'); }
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)

New Kind of “Runt” Supernovae Could be Lurking Unseen

26 Mar , 2013

by

Imagine this “Death from the Skies” scenario; a tiny supernova lurks unseen near our Sun. Astronomers from the Harvard-Smithsonian Center for Astrophysics (CfA) announced the discovery of just such an object today and while it is not nearby, this new kind of supernova is so faint it has been hiding in the shadows.

Until now, supernovae have come in two main versions. In one scenario, a huge star, 10 to 100 times more massive as our Sun, collapses causing a colossal stellar explosion. Another scenario, known as Type Ia supernovae, occurs when material from a parent star streams onto the surface of a white dwarf. Over time, so much material falls onto the white dwarf that it raises the core temperature igniting carbon and causing a runaway fusion reaction. This event completely disrupts the white dwarf and results in a colossal stellar explosion.

Now astronomers have found a third type that is fainter and less energetic than a Type Ia. Called a Type Iax supernova, it is “essentially a mini supernova,” says lead author of the study Ryan Foley, Clay Fellow at the Harvard-Smithsonian Center for Astrophysics (CfA). “It’s the runt of the supernova litter.”

Being only about one-hundredth as bright as their supernova siblings, Foley calculates that Type Iax supernovae are about as third as common as Type Ia supernovae. The researchers also did not find them in elliptical galaxies, filled with older stars, suggesting that Type Iax supernovae come from young star systems.

So far, Foley and his team identified 25 examples of this new type of supernova. Based on observations, the team found that the new Type Iax supernovae come from binary star systems containing a white dwarf and a companion star that has burned all of its hydrogen, leaving an outer layer that is helium rich.

In a press release, Foley says they are not sure what triggers the Type Iax supernova. One explanation involves the ignition of the outer helium layer from the companion star. The resulting shockwave slams into the white dwarf and disrupts it, causing the explosion. Alternately, the white dwarf might ignite first due to the overlying helium shell it has collected from the companion star.

“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,” says Foley. “The star will be battered and bruised but it might live to see another day.”

Supernovae explosions release so much energy as heat and light that they outshine entire galaxies for brief periods of time. The extremely hot conditions naturally create new heavier elements, such as gold, lead, nickel, zinc and copper. The explosion enriches the surrounding area leaving material for new stars to form.

“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.”

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

, ,



Sort by:   newest | oldest | most voted
Lenard Lindstrom
Guest
Lenard Lindstrom
March 26, 2013 9:41 PM

So what distinguishes a Type Iax supernova from a helium nova?

Torbjörn Larsson
Guest
March 26, 2013 10:18 PM
Here is an Astrobites with similar models. Figure 2 is a nice summary. “A double white dwarf explosion addresses the problems of the white dwarf/red giant model: double-degenerate pairs are both common and would leave no trace (when one white dwarf explodes, so would the other). Pakmor et al. suggest a new explosion mechanism for the white dwarf/white dwarf pair–one that could lead towards a single model for all Type Ia supernovae. In the Pakmor et al. model, a carbon and oxygen white dwarf grabs helium from a second, lower mass white dwarf, which can either be composed of carbon and oxygen, or of pure helium (Figure 2). (Helium white dwarfs come from very low mass stars, in… Read more »
Surak
Member
Surak
March 26, 2013 8:36 PM

Pardon my ignorance, but isn’t this a type of Nova … not Supernova?

Isaac Kirkland
Guest
Isaac Kirkland
March 26, 2013 9:02 PM

Sounds like it to me Ken. Especially if the white dwarf survives, unless “they” have changed the novas’ respective definitions.

Lawrence B. Crowell
Member
Lawrence B. Crowell
March 27, 2013 1:51 PM

It is sort of in between the two in a way. However, because this involves a fusion “flash” of helium it fits more within the definition of a supernova.

LC

Serve vaessen
Member
March 27, 2013 9:02 AM

Which helium layer does explode? The one on the white dwarf or the outher helium layer of the companion star? The CfA press release suggests it’s the helium layer on the white dwarf, but doesn’t state this litterally. I’s a bit uncleaur what John means by the ‘outher helium layer from the companion star.’ Does this mean that de helium layer on the surface of the white dwarf originated on the companion star? In that case the explosion takes place on the white dwarf. Or does he mean the helium layer of the companion star, in wich case the explosion happens on the companion star. Who can bring light into the darkness?

SteveZodiac
Member
SteveZodiac
March 27, 2013 3:37 PM

I wonder why all the “layman” explanations of white dwarfs never mention electron degenerate matter. Surely it isn’t too taxing on the audience to explain that it doesn’t expand when the temperature rises so any increase in temperature causes a runaway reaction.

Astrostevo
Member
Astrostevo
March 28, 2013 12:59 AM

Seems more like a type of cataclysmic variable – dwarf nova more than a proper supernovae variety to me.

Tim Amato
Guest
Tim Amato
March 28, 2013 2:24 AM

—-Either way, it appears that in many cases the white dwarf survives the explosion—-

Does this suggest that in it’s current environment it could possibly explode again?

Read more: http://www.universetoday.com/101005/new-kind-of-runt-supernovae-could-be-lurking-unseen/#ixzz2OnUDXvuX

nannasin smith
Guest
nannasin smith
March 28, 2013 6:24 AM

everything that can explode..

LM250

Asperger+
Guest
March 29, 2013 3:09 PM

A “runt” super nova, with the equivalent of only 50 MiIl years of solar nucleair power. Maybe meganova would be clearer then mini-supernova??

wpDiscuz