• UCSBgauchos twitter avatar
    Cal Poly Edges Gauchos 73-72 With Late Basket https://t.co/B3JF2mtSt4
    1 hour 34 min ago
  • AS_UCSB twitter avatar
    CAMPUS JOB ALERT: @SBLivingHistory is seeking curious and creative types to join our team. https://t.co/FeQ8ybNJcQ https://t.co/o61fO77L50
    2 hours 17 min ago
  • UCSBgauchos twitter avatar
    UCSB MVB led 11-9 in the 5th Wednesday night, the team's first home match in 46 days and first game-action in two w… https://t.co/4zjvsMOFle
    2 hours 32 min ago
  • UCSBgauchos twitter avatar
    Luke Andrews (7 IP, 1 R, 4 H) absolutely DEALT for @UCSB_Baseball today, leading the Gauchos to a 7-2 Opening Day w… https://t.co/JUpY8CLyTn
    5 hours 48 min ago
  • ucsantabarbara twitter avatar
    Sherie Labedis’s journey to reunite with a friend she lost touch with after the Civil Rights Movement brings her to… https://t.co/le1uWZrDo7
    7 hours 57 min ago
  • ArtsandLectures twitter avatar
    RT @TylerHayden1: Talked with NASA commander and crack photographer @AstroTerry about his book and upcoming talk in S.B. @ArtsandLectures h…
    7 hours 58 min ago
  • UCSBgauchos twitter avatar
    First-Place UCSB Travels to UC Irvine Thursday for Another 1-2 Showdown https://t.co/HH08BS8tGe
    8 hours 59 min ago
  • brenucsb twitter avatar
    New Marine Protected Area Alert! Seychelles is home to giant tortoises, tuna, sharks, & scores of other marine spec… https://t.co/GhqaS4YmRE
    9 hours 17 min ago
  • UCSBLibrary twitter avatar
    RT @CSEP_UCSB: The sun is shining, the breeze is cool, time to snuggle up to your monitor and visit #ArtofScience #Voting! Cast your vote f…
    10 hours 37 min ago
  • UCSBgauchos twitter avatar
    UCSB Hosts Dayton, San Diego for Gaucho Classic I https://t.co/NwYtLZIfC7
    10 hours 49 min ago
  • ArtsandLectures twitter avatar
    RT @hfaucsb: It's foolish to think that politics is an expression of moral purity" - Pulitzer Prize winning playwright Tony Kushner at UCSB…
    10 hours 52 min ago
  • ArtsandLectures twitter avatar
    10 hours 52 min ago
  • ArtsandLectures twitter avatar
    @AstroTerry @NatGeoLive @NatGeoBooks @NatGeoPR woot woot! see you there!
    10 hours 52 min ago
  • ArtsandLectures twitter avatar
    RT @AstroTerry: If you are in Santa Barbara, CA on February 26, come see me at UCSB Campbell Hall and experience the beauty of our planet f…
    10 hours 52 min ago
  • brenucsb twitter avatar
    "Most problems require multiple skillsets and disciplinary expertise to solve, so if I didn’t collaborate I wouldn’… https://t.co/Owza9Ezl0N
    10 hours 52 min ago

A Star That Would Not Die

UCSB astrophysicists and LCO astronomers study a supernova that challenges known theories of how certain stars end their lives
Wednesday, November 8, 2017 - 10:00
Santa Barbara, CA


An artist's impression of a supernova.

Photo Credit: 

NASA, ESA, and G. Bacon (STScI)

Arcavi, Howell & Bildsten.jpg

Left to right: Iair Arcavi, Andy Howell and Lars Bildsten.

Photo Credit: 

Sonia Fernandez

Supernovae,​ ​the​ ​explosions​ ​of​ ​stars,​ ​have​ ​been​ ​observed​ ​by​ ​the​ ​thousands.​ ​And in all cases,​ ​the transient astronomical events​ ​signaled​ ​the​ ​death​ ​of​ ​those​ ​stars.​ ​

Now, astrophysicists at UC Santa Barbara and astronomers​ ​at​ ​Las​ ​Cumbres​ ​Observatory​ (LCO) ​have reported​ ​a​ ​remarkable​ ​exception​:​ ​a​ ​star​ ​that​ ​exploded​ ​multiple​ ​times​ ​over​ ​a​ ​period​ ​of more​ ​than​ ​50​ ​years.​ ​Their​ ​observations, published in the journal Nature,​ ​are​ ​challenging​ ​existing​ ​theories​ ​on​ ​these cosmic​ ​catastrophes. 

“This​ ​supernova​ ​breaks everything​ ​we​ ​thought​ ​we​ ​knew​ ​about​ ​how​ ​they​ ​work,” said lead author Iair Arcavi, a NASA Einstein postdoctoral fellow in UC Santa Barbara’s Department of Physics and at LCO. “It’s​ ​the​ ​biggest​ ​puzzle​ ​I’ve encountered​ ​in​ ​almost​ ​a​ ​decade​ ​of​ ​studying​ ​stellar​ ​explosions.”

When​ ​​iPTF14hls was​ ​discovered​ ​in​ ​September​​ ​2014​ ​by​ ​the Caltech-led Palomar​ ​Transient​ ​Factory,​ ​it​ ​looked​ ​like​ ​an​ ​ordinary​ ​supernova.​ ​But several​ ​months​ ​later, the scientific team noticed​ that​ ​the​ ​supernova, once faded, was​ ​growing​ ​brighter​. It was a phenomenon they had never seen before.

A​ ​normal​ ​supernova​ ​rises​ ​to​ ​peak​ ​brightness​ ​and​ ​fades​ ​over​ ​100​ ​days.​ ​Supernova iPTF14hls,​ ​on​ ​the​ ​other​ ​hand,​ ​grew​ ​brighter​ ​and​ ​dimmer​ ​at​ ​least​ ​five​ ​times​ ​over​ ​three years. 

When​ ​the scientists​ ​examined ​archival​ ​data,​ ​they​ ​were​ ​astonished​ ​to​ ​find evidence​ ​of​ ​an​ ​explosion​ ​in​ ​1954​ ​at​ ​the​ ​same​ ​location.​ ​Somehow this​ ​star​ survived​ ​that explosion​ ​and​ ​then exploded​ ​again​ ​in​ ​2014. In the​ ​study, the authors​ ​calculated​ ​that​ ​the​ ​exploding star​ ​was​ ​at​ ​least​ ​50​ ​times​ ​more​ ​massive than​ ​the​ ​sun​ ​and​ ​probably​ ​much​ ​larger.​ ​

“Supernova​ ​iPTF14hls​ ​may​ ​be​ ​the​ ​most massive​ ​stellar​ ​explosion​ ​ever​ ​seen,” explained co-author Lars Bildsten, director of UCSB’s Kavli Institute for Theoretical Physics. “​​For me, the most remarkable aspect of this supernova was its long duration, something we have never seen before. It certainly puzzled all of us as it just continued shining.” As part of this effort, Bildsten worked with UC Berkeley astrophysicist Dan Kasen, exploring many possible explanations.

The earlier explosion in 1954 provided an important clue, suggesting that iPTF14hls​ could be the first example of a​ ​pulsational​ ​pair​-instability supernova.​ ​Theory​ ​holds​ ​that​ the cores of ​massive​ ​stars​ ​become​ ​so​ ​hot​ ​that energy​ ​is​ ​converted​ ​into​ ​matter​ ​and​ ​antimatter.​ ​This​ ​causes​ ​an​ ​explosion​ ​that blows​ ​off​ ​the​ ​star’s outer​ ​layers​ ​and​ ​leaves​ ​the​ ​core​ ​intact. Such a​ ​process​ ​can​ ​repeat over​ ​decades​ ​before​ ​the​ ​final​ explosion​ ​and​ subsequent ​collapse​ ​to​ ​a​ ​black​ ​hole. 

“These​ ​explosions​ ​were​ ​only​ ​expected​ ​to​ ​be​ ​seen​ ​in​ ​the​ ​early​ ​universe ​and​ ​should​ ​be extinct​ ​today,” said co-author Andy Howell, a UCSB adjunct faculty member who leads the supernova group at LCO. “This​ ​is​ ​like​ ​finding​ ​a​ ​dinosaur​ ​still​ ​alive​ ​today.​ ​If​ ​you​ ​found​ ​one,​ ​you would​ ​question​ ​whether​ ​it​ ​truly​ ​was​ ​a​ ​dinosaur.”

The pulsational​ ​pair​-instability ​theory​ ​may​ ​not​ ​fully​ ​explain​ ​all​ ​the​ ​data obtained​ ​for​ ​this​ ​event because the ​energy​ ​released​ ​by​ ​the​ ​supernova ​​is​ ​more than​ ​the​ ​theory​ ​predicts. This means​ iPTF14hls​​ ​may​ ​be​ a completely​ ​new kind of supernova.

LCO’s ​supernova​ ​group ​continues​ ​to​ ​monitor​ ​iPTF14hls,​ ​which​ ​remains​ ​bright three​ ​years​ ​after​ ​it​ ​was​ ​discovered. Their​ ​global​ ​telescope​ ​network​ ​is​ ​uniquely​ ​designed​ ​for​ ​this type​ ​of​ ​sustained​ ​observation, which has allowed researchers to observe​ ​ iPTF14hls ​every​ ​few​ ​days​ ​for several​ ​years.​ ​Such​ ​long-term​ ​consistent​ ​monitoring​ ​is​ ​essential​ ​for​ ​the​ ​study​ ​of​ ​this​ ​very unusual​ ​event. 

“We​ ​could​ ​not​ ​have​ ​kept​ ​tabs​ ​on​ ​iPTF14hls​ ​for​ ​this​ ​long ​and​ ​collected​ ​data​ ​that challenges​ ​all​ ​existing​ ​supernova​ ​theories​ ​if​ ​it​ ​weren’t​ ​for​ ​the global telescope network,” Arcavi​ ​said.​ ​“I can’t​ ​wait​ ​to​ ​see​ ​what​ ​we’ll​ ​find​ ​by​ ​continuing to look​ ​at​ ​the​ ​sky​ ​in​ ​the​ ​new​ ​ways​ ​that​ ​such a setup​ ​allows.”

This research was supported by the National Science Foundation and the Gordon and Betty Moore Foundation.

Contact Info: 

Julie Cohen
(805) 893-7220