Physics
Today: A
white dwarf
star called V445 in the constellation of Puppis, that is
digesting its closest neighbor,
is a prime
candidate to explode as a Type Ia Supernova, ejecting a
large quantity of matter into space.V445 Puppis has been under
a two-year observation by the
European
Southern Observatory's Very Large Telescope. The star
was
discovered by a amateur Japanese astronomer when it became
visible as a nova in November 2000. It is the only nova
appearing that has no hydrogen and provides the first evidence
for an outburst on the surface of a white dwarf dominated by
helium."This is critical, as we know that
Type
Ia supernovae lack hydrogen and the companion star in V445
Pup fits this nicely by also lacking hydrogen," says
Danny
Steeghs, from the University of Warwick, and one of the key
team members observing the star. A earlier paper by astronomers
Mariko Kato
and
Izumi
Hachisu that modeled the star's behavior
suggested as
much.
The images (above. Credit: ESO) show a bipolar shell,
initially with a very narrow waist, with lobes on each side.
Two knots are also seen at both the extreme ends of the shell,
which appear to move at about 30 million kilometers per
hour.The shell—unlike any previously observed for a
nova—is itself moving at about 24 million kilometers per
hour. A thick disc of dust, which must have been produced
during the last outburst, obscures the two central stars."As
the white dwarf feeds on its companion, the captured gas
accumulates on its surface until thermonuclear reactions begin,
causing a massive explosion which ejects matter out into space
at phenomenal speeds," says co-researcher
Tim O'Brien, of the
Jodrell Bank Centre for
Astrophysics in the UK.If the white dwarf continues to gain
mass, "it will eventually reach a point where it will be ripped
apart in a titanic supernova explosion and its cycle of
outbursts will come to an end," adds O'Brien.Type Ia supernovae
are critical for studies of
dark
energy and for
measuring
distances in the universe.V445 Puppis is over 10,000 times
brighter than the Sun, implying that it is near its fatal limit
to turn into a supernova.
Patrick
Woudt, from the University of Cape Town, and the lead
author of
an
Astrophysical Journal paper describing V445 Puppis
says that "one of the major problems in modern astrophysics is
the fact that we still do not know exactly what kinds of
stellar system explode as a Type Ia supernova" which is "rather
embarrassing.""Whether V445 Puppis will eventually explode as a
supernova, or if the current nova outburst has pre-empted that
pathway by ejecting too much matter back into space is still
unclear," Woudt adds. "But we have here a pretty good suspect
for a future Type Ia supernova."
Related Link
The
expanding bipolar shell of the helium nova V445
Puppis
