Onlangs stuurde ik naar deze lijst het persbericht "Astronomen brengen baby-quasar in kaart". Gerard Peet vroeg zich af of nu een positie op 1.5 miljard jaar leeftijd van het heelal en een afstand van 13.5 miljard lichtjaar betekent dat het heelal volgens deze waarnemingen 15 miljard jaar oud is. Ik vroeg het aan een van de auteurs. Antwoord: mogelijk. De rekenkundige fout in de leeftijd van het heelal uit de achtergrondstraling is klein, maar die leeftijd is ook modelafhankelijk. De totale fout kan dus (veel) groter zijn. Het antwoord van prof. Gurvits volgt hieronder. Met vriendelijke groet, Jan de Boer ---------------------------------------------------------------------- Drs. J.A. de Boer, secretaris Koninklijke Nederlandse Vereniging voor Weer- en Sterrenkunde Prinses Irenelaan 1, 9765 AL Paterswolde E-mail [log in to unmask] KNVWS op www.sterrenkunde.nl Tel. 050 309 4290 ------------------------------------------------------------ ----- Original Message ----- From: "Leonid Gurvits" To: <[log in to unmask]> Sent: Wednesday, June 11, 2008 11:14 PM Subject: Re: Fw: Fw: Astronomen brengen baby-quasar in kaart Dear Mr. de Boer, Thank you for the interst and request for clarification. The "distance" (or "light travel time") for the source of our interst is derived from its redshift - the measure of cosmological expansion of the Universe. In the case of the quasar J1427+3312, the redshift is 6.12. This value corresponds to more than 90% (to be precise - 93%) of the age of the Universe. “Translation” of this “relative” timescale into “absolute” one, expressed in years, involves cosmological parameters which define the cosmological model of the Universe, such as the Hubble constant, the density values for various substances of the Universe (baryons, dark matter, dark energy), and others. Over the last years, the latter have become known to us with better accuracy. Some experiments, such as the Cosmic Microwave Background Anisotropy measurements conducted with the NASA WMAP mission give the age of the Universe of 13.72 Gyears with the formal uncertainty (1 sigma RMS) of about 1%. However, this is still a model-dependent result. Verification of the result by means of further cosmological observations (e.g. with the ESA CMB mission Planck and various cosmological tests with discrete sources – supernovae, quasars, galaxies) is one of the most topical tasks of modern cosmology. The most important “property” of the quasar of our interest, J1427+3312, is its location at the age of the Universe which is less than 10% of the Universe’s present age. What exactly is that age is of secondary importance to that property. The values 15, 13.5 and 1.5 Gyears are illustrative and should be seen only as an indication of the cosmological timescale rather than precise "passport" biodata. The latter are still a subject of further investigation. A slightly more detailed version of the press release is posted at the following JIVE web page http://www.jive.nl/press_release_J1427.html I am happy to provide further comments on the matter. Yours sincerely, Leonid Gurvits ============================= Prof. dr. Leonid Gurvits Head of Space Science, Senior Astronomer Joint Institute for VLBI in Europe P.O. Box 2, 7990 AA Dwingeloo The Netherlands