A tist’s
co cept
of
a
close-up
aked-eye
view
of
a
GRB.
C edit:
NASA
Fo
mo e
tha
half
a
ce tu y,
gamma- ay
bu sts
have
emai ed
o e
of
the
most
puzzli g
eve ts
obse ved
i
space.
These
bu sts
a e
sudde
flashes
of
gamma
ays,
a
ve y
high-e e gy
fo m
of
light.
They
ca
appea
f om
almost
a y
di ectio
i
the
sky
a d
ca
last
f om
less
tha
a
seco d
to
seve al
mi utes.The
discove y
of
the
gamma
ays
happe ed
ve y
u expectedly.
Acco di g
to
NASA,
i
July
1967,
US
satellites
called
Vela
3
a d
Vela
4
we e
watchi g
fo
sig s
of
uclea
weapo s
tests
that
could
violate
the
Nuclea
Test
Ba
T eaty.
I stead,
the
satellites
detected
b ief
flashes
of
high-e e gy
photo s
o
gamma
ays
comi g
f om
space.At
fi st,
scie tists
did
ot
k ow
what
they
we e
seei g.
Some
thought
the
bu sts
might
be
comi g
f om
somewhe e
elatively
close
to
Ea th,
pe haps
withi
the
Sola
System
o
the
Milky
Way.
Othe s
believed
they
could
be
comi g
f om
much
fa the
away.
But
they
could
ot
immediately
co ect
the
bu sts
to
a y
k ow
sta s
o
galaxies.The
myste y
co ti ued
fo
yea s
because
the
bu sts
disappea ed
almost
as
quickly
as
they
appea ed.
O ce
a
bu st
faded,
the e
was
o
obvious
object
left
behi d
that
could
be
studied.
A
accide tal
discove y
The
Vela
satellites
we e
built
fo
a
ve y
diffe e t
pu pose.
They
ca ied
detecto s
desig ed
to
ide tify
X- ays,
gamma
ays
a d
eut o s
that
could
i dicate
a
uclea
explosio .
The
fi st
gamma- ay
bu st
was
detected
o
July
2,
1967,
but
scie tists
did
ot
dete mi e
what
the
sig al
ep ese ted
u til
much
late .Los
Alamos
scie tists
studied
a
umbe
of
simila
eve ts
eco ded
by
the
Vela
satellites.
I
1973,
they
published
thei
fi di gs
o
16
bu sts
obse ved
betwee
July
1969
a d
July
1972.
Thei
co clusio
was
that
the
gamma- ay
bu sts
we e
of
cosmic
o igi .Othe
spacec aft
soo
added
to
the
evide ce.
The
Soviet
Ko us
satellites
published
data
i
1974
that
co fi med
the
detectio
of
these
gamma- ay
bu sts.I
1976,
scie tists
bega
the
I te pla eta y
Netwo k,
o
IPN,
which
used
gamma- ay
detecto s
o
spacec aft
studyi g
the
Su
a d
pla ets.
The
detecto s
wo ked
togethe
to
locate
bu sts
th ough
a
p ocess
called
t ia gulatio .
By
a owi g
the
positio s
of
the
bu sts
to
a
few
a c
mi utes,
scie tists
fou d
that
the
sou ces
did
ot
match
k ow
X- ay
emitte s
o
othe
familia
sou ces.
Eve
the ,
the
o igi
of
the
bu sts
emai ed
u ce tai .
P eside t
Joh
F
Ke edy
lea i g
about
Vela
i
1962
(Sa dia
Natio al
lab
photo)
A
majo
b eakth ough
A
majo
cha ge
came
with
NASA’s
Compto
Gamma
Ray
Obse vato y,
lau ched
i
1991.
O e
of
its
i st ume ts,
the
Bu st
a d
T a sie t
Sou ce
Expe ime t,
o
BATSE,
was
built
to
study
gamma- ay
bu sts.BATSE
detected
mo e
tha
2,700
bu sts
du i g
its
i e
yea s
of
ope atio .
Its
obse vatio s
showed
that
the
bu sts
we e
sp ead
u ifo mly
ac oss
the
sky
athe
tha
bei g
co ce t ated
alo g
the
pla e
of
the
Milky
Way.This
was
a
impo ta t
clue.
If
the
bu sts
we e
comi g
f om
objects
i side
ou
galaxy,
scie tists
would
have
expected
thei
dist ibutio
to
follow
the
Milky
Way
mo e
closely.
I stead,
the
obse vatio s
showed
that
gamma- ay
bu sts
we e
comi g
f om
fa
outside
the
galaxy.That
c eated
a
ew
p oblem.
If
the
bu sts
we e
billio s
of
light-yea s
away
a d
could
still
be
detected,
the
eve ts
p oduci g
them
had
to
elease
a
e o mous
amou t
of
e e gy.I
1997,
the
Italia -Dutch
BeppoSAX
satellite
helped
take
the
ext
majo
step.
It
detected
a
X- ay
afte glow
associated
with
a
gamma- ay
bu st.
This
gave
ast o ome s
a
way
to
study
what
happe ed
afte
the
i itial
flash
a d
helped
establish
that
gamma- ay
bu sts
we e
ext agalactic,
with
some
comi g
f om
ma y
billio s
of
light-yea s
away.Ast o omy
obse vatio s
late
showed
that
these
eve ts
could
elease
a
amou t
of
e e gy
compa able
to
that
of
a
supe ova
i
seco ds.
Thei
peak
lumi osities
ca
be
100
billio
billio
times
that
of
the
Su
a d
a
billio
times
g eate
tha
eve
the
b ightest
supe ovas.
Sea ch
co ti ued
The
discove y
of
X- ay
afte glows
i
the
late
1990s
ope ed
a
ew
pe iod
of
gamma- ay
bu st
esea ch.
Obse vatio s
of
some
bu sts
also
fou d
eleme ts
such
as
i o ,
silico ,
sulfu
a d
a go
a ou d
the
eve ts.
These
eleme ts
a e
associated
with
supe ovas
a d
helped
st e gthe
the
li k
betwee
some
gamma- ay
bu sts
a d
the
deaths
of
massive
sta s.I
1999,
the
afte glow
of
GRB990123
was
detected
withi
seco ds
of
the
o igi al
bu st.
Scie tists
studyi g
it
co cluded
that
the
e e gy
was
cha elled
i to
a ow
jets
a d
that
gamma- ay
bu sts
ca
be
detected
whe
o e
of
those
jets
is
aimed
towa ds
us.The
same
pe iod
also
b ought
evide ce
co ecti g
some
bu sts
with
supe ovas.
Obse vatio s
of
GRB990705
showed
a
i o -abso ptio
featu e
i
its
afte glow
that
was
cha acte istic
of
a
supe ova.
Late
obse vatio s
of
GRB991216
fou d
i o
li es
i
its
afte glow
as
well.By
2003,
NASA
had
a ou ced
st o g
evide ce
that
lo g-du atio
gamma- ay
bu sts
we e
fo med
by
the
deaths
of
massive
sta s
a d
the
simulta eous
c eatio
of
black
holes.
Seei g
gamma
ays
f om
Ea th
Gamma
ays
ca ot
each
Ea th’s
su face
di ectly
because
they
a e
blocked
by
the
atmosphe e.
Scie tists
ca ,
howeve ,
study
ve y-high-e e gy
adiatio
f om
some
gamma- ay
bu sts
usi g
g ou d-based
obse vato ies,
Qua ta
magazi e
w ites.Gamma
ays
i te act
with
pa ticles
i
Ea th’s
atmosphe e.
These
i te actio s
ca
p oduce
pa ticles
movi g
faste
tha
the
speed
of
light
i
ai .
They
the
p oduce
a
blue
glow
k ow
as
Che e kov
adiatio .
Scie tists
ca
detect
this
glow
a d
use
it
to
study
ve y
high-e e gy
gamma
ays.This
app oach
has
a
adva tage.
Ea th’s
atmosphe e
p ovides
a
much
la ge
collecti g
a ea
tha
a
si gle
telescope,
givi g
scie tists
a
bette
cha ce
of
detecti g
a e,
ve y
high-e e gy
gamma- ay
bu sts.The
fi st
obse vatio
of
a
ult ahigh-e e gy
gamma- ay
bu st
usi g
this
method
came
i
July
2018.
The
High
E e gy
Ste eoscopic
System,
o
HESS,
i
Namibia
detected
adiatio
f om
the
afte glow
of
a
gamma- ay
bu st.The
adiatio
was
ot
f om
the
i itial
bu st
itself.
I stead,
the
jet
f om
the
bu st
had
collided
with
mate ial
th ow
out
by
the
sta
du i g
the
supe ova.
The
collisio
accele ated
pa ticles
to
ve y
high
speeds,
p oduci g
elect omag etic
adiatio
that
eve tually
eached
Ea th.
A
lo ge -lasti g
afte glow
Scie tists
late
obse ved
a
eve
lo ge
high-e e gy
afte glow
f om
GRB
190829A.
The
bu st
was
about
1
billio
light-yea s
away,
elatively
close
compa ed
with
some
othe
gamma- ay
bu sts.
HESS
studied
it
fo
56
hou s
a d
fou d
that
the
highe -e e gy
adiatio
co ti ued
fo
mo e
tha
five
times
lo ge
tha
the
ea lie
esult
eco ded
i
2018.“This
is
basically
a
b eakth ough
esult,”
B ia
Reville,
a
physicist
at
the
Max
Pla ck
I stitute
fo
Nuclea
Physics
i
Ge ma y,
told
Qua ta
magazi e.
“To
detect
ve y-high-e e gy
gamma- ay
photo s
up
to
th ee
ights
afte
the
explosio
is
just
eally
somethi g.”The
obse vatio
has
aised
questio s
about
the
elatively
simple
models
scie tists
use
to
explai
how
gamma- ay
bu sts
a e
p oduced.
It
suggests
that
the
physics
i volved
may
be
mo e
complicated
tha
p eviously
thought.
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