Eta Carinae Continues Its Display
One of our Galaxy's most massive and brightest stars, Eta Carinae, may
well be powered by a new type of stellar explosion, fainter than
a regular supernova.
Eta Carinae is surrounded by a gas and dust cloud, known as the
Homunculus Nebula, created during an outburst of the star in 1843. This
material has since been expanding outwards from the central star.
Aside from the Homunculus nebula, a faint shell of debris from
an earlier explosion is also detected. This material is believed to be
moving at around 650 km per second.
Using the Gemini South 8-metre Blanco 4-metre telescopes in Chile,
Nathan Smith of University of California, Berkeley and his colleagues
have studied Eta Carinae in detail.
They noticed rapidly expanding filaments of gas speeding away from
the star at five times the speed of the debris in the Homunculus
nebula.
Smith says, 'The new observations show very fast material – much
faster than we have seen previously – that originated in the same 1843
event that ejected the slower Homunculus. The speeds are closer to
speeds one normally sees in a supernova, but that doesn't mean that
this 1843 event was a supernova. In fact, it wasn't, but it does seem
to have been an explosion that behaved similar to a supernova but with
less total energy.'
More exciting is Smith's prediction that the faster material from
the 1843 event is now catching up with the older material, which is
generating X-rays observed by the Chandra X-ray Observatory.
Eta Carinae, probably once had the mass of 150 Suns, but is already
known to be blowing off huge amounts of mass as it approaches the end
of its life. Estimated to now have the mass of around 90 Suns, the
endpoint should be a supernova, probably leaving behind a black hole,
although this is unlikely to happen in our lifetimes.
Eta Carinae has the co-ordinates
RA 10 45 03.6
dec -59 41 04.3
and will become accessible from FT South by late October
