and an­ni­hi­late each oth­er. These events would re­sult in emis­si­ons of elec­tric­ally charged par­t­i­cles.

Such a sign of dark mat­ter an­ni­hila­tion may have been de­tected high above the skies of Ant­arc­ti­ca, ac­cord­ing to an in­terna­tional re­search team. The group re­ports the find­ings in the Nov. 20 is­sue of the re­search jour­nal Na­ture.

The in­ves­ti­ga­tors recorded what they said was an un­ex­pectedly high amount of the charged par­t­i­cles, called elec­trons, at en­er­gies con­sist­ent with the­o­ret­i­cal pre­dic­ti­ons about the dark mat­ter.

The spe­cif­ic dark mat­ter “an­ni­hila­tion sig­na­ture” is con­sist­ent with the idea that dark mat­ter con­sists of com­po­nents called Ka­lu­za-Klein par­t­i­cles, ac­cord­ing to the re­search group. These par­t­i­cles emerge from the­o­ries of the uni­verse in­volv­ing ex­tra di­men­si­ons be­yond those which we can nor­mally detect—the­o­ries that in turn have been in­voked to show that the var­i­ous forc­es of na­ture could pos­sess an un­der­ly­ing un­ity.

However, the detected elec­trons could also come from cel­es­tial ob­jects un­re­lated to dark mat­ter, such as so-called pul­sars or mi­cro­qua­sars, the team noted.

The de­tec­ti­ons were made us­ing a high-al­t­i­tude bal­loon-borne de­vice called an ad­vanced thin ion­izati­on cal­o­rim­e­ter.

Be­cause, as Ein­stein showed, mat­ter and en­er­gy are ul­ti­mately equiv­a­lent, dark mat­ter would al­so be a part of the en­er­gy in the uni­verse. Cos­mol­o­gists es­ti­mate that dark mat­ter com­prises 23 per­cent of all en­er­gy in the cos­mos. An equally mys­te­ri­ous “dark en­er­gy,” which drives ga­lax­ies apart, is thought to take up anoth­er 73 per­cent or so. Or­di­nary, vis­i­ble mat­ter is be­lieved to rep­re­sent only four per­cent of the to­tal en­er­gy.

The team con­sisted of re­search­ers from Pur­ple Moun­tain Ob­serv­a­to­ry in Nan­jing, Chi­na; the Mar­shall Space Flight Cen­ter in Hunts­ville, Al­a.; the Uni­ver­s­ity of Mar­y­land; Mos­cow State Uni­ver­s­ity; and Lou­i­si­ana State Uni­ver­s­ity.

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Telltale signs may have turned up of a mysterious substance that pervades the universe but has never been seen, astronomers say. The “dark matter” is believed to make up five-sixths of the physical material in the universe, but has revealed no sign of its existence other than through its gravitational pull. For decades, physicists have tried to figure out just what the stuff is. However, a number of theories hold that signature signs of dark matter could be detected when particles of the stuff meet and annihilate each other. These events would result in emissions of electrically charged particles. Such a sign of dark matter annihilation may have been detected high above the skies of Antarctica, according to an international research team. The group reports the findings in the Nov. 20 issue of the research journal Nature. The investigators recorded what they said was an unexpectedly high amount of the charged particles, called electrons, at energies consistent with theoretical predictions about the dark matter. The specific dark matter “annihilation signature” is consistent with the idea that dark matter consists of components called Kaluza-Klein particles, according to Wefel’s team. These particles emerge from theories of the universe involving extra dimensions beyond those which we can normally detect—theories that in turn have been invoked to show that the various forces of nature could possess an underlying unity. The detections were made using a high-altitude balloon-borne device called an advanced thin ionization calorimeter. Because, as Einstein showed, matter and energy are ultimately equivalent, dark matter is also a part of the energy in the universe. Cosmologists estimate that dark matter comprises 23 percent of all energy in the cosmos. An equally mysterious “dark energy,” which drives galaxies apart, is thought to take up another 73 percent or so. Ordinary, visible matter is believed to represent only four percent of the total energy. The team consisted of researchers from Purple Mountain Observatory in Nanjing, China; the Marshall Space Flight Center in Huntsville, Alabama; the University of Maryland; Moscow State University; and Louisiana State University.