Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: quibitheed on 19/04/2010 10:36:58
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http://www.newscientist.com/article/dn18775-mysterious-radio-waves-emitted-from-nearby-galaxy.html (http://www.newscientist.com/article/dn18775-mysterious-radio-waves-emitted-from-nearby-galaxy.html)
"Yet it does seem to be moving – and fast: its apparent sideways velocity is four times the speed of light.
A curious object indeed....anyone care to speculate?
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The simplest solution is that the radio source is not actually a moving object as such, but rather the moving point of interaction between a shell of very fast (but sub-luminal) gas thrown off by a star and a relatively stationary band of cool interstellar gas/dust.
The easiest way to imagine it is by thinking of ocean waves striking a beach at an angle and how the breaking wavefronts travel along the beach at a higher speed than their forward speed through the water.
If you start with the waves moving parallel to the beach then the speed that the wavefronts will travel along the beach is the same as their speed through the water but if the wind swings round, so that the waves start hitting the beach at an angle, then although the waves may still be moving forward at the same speed as before, the point at which each wavefront breaks upon the beach moves along the beach faster than the waves are moving through the water. If the wind eventually swings even further around, so that the waves are traveling directly towards the beach i.e. at 90 degrees to the beach, the wavefront will break at every point along the beach simultaneously.
What we can do then, is to think of the shell of energetic gas thrown off by the star as an ocean wave and the band of cool interstellar gas as the beach. When the shell of energetic gas collides with the band of cool interstellar gas it heats it up and generates the radio signals that have been detected, which is equivalent to the ocean wave breaking on the beach.
However, because the shell of energetic gas is colliding with the band of cool gas at an oblique angle the collision isn't occurring all along the band of cool gas simultaneously but has started at one end and is traveling along the band, doing so at a higher speed that the shell of energetic gas is actually moving.
Neither of the two real objects concerned i.e. the shell of energetic gas and the band of cool gas are traveling faster than 'c', but the point where they collide and which acts as the radio source can travel faster than 'c'. It is not a 'real' object though, so nothing is actually violating the speed of light limit.
Note that this is just one possible solution.
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"A bright spot of radio emission emerged over only a few days, quite rapidly in astronomical terms. Since then it has done very little except baffle astrophysicists. It certainly does not fit the pattern of radio emissions from supernovae: they usually get brighter over a few weeks and then fade away over months, with the spectrum of the radiation changing all the while. The new source has hardly changed in brightness over the course of a year, and its spectrum is steady."
If it was two gases producing it, how can it be called 'steady'. Shouldn't it vary over time? To behave the same means that it must have 'moved' as one single spot of unvarying brightness over one year? Can a gas do that when it meets another at an angle, create one single 'moving' spot, releasing energy of the same intensity, over a year? That's not how I expect gases to behave, although it seems quite a bit away, doesn't it?
There should be a possibility to test it in a computer model though? We do know something of gases. As for the idea of a black hole, how would that create the illusion of moving, or do they mean a 'roving black hole' then?
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I think we'd really have to see the data, and have the wherewithall to make sense of it to really comment much further. However, according to our current understanding of physics, it cannot be a real object moving at > 'c'.
So either it is a real object and 'c' is not a an absolute limit, or it's not a real object and the 'c' limit has not been exceeded.
In referring to BH's, I don't think they were thinking in terms of a BH actually moving that quickly but instead, a spinning BH could be issuing a 'jet' from its poles, in a similar manner to the way that spinning neutron stars are believed to be pulsars, and the 'jet' could be sweeping across something, with the same effect as obliquely colliding bands of gas. Once again though, it's not a real object that's moving > 'c' but the point of interaction between two slower structures.
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Thanks for the reply [:)]
I can just about follow what you are getting at and see its logic yet if that were the case I do find it difficult to explain the objects "steady" signature. But, as you say, without more data.....
This is not the first time I have come across brief statements about objects that appear to be moving >c. The first one was the most memorable. It appeared on the Nine O'clock News in about 1977 where in the opening 'headlines' the statement was made that "Scientists have detected an object travelling through the solar system at faster than light speed". My Dad, brother and I waited and waited but the news finished without any further mention of it. Curious. That like other anomalous reports on a wide variety of observations, like stars with isotopic spectra's that give them birth dates older than the big bang, do crop up fairly often. And it makes me wonder how many more rogue spanner in the works observations have been made and never reported. If anyone has others to share I'd love to hear them.
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LeeE.
Nice explanation of your thoughts.
No, I didn't expect 'ftl' either :)
But it's quite interesting all the same.