The mystery of pulsar rarity at the center of our galaxy

The mystery of pulsar rarity at the center of our galaxy
The galactic core, observed using infrared light and X-ray light. Credit: NASA, ESA, SSC, CXC, and STScI

The galactic center is a happening place, with lots of gas, dust, stars, and surprising binary stars orbiting a supermassive black hole about three million times the size of our sun. With so many stars, astronomers estimate that there should be hundreds of dead ones. But to date, scientists have found only a single young pulsar at the galactic center where there should be as many as 50.

The question thus arises: where are all those rapidly spinning, dense stellar corpses known as pulsars? Joseph Bramante of Notre Dame University and astrophysicist Tim Linden of the University of Chicago have a possible solution to this missing-pulsar problem, which they describe in a paper accepted for publication in the journal Physical Review Letters.

Maybe those pulsars are absent because , which is plentiful in the , gloms onto the pulsars, accumulating until the pulsars become so dense they collapse into a black hole. Basically, they disappeared into the fabric of space and time by becoming so massive that they punched a hole right through it.

Dark matter, as you may know, is the theoretical mass that astrophysicists believe fills roughly a quarter of our universe. Alas, it is invisible and undetectable by conventional means, making its presence known only in how its gravitational pull interacts with other stellar objects.

One of the more popular candidates for dark matter is Weakly Interacting Massive Particles, otherwise known as WIMPs. Underground detectors are currently hunting for WIMPs and debate has raged over whether gamma rays streaming from the galactic center come from WIMPs annihilating one another.

In general, any particle and its antimatter partner will annihilate each other in a flurry of energy. But WIMPs don't have an antimatter counterpart. Instead, they're thought to be their own antiparticles, meaning that one WIMP can annihilate another.

But over the last few years, physicists have considered another class of dark matter called asymmetric dark matter. Unlike WIMPs, this type of dark matter does have an antimatter counterpart.

Asymmetric dark matter appeals to physicists because it's intrinsically linked to the imbalance of matter and antimatter. Basically, there's a lot more matter in the universe than antimatter – which is good considering anything less than an imbalance would lead to our annihilation. Likewise, according to the theory, there's much more dark matter than anti-dark-matter.

Physicists think that in the beginning, the Big Bang should've created as much matter as antimatter, but something altered this balance. No one's sure what this mechanism was, but it might have triggered an imbalance in dark matter as well – hence it is "asymmetric".

The mystery of pulsar rarity at the center of our galaxy
Cosmic Infrared Background ExpeRIment (CIBER) simulation of the density of matter when the universe was one billion years old, as produced by large-scale structures from dark matter. Credit: Caltech/Jamie Bock

Dark matter is concentrated at the galactic center, and if it's asymmetric, then it could collect at the center of pulsars, pulled in by their extremely strong gravity. Eventually, the pulsar would accumulate so much mass from dark matter that it would collapse into a black hole.

The idea that dark matter can cause pulsars to implode isn't new. But the new research is the first to apply this possibility to the missing-pulsar problem.

If the hypothesis is correct, then pulsars around the galactic center could only get so old before grabbing so much dark matter that they turn into . Because the density of dark matter drops the farther you go from the center, the researchers predict that the maximum age of pulsars will increase with distance from the center. Observing this distinct pattern would be strong evidence that dark matter is not only causing pulsars to implode, but also that it's asymmetric.

"The most exciting part about this is just from looking at pulsars, you can perhaps say what dark matter is made of," Bramante said. Measuring this pattern would also help physicists narrow down the mass of the .

But as Bramante admits, it won't be easy to detect this signature. Astronomers will need to collect much more data about the galactic center's pulsars by searching for radio signals, he claims. The hope is that as astronomers explore the galactic center with a wider range of radio frequencies, they will uncover more pulsars.

But of course, the idea that dark matter is behind the missing pulsar problem is still highly speculative, and the likelihood of it is being called into question.

"I think it's unlikely—or at least it is too early to say anything definitive," said Zurek, who was one of the first to revive the notion of asymmetric dark matter in 2009. The tricky part is being able to know for sure that any measurable pattern in the pulsar population is due to dark-matter-induced collapse and not something else.

The mystery of pulsar rarity at the center of our galaxy
Artist’s illustration of a pulsar that was found to be an ultraluminous X-ray source. Credit: NASA, Caltech-JPL

Even if astronomers find this pulsar signature, it's still far from being definitive evidence for asymmetric dark matter. As Kathryn Zurek of the Lawrence Berkeley National Laboratory explained: "Realistically, when dark matter is detected, we are going to need multiple, complementary probes to begin to be convinced that we have a handle on the theory of dark matter."

And asymmetric dark matter may not have anything to do with the missing pulsar problem at all. The problem is relatively new, so astronomers may find more plausible, conventional explanations.

"I'd say give them some time and maybe they come up with some competing explanation that's more fleshed out," Bramante said.

Nevertheless, the idea is worth pursuing, says Haibo Yu of the University of California, Riverside. If anything, this analysis is a good example of how scientists can understand dark matter by exploring how it may influence astrophysical objects. "This tells us there are ways to explore dark matter that we've never thought of before," he said. "We should have an open mind to see all possible effects that dark matter can have."

There's one other way to determine if dark matter can cause pulsars to implode: To catch them in the act. No one knows what a collapsing pulsar might look like. It might even blow up.

"While the idea of an explosion is really fun to think about, what would be even cooler is if it didn't explode when it collapsed," Bramante said. A pulsar emits a powerful beam of radiation, and as it spins, it appears to blink like a lighthouse with a frequency as high as several hundred times per second. As it implodes into a black hole, its gravity gets stronger, increasingly warping the surrounding space and time.

Studying this scenario would be a great way to test Einstein's theory of general relativity, Bramante says. According to theory, the pulse rate would get slower and slower until the time between pulses becomes infinitely long. At that point, the pulses would stop entirely and the would be no more.


Explore further

A warm dark matter search using XMASS: Editors' suggestion of Physical Review Letters

More information: "Detecting Dark Matter with Imploding Pulsars in the Galactic Center." Phys. Rev. Lett. 113, 191301 – Published 3 November 2014. journals.aps.org/prl/abstract/ … ysRevLett.113.191301
Journal information: Physical Review Letters

Source: Universe Today
Citation: The mystery of pulsar rarity at the center of our galaxy (2014, November 6) retrieved 18 September 2019 from https://phys.org/news/2014-11-mystery-pulsar-rarity-center-galaxy.html
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Nov 06, 2014
I have a question and speculation( please be gentle) black holes have rotation and charge right? and the densest heaviest things generally drift more towards the middle density. Well is it possible that black holes and dead celestial bodies migrate quicker to the SMBH sag*a faster and that might not be why we detect them as much. I remember reading that star clusters to similar things with their heaviest bodies and always figured with not much evidence or searching that its probably that black holes and neutron stars could be attracted to sag*A in a similar way . This was still a kewl article :)

Nov 06, 2014
Probably more the case that stars large enough to make pulsars dont form in the inner galaxy. The thick clouds of cold gas are pushed away from the center of the galaxy.

Nov 06, 2014
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Nov 06, 2014
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Nov 06, 2014
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Nov 07, 2014
The pulsars aren't the only problem of naive astrophysics
@ZEPHIR / tritace
naivety means: (Of a person or action) showing a lack of experience, wisdom, or judgement:
http://www.oxford...sh/naive

this means that Naive would be someone who believed in something that was proven false -
something like... well, YOU believing in aw
except that you've been taught that it doesn't exist
so that makes you stupid, not naive

aw/daw is falsified here: http://exphy.uni-...2009.pdf

this means that we have empirical evidence that it does not exist
that evidence is to a high degree of accuracy as well

this means that you promote something that is proven not to exist
it also means your conjecture must be false as it is based upon a false premiss

Nov 07, 2014
The problem is relatively new, so astronomers may find more plausible, conventional explanations.


Though I usually agree looking for more plausible, conventional methods, is this theory really that implausible? And if so, just because DM hasn't been seen/identified yet?

Whatever DM is, we are at least sure it has gravity and we're pretty sure about how much should be floating around saggy A. So it shouldn't be too unconventional to account for it.

Anyhow, Dark Matter sounds too mysterious for layman crackpot morons not to come up with some evil science-debunking tin foil hat theory. I still vote for calling it "seethrough stuff"


Nov 07, 2014
Captain Stumpy wrote, "...it also means your conjecture must be false as it is based upon a false premiss."

Premise, actually.

But there's a little ol' defect in this statement that's bigger than a misspelling.

In logic, a conclusion based on a false premise isn't necessarily false. It's merely unsupported by the logic offered.

The rest of the good Captain's post is accurate. AWT is a mess of illogical, internally-inconsistent ideas supported by ruthlessly cherry-picked evidence and believed with sincere and total conviction by the mentally ill.

Valid, experimentally-supported explanations for dark energy and dark matter aren't known. The logically-correct stance to take with respect to the unknown is not certainty, but tolerance of uncertainty pending better information.

The inability to tolerate uncertainty is a strong symptom of mental illness.


Nov 07, 2014
Premise, actually
But there's a little ol' defect in this statement that's bigger than a misspelling
In logic, a conclusion based on a false premise isn't necessarily false. It's merely unsupported by the logic offered
@Urgelt
my auto-correct spell check sucks

thank you for the clarification

what i am referring to, specifically with zephir is:
Z bases conclusions upon a false premise that is not logically supported by the logic offered, but this is also part of a psychosis

zephir likely suffers from a psychosis called Delusional disorder, which
is an uncommon psychiatric condition in which the patients present with delusions, but with no accompanying prominent hallucinations, thought disorder, mood disorder, or significant flattening of affect
although it is entirely possible that drugs are involved, i would suggest, due to the consistency and lack of fluctuations that commonly come with drug use, that Z is not on drugs

or he is schizophrenic

Nov 07, 2014
Continued @Urgelt
so, yes, i agree with you!

and especially with your finishing comments
The logically-correct stance to take with respect to the unknown is not certainty, but tolerance of uncertainty pending better information.

The inability to tolerate uncertainty is a strong symptom of mental illness
isn't that why things move from conjecture to hypothesis to theory in science?

this is also why it irritates me when the pseudoscience crowd posts BS
it is not a matter of uncertainty with regard to certain pseudoscience topics (aw/daw, eu, creationists)
the topics are debunked and there is empirical evidence against them making the subjects
a mess of illogical, internally-inconsistent ideas supported by ruthlessly cherry-picked evidence and believed with sincere and total conviction by the mentally ill
(GREAT description, BTW)

i prefer uncertainty to stupidity

tis better to patiently (or not) wait for empirical evidence than be proven an idiot publicly

Nov 09, 2014
I don't know what's worse. The article or the comments...

Nov 09, 2014
EU TheTheoryis FAR from being debunked little stunpydick. Its gaining ground almost daily. Cant you read Stumpydick?

Nov 09, 2014
EU TheTheoryis FAR from being debunked little stunpydick. Its gaining ground almost daily. Cant you read Stumpydick?
@deleriousGROUPIE
yes
i read you posting personal conjecture without a shred of scientific evidence

would you please explain how the plasma's carved the grand canyon without (like you) leaving ANY scientific evidence?
or perhaps you would like to show how the plasma's formed the moon craters and not all those pesky OBSERVED asteroids?

eu is DEBUNKED and they refuse to publicly debate actual physicists because they know they have NO empirical evidence
They are Con-men wanting suckers to buy their books
and you got suckered, so now you try to justify it by spreading lies without substantiating evidence

your eu faith belongs in the trash bin, just like zephir's aw/daw
eu is an epic failure

http://www.tim-th...sun.html

more debunking of eu & proof astro's know plasma physics
http://arxiv.org/...92v1.pdf

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