Our galaxy might hold thousands of ticking 'time bombs'

Sep 06, 2011
New research shows that some old stars known as white dwarfs might be held up by their rapid spins, and when they slow down, they explode as Type Ia supernovae. Thousands of these "time bombs" could be scattered throughout our Galaxy. In this artist's conception, a supernova explosion is about to obliterate an orbiting Saturn-like planet. Credit: David A. Aguilar (CfA)

(PhysOrg.com) -- In the Hollywood blockbuster "Speed," a bomb on a bus is rigged to blow up if the bus slows down below 50 miles per hour. The premise - slow down and you explode - makes for a great action movie plot, and also happens to have a cosmic equivalent.

New research shows that some old stars might be held up by their rapid spins, and when they slow down, they explode as supernovae. Thousands of these "time bombs" could be scattered throughout our Galaxy.

"We haven't found one of these 'time bomb' stars yet in the , but this research suggests that we've been looking for the wrong signs. Our work points to a new way of searching for supernova precursors," said Rosanne Di Stefano of the Harvard-Smithsonian Center for Astrophysics (CfA).

The specific type of Di Stefano and her colleagues studied is called a . It occurs when an old, compact star known as a white dwarf destabilizes.

A white dwarf is a stellar remnant that has ceased nuclear fusion. It typically can weigh up to 1.4 times as much as our Sun - a figure called the Chandrasekhar mass after the astronomer who first calculated it. Any heavier, and gravity overwhelms the forces supporting the white dwarf, compacting it and igniting runaway that blows the star apart.

There are two possible ways for a white dwarf to exceed the Chandrasekhar mass and explode as a Type Ia supernova. It can accrete gas from a donor star, or two white dwarfs can collide. Most astronomers favor the first scenario as the more likely explanation. But we would expect to see certain signs if the theory is correct, and we don't for most Type Ia supernovae.

For example, we should detect small amounts of hydrogen and near the explosion, but we don't. That gas would come from matter that wasn't accreted by the white dwarf, or from the disruption of the companion star in the explosion. Astronomers also have looked for the donor star after the supernova faded from sight, without success.

Di Stefano and her colleagues suggest that white dwarf spin might solve this puzzle. A spin-up/spin-down process would introduce a long delay between the time of accretion and the explosion. As a white dwarf gains mass, it also gains angular momentum, which speeds up its spin. If the white dwarf rotates fast enough, its spin can help support it, allowing it to cross the 1.4-solar-mass barrier and become a super-Chandrasekhar-mass star.

Once accretion stops, the white dwarf will gradually slow down. Eventually, the spin isn't enough to counteract gravity, leading to a Type Ia supernova.

"Our work is new because we show that spin-up and spin-down of the white dwarf have important consequences. Astronomers therefore must take angular momentum of accreting white dwarfs seriously, even though it's very difficult science," explained Di Stefano.

The spin-down process could produce a time delay of up to a billion years between the end of accretion and the supernova explosion. This would allow the to age and evolve into a second white dwarf, and any surrounding material to dissipate.

In our Galaxy, scientists estimate that there are three every thousand years. If a typical super-Chandrasekhar-mass white dwarf takes millions of years to spin down and explode, then calculations suggest that there should be dozens of pre-explosion systems within a few thousand light-years of Earth.

Those supernova precursors will be difficult to detect. However, upcoming wide-field surveys conducted at facilities like Pan-STARRS and the Large Synoptic Survey Telescope should be able to spot them.

"We don't know of any super-Chandrasekhar-mass in the Milky Way yet, but we're looking forward to hunting them out," said co-author Rasmus Voss of Radboud University Nijmegen, The Netherlands.

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More information: This research appears in a paper in the Sept. 1 issue of The Astrophysical Journal Letters and is available online.

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tkjtkj
4.5 / 5 (6) Sep 06, 2011
..New research shows that some old stars might be held up by their rapid spins, and when they slow down, they explode as supernovae.


Are we being averse to the term 'centrifugal force'?? Being "held up" is just pure, plain bad English. Even later in the article it is not clearly explained that 'entropy vrs gravity' are the forces at work here ..
But this is the first ive come across this explanation for white dwarf behaviour .. sounds quite reasonable ..

Noumenon
3.7 / 5 (6) Sep 06, 2011
Entropy is just as poor a description as it's not a force, but a thermodynamic tendency.

I don't think the author meant the phrase "held-up" to indicate a force, but rather a state of the star. They could have said that the star is held-up (or prevented from collapse) by temperature and radiation and/or the centrifugal force of angular momentum.
Roland
5 / 5 (1) Sep 06, 2011
I've got a problem with the spin-down part. That's a loss of energy. Where does it go? The earth used to spin faster, but that energy went to the moon causing it to move away. That decreases tidal drag which causes the energy transfer rate to decline. It's self-limiting. So the companion star would move away, reducing its ability to donate mass, and the spin rate would stabilize.
TopherTO
4.9 / 5 (10) Sep 06, 2011
Let this article mark the first, and last, use of the movie Speed in reference to understanding cosmological events.

Understanding Keanu's acting success is more abstract than any Fermi paradox or Drake equation.
SemiNerd
5 / 5 (2) Sep 06, 2011
Its called space time frame drag. The amount of energy a white dwarf uses to drag the space around it gradually slows it.
Temple
4.6 / 5 (11) Sep 06, 2011
Regretfully,
Oliver K. Manuel
Former PI for NASA's Apollo Program


Objection: Relevance?
Dokudango
5 / 5 (6) Sep 06, 2011
Omatumr...you might want to get that checked.
yyz
5 / 5 (5) Sep 06, 2011
"The spin-down process could produce a time delay of up to a billion years between the end of accretion and the supernova explosion. This would allow the companion star to age and evolve into a second white dwarf..."

In some binary systems, the secondary star may continue periodic mass transfer to the newly minted neutron star, in the process spinning it up into a millisecond pulsar(MSP). These type of evolved systems are thought to be related to the "black widow" MSPs consisting of a MSP and a very low mass compact companion.

Recently work was published about one such peculiar system, PSR J1719-1438, consisting of a MSP and a dense "planet" the mass of Jupiter but thought (in part because of it's inferred density) to be an evolved ultra low mass carbon white dwarf in a 2.2hr orbit: http://arxiv.org/...01v1.pdf

This system is thought to represent a binary companion that just escaped it's "black widow" pulsar.
technodiss
not rated yet Sep 06, 2011
finished reading the comments and i'm so pleased to see people using the correct 'centrifugal' instead of the dumbed down 'centripetal'. glad to see someone else was paying attention in science class
Jeddy_Mctedder
2.8 / 5 (6) Sep 06, 2011
man , i was worried about asteroids hitting earth last week, now this! damn you science!
hard2grep
2 / 5 (3) Sep 06, 2011
What if.... a high mass rogue object passed nearby. Here is another thought... what if the sun blows its outer shell destroying much of the inner solar system leaving excess gas to be accumulated by Jupiter and Saturn. Would there be another sun created out of Jupiter or a binary dwarf system? I know the sun isn't supposed to go supernovae, but it still might have enough to puff a smoke ring.
tkjtkj
not rated yet Sep 06, 2011
What if.... a high mass rogue object passed nearby. Here is another thought... what if the sun blows its outer shell destroying much of the inner solar system leaving excess gas to be accumulated by Jupiter and Saturn. Would there be another sun created out of Jupiter or a binary dwarf system? I know the sun isn't supposed to go supernovae, but it still might have enough to puff a smoke ring.


you mean the mass of our sun is too little to go supernova? .. that one solar mass doesnt make it?
But aren't there opinions that our sun already DID go SN ?
omatumr
1 / 5 (13) Sep 06, 2011
But aren't there opinions that our sun already DID go SN ?


Yes, of course. Here are observations that consensus scientists ignored so world leaders could pretend the Sun is a steady H-fusion reactor that does NOT cause climate change:

www.omatumr.com/D...ata1.htm

www.omatumr.com/D...Data.htm

www.omatumr.com/D...Data.htm

www.omatumr.com/D...Data.htm

www.omatumr.com/D...Data.htm

www.omatumr.com/D...Data.htm

www.omatumr.com/D...Data.htm

www.omatumr.com/D...Data.htm

www.omatumr.com/D...Data.htm

www.omatumr.com/D...Data.htm

www.omatumr.com/D...Data.htm

Summary:
www.omatumr.com/i...Fig1.htm

www.omatumr.com/i...Fig2.htm

www.omatumr.com/i...Fig3.htm

www.omatumr.com/i...Fig4.htm

www.omatumr.com/P...core.htm

After giving away their independence, the space science program was essentially abandoned by the politicians.

Zed123
4 / 5 (6) Sep 06, 2011
@ omatumr ---- Buddy, you need some serious help....
Jayded
3.3 / 5 (6) Sep 06, 2011
@omatumr - I thought we had this discussion. what is with your persistent belief is solar radiation driven climate change? The figures simply do not add up, they do not balance. The sun could be responsible for part of what is seen but not everything. Honestly dude, time to up the dose of prescription meds.
omatumr
1 / 5 (9) Sep 06, 2011
@omatumr - The figures simply do not add up


Is that why data were hidden or ignored? Climate data, nuclear rest mass data, Jupiter data, Apollo data, etc.

Isotope data from the 1995 Galileo Jupiter probe - when released in 1998 [1] - confirmed 1975-1983 reports [2-6]: The Sun is NOT a steady H-fusion reactor as assumed in SSM and AGW models.

1. www.lpi.usra.edu/...5011.pdf

2. "Elemental and isotopic inhomogeneities in noble gases: The case for local synthesis of the chemical elements", Trans MO Acad Sci 9, 104-122 (1975)

3. www.omatumr.com/a...enon.pdf

4. www.nature.com/na...5a0.html

5. www.omatumr.com/a...lies.pdf

6. www.omatumr.com/a...nces.pdf

Conclusion: AGW and SSM are two peas in the propaganda pod that weakened the value of the our scientific, social and economic system

Regretfully it took 40 years to decipher that puzzle!

Oliver K. Manuel
omatumr
1.1 / 5 (8) Sep 07, 2011
Here is the video recording of NASA Administrator releasing the Jupiter isotope data in 1998.

www.youtube.com/w...IFmZpFco
vidar_lund
5 / 5 (1) Sep 07, 2011
@technodiss
finished reading the comments and i'm so pleased to see people using the correct 'centrifugal' instead of the dumbed down 'centripetal'. glad to see someone else was paying attention in science class

Actually there is no such thing as 'centrifugal' force. The perceived force is nothing but a result of a change in a moving body's momentum. There is no actual force pulling the surface of the white dwarf out.
Crazy_council
not rated yet Sep 07, 2011
Its called space time frame drag. The amount of energy a white dwarf uses to drag the space around it gradually slows it.


i thought the same. I wander, if you knew the exact size of the star, and the entropy of the dragging effect, you could work out the size and spin rate of the fabric of the universe.

I have always suspected that the spin rate of the fabric of the universe is the key to understanding the forces we see.
Crazy_council
3 / 5 (2) Sep 07, 2011
omatumr

If the output of the sun had a significant enough effect on the global temp ( more then the other moddles ). the temp curves would closly follow our orbital differences ( i hope i said the correct ). And we would be able to predict with some accurcy, warming or cooling.

We should have frozen regularly on the swing out, and close to boiled on the swing in.

It makes sence to me that the other contributing effects on warming/cooling probebly concel out any overriding affect of the change in output/distance from the sun.
Thecis
not rated yet Sep 07, 2011
Actually there is no such thing as 'centrifugal' force. The perceived force is nothing but a result of a change in a moving body's momentum. There is no actual force pulling the surface of the white dwarf out.


No, there is a force pushing the surface out. It's origin lies in the fusion and the energy that comes from that fusion. Gravity is holding the star together, the whole is in "balance" (at least at our time scale).
SteveL
5 / 5 (5) Sep 07, 2011
Oliver: I have significant issues with your theory that President Nixon and other world leaders conspired to dupe humanity by suppressing the neutron repulsion theory and introducing global warming as a world unifying issue in order to end the cold war.

First and foremost is that President Nixon was one of the most disliked presidents in the last several generations and the thought that liberal politicians, educators and scientests would fall in line with the cover-up rather than to expose "the truth" is non-sensical.

Secondly, I lived through a good portion of the cold war and during that entire time I never once heard of global warming or climate change. Those issues came to the forefront after the fall of the Berlin Wall in 1989. The very first public comment about climate change that I have found record of came from James Hansen in his testimony before the US Senate stating that the extended drought in North America was likely cause by "Global Warming" in 1988 - after Nixon
Twin
not rated yet Sep 10, 2011
Back in the 70's it was global "cooling" and Nixon was there (President 1969 to 1974).
Global cooling was a big deal then.
I guess it wasn't ominous enough though.
Twin
1 / 5 (1) Sep 10, 2011
BTW, It's not global warming anymore; it "climate change".
jsdarkdestruction
3 / 5 (2) Sep 12, 2011
the great thing is that oliver only found out about the pulsar sun and neutron repulsion according to him in 2003. so nixon and everyone must of been able to see into the future to block his theory some 40 yrs before it ever existed......

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