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“King” of star explosions seen

May 7, 2007
Courtesy NASA Marshall Space Flight Center
and World Science staff

As­tro­no­mers have de­tected the bright­est stel­lar ex­plo­sion, or su­per­no­va, on rec­ord. They say it may be a new type of su­per­no­va that may also oc­cur be­fore long in our own ga­l­axy—what one re­search­er said would be his­to­ry’s most awe­some star show.

The top pan­el is an artist's il­lus­tra­tion that shows what SN 2006gy may have looked like if viewed from near­by. The bot­tom left pan­el is an in­fra­red im­age from the Lick Ob­serv­a­to­ry, of NGC 1260, the gal­axy con­tain­ing SN 2006gy. The pan­el to the right shows Chan­dra's X-ray im­age of the same field of view, again show­ing the core of the gal­axy and SN 2006gy. (Image cre­dits: Il­lus­t­ra­tion: NA­SA/CXC/M. Weiss; X-ray: NA­SA/CXC/UC Ber­ke­ley/N. Smith et al.; IR: Lick/UC Ber­ke­ley/J. Bloom & C. Han­sen)


The find­ing comes from ob­ser­va­tions by NASA’s Chan­dra X ray Ob­serv­a­to­ry and ground-based tele­scopes. It in­di­cates vi­o­lent ex­plo­sions of ex­treme­ly mas­sive stars were fair­ly com­mon in the ear­ly uni­verse, sci­en­tists said.

“This was a tru­ly mon­strous ex­plo­sion, a hun­dred times more en­er­get­ic than a typ­i­cal su­per­no­va,” said Na­than Smith of the Uni­ver­si­ty of Cal­i­for­nia at Berke­ley, who led a team of as­tro­no­mers in the re­search. 

“That means the star that ex­plod­ed might have been as mas­sive as a star can get, about 150 times [the weight] of our sun. We’ve nev­er seen that be­fore.” 

As­tro­no­mers think many of the first gen­er­a­tion of stars were this mas­sive, and this new su­per­no­va may thus pro­vide a rare glimpse of how the first stars died.

The su­per­no­va, known as SN 2006gy, pro­vides ev­i­dence that the death of such mas­sive stars is fun­da­men­tal­ly dif­fer­ent from the­o­ret­i­cal pre­dic­tions, re­search­ers claimed.

“Of all ex­plod­ing stars ev­er ob­served, this was the king,” said Al­ex Fil­ip­penko, lead­er of the ground-based ob­ser­va­tions at the Lick Ob­serv­a­to­ry at Mt. Ham­il­ton, Calif., and the Keck Ob­serv­a­to­ry in Mauna Kea, Ha­waii. 

“We were as­ton­ished to see how bright it got, and how long it last­ed.” The Chan­dra ob­ser­va­tion al­lowed the team to rule out the most like­ly al­ter­na­tive ex­pla­na­tion for the su­per­no­va, the as­tro­no­mers said: that a white dwarf star on­ly slight­ly heav­i­er than the sun ex­plod­ed in­to a dense, hydrogen-rich en­vi­ron­ment. In that event, SN 2006gy should have been 1,000 times brighter in X-ray light than what Chan­dra de­tected, they said.

“This pro­vides strong ev­i­dence that SN 2006gy was, in fact, the death of an ex­treme­ly mas­sive star,” said Dave Poo­ley of the Uni­ver­si­ty of Cal­i­for­nia at Berke­ley, who led the Chan­dra ob­ser­va­tions.

The star that pro­duced SN 2006gy ap­par­ent­ly blew off a large amount of mass be­fore ex­plod­ing, as­tro­no­mers said. This large mass loss is si­m­i­lar to that seen from Eta Cari­nae, a mas­sive star in our gal­axy, rais­ing sus­pi­cion that Eta Cari­nae may be poised to ex­plode as a su­per­no­va. Al­though SN 2006gy is in­trin­si­cal­ly the bright­est su­per­no­va ev­er, it is in the gal­axy NGC 1260, some 240 mil­lion light years away. Howev­er, Eta Cari­nae is on­ly about 7,500 light years away in our own Milky Way gal­axy. A light year is the dis­tance light travels in a year.

“We don’t know for sure if Eta Cari­nae will ex­plode soon, but we had bet­ter keep a close eye on it just in case,” said Ma­rio Livio of the Space Tel­e­scope Sci­ence In­sti­tute in Bal­ti­more, who was not in­volved in the re­search. “Eta Cari­nae’s ex­plo­sion could be the best star-show in the his­to­ry of mod­ern civ­i­liza­tion.” 

Su­per­novas usu­al­ly oc­cur when mas­sive stars ex­haust their fu­el and col­lapse un­der their own grav­i­ty. In the case of SN 2006gy, as­tro­no­mers think some­thing else may have trig­gered the blast. Un­der some con­di­tions, a mas­sive star’s co­re could pro­duce so much ra­di­a­tion in the form of gam­ma rays that some of the en­er­gy from the ra­di­a­tion con­verts in­to mat­ter. This takes the form of par­t­i­cles paired up with en­ti­ties that are in a sense their evil twins, called anti-par­t­i­cles. This leads to a drop in en­er­gy that causes the star to col­lapse un­der its own mighty grav­i­ty.

Next, runa­way ther­mo­nu­cle­ar re­ac­tions en­sue and the star ex­plodes, spew­ing the re­mains in­to space. The SN 2006gy da­ta sug­gest that it may have been more com­mon than pre­vi­ously be­lieved for the first stars to die in spec­tac­u­lar su­per­no­vas, ast­ro­nom­ers said. An alternative fate theo­rized for these ob­jects is to col­lapse into black holes, ob­jects so com­pact that their gra­vi­ta­tion­al force runs out of cont­rol and they start to suck in everything near­by, in­clud­ing light.

“In terms of the ef­fect on the ear­ly uni­verse, there’s a huge dif­fer­ence be­tween these two pos­si­bil­i­ties,” said Smith. “One pol­lutes the gal­axy with large quan­ti­ties of new­ly made el­e­ments and the oth­er locks them up for­ev­er in a black hole.” The find­ings  are to ap­pear in a forth­com­ing issue of the re­search pub­li­ca­tion As­t­ro­phys­i­cal Jour­nal.


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Astronomers have detected the brightest stellar explosion, or supernova, on record, and say it may be a new type of supernova. The findings come from observations by NASA’s Chandra X ray Observatory and ground-based optical telescopes. This discovery indicates that violent explosions of extremely massive stars were fairly common in the early cosmos—and that a similar explosion may be ready to go off in our own galaxy, scientists said. “This was a truly monstrous explosion, a hundred times more energetic than a typical supernova,” said Nathan Smith of the University of California at Berkeley, who led a team of astronomers from California and the University of Texas in Austin. “That means the star that exploded might have been as massive as a star can get, about 150 times [the weight] of our sun. We’ve never seen that before.” Astronomers think many of the first generation of stars were this massive, and this new supernova may thus provide a rare glimpse of how the first stars died. It’s unprecedented, though, to find such a massive star and witness its death, they said. The supernova, known as SN 2006gy, provides evidence that the death of such massive stars is funda mentally different from theoretical predictions, researchers claimed. “Of all exploding stars ever observed, this was the king,” said Alex Filippenko, leader of the ground-based observations at the Lick Observatory at Mt. Hamilton, Calif., and the Keck Observatory in Mauna Kea, Hawaii. “We were astonished to see how bright it got, and how long it lasted.” The Chandra observation allowed the team to rule out the most likely alternative explanation for the supernova, the astronomers said: that a white dwarf star only slightly heavier than the sun exploded into a dense, hydrogen-rich environment. In that event, SN 2006gy should have been 1,000 times brighter in X-ray light than what Chandra detected, they said. “This provides strong evidence that SN 2006gy was, in fact, the death of an extremely massive star,” said Dave Pooley of the University of California at Berkeley, who led the Chandra observations. The star that produced SN 2006gy apparently blew off a large amount of mass before exploding, astronomers said. This large mass loss is similar to that seen from Eta Carinae, a massive star in our galaxy, raising suspicion that Eta Carinae may be poised to explode as a supernova. Although SN 2006gy is intrinsically the brightest supernova ever, it is in the galaxy NGC 1260, some 240 million light years away. However, Eta Carinae is only about 7,500 light years away in our own Milky Way galaxy. “We don’t know for sure if Eta Carinae will explode soon, but we had better keep a close eye on it just in case,” said Mario Livio of the Space Telescope Science Institute in Baltimore, who was not involved in the research. “Eta Carinae’s explosion could be the best star-show in the history of modern civilization.” Supernovas usually occur when massive stars exhaust their fuel and collapse under their own gravity. In the case of SN 2006gy, astronomers think that a very different effect may have triggered the explosion. Under some conditions, the core of a massive star produces so much radiation in the form of gamma rays that some of the energy from the radiation converts into matter, forming pairs of particles and mirror-image-like anti-particles. This leads to a drop in energy that causes the star to collapse under its own mighty gravity. After this violent collapse, runaway thermonuclear reactions ensue and the star explodes, spewing the remains into space. The SN 2006gy data suggest that it may have been more common than previously believed for the first stars to die in spectacular supernovas, rather than completely collapsing to a black holes as theorized, according to the team. “In terms of the effect on the early universe, there’s a huge difference between these two possibilities,” said Smith. “One pollutes the galaxy with large quantities of newly made elements and the other locks them up forever in a black hole.” The results from Smith and his colleagues are to appear in the research publication Astro physical Journal.