Daily Image
21-09-2007ET phone home!
| Submitter: | Michael Garrett |
| Description: | ET phone home! Astronomers are driven by the need to understand the evolution of the Universe across cosmic time: from the smooth, almost featureless microwave background radiation associated with the afterglow of the big bang, to the rich and complex systems of stars and galaxies that we see all around us today. A very special example of this complexity is life itself, and intelligent life and human beings in particular. One of the most compelling questions is whether this complexity is unique to planet Earth or whether intelligent life is wide-spread across the galaxy and the rest of the Universe. In recent years, searches for Extra-terrestrial Civilisations (ETC) have been spear-headed by the SETI institute (www.seti.org), but so far searches for artificial radio signals have been unsuccessful (or so we are told!). Next generation radio telescopes can do much better than existing instruments. LOFAR may well be the instrument of choice for such searches - (i) LOFAR operates at low radio frequencies where we expect leakage radiation (i.e. narrow band signals from extra-terrestrial TV and radio broadcasts) to be brightest (at least for some significant part of an ETC's lifetime), (ii) LOFAR is more sensitive and has better spectral resolution than any other telescope at these low frequencies, and (iii) LOFAR also has a huge field of view, permitting many stars to be surveyed simultaneously. Most SETI surveys assume that natural emission from an ETC's parent star will be insignificant compared to artificial, narrow-band tv and radio signals. However, this is based on our detailed understanding of one star, the Sun. In order to study the statistical properties of normal, solar type stars, Ivan Marti-Vidal (U of Valencia) and I, have stacked 32000 NVSS 1.4 GHz VLA images together, with each radio image centred on a magnitude limited sample of G-type (solar-like) stars, drawn from the Sloan Digital Sky Survey (SDSS). The stacked image (see above) reaches a noise level of only a few microJy, and, as expected, there is no statistical detection of natural emission from this class of star. Any ETC signal would surely be washed out by the large size of our sample and the very poor spectral resolution employed. Nevertheless, it is fun to stare at this image and wonder whether signals from an ETC might be lurking there, buried deep in the noise of this image. Perhaps LOFAR will one day detect such ETC signals - time will tell! |
| Copyright: | ASTRON |
| Tweet |  |