Space

August 6, 2014

NASA’s Hubble finds supernova star system linked to potential ‘Zombie Star’

The two inset images show before-and-after images captured by NASA’s Hubble Space Telescope of Supernova 2012Z in the spiral galaxy NGC 1309. The white X at the top of the main image marks the location of the supernova in the galaxy.

Using NASA’s Hubble Space Telescope, a team of astronomers has spotted a star system that could have left behind a “zombie star” after an unusually weak supernova explosion.

A supernova typically obliterates the exploding white dwarf, or dying star. On this occasion, scientists believe this faint supernova may have left behind a surviving portion of the dwarf star – a sort of zombie star.

While examining Hubble images taken years before the stellar explosion, astronomers identified a blue companion star feeding energy to a white dwarf, a process that ignited a nuclear reaction and released this weak supernova blast. This supernova, Type Iax, is less common than its brighter cousin, Type Ia. Astronomers have identified more than 30 of these mini-supernovas that may leave behind a surviving white dwarf.

“Astronomers have been searching for decades for the star systems that produce Type Ia supernova explosions,” said scientist Saurabh Jha of Rutgers University in Piscataway, New Jersey. “Type Ia’s are important because they’re used to measure vast cosmic distances and the expansion of the universe. But we have very few constraints on how any white dwarf explodes. The similarities between Type Iax’s and normal Type Ia’s make understanding Type Iax progenitors important, especially because no Type Ia progenitor has been conclusively identified. This discovery shows us one way that you can get a white dwarf explosion.”

The team’s results will appear in the Thursday, Aug. 7 edition of the journal Nature.

The weak supernova, dubbed SN 2012Z, resides in the host galaxy NGC 1309 which is 110 million light-years away. It was discovered in the Lick Observatory Supernova Search in January 2012. Luckily, Hubble’s Advanced Camera for Surveys also observed NGC 1309 for several years prior the supernova outburst, which allowed scientists to compare before-and-after images.

Curtis McCully, a graduate student at Rutgers and lead author of the team’s paper, sharpened the Hubble pre-explosion images and noticed a peculiar object near the location of the supernova.

“I was very surprised to see anything at the location of the supernova. We expected  the progenitor system would be too faint to see, like in previous searches for normal Type Ia supernova progenitors. It is exciting when nature surprises us,” McCully said.

After studying the object’s colors and comparing with computer simulations of possible Type Iax progenitor systems, the team concluded they were seeing the light of a star that had lost its outer hydrogen envelope, revealing its helium core.

The team plans to use Hubble again in 2015 to observe the area, giving time for the supernova’s light to dim enough to reveal any possible zombie star and helium companion to confirm their hypothesis.

“Back in 2009, when we were just starting to understand this class, we predicted these supernovae were produced by a white dwarf and helium star binary system,” said team member Ryan Foley of the University of Illinois at Urbana-Champaign, who helped identify Type Iax supernovae as a new class. “There’s still a little uncertainty in this study, but it is essentially validation of our claim.”

One possible explanation for the unusual nature of SN 2012Z is that a game of seesaw ensued between the bigger and smaller of the star pair. The more massive star evolved more quickly to expand and dump its hydrogen and helium onto the smaller star. The rapidly evolving star became a white dwarf. The smaller star bulked up, grew larger and engulfed the white dwarf. The outer layers of this combined star were ejected, leaving behind the white dwarf and the helium core of the companion star. The white dwarf siphoned matter from the companion star until it became unstable and exploded as a mini-supernova, leaving behind a surviving zombie star.

Astronomers already have located the aftermath of another Type Iax supernova blast. Images were taken with Hubble in January 2013 of supernova 2008ha, located 69 million light-years away in the galaxy UGC 12682, in more than four years after it exploded. The images show an object in the area of the supernova that could be the zombie star or the companion. The findings will be published in The Astrophysical Journal.

“SN 2012Z is one of the more powerful Type Iax supernovae and SN 2008ha is one of the weakest of the class, showing that Type Iax systems are very diverse,” explained Foley, lead author of the paper on SN 2008ha. “And perhaps that diversity is related to how each of these stars explodes. Because these supernovae don’t destroy the white dwarf completely, we surmise that some of these explosions eject a little bit and some eject a whole lot.”

The astronomers hope their new findings will spur the development of improved models for these white dwarf explosions and a more complete understanding of the relationship between Type Iax and normal Type Ia supernovae and their corresponding star systems.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington.

For images and more information about Hubble, visit http://www.nasa.gov/hubble and http://hubblesite.org/news/2014/32.




All of this week's top headlines to your email every Friday.


 
 

 

News Briefs February 27, 2015

Ukraine will start pulling back heavy weapons in the east Ukraine’s military says it will start pulling back its heavy weapons from the front line with Russian-backed separatists as required under a cease-fire agreement. The Defense Ministry said in a statement Feb. 26 that it reserved the right to revise its withdrawal plans in the...
 
 

Northrop Grumman’s AstroMesh reflector successfully deploys for NASA’s SMAP satellite

The NASA Jet Propulsion Laboratory successfully deployed the mesh reflector and boom aboard the Soil Moisture Active Passive spacecraft, a key milestone on its mission to provide global measurements of soil moisture. Launched Jan. 31, SMAP represents the future of Earth Science by helping researchers better understand our planet. SMAP’s unmatched data capabilities are enabled...
 
 
NASA photograph by Brian Tietz

NASA offers space tech grants to early career university faculty

NASA photograph by Brian Tietz Tensegrity research is able to simulate multiple forms of locomotion. In this image, a prototype tensegrity robot reproduces forward crawling motion. NASA’s Space Technology Mission Director...
 

 
navy-china

USS Fort Worth conducts CUES with Chinese Navy

The littoral combat ship USS Fort Worth (LCS 3) practiced the Code for Unplanned Encounters at Sea (CUES) with the People’s Liberation Army-Navy Jiangkai II frigate Hengshui (FFG 572) Feb. 23 enhancing the professional ma...
 
 

AEGIS tracks, simulates engagement of three short-range ballistic missiles

The Missile Defense Agency and sailors aboard the guided-missile destroyers USS Carney (DDG 64), USS Gonzalez (DDG 66), and USS Barry (DDG 52) successfully completed a flight test involving the Aegis Ballistic Missile Defense weapon system. At approximately 2:30 a.m., EST, Feb. 26, three short-range ballistic missile targets were launched near simultaneously from NASA’s Wallops...
 
 

DOD seeks novel ideas to shape its technological future

The Defense Department is seeking novel ideas to shape its future, and officials are looking to industry, small business, academia, start-ups, the public – anyone, really – to boost its ability to prevail against adversaries whose access to technology grows daily. The program, called the Long-Range Research and Development Plan, or LRRDP, began with an...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>