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