Type I supernovae due to planetary impacts?

The news release below discusses observations of a companion star to a
Type I supernova. It mentions that there had been difficulty
confirming the theory that a companion star was necessary for Type I
supernova to occur.
This page also discusses the difficulty in confirming the theory for
Type Ia supernovae:

Source for major type of supernova explosions found
NATIONAL OPTICAL ASTRONOMY OBSERVATORY NEWS RELEASE
Posted: August 6, 2003
"The search for a progenitor for Type Ia supernovae has gone on for so
long that it almost became a point of embarrassment for scientists in
the field," Suntzeff notes. "Supernova 2002ic may not be the prototype
for all Type Ia's, but it is certainly the first crack in the puzzle."
http://spaceflightnow.com/news/n0308/06supernova/

I've been wondering if celestial impacts are common in stellar system
evolution:

From: Robert Clark )
Subject: Re - Strangest Star known is the 'Talk of Astronomy'
Newsgroups: sci.astro, alt.astronomy, sci.physics, alt.fan.art-bell
Date: 2003-09-18 05:27:30 PST
http://groups.google.com/groups?selm...g.g oogle.com


Then the explosions seen in Type I supernovae may be due to impacts
of planets to their parent star. This would explain the high amount of
heavy metals seen in such explosions.
In these latest observations of companion stars to the supernovae,
this might be due to the rare cases of planetary systems in binary or
multiple star systems (the rarity being due to gravitational
instability.)

Bob Clark


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************************************************** ***********************
European Space Agency
Science News Release SNR 1-2004
Paris, France 7 January 2004

First supernova companion star found

A joint European/University of Hawaii team of astronomers has for the
first time
observed a stellar 'survivor' to emerge from a double star system
involving an
exploded supernova.

Supernovae are some of the most significant sources of chemical
elements in the
Universe, and they are at the heart of our understanding of the
evolution of
galaxies.

Supernovae are some of the most violent events in the Universe. For
many years
astronomers have thought that they occur in either solitary massive
stars (Type
II supernovae) or in a binary system where the companion star plays an
important
role (Type I supernovae). However no one has been able to observe any
such
companion star. It has even been speculated that the companion stars
might not
survive the actual explosion ...

The second brightest supernova discovered in modern times, SN 1993J,
was found
in the beautiful spiral galaxy M81 on 28 March 1993. From archival
images of
this galaxy taken before the explosion, a red supergiant was
identified as the
mother star in 1993 -- only the second time astronomers have actually
seen the
progenitor of a supernova explosion (the first was SN 1987A, the
supernova that
exploded in 1987 in our neighbouring galaxy, the Large Magellanic
Cloud).

Initially rather ordinary, SN 1993J began to puzzle astronomers as its
ejecta
seemed too rich in the chemical element helium and instead of fading
normally it
showed a bizarre sharp increase in brightness. The astronomers
realised that a
normal red supergiant alone could not have given rise to such a weird
supernova.
It was suggested that the red supergiant orbited a companion star that
had
shredded its outer layers just before the explosion.

Ten years after this cataclysmic event, a European/University of
Hawaii team of
astronomers has now peered deep into the glowing remnants of SN 1993J
using the
NASA/ESA Hubble Space Telescope's Advanced Camera for Surveys (ACS)
and the
giant Keck telescope on Mauna Kea in Hawaii. They have discovered a
massive star
exactly at the position of the supernova that is the long sought
companion to
the supernova progenitor.

This is the first supernova companion star ever to be detected and it
represents
a triumph for the theoretical models. In addition, this observation
allows a
detailed investigation of the stellar physics leading to supernova
explosions.
It is now clear that during the last 250 years before the explosion 10
solar
masses of gas were torn violently from the red supergiant by its
partner. By
observing the companion closely in the coming years it may even be
possible to
detect a neutron star or black hole emerge from the remnants of the
explosion
'in real time'.

Given the paucity of observations of supernova progenitor systems this
result,
published in Nature on 8 January 2004, is likely to "be crucial to
understanding
how very massive stars explode and why we see such peculiar
supernovae"
according to first author Justyn R. Maund from the University of
Cambridge, UK.

Stephen Smartt, also from the University of Cambridge, says:
"Supernova
explosions are at the heart of our understanding of the evolution of
galaxies
and the formation of chemical elements in the Universe. It is
essential that we
know what type of stars produce them." For the last ten years
astronomers have
believed that they could understand the very peculiar behaviour of
1993J by
invoking the existence of a binary companion star and now this picture
has
proved correct.

According to Rolf Kudritzki from the University of Hawaii, "The
combination of
the outstanding spatial resolution of Hubble and the huge light
gathering power
of the Keck 10m telescope in Hawaii has made this fantastic discovery
possible."

Supernovae occur when a star of more than about eight times the mass
of the Sun
reaches the end of its nuclear fuel reserves and can no longer produce
enough
energy to keep the star from collapsing under its own immense weight.
The core
of the star collapses, and the outer layers are ejected in a
fast-moving shock
wave. This huge energy release causes the visible supernova we see.
While
astronomers are convinced that observations will match this
theoretical model,
they are in the embarrassing position that they have confidently
identified only
two stars that later exploded as supernovae -- the precursors of
supernovae
1987A and 1993J.

There have been more than 2000 supernovae discovered in galaxies
beyond the
Milky Way and there appear to be about eight distinct sub-classes.
However
identifying which stars produce which flavours has proved incredibly
difficult.
This team has now embarked on a parallel project with the Hubble Space
Telescope
to image a large number of galaxies and then wait patiently for a
supernova to
explode. Supernovae appear in spiral galaxies like M81 on average once
every 100
years or so. The team, led by Stephen Smartt, hope to increase the
numbers of
supernova progenitors known from 2 to 20 over the next five years.

Notes for editors

The team is composed of Stephen J. Smartt and Justyn R. Maund
(University of
Cambridge, UK), Rolf. P. Kudritzki (University of Hawaii, USA),
Philipp
Podsiadlowski (University of Oxford, UK) and Gerry F. Gilmore
(University of
Cambridge, UK).

Animations of the discovery and general Hubble Space Telescope
background
footage are available from
http://www.spacetelescope.org/video/heic0401_vnr.html

For more information, please contact:

Justyn R. Maund
University of Cambridge
Tel: +44 (0)1223 337544
E-mail:

Stephen Smartt
University of Cambridge
Tel: +44 (0)1223 766 651
E-mail:

Rolf. P. Kudritzki
Institute for Astronomy
University of Hawaii
Tel: +1 808 956 8566
E-mail:

Lars Lindberg Christensen
Hubble European Space Agency Information Centre
Garching, Germany
Tel: +49 89 3200 6306 (089 within Germany)
E-mail:

[NOTE: Images supporting this release are available at
http://sci.esa.int/science-e/www/obj...objectid=34455 ]


************************************************** ***********************

Robert Clark wrote:

The news release below discusses observations of a companion star to a
Type I supernova. It mentions that there had been difficulty
confirming the theory that a companion star was necessary for Type I
supernova to occur.

This page also discusses the difficulty in confirming the theory for
Type Ia supernovae:

Source for major type of supernova explosions found
NATIONAL OPTICAL ASTRONOMY OBSERVATORY NEWS RELEASE
Posted: August 6, 2003
"The search for a progenitor for Type Ia supernovae has gone on for so
long that it almost became a point of embarrassment for scientists in
the field," Suntzeff notes. "Supernova 2002ic may not be the prototype
for all Type Ia's, but it is certainly the first crack in the puzzle."
http://spaceflightnow.com/news/n0308/06supernova/


More
http://arxiv.org/abs/astro-ph/0308018
http://www.noao.edu/image_gallery/html/im0842.html


http://arxiv.org/abs/astro-ph/0308018

Bruce Scott TOK ] wrote in message ...
Bob Clark wrote:

| Then the explosions seen in Type I supernovae may be due to impacts
| of planets to their parent star. This would explain the high amount of
| heavy metals seen in such explosions.

Planets have really small amounts of energy available for a supernova,
and are really small in size compared to the parent star.
....
In the models these articles talk about, the companion is a compact star
which accumulates enough material from its distended primary to undergo
core collapse.

Our Sun has over 99.8 percent of the mass in the Solar System. None
of our planets would bother our Sun much. The existence of binary
stars suggests the possibility of large companions, and many detected
planets are much larger than Jupiter. Large planets which formed at
time of stellar formation would contain similar elements as their sun,
so collision would not add significant amounts of heavy metals thus if
such cause explosions then heavy metals would not be a signature of
all such events.

However, note that the theories which involve companion stars (whether
the companion accumulates enough material for a catastrophic action or
the large star loses enough mass to become unstable) imply situations
which can not last long in stellar time scales (either due to
impending orbital decay collision or presence of a red giant or
supergiant). This means that these stars formed recently enough to
include many heavy elements. Thus an explosion would reveal heavy
elements.

Of course, as stellar explosions are also believed to be involved in
creation and dispersal of these heavy elements, such elements would
also be present if that type of explosion is being observed.