A BIG BANG: In dense neighborhoods of space, two dense stellar remnants known as white dwarfs may collide from time to time. Such a smashup, according to recent computer modeling, could mimic the properties of supernovae produced by more conventional means.
Image: James Guillochon, UCSC
-
The Best Science Writing Online 2012
Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way...
Read More »
Stellar explosions known as type Ia supernovae have proved invaluable to astrophysicists as markers of cosmic distance. Their brightness and consistency in observed properties allow astronomers to use them as "standard candles" to determine distances to objects in the sky. Just a decade ago type Ia supernovae took center stage when researchers harnessed them as evidence that the universe is accelerating in its expansion under the sway of a previously undiscovered influence known as dark energy.
But the mechanisms for forming type Ia supernovae are still not well understood, and a new simulation suggests that a variety of scenarios could lead to these events, which explode with an estimated force of 10 octillion (1028) megatons—more than a billion times as bright as the sun. The standard model holds that a white dwarf—a dense, shrunken remnant of a star that has exhausted its fuel—grows beyond its sustainable mass (approximately 1.4 times the mass of the sun) by accreting matter from a stellar neighbor or by merging with a co-orbiting white dwarf. The result is a runaway nuclear reaction that ignites the previously dim dwarf in a flash of radiation that can be seen billions of light-years across the universe. The use of supernovae as standard candles relies in part on the supposition that a roughly equal amount of fuel is being consumed in each event.
In a paper published in the November 10 Astrophysical Journal Letters, a group of researchers proposes an addition to the family of type Ia progenitors. Rather than a mass transfer or outright merger between a pair of stars locked in an orbital dance, two unbound white dwarfs residing in a dense stellar grouping could collide head-on. The shock of the impact, according to the team's supercomputer simulations, could trigger a thermonuclear reaction that mimics more traditional type Ia supernovae but may burn more fuel than is consumed in the standard 1.4–solar mass event. Some binary-merger scenarios have also been implicated in supersize type Ia explosions, and such variations in supernova starting conditions could complicate their use in future high-precision distance measurements.
Study co-author Enrico Ramirez-Ruiz, an astrophysicist at the University of California, Santa Cruz, points out that in some regions of space, such as in globular clusters, the stellar population density is roughly a million times that of our solar system's relatively sparse environs. "The density of white dwarfs in the cores of globular clusters could be very high," he says, "so the probability of them interacting in a collision is non-negligible."
Ramirez-Ruiz and his co-authors are cautious in their assessment of the contribution of their proposed mechanism to the sum total of observed type Ia supernovae, estimating that colliding white dwarfs likely account for one in a hundred such explosions or fewer. "Nonetheless, it's intriguing," says astronomer Douglas Leonard of San Diego State University, who did not contribute to the study.
"Type Ia supernovae are very exciting objects observationally for cosmology and distance measurements, and yet the embarrassing little secret is that we still don't really know what is exploding," Leonard says. It is widely believed that white dwarfs are at the heart of the events, but the mechanism by which the stellar remnants are ignited remains an open question. "It's a great time to be a theorist," he adds. "If you can figure out some clever way to get them to explode, all bets are still on the table, and you may just turn out to be right."
The more the stellar explosions are studied in detail, he notes, the more diversity they reveal and the more it appears that multiple paths may lead to type Ia supernovae. "There may be many different ways that you can lead a white dwarf to explode, and this one certainly seems reasonable," Leonard says.
Ramirez-Ruiz points out that despite the low estimated abundance rate of collision-induced supernovae, large-scale bulk surveys in the coming years may net hundreds of thousands of type Ia events, including hundreds of the new variety annually. "Once you have such a large number of type Ia's that you're assembling to do cosmology, how standard your model is depends on whether other channels will pollute your sample," he says.
See what we're tweeting about
12 Comments
Add CommentThe progress of science marches on....I believe that there is the likelyhood that future cosmologists will see our idea of "dark matter" as something akin to the interstellar "ether" that was presumed to encompass everything until the late 19th/early 20th century.
Reply | Report Abuse | Link to thisI think you might be on to something here Ungolythe. On the other hand, this stuff we call "dark matter" might account for the distortion in the light waves passing through it causing what we surmise to be "red-shift" and in reality the Universe is a lot smaller than we think!
Reply | Report Abuse | Link to thiscool
Reply | Report Abuse | Link to thiscool stars
Reply | Report Abuse | Link to thisI know right lol
Reply | Report Abuse | Link to thishi
Reply | Report Abuse | Link to thishi it looks kind of like my medication
Reply | Report Abuse | Link to thisGreat story, but I just wanted to point out...
Reply | Report Abuse | Link to thisThis is the funniest headline I have ever read.
With science wrong, and no binary system as the la supernova, slip in a 1 1/3rd size star. The first sign of trouble would be the heliosphere losing energy from its N/S poles Coronal Axis. The axis normally reaches out to define the heliosphere of vibrating, Standing Magnetic Waves (SMW) filled with solar wind pos. protons. That material and vibrating effects combination, created a force field sphere with a bright gas ribbon around the interior equatorial circle. The bright circle came from arcing of 16 galaxy-like arms, whose depleting energy was induced AC electromagnetic (EM) energy from the upper surfaces SMW induction zone of its one of the 16 swirls of ionized plasma dynamos SMW are likely created of helium by pulsing energy forcing electrons away.
Reply | Report Abuse | Link to thisThe arms wrapping around the star; of electromagnetic field lines (EM-FL); in increasing sized spirals; had been suppositioned as Interplanetary Magnetic Fields (IMF). Being an AC-EM energy, then their magnetic surround would have been little with not much proton mass being attached and visible: But, there would have been enough energy to alter neutrino flavor.
Our stars dynamos are seen in NG mag, July 2004 P 19. The equatorial belt rolls across the dynamos, while the dynamos roll across the helium tachocline. The 3 items resemble a roller bearing, with tachocline as inner race, the belt as outer race and dynamos as rollers. From the rollers 16 EM-FL rise up and back to the left to exit to corona and back to the opposed di-polar dynamo end. The lean is because the belt drags the 16 dynamos; as a unit; to advance around the star, but the convection zone EM-FL, hold the works from rotating with the belt. Spicules bases are the small cyclonic storms at high latitudes.
When the cores hydrogen is depleted, and with no reactor effluent being produced, the helium tachocline collapses, which drops the rotating dynamos of proton/electron mix to crash upon the heavier helium. At the same time the heliosphere loses its fusion reaction energy, and draws back along the solar plain with its huge load of hot protons, dragging all bodies along towards the central mass until the sudden stop readies the mass for fusion reactions.
With much helium; to be fed the pulses of created fusion reaction EM energy; the heliums electrons would vibrate and flee away from the atoms other particals, and continue to do that as long as the laser-like pulses continue to affect the helium, which helium would show a high affinity. That effect is called, Ponderomotive Force. So, the helium lobes resemble the laboratory image mentioned below. In both images knots of electrons are pressed away faster than the helium atoms more visible particals; termed as lobes. The images differences are size.
Possibly Ulli Eichmann and associates; whose letter to the Journal Nature of Vol. 461- 29 Oct. 2009 on P. 1261, could explain what occurs to helium when pulsations of an energy; much stronger than the laser they used against a helium atom; are presented.
The Ancient One
That went straight over my head!
Reply | Report Abuse | Link to thisBy the way, Oh Ancient One, are you a computer program that generates random but realistic looking text? There's a certain cadence in your writing that makes me think that you're from an astrophysical version of Andrew Bulkan's Postmodernism Generator.
Moving back onto the subject, 10^28 megatons is quite a difficult to grasp figure - I certainly wouldn't want one of them going off in my kitchen... So in mass energy equivalence it's 4.67x10^25 kg - still too big... but is 1/42,000 of the mass of the sun, too small, but is a mere 7.8 times the mass of the earth being annihilated in one of these explosions. I can just about grasp that now.
Reply | Report Abuse | Link to thisI was expecting it to be at least a Jupiter mass energy equivalent going off in one go to be detectable right the other end of the universe...
The article fails to explicitly mention whether any such events have ever been detected, so I presume this is a purely fictitious, I mean theoretical, event. In this case, I wonder how reliable the nicely estimated 1 in 100 percentage of detected events identified as type Ia SN was arrived at? Might as well have guessed 100 in 100… I think I could write better speculations than those discussed in this article. Thanks for the info...
Reply | Report Abuse | Link to this