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SEVERAL experiments on board the Hubble Space Telescope have already
produced remarkable images, despite the spherical aberration accidentally
ground into the primary mirror. Several novae, galactic nuclei and star
clusters are among the first images.

Hubble’s Faint Object Camera, built by the European Space Agency, has
thrown new light on R Aquarii, a double star 700 light years away, a member
of a class of ‘symbiotic’ stars. Here, a white dwarf is fed with material
from a nearby companion star. Every few hundred years, the white dwarf ignites
this material, creating a nova. The process is important because it disgorges
the heavy elements needed to make stars and planets.

The camera’s detailed images have shown linear filaments of plasma which
have been ejected at high speeds from the core of the double star. The jets
are 10 times the size of the Solar System. Amid the jets sits an unidentified
object, described only as ‘bizarre’ by Francesco Paresce, an astronomer
with the European Space Agency.

Hubble has illuminated another mystery within the galaxy NGC₁068,
an ‘active’ spiral galaxy about 30 million light years away. Its disturbed
nucleus is emitting a cone of extremely bright ionised gas, one-fiftieth
the luminosity of the entire Milky Way. The energy needed for such luminosity
could come from a black hole, according to Holland Ford of Johns Hopkins
University in Baltimore, Maryland. ‘Supermassive’ black holes, with masses
up to a billion times the mass of the Sun, are thought to lurk in the hearts
of a range of active galaxies.

Images of NGC₁068 taken by Hubble’s wide field planetary
camera suggest that an opaque torus of dust is obscuring a black hole. Ford
and his colleagues see ionised gas shooting out of the torus’s hole to form
a cone of clouds.

The Faint Object Camera has also been used to search for a nova that
expired 50 years ago. Astronomers believe that the faint image of the exhausted
nova is buried in a dense grouping of stars called the M14 globular cluster.
Ground-based images frame a view of 20 arcseconds in which about 15 stars
can be distinguished. But Hubble’s camera reveals more than 200 individual
stars in the same area.

According to Bruce Margon of the University of Washington, the camera
has added ‘chaos’ by increasing the number of possible candidates for the
nova. ‘But it was a big test for the Faint Object Camera,’ he says. ‘And
it succeeded.’

Å®ÉúСÊÓƵs at NASA and ESA are studying the aberration they see on board
Hubble. So far, there is a 10 per cent difference between the image they
see and the image they ought to be seeing, according to Chris Burrows of
ESA.

The two agencies hope to design compensatory optics on a new planetary
camera that will improve Hubble’s performance to within 5 per cent of that
originally planned. NASA would then launch a shuttle in June 1993 to install
the new camera and a new set of solar panels, and so improve both the optics
and remove some jitter in the craft.

Debate continues on how or whether to modify ESA’s camera. ‘We don’t
think all the fixes should just be on NASA’s (planetary) camera,’ says Duccio
Macchetto, in charge of the Faint Object Camera, even though it is more
seriously handicapped by the primary mirror’s aberration. A shuttle crew
might be sent to retrieve the camera and modify it in the shuttle’s Spacelab
laboratory.

Ricardo Giacconi, director of the Space Telescope Science Institute
at Johns Hopkins University, says a repair plan should emerge within the
month.

Giacconi says he is ‘cheerfully depressed’ with the performance of Hubble
so far. He is cheerful because computers have unravelled images from Hubble
to reveal details never seen before. The technique the astronomers have
used to remove the effects of distortion is known as computerised ‘deconvolution’.

But, Giacconi said last week at the institute, ‘for two to three years
we won’t be able to do the science we planned on’.

According to Macchetto, about half the planned experiments for the Faint
Object Camera must be abandoned. The rest will require about twice as much
observation time to help to penetrate the foggy halo around each image caused
by the distortion in Hubble’s mirror.