With an orbiting space VLBI antenna like 
VSOP
it is
now possible to increase the angular resolution in VLBI imaging by a
factor of 3-5 above the resolution
obtained from earth based VLBI observations. VSOP is a Japanese 8 meter
radio antenna operating at 1.6 and 5 GHz.
Its orbit is elliptical with an apogee of 21,000 km,
a perigee of 560 km, and an orbital period of 6 hours (for details see
eg. Hirabayashi et al. 1998, Science 281, 182 (Iss. 5384)).
The figure above sketches the interferometer geometry in
a
recent observation of the far distant quasar 0836+71, 10 billion
light years away from us. The radio telescopes on earth and the VSOP
satellite
synthesize a gigantic radio telescope with a diameter as
large as the orbit of VSOP (21,000 km). The colored images
inserted in the figure, show the radio maps of this quasar as obtained
during the experiment in September 1997.
On the right we see the radio map made using only the ground array.
Details as small as 2 10-3 arc secs are visible. The highly
collimated outflow is a typical feature observed in
many quasars. Physically it is a flow of very energetic particles
(mainly relativistic electrons or positrons) emanating with a speed as
high as the velocity of light from the core of the quasar. This core is
extremely luminous and presumably
harbors a black hole as heavy as several billion solar masses. The
central and the left image show the inner part of the jet
in more detail, now with higher resolution by adding the data from the
orbiting antenna. The resolution in the left-most
image is only 0.3 10-3 arc secs, allowing to see structures
as small as 3 light years. Most interestingly the jet now shows
kinks and bends, indicative of violent hydrodynamical processes acting
in the inner jet.
From the maps it is also obvious that the supermassive
black hole which triggers the generation of this jet, must be - despite
its high mass - much smaller than this 3 light years. In this small
volume, a luminosity of about 1047 erg/s is produced.
This corresponds
to 1014 (that is, 10 million times 10 million) times the
power of the sun!
(Thomas Krichbaum,
Andrew
Lobanov, Copyright MPIfR 1998)
(Courtesy of data: A. Lobanov, T. Krichbaum, A.
Witzel, A. Kraus, J.A. Zensus, S. Britzen, K. Otterbein, C.A. Hummel
& K. Johnston, 1998,
Astron. & Astrophys., 340, L60.)
public_at_mpifr-bonn.mpg.de
