The Oldest, Loneliest Supernova A distant stellar explosion, the oldest of its kind, may help reveal the cause behind one type of supernova.
Astronomers have
discovered a supernova
that is the oldest and most
distant of its kind. At over
10 billion years old, the
explosion, a Type Ia
supernova dubbed
"Wilson" by its
discoverers, lies at a
redshift of 1.9 and is now
the farthest marker on
astronomers' supernova-
based cosmic yardstick.
With this yardstick
astronomers measure
distances in the universe
and the universe's
expansion rate.
Officially named SN
UDS10Wil, the record-
breaker comes from the
CANDELS+CLASH Supernova
Project, a near-infrared
observing campaign
surveying the early
universe with the Hubble
Space Telescope. The team
is naming the supernovae
they discover after U.S.
presidents; this one is
after Woodrow Wilson,
the 28th U.S. president.
The first I heard of this
study was not from the
press announcement but
from my friend and former
classmate, David Jones
(Johns Hopkins University)
— who happens to be the
paper's lead author.
"We've never seen an
object like this so early in
the universe," David said
when I called him up to
chat. The previous record-
holder was found by a
survey led by Saul
Perlmutter (University of
California, Berkeley) and
announced only this
January; before that the
trophy belonged to Adam
Riess (JHU, David's advisor)
and his team's SN Primo.
In the late 1990s, Riess
and Perlmutter were key
players on competing
teams that raced to
announce the discovery of
the accelerating universe.
For that discovery they
shared the 2011 Nobel
Prize in Physics with
Riess's teammate, Brian
Schmidt (Australian
National University). But
Riess cuts short the notion
of any celebratory trash
talk. "The fact that it's a
record-holder is nice, but
what's really interesting is
the implications," he says.
In fact, David explains, the
team knew Hubble had
the capability to find a
supernova at these
distances. "The exciting
part," he says, "is we
haven't found more of
them." The team thinks
that the dearth of
supernovae like Wilson in
the early universe is an
important clue to the
origin of these massive
explosions.
We know that Type Ia
supernovae are the
demolitions of white
dwarfs, stellar cores left
over from the fairly quiet
deaths of Sun-like stars.
White dwarfs are made up
of matter that is under
tremendous pressure and
primed to explode if their
masses exceed 1.4 Suns.
There are two main
models for how white
dwarfs fatten up to reach
that critical mass. One is
that a white dwarf slowly
sucks matter off a swollen,
aging companion star
called a red giant. In the
other model, the
companion is also a white
dwarf, and the merger of
the two dwarfs' triggers
the explosion.
While both scenarios
result in the same event,
and both may be
sometimes true
(observations support
both models), the mass
transfer model produces
supernovae promptly and
consistently. Thus, if most
Type Ia's are due to the
mass-transfer model, the
universe's supernova
production line comes
online around the same
time the early universe is
making vast amounts of
stars — meaning there
ought to be many
supernovae at Wilson-
esque ages.
But if colliding white
dwarfs are the culprit, the
universe's supernova
production line turns on
abruptly, when the closest
binary systems begin
colliding. That would
mean that, as astronomers
look farther into the
universe and therefore
deeper back in time, the
number of supernovas
should drop precipitously
as we reach the early
universe, with vast
numbers of stars sitting
around waiting around for
the assembly line to start
up.
discovered a supernova
that is the oldest and most
distant of its kind. At over
10 billion years old, the
explosion, a Type Ia
supernova dubbed
"Wilson" by its
discoverers, lies at a
redshift of 1.9 and is now
the farthest marker on
astronomers' supernova-
based cosmic yardstick.
With this yardstick
astronomers measure
distances in the universe
and the universe's
expansion rate.
Officially named SN
UDS10Wil, the record-
breaker comes from the
CANDELS+CLASH Supernova
Project, a near-infrared
observing campaign
surveying the early
universe with the Hubble
Space Telescope. The team
is naming the supernovae
they discover after U.S.
presidents; this one is
after Woodrow Wilson,
the 28th U.S. president.
The first I heard of this
study was not from the
press announcement but
from my friend and former
classmate, David Jones
(Johns Hopkins University)
— who happens to be the
paper's lead author.
"We've never seen an
object like this so early in
the universe," David said
when I called him up to
chat. The previous record-
holder was found by a
survey led by Saul
Perlmutter (University of
California, Berkeley) and
announced only this
January; before that the
trophy belonged to Adam
Riess (JHU, David's advisor)
and his team's SN Primo.
In the late 1990s, Riess
and Perlmutter were key
players on competing
teams that raced to
announce the discovery of
the accelerating universe.
For that discovery they
shared the 2011 Nobel
Prize in Physics with
Riess's teammate, Brian
Schmidt (Australian
National University). But
Riess cuts short the notion
of any celebratory trash
talk. "The fact that it's a
record-holder is nice, but
what's really interesting is
the implications," he says.
In fact, David explains, the
team knew Hubble had
the capability to find a
supernova at these
distances. "The exciting
part," he says, "is we
haven't found more of
them." The team thinks
that the dearth of
supernovae like Wilson in
the early universe is an
important clue to the
origin of these massive
explosions.
We know that Type Ia
supernovae are the
demolitions of white
dwarfs, stellar cores left
over from the fairly quiet
deaths of Sun-like stars.
White dwarfs are made up
of matter that is under
tremendous pressure and
primed to explode if their
masses exceed 1.4 Suns.
There are two main
models for how white
dwarfs fatten up to reach
that critical mass. One is
that a white dwarf slowly
sucks matter off a swollen,
aging companion star
called a red giant. In the
other model, the
companion is also a white
dwarf, and the merger of
the two dwarfs' triggers
the explosion.
While both scenarios
result in the same event,
and both may be
sometimes true
(observations support
both models), the mass
transfer model produces
supernovae promptly and
consistently. Thus, if most
Type Ia's are due to the
mass-transfer model, the
universe's supernova
production line comes
online around the same
time the early universe is
making vast amounts of
stars — meaning there
ought to be many
supernovae at Wilson-
esque ages.
But if colliding white
dwarfs are the culprit, the
universe's supernova
production line turns on
abruptly, when the closest
binary systems begin
colliding. That would
mean that, as astronomers
look farther into the
universe and therefore
deeper back in time, the
number of supernovas
should drop precipitously
as we reach the early
universe, with vast
numbers of stars sitting
around waiting around for
the assembly line to start
up.
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