Thursday, July 17, 2008

Magnetic Galaxies


From the European Southern Observatory at Paranal Chile: Astronomers have found that young galaxies are surprisingly magnetic. Early in the Universe's history, these galaxies already had strong magnetic fields. This will force a rethink of how galaxies, including the Milky Way, first formed.

Quasars are extremely bright objects that predate the galaxies. By observing distant quasars, astronomers found that their light had passed through magnetic fields. These fields corresponded to the locations of galaxies. When the Universe was only 1/3 its present age, the magnetic fields were as strong as they are today. The results appear in the July 17 issue of NATURE.

We must ask, what caused the fields in the first place? Every galaxy ever examined contains at its centre a supermassive Black Hole. This singularity causes huge magnetic fields to form in its vicinity. If the field billions of years ago was just as strong, the Black Hole must have been just as big. Rather than growing along with the galaxy, the Black Hole was supermassive from the start. The quasars, even older, contained giant Black Holes when the Universe was extremely young.

More and more evidence indicates that supermassive Black Holes are primordial, formed from quantum fluctuations shortly after the Big Bang. Previously scientists thought that Primordial Black Holes were tiny because of the speed of light. Size of a PBH is limited by a horizon distance within light's reach. The supermassive Black Holes within galaxies, including ours, indicate a changing speed of light.

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3 Comments:

Blogger mark said...

it's beautiful

5:59 AM  
Blogger nige said...

That's fascinating news! Usually the mechanism for magnetic fields is the circulation of electric charge, otherwise magnetic particles would soon disappear as the organization of magnetic dipoles disappeared.

Because electromagnetism is a strong fundamental force compared to gravity, and because gravity seems to dominate in the structure of the solar system, galaxies and the universe, it's clear that any net electric charges on large objects like stars are relatively small.

One approach to the problem of whether stars are electrically charged is to examine the contents of the solar wind which they emit. If there is an excess of negative over positive charges escaping from the sun, then the sun will be left with an electric charge.

However, both electrons and protons form the solar wind. It's obvious that if the sun allowed mainly electrons to escape (because they're lighter and for a given velocity in the ionized plasma at the sun's surface they have less weight binding them to the sun by gravity than protons), then that excess of electrons escaping would leave the sun with a net positive charge.

This would eventually start to pull back electrons, while some protons would start to escape far more easily because they'd be repelled away from the positive charged sun (despite their large mass). Hence, there is an automatic mechanism in place whereby any net electric on a star will soon be cancelled out, and after a few oscillations between negative and positive net charge, a star will settle down in an electrically neutral equilibrium.

It's similar with planets. If gravity draws more of the heavy protons in the solar wind to a planet than light electrons, the the planet will acquire a positive electric charge.

But as that occurs, the planet will become repulsive to protons and very attractive to electrons! So it will soon stop attracting so many heavy protons by gravity, and start instead attracting an excess of electrons due to the positive charge it has!

So it will rapidly become electrically neutral.

This simple mechanism means that you should expect all stars and other objects like planets in space to be electrically neutral.

So the idea that the magnetic fields in a galaxy are due to electrically charged circulating stars and planets is wrong.

So I think it's fascinating that supermassive black holes are responsible for those magnetic fields!

"More and more evidence indicates that supermassive Black Holes are primordial, formed from quantum fluctuations shortly after the Big Bang."

That's a very interesting idea! I wonder exactly what the mechanism is for the magnetic field? If the black hole is electrically charged and is spinning, then it would have a magnetic field?

One observed feature of a black hole is the effect of gravity, so that in the mainstream model of quantum gravity (exchange of spin-2 gravitons between mass-energy regions), gravitons must be able to escape from a black hole gto cause gravitational effects.

By analogy to this escape gravitons to cause gravitational effects, electromagnetic gauge bosons would also be able to escape from a black hole in the same way, causing external magnetic fields as a result of the spinning charged matter inside the black hole!

If so, maybe we could calculate the amount of electric charge inside the black hole that is required to produce the observed magnetic field outside the black hole? Or is there another mechanism involved? Rotating neutron stars like pulsars are surrounded by very strong magnetic fields, too.

12:40 PM  
Blogger L. Riofrio said...

Thanks mark, I enjoy your indifferent eye too. Friday's post is even more spectacular.

For nige: Your ideas on electromagnetism are always informed and thoughtful.

4:59 PM  

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