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Supernovae are among astronomers most important tools for exploring the history of the universe. Their frequency allows us to examine how active star formation was, how heavy elements have developed, and the distance to galaxies across vast distances. Yet even these titanic explosions are only so bright, and there’s an effective limit on how far we can detect them with the current generation of telescopes. However, this limit can be extended with a little help from gravity.
One of the consequences of Einstein’s theory of general relativity is that massive objects can distort space, allowing them to act as a lens. While first postulated in 1924, and proposed for galaxies by Fritz Zwicky in 1937, the effect wasn’t observed until 1979 when a distant quasar, an energetic core of a distant galaxy, was split in two by the gravitational disturbances of an intervening cluster of galaxies.
While lensing can distort images, it also provides the possibility that it may magnify a distant object, increasing the amount of light we receive. This would allow astronomers to probe even more distant regions with supernovae as their tool. But in doing so, astronomers must look for these events in a different manner than most supernova searches. These searches are generally limited to the visible portion of the spectrum, the portion we see with our eyes, but due to the expansion of the universe, the light from these objects is stretched into the near-infrared portion of the spectrum where few surveys to search for supernovae exist.
But one team, led by Rahman Amanullah at Stockholm University in Sweden, has conducted a survey using the Very Large Telescope array in Chile, to search for supernovae lensed by the massive galaxy cluster Abell 1689. This cluster is well known as a source of gravitationally lensed objects, making visible some galaxies that formed shortly after the Big Bang.
In 2009, the team discovered one supernova that was magnified by this cluster that originated 5-6 billion lightyears away. In a new paper, the team reveals details about an even more distant supernova, nearly 10 billion lightyears distant. This event was magnified by a factor of 4 from the effects of the foreground cluster. From the distribution of energy in different portions of the spectrum, the team concludes that the supernova was an implosion of a massive star leading to a core-collapse type of supernova. The distance of this event puts it among the most distant supernovae yet observed. Others at this distance have required extensive time using the Hubble telescope or other large telescopes.
I wonder if a gravitational lens might amplify the effects of a ‘gravity wave’? making them easier to discern? and if so, how that effect might be observed?
Or is it that a gravitational lens IS the effect of a (continuous?) gravity wave?
A gravity wave is similar to an electromagnetic wave in that both are the occurrence of the field which propagates at the speed of light and is removed form their source. A static gravity field might be compared to the Coulomb field of an electric charge. In that case the field is tied to their source. The gravitational lens is generically not that different from the gravity field of the sun, which deflects the path of light rays from distant stars.
As for mini-black holes, or quantum black holes, it is possible that quantum amplitudes for quantum black holes can exist in trans-TeV physics. These are not black holes per se, but are amplitudes with BPS Noether charges with black hole-like properties. A somewhat larger mini-black hole, say with 10^{15} g of mass or larger, exhibit a classical back reaction when they absorbe or emit a quanta of radiation. However, this is a very tiny amount of energy.
LC
LC, with all the g-waves having different origins, propagation speeds, propagation strengths how are we expected to sort the data into the proper niches.
When looking for those g-waves having a Big Bang origin we would need to have a lot of the background noise already measured to subtract from the metric in the correct fashion to determine origin and type — which is whatever it might be.
In practice, the use of an optical prism for optical waves, a group-velocity dispersion (GVD) prism for higher and lower frequencies than our selected visible white light, reveal the side bands, the standing waves, the notching of all these frequencies we measure. Something such as this is probable for g-waves. For example, g-waves may act much as EM waves in that they can reinforce, cancel, in effect disturb the ‘contents’ of a fellow traveler or an intersecting intruder.
If AM vs FM methods of g-wave propagation exist and can be measured across the g-wave spectrum what might we find.
Can another massive object such as our sun change the q-wave crests and troughs such that at some point in our (or the satellite system being used) yearly orbit around such a massive body as the Sun those measured g-waves will measurably reflect that interference or reinforcement effect.
Mary
Gravity waves are not quite the same as optical waves with respect to dispersion. First off, in vacuum gravity waves move at the universal speed, v = c, the speed of light. Gravity waves are fundamentally nonlinear, and only in the weak limit do they asymptote to linearity. For there to be dispersion of a linear weak gravity wave there has to be a strong coupling with matter. In electromagnetism the electric displacement vector D = ?E and magnetic intensity H = B/? reflect material interactions so that c’ = 1/sqrt{??} which can in general be different from c with c’ = c/n. The only way I could imagine something like this happening is for a gravity wave passing through a neutron star. The neutron star might act as a spherical lens. However, I am not sure about this. Even if this is the case a gravity wave propagating from the distant universe will only have a tiny change when it passes through a dense body.
LC
Yes this would magnify a gravity wave. A gravity wave from a distance would be weak and essentially a linear wave. A gravity wave has energy content to it, though that is difficult to define for a strong gravity wave it is easy enough for a weak linear wave, and the wave would move in accordance with a background spacetime curvature. By virtue of being a linear wave it would behave exactly as would an electromagnetic wave, or light.
LC
Wondering, or is that wandering further? Has anyone using LIGO experimentation thought of looking at gravity waves as a method of communication?
Yes please… http://astronomyonline.org/Astrobiology/SETIAlternatives.asp
Curiously, should the CERN discovery of ‘faster than light’ neutrino’s prove justified, how might neutrino’s then be ‘bounced’ off a large gravity well to propagate a signal? Am I getting ahead of myself here? LOL~
There is a problem with trying to send a signal with gravity waves. To send a signal one has to set up the signal source in some set of initial conditions. With EM fields since there are positive and negative charges this is not too big a problem, for the information with setting up the initial conditions is small due to equal + and – charges. With mass you do not have this advantage. So setting up the initial conditions becomes part of the signal, which further determines your signal later in time. This is the Cauchy data problem, which is a tough issue in general relativity.
It also has to be pointed out that mass-energy couples to curvature by a coupling 8?G/c^4. I leave it as an exercise to compute this and see how small it is. Getting a sufficient amount of mass-energy together to send a signal with a gravity wave would be tough.
I would for now ignore the faster than light neutrino matter. I really think this is going to blow over. This measurement is not consistent with supernova SN1987A data.
LC
Agreed.. the FTL finding will probably turn out to be a sensor anomaly or data processing gap in the instrumentation. ~Poof~
GWT = Gravity Wave Transmitter, or is that God What Tenacity? How about ‘pinging’ a (mini?) black hole by injecting pulsed mass concentrations?