Gemini North Reveals Pearl-Like Knots in the Remnant of a Supernova Witnessed in the Year 1181

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Supernova remnant Pa 30

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Gemini North’s laser shines through airglow

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Pan on supernova remnant Pa 30


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Zooming into supernova remnant Pa 30

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Cascading knot structure of historic supernova remnant are uncovered in new observations from the Gemini North telescope in Hawai‘i

The Gemini North telescope located on Maunakea in Hawai‘i has revealed the most detailed view yet of Pa 30, the likely remnant of the historic supernova seen in the year 1181. The new observations reveal that its famous “firework” filaments are not smooth streaks, but chains of tiny knots.

No, this is not a firework display. This is Pa 30 — the likely remnant of the historic supernova witnessed in the year 1181, now captured here in unprecedented detail by the Gemini North telescope, one half of the International Gemini Observatory, partly funded by the U.S. National Science Foundation (NSF) and operated by NSF NOIRLab. This image was captured with the Gemini Multi-Object Spectrograph (GMOS), and it shows that the remnant’s unmistakable firework-shaped ejecta take a cascading knot-like structure.

The historic supernova, named SN 1181, is one of only five supernovae in the Milky Way that were observed from Earth before the invention of the telescope. Eight separate texts show that Chinese, Japanese, and Arabic astronomers first observed the supernova between 4 and 6 August 1181. The supernova remained visible in the constellation Cassiopeia for 185 days. According to what we know about how stars end their lives, the colossal explosion would have left something behind. Pa 30, a system composed of a blue central star and surrounding firework-shaped shell, is the top candidate for this supernova remnant.

Pa 30 was only discovered in 2013 through a citizen science campaign to find planetary nebulae in Wide-field Infrared Survey Explorer (WISE) data. It was the 30th nebula found by American amateur astronomer Dana Patchick. Follow-up imaging on the KPNO 2.1-meter Telescope and the Hiltner 2.4-meter Telescope, both located at NSF Kitt Peak National Observatory (KPNO), a Program of NSF NOIRLab, revealed faint, diffuse nebular emission and remarkable radial filaments threading the nebula in a nearly perfect sphere. Based on its estimated age and brightness, scientists consider Pa 30 to be the likely remnant of SN 1181.

Analysis of the new observations from Gemini North, which was led by Timothy Cunningham (Center for Astrophysics — Harvard & Smithsonian) and Ilaria Caiazzo (Institute of Science and Technology Austria), reveals about ten times more filamentary structure in Pa 30 than previously seen. It also shows that the radial filaments are made of consistent chains of tiny knots of gas, rather than smooth streaks as previously thought. This knotty structure suggests that there may have been thermal or density variations in the circumstellar medium that shaped the supernova ejecta as it expanded radially away from the explosion.

Pa 30 is unique among all known supernova remnants. The central star remaining after the explosion, IRAS 00500+6713, is extremely hot, with a temperature of about 200,000°C (~360,000°F). It also possesses very fast stellar winds that move at around 16,000 kilometers per second (~10,000 miles per second).

Surviving remnant stars are expected to be “kicked” away during the powerful supernova explosion. However, the central star of Pa 30 appears almost exactly centered in the remnant. This curious configuration implies that the explosion was quite symmetrical, and it rules out a large kick that could have knocked the star off-center. From this, the researchers conclude that SN 1181 was an extremely rare Type Iax supernova. Unlike the standard high-energy explosions of Type Ia supernovae that wipe out their stars, Type Iax supernovae are lower-energy, incomplete explosions that leave behind a surviving remnant star. Pa 30 is the only known Type Iax remnant in the Milky Way.

The story of SN 1181 is one of humans working together, across time and space, to understand the changing Universe. As new astronomical questions arrive every day, SN 1181 invites us to wonder what mysteries remain unsolved from the distant past.

Source: NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab)/News

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More information

Analysis of this data is presented in a paper titled “Detection of knots in the supernova type Iax remnant Pa 30” appearing in The Astrophysical Journal. DOI: 10.3847/1538-4357/ae9cb2

The team is composed of T. Cunningham (Center for Astrophysics — Harvard & Smithsonian [CfA]; now University of Warwick), I. Caiazzo (Institute of Science and Technology Austria), J. C. Raymond (CfA), and S. J. Kenyon (CfA).

NSF NOIRLab, the U.S. National Science Foundation center for ground-based optical-infrared astronomy, operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), NSF Kitt Peak National Observatory (KPNO), NSF Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and NSF–DOE Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona.

The scientific community is honored to have the opportunity to conduct astronomical research on I’oligam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence of I’oligam Du’ag to the Tohono O’odham Nation, and Maunakea to the Kanaka Maoli (Native Hawaiians) community.

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Links

• Explore Pa 30 in more detail
• Read the paper: Detection of knots in the supernova type Iax remnant Pa 30
• ISTA press release
• CfA press release
• Photos of the Gemini North telescope
• Videos of the Gemini North telescope
• Check out other NOIRLab Photo Releases

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Contacts:

Timothy Cunnigham
Center for Astrophysics — Harvard & Smithsonian
Email: timothy.cunningham@cfa.harvard.edu

Ilaria Caiazzo
Institute of Science and Technology Austria
Email: ilaria.caiazzo@ist.ac.at

Josie Fenske
Public Information Officer
NSF NOIRLab
Email: josie.fenske@noirlab.edu

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Extragalactic peculiarity

ESO 162-17 

Credit: ESA/Hubble & NASA

This galaxy goes by the name of ESO 162-17 and is located about 40 million light-years away in the constellation of Carina. At first glance this image seems like a fairly standard picture of a galaxy with dark patches of dust and bright patches of young, blue stars. However, a closer look reveals several peculiar features.

Firstly, ESO 162-17 is what is known as a peculiar galaxy — a galaxy that has gone through interactions with its cosmic neighbours, resulting in an unusual amount of dust and gas, an irregular shape, or a strange composition.

Secondly, on 23 February 2010 astronomers observed the supernova known as SN 2010ae nestled within this galaxy. The supernova belongs to a recently discovered class of supernovae called Type Iax supernovae. This class of objects is related to the better known Type-Ia supernovae.

Type Ia supernovae result when a white dwarf accumulates enough mass either from a companion or, rarely, through collision with another white dwarf, to initiate a catastrophic collapse followed by a spectacular explosion as a supernova.  Type Iax supernovae also involve a white dwarf as the central star, but in this case it may survive the event. Type Iax supernovae are much fainter and rarer than Type Ia supernovae, and their exact mechanism is still a matter of open debate.

The rather beautiful four-pointed shape of foreground stars distributed around ESO 162-17 also draws the eye. This is an optical effect introduced as the incoming light is diffracted by the four struts that support the Hubble Space Telescope’s small secondary mirror.

Source: ESA/HUBBLE - Space Telescope

NASA's Hubble Finds Supernova Star System Linked to Potential 'Zombie Star'

Supernova 2012Z in Spiral Galaxy NGC 130

Credit: NASA, ESA, C. McCully and S. Jha (Rutgers University), R. Foley (University of Illinois), and Z. Levay (STScI).

Acknowledgment: Hubble Heritage Team (STScI/AURA), and A. Riess (JHU/STScI)

 Release Images

Astronomers using NASA's Hubble Space Telescope for the first time have spotted a star system that later produced an unusual supernova explosion of a white dwarf, the stripped-down core of an ordinary star at the end of its life.

Examining archived Hubble images taken before the supernova, astronomers say they have detected the blue companion star of the white dwarf. The white dwarf slowly siphoned fuel from its companion, eventually igniting a runaway nuclear reaction in the dead star, and producing a weak supernova blast.

This particular supernova is classified as a Type Iax, a recently identified class of stellar explosion. These exploding stars are less energetic and fainter than Type Ia supernovae, which also originate from exploding white dwarfs in binary systems. Astronomers originally thought these weaker stellar blasts were unique Type Ia supernovae. So far, they have identified more than 30 of these mini-explosions, which occur at one-fifth the rate of Type Ia supernovae.

"Astronomers have been searching for decades for the progenitors of Type Ia's," said 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 tomorrow in the journal Nature.

The weak supernova, dubbed SN 2012Z, was found in the Lick Observatory Supernova Search in January 2012. Fortuitously, Hubble's Advanced Camera for Surveys also observed the supernova's host galaxy, NGC 1309, in 2005, 2006, and 2010, before the supernova outburst. NGC 1309 resides 110 million light-years away. Curtis McCully, a graduate student at Rutgers and lead author of the team's paper, reprocessed the pre-explosion images to make them sharper and noticed an object at the supernova's position. "I was very surprised to see anything at the supernova's location. We expected that 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.

The likelihood that the object detected was just a chance alignment unrelated to the supernova is less than one percent. After studying the object's colors and computer simulations showing possible type Iax progenitor systems, the team concluded that what they were seeing was most likely the light of a star that had lost its outer hydrogen envelope, revealing its helium core.

"Back in 2009, when we were just starting to understand this class, we predicted that 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 with this Hubble study, but it is essentially validation of our claim."

According to the team, one possible scenario for the oddball star system predicts that a seesaw game ensues between the stars, with each star donating mass to the other. The stars originally weighed about seven and four times that of our Sun, respectively. The more massive seven-solar-mass star evolves quickly, dumping its hydrogen and helium onto its smaller companion. Now slimmed down to just one solar mass, the once-more- massive star is left with a carbon and oxygen core, becoming a white dwarf. The companion star, which began with just four solar masses, is now bulked up and begins to evolve quickly, growing larger and engulfing the white dwarf. The outer layers of this "combined" star are ejected, leaving behind the white dwarf and the two-solar-mass helium core of the companion star. The white dwarf is still siphoning matter from its partner until it becomes unstable and explodes as a mini-supernova, ejecting about half a solar mass of material.

Unlike a normal Type Ia supernova, which destroys its white dwarf, the explosion of a Type Iax is thought to leave behind a battered and bruised white dwarf. Since this dead star comes back to life as it explodes, astronomers have nicknamed it a "zombie star."

The team acknowledges that they can't totally rule out other possibilities for the object's identity, including the possibility that it was simply a single, massive star that exploded as a supernova. To settle those uncertainties and confirm their hypothesis, the team plans to use Hubble again in 2015 to observe the area when the supernova's light has dimmed enough to show any possible zombie star and helium companion.

The astronomers already have seen the aftermath of one Type Iax supernova blast. Hubble images taken of supernova 2008ha in January 2013, more than four years after it exploded, show an object at the supernova's location. The supernova resides in the galaxy UGC 12682, located 69 million light-years away. The object could be either the zombie remnant star or the companion. Based on the object's colors, the team suggests in a separate paper that the star is the companion, weighing more than three solar masses. It is significantly less luminous and redder than the SN 2012Z progenitor system. The findings will be published in the Aug. 11 issue of 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, the SN 2008ha paper's lead author. "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 progenitors.

CONTACT

Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4493 / 410-338-4514
dweaver@stsci.edu / villard@stsci.edu

Source: HubbleSite

Astronomers Discover a New Kind of Supernova

This artist's conception shows the suspected progenitor of a new kind of supernova called Type Iax. Material from a hot, blue helium star at right is funneling toward a carbon/oxygen white dwarf star at left, which is embedded in an accretion disk. In many cases the white dwarf survives the subsequent explosion.  Credit: Christine Pulliam (CfA). High Resolution Image (jpg) - Low Resolution Image (jpg)

Cambridge, MA - Until now, supernovas came in two main "flavors." A core-collapse supernova is the explosion of a star about 10 to 100 times as massive as our sun, while a Type Ia supernova is the complete disruption of a tiny white dwarf. Today, astronomers are reporting their discovery of a new kind of supernova called Type Iax. This new class is fainter and less energetic than Type Ia. Although both varieties come from exploding white dwarfs, Type Iax supernovas may not completely destroy the white dwarf. 

"A Type Iax supernova is essentially a mini supernova," says lead author Ryan Foley, Clay Fellow at the Harvard-Smithsonian Center for Astrophysics (CfA). "It's the runt of the supernova litter." 

Foley and his colleagues identified 25 examples of the new type of supernova. None of them appeared in elliptical galaxies, which are filled with old stars. This suggests that Type Iax supernovas come from young star systems.

Based on a variety of observational data, the team concluded that a Type Iax supernova comes from a binary star system containing a white dwarf and a companion star that has lost its outer hydrogen, leaving it helium dominated. The white dwarf collects helium from the normal star. 

Researchers aren't sure what triggers a Type Iax. It's possible that the outer helium layer ignites first, sending a shock wave into the white dwarf. Alternatively, the white dwarf might ignite first due to the influence of the overlying helium shell. 

Either way, it appears that in many cases the white dwarf survives the explosion, unlike in a Type Ia supernova where the white dwarf is completely destroyed. "The star will be battered and bruised, but it might live to see another day," says Foley. 

Foley calculates that Type Iax supernovas are about a third as common as Type Ia supernovas. The reason so few have been detected is that the faintest are only one-hundredth as bright as a Type Ia. 

"Type Iax supernovas aren't rare, they're just faint," explains Foley. "For more than a thousand years, humans have been observing supernovas. This whole time, this new class has been hiding in the shadows." 

The Large Synoptic Survey Telescope, in which the CfA is a partner, could discover thousands of Type Iax supernovas over its lifetime. 

This research has been accepted for publication in The Astrophysical Journal and is available online.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

For more information, contact:

David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
daguilar@cfa.harvard.edu
 
Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463
cpulliam@cfa.harvard.edu

Source:  Harvard-Smithsonian Center for Astrophysics