Sunday, August 19, 2007

Pulsar in Galactic Halo


In 1967 the first pulsar was discovered by graduate student Jocelyn Bell with her thesis advisor Anthony Hewish. The pulsar's regular radio pulse was at first thought to be a signal from extraterrestrials. Today they are theorised to be rapidly rotating neutron stars sending beams into Space like lighthouses. 40 years after discovery, the source of pulsar's enormous energy has remained a mystery. For their work on pulsars Hewish was awarded a Nobel Prize, Bell was not. (Memo: Leave thesis advisor out of research.) This year Jocelyn Bell was named a Dame of the British Empire.

Caltech astrophysicist Fritz Zwicky was known for speaking his mind. He described certain colleagues as "spherical bastards" meaning they appeared as such from any angle! Zwicky's expertise on spherical matters was unquestionable. In the 1930's he used the Virial Theorem on the Coma Cluster of galaxies to deduce a halo of invisible mass. In the 1970's astronomer Vera Rubin used galactic rotation curves to similiarly conclude that most of a galaxy's mass was dark. Nature of the "dark" mass surrounding our galaxy has long been a mystery.

This year one discovery may shed light on both mysteries. Astronomer Robert Rutledge of McGill University and colleagues have reported Discovery of an Isolated Compact Object at High Galactic Latitude. Object J141256.0+792204 is apparently a pulsar located in our Milky Way's dark halo, approximately 5100 parsecs above the galactic disk. This object was discovered by the ROSAT spacecraft with further observations by SWIFT, the Chandra X-ray Observatory and our Gemini North telescope on Mauna Kea.

A pulsar's twin beams propagate along magnetic field lines. Their axis is independent of the neutron star's spin axis, causing them to be dragged around like lighthouse beams. Some pulsars are magnetars, with magnetic fields too powerful for our physics to describe. Twin beams of radiation and a magnetic field are both signs of a Black Hole.

The Black Hole could not have been created by the neutron star, or even by the supernova explosion that created the pulsar. The singularity must have been there billions of years before, when the progenitor star was first created. How stars collapsed from diffuse gas has also been a mystery. Black Holes provide the missing link to understand star formation.

The Big Bang created billions of singularities. These were formed from tiny quantum fluctuations grown large by expansion of the Universe. Size of a primordial Black Hole is limited by a horizon related to the speed of light. Because c was much higher, PBH's formed in a variety of sizes. The largest formed voids, clusters and galaxies. Smaller Black Holes were drawn to the big ones, creating dark haloes around galaxies. Many times these smaller holes have collided with the galaxy's dusty disk, and we are the result.

A Black Hole colliding with a dust cloud will draw matter to it but not suck everything up. The small amount that is eaten will turn into energy and cause the rest to grown extremely hot. Heat of millions of degrees is the ONLY process that can ignite nuclear fusion and the birth of a star. Infant stars, which astronomers call Herbig-Haro objects, exhibit the twin beams of a Black Hole. While most of the Sun's energy comes from nuclear fusion, the Black Hole is quietly contributing to the star's power output. Presence of the Black Hole caused the Sun to collapse in the first place, and allows it to burn steadily for billions of years.

Our theories of the Sun have advanced over time. As late as the 1920’s most astronomers would lecture that our Sun was made of iron, and glowed in the sky like a hot poker. Only a young astronomer named Cecilia Payne suggested that the Sun’s spectral lines could be interpreted as hydrogen. Because Payne was a woman, her idea was roundly dismissed. The equations of nuclear fusion were still being worked out, and most scientists doubted that Black Holes exist.

Black Hole energy and nuclear fusion are two of many processes occuring inside stars. As our knowledge of physics advances, so must theories of the Sun. Physicists have long sought to produce energy via nuclear fusion. Despite decades of work and billions of dollars, they have been unable to produce a sustained reaction. Hint: You need a Black Hole.

Only occasionally will a Black Hole reveal its presence. If a dying star is over Chandrasekhar's limit of 1.4 solar masses, it will eventually collapse catastrophically. Sudden influx of a star's mass into the Black Hole is the ONLY mechanism powerful enough to ignite a supernova. This titanic explosion rips the outer layers away, leaving behind a small dense remnant, a neutron star. If the Black Hole has enough angular momentum, it will produce a magnetic field and twin jets. Because the jet axis is often different from the neutron star's rotation axis, the jets will rotate through Space exactly as observed. A Black Hole is the ONLY mechanism that could produce twin jets and a magnetic field.

A Black Hole is the ONLY object that can make billions of clouds collapse into stars, the ONLY mechanism that can power a supernova, and the ONLY mechanism that can create the jets and magnetic field of a pulsar. Black Holes could be ubiquitous, from the galactic halo to the interior of our Sun. The 95.49% of our Universe that is not baryons could be dominated by Black Holes.

Discovery of a pulsar in the Milky Way's dark halo may also be seen as discovery of a Black Hole. Ruttledge's team notes that this pulsar in the galactic halo could be the tip of an iceberg. For every Black Hole that can be found by its pulsar jets, there could be many more without jets. The galaxy's invisible halo of dark mass could be filled with Black Holes. There are more things in Heaven and Earth, Horatio, than are dreamt of in your philosophy.

This week Advanced Nanotechnology hosts the Carnival Of Space!

Labels: , , ,

15 Comments:

Anonymous riqie arneberg said...

The pulsar's regular radio pulse was at first thought to be a signal from extraterrestrials.

Today they are theorised to be rapidly rotating neutron stars


All this begs the question "How do the ETs set these stars to rotating?.........

8:28 AM  
Anonymous Anonymous said...

Louise said "... In 1967 the first pulsar was discovered by graduate student Jocelyn Bell with her thesis advisor Anthony Hewish ...".

Actually (as with GRBs) the first human discovery of pulsars was by the USA Military. According to a blog at scienceblogs.com slash catdynamics slash 2007 slash 08 slash schisler.php
"... at the 40 Years of Pulsars conference ...
A gentleman named Charles Schisler stood to speak, introduced by Jocelyn Bell herself, he was a USAF officer ... He was on radar duty, looking for ICBMs coming over the pole or pacific ... He noticed ... a fluctuating signal, which was fixed in RA, and logged it - this was summer of 1967 ...
The next day the signal was there again, but 4 minutes early ... he recognised sidereal drift and figured he had a celestial source.
He went and looked up the sky position, and found it was in Taurus - the Crab Nebula. ...
He asked his superiors what to do, it was not "in their mission", so the sources were noted as background ...
others have mentioned ... that the ... DEW line of early warning stations in the arctic back then ... had seen pulsars ... as early as 1964 for the Thule stations. But, it was all anecdotal. Schisler kept logs and he still has them ...
But, the information, which reveals the DEW radar capabilities was classified. ...".

I wonder how much the USA classified community today knows about physics that is now not disclosed to the public.

Tony Smith

9:33 AM  
Anonymous alex said...

"The Big Bang created billions of singularities. These were formed from tiny quantum fluctuations grown large by expansion of the Universe. Size of a primordial Black Hole is limited by a horizon related to the speed of light"

It is an interesting idea.There is a proof for this statement?

8:01 PM  
Blogger L. Riofrio said...

LOL, riqie. The same way they built pyramids?

For Tony: The DEW discovery is fascinating and deserves its own post.

8:50 PM  
Anonymous mendo said...

Thanks for another interesting post!

One thing about pulsars, I'd thought that the main energy source in a pulsar is its huge rotational kinetic energy? The increase in the period of the Crab pulsar indicates its losing rotational kinetic energy at a rate 10000 times the solar luminosity!

You also mentioned that black holes could start star formation, is your model that the BH gradually accretes matter to form the star, or that its influence is the trigger for stellar mass molecular cloud collapse? In either case, whats the typical BH mass in these scenarios - that's something I don't have a feel for at the moment.

Cheers,

Mendo.

12:53 PM  
Blogger Ryan said...

I'm just a Dumb-ass guy with a BS in Engineering Physics... So I have to ask: If you are right that Black Holes are all about the us (Likely)... How do we safely catch one? (shouldn't there be one in the asteroid belt?) Then the next question is: What can we use it for? (Power? Propulsion?)

1:46 PM  
Blogger L. Riofrio said...

For mendo: The source of a pulsar's energy has been a mystery. A Black Hole would trigger collapse of a gas cloud into a star. Typical mass is about 10^12 kg.

For ryan: No need to downplay your education. If you agree that BH's could exist in the solar system you are ahead of most scientists.

A Black Hole can be caught Ghostbuster-style: hit it with an electric charge and capture it in a magnetic field.

A large asteroid like Ceres, which may somehow be warm enough for liquid water, is a good place to look for one.

Even a tiny BH has immense energy, enough to satisfy any Earthly need. That energy can also be used to move the BH.

7:32 PM  
Anonymous alex said...

To ryan:

It is O'K.It is a science fiction blog.

7:54 PM  
Anonymous Anonymous said...

"A Black Hole is the ONLY object that can make billions of clouds collapse into stars, the ONLY mechanism that can power a supernova, and the ONLY mechanism that can create the jets and magnetic field of a pulsar."

It would really help your case if you actually supported these statements with, yknow, facts.

The main fact I was keeping in mind as I read this post was that the vast majority of astrophysicists disagrees with you on all three of your claims.

7:15 AM  
Blogger Philip said...

I'm afraid I don't understand your interpretation at all. Without going into the black hole statements you made, the basic premise is, I think, in error: the authors of the paper you cite show that this object is consistent with a nearby pulsar, and inconsistent with it being a distant one. It's at high Galactic latitude, but that doesn't mean it's high off the Galactic plane *unless* it's far away. Their results show it's most likely nearby, so it's not all that far off the plane.

7:34 AM  
Anonymous mendo said...

I have to agree with Philip, as reading the paper (revised version), the object could be several kpc above the galactic plane, but the observations are much more consistent with it being nearby.

Louise, you said:

For mendo: The source of a pulsar's energy has been a mystery. A Black Hole would trigger collapse of a gas cloud into a star. Typical mass is about 10^12 kg.

I don't think the energy source is such a mystery, the measured spin down rates combined with neutron star models show rotational energy loss can account for the observed power output (magnetars might be an exception here). This short review from Jodrell Bank is quite interesting on these aspects:

http://www.jb.man.ac.uk/research/pulsar/Education/jenam.pdf

Plus, as the central densities of neutron stars are estimated at 10^11 to 10^12kgcm^-3, I don't get how a 10^12kg BH at the core has much influence outside a tiny central region. Do you see a black hole as the energy source of a pulsar, or just as something that supplies the magnetic field?

Cheers,

Mendo.

1:36 PM  
Anonymous Anonymous said...

You postulate the existence of many small black holes; however, if Dr. Hawkings is correct, hawking radiation should have caused most of these small black holes to evaporate by now. How do you account for their continued existence?

7:51 AM  
Blogger L. Riofrio said...

Size of a Black Hole is limited by a "horizon distance" related to the speed of light. Once it was thought that PBH's would be tiny and would largely have evaporated by now. Because c was much faster near the Big Bang, singularities could have formed in a variety of sizes. If you doubt that, check out "A Hole in the Universe."

9:17 AM  
Blogger alex kaplan said...

This comment has been removed by the author.

11:42 PM  
Blogger alex kaplan said...

No one ever prove that с was greater at the big bang.And there is no connection to the void in the universe

11:43 PM  

Post a Comment

Links to this post:

Create a Link

<< Home

Locations of visitors to this page