Lawrence Berkeley National Laboratory
Lawrence Berkeley National Laboratory
Title
Discovery of the Most Distant Supernovae and the Quest for Omega
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Author
Goldhaber, G.
Publication Date
2008-09-24
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University of California
LBL-36361
UC-414
Lawrence
Berkeley
Laboratory
UNIVERSITY
OF
CALIFORNIA
Physics Division
Talk presented at the First Arctic Workshop on Future Physics and
Accelerators, Saariselka, Lappland, Finland, August 21-26, 1994,
and to be published in the Proceedings
Discovery
of
the Most Distant Supernovae
and the Quest for
.Q
G.
Goldhaber,
s.
Perlmutter, S. Gabi, A. Goobar, A. Kim, M. Kim,
R.
Pain,
C.
Pennypacker,
I.
Small, B. Boyle,
R.
Ellis,
R.
McMahon,
P.
Bunclark,
D.
Carter, and
R.
Terlevich
May 1994
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Prepared
for the U.S.
Department
of
Energy
under
Contract
Number
DE-AC03-
76SFOOO98
LBL-36361
UC-4l4
Discovery
of
the Most Distant Supernovae and the Quest for Q
Gerson Goldhaber and Saul Perlmutter
Lawrence Berkeley Laboratory and Center for Particle Astrophysics
University
of
California, Berkeley, CA 94720
Silvia Gabi, Ariel Goobar, Alex Kim, Mathew Kim, and Reynald Pain
Lawrence Berkeley Laboratory, University
of
California
Berkeley,
CA
94720
Carl Pennypacker and Ivan Small
Lawrence Berkeley Laboratory and Space Sciences Laboratory
University
of
California, Berkeley, CA 94720
Brian Boyle, Richard Ellis, and Richard McMahon
Institute
of
Astronomy, Cambridge, United Kingdom
and
Peter Bunc1ark, Dave
Ca..'1:er,
and Roberto Terlevich
Royal Greenwich Observatory, Cambridge, United Kingdom
May 1994
This work was supported in part by the U.S. Department
of
Energy under Contract No. DE-AC03-76SFOOO98,
Center for Particle Astrophysics under NSF Contract No. AST-9120005, the Swedish Natural Science Research
Council, and by IN2P3, Paris, France.
Talk
presented
at
the
First
Arctic
Workshop
on
Future
Physics
and
Accelerators,
August
21-26, 1994, Saariselka,
Lappland,
Finland.
DISCOVERY
OF
THE
MOST
DISTANT
SUPERNOVAE
AND
THE
QUEST
FOR
fl*
GERSON
GOLDHABER
and
SAUL
PERLMUTIER
Lawrence Berkeley Laboratory
(2
Center
for
Particle
Astrophysics
University
of
California at Berkeley
Berkeley, California 94720, USA
and
SILVIA
GABI,
ARIEL
GOOBAR!t
ALEX
KIM,
MATHEW
KIM,
and
REYNALD
PAINĀ§
Lawrence
Berkeley
Laboratory, Berkeley,
CA
97420, USA
and
CARL
PENNYPACKER,
and
IVAN
SMALL
Lawrence Berkeley Laboratory
fj
Space Sciences Laboratory, Berkeley,
CA
94720
and
BRIAN
BOYLE,
RICHARD
ELLIS,
and
RICHARD
MCMAHON
Institute
of
Astronomy,
Cambridge, United
Kingdom
and
PETER
BUNCLARK,
DAVE
CARTER,
and
ROBERTO
TERLEVICH
Royal Greenwich Observatory, Cambridge, United
Kingdom
ABSTRACT
A search for cosmological
supernovae
has
discovered a
number
of
a
type
la
super-
novae.
In
particular,
one
at
z = 0.458 is
the
most
distant
supernova
yet
observed.
There
is
strong
evidence
from
measurements
of
nearby
type
Ia
supernovae
that
they
can
be
considered
as
"standard
candles".
We
plan
to
use
these
supernovae
to
measure
the
deceleration
in
the
general
expansion
of
the
universe.
The
aim
of
our
experiment
is
to
try
and
observe
and
measure
about
30
such
distant
supernovae
in
order
to
obtain
a
measurement
of
the
deceleration
para:meter
qo
which
is
related
to
fl.
Here nis
the
ratio
of
the
density
of
the
universe
to
the
critical
density,
and
we
expect
a
measurement
with
an
accuracy
of
about
30%.
One
of
the
fundamental
problems
in
particle
astrophysics is
the
question,
how
to
determine
the
density
of
the
Universe? As a lower
limit
we
have
the
density
in
-This
work
was
supported
in
part
by
the
United
States
Department
of
Energy,
contract
numbers
DE-AC03-76SF00098,
CfPA,
and
NSF
contract
number
AST-9120005
tFunded
in
part
by
the
Swedish
Natural
Science Research Council
tPresent
address
University
of
Stockholm,
Stockholm,
Sweden.
Ā§Funded
in
part
by
IN2P3,
Paris
France.
visible
baryonic
matter,
which
stands
at
about
0.01 of
the
critical density,
Pc.
If
the
current
density, p, is
greater
than
Pc,
gravitational
attraction
will
eventually
cause
the
expansion
of
the
universe
to
cease,
and
contraction
to
begin.
If
p <
Pc
the
expansion
of
the
universe would continue forever.
The
ratio
p/
Pc
is
denoted
by
fl.
At
present,
estimates
of
fl,
based
on
a
variety
of
experiments,
range from 0.1
to
1.5.
Since
the
light
emitting
matter
contributes
roughly 0.01
to
fl, a
measurement
of
fl
would
determine
the
amount
of
dark
matter
in
the
universe.
Our
work
is
based
on
the
study
of
type
Ia
SNe
in
that
they
represent
"standard
candles"
which,
because
of
their
brightness
can
be
observed
out
to
very large distances.
One
SN we discovered, SN1992bi, is
the
most
distant
SN ever observed
with
a red
shift
z = 0.458
or
a distance
of
about
5 billion light years.
This
implies
that
the
light
we
observed
in
April
'92 corresponds
to
an
explosion which occured
at
the
time
of
the
creation
of
our
solar system.
There
is good evidence
that
type
Ia
Supernovae (SNe),
the
brightest
of
all
the
different
types
of
SNe, have a fixed brightness. A plausible
explanation
for this
behavior
is
that
type
Ia
SNe
are
the
consequence of
the
explosion
of
a
white
dwarf
star
as
it
reaches
a critical
mass,
of 1.4 solar masses,
the
Chandrasekhar
limit.
A
white
dwarf
is a
star
that
has
burned
all of
its
hydrogen
and
helium
to
carbon
nitrogen
and
oxygen
and
;I.e: a
result
h,,~
colla.psed
under
the
gravitational force
to
a
degenerate
electron
gas
in
which
the
C,
Nand
0 nuclei
are
embedded.
The
white
dwarf
thus
has
the
mass
of
the
order
of
the
mass
of
the
sun
but
a
radius
comparable
to
that
of
the
earth.
If
this
white
dwarf
is
in
a
binary
system
with
another
star,
a
very
common
occurrence,
it
can
accrete
matter
from
the
companion
star
and
will
then
collapse
when
the
gravitational
force exceeds
the
degeneracy pressure.
In
this
collapse
the
temperature
rises
to
the
point
at
which
the
C,
N
and
0 nuclei fuse and
produce
higher
mass
nuclei,
within
seconds. Since
the
original nuclei all have equal
number
of
protons
and
neutrons
the
fusion
products
will also.
The
fusion process
stops
at
56Ni, a
radioactive
isotope
with
equal
number
of
protons
and
neutrons.
In
fact
an
enormous
amount
of
56Ni
is
produced,
0.6 of a solar mass.
In
the
implosion
under
gravity
the
star
collapses
and
then
rebounds
within
seconds.
On
rebound
the
newly
produced
material
is
ejected
with
velocities of
about
10,000
km/sec.
At
first,
light
is
unable
to
penetrate
the
very dense
material.
Over
a period of
about
15 days
light
begins
to
penetrate
and
reaches a
maximum
value.
It
is during
this
period
that
we first discover
the
SN
as we will describe below.
The
light observed is
produced
by
ionization
from
the
56Ni
decay
products.
This
isotope
has a half life of 6 days which
then
decays
to
56CO
which
has
a
half
life
of
77
days which
then
decays
to
stable
56Fe.
The
light
curve,
one
observes from
type
Ia
SNe (in blue filter), has
the
character-
istic
exponential
decay
features corresponding
to
these
two lifetimes as modified by
absorption
in
the
expanding
ejecta. Fig. 1 shows
this
light curve for a
compilation
of
22
SNe
by
Branch
and
Tarnmann.
(1)
It
also
illustrates
the
degree of uniformity
of
the
SN
Ia
light
curves.
The
scale shown is in
magnitudes,
a logarithmic scale,
with
all
individual
SN
data
aligned
with
the
curve. Fig. 2
illustrates
the
degree of uniformity
of
the
type
Ia
SNe.
What
is
plotted
is
the
absolute
magnitude
for
30
SNe
la. We
note
a
large
peak
at
absolute
magnitude
ME
~
-19,
where
ME
is
the
magnitude
2