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See also: The Homestake experiment 252–53 ■ Discovering black holes 254
X-rays can cause damage and
mutations when they impact
on soft, living cells.
The first glimpse of the sun’s
X-rays came in the late 1940s,
during a US Naval Research
Laboratory (NRL) program to
study Earth’s upper atmosphere.
A team led by US rocket scientist
Herbert Friedman fired German
V-2 rockets into space equipped
with X-ray detectors—essentially
modified Geiger counters. These
experiments provided the first
incontrovertible evidence of
X-rays from the sun. By 1960,
researchers were using Aerobee
sounding rockets to detect X-rays,
and the first X-ray photos of the
sun were taken from an Aerobee
Hi. Two years later, the first cosmic
X-ray source was detected.Extrasolar X-rays
Riccardo Giacconi, an Italian
astrophysicist then working for
American Science and Engineering
(AS&E), had successfully petitioned
NASA to fund his team’s X-ray
experiment. The team’s first rocket
mis fired in 1960, but by 1961 it had
a new, improved experiment ready
for launch. This instrument was
one hundred times more sensitive
than any flown to date. Using a
large field of view, the team hoped
to observe other X-ray sources in
the sky. Success followed a year
later: the rocket aimed its camera
first at the moon and then away
from it. What the camera saw came
as a complete surprise to the team.
The instrument detected the X-ray
“background”—a diffuse signal
coming from all directions—and
a strong peak of radiation in the
direction of the galactic center.
Stars like the sun emit about
a million times more photons
at visible light frequencies than
they do as X-rays. The source of ❯❯NEW WINDOWS ON THE UNIVERSE
Riccardo Giacconi
Born in Genoa, Italy, in 1931,
Riccardo Giacconi lived in
Milan with his mother,
a mathematics and physics
high school teacher. She
instilled a love of geometry
in the young Riccardo.
Giacconi’s first degree
was from the University
of Milan. With a Fulbright
Scholarship, he moved to
Indiana University in the
US, and then to Princeton,
to study astrophysics.
In 1959, Giacconi joined
American Science and
Engineering, a small firm in
Cambridge, Massachusetts.
AS&E built rocket-borne
monitoring equipment for
measuring electrons and
artificial gamma-ray bursts
from nuclear weapons.
Giacconi was tasked with
developing instruments
for X-ray astronomy. He
was at the heart of most of
the breakthroughs in X-ray
astronomy, and in 2002,
he was awarded a share
of the Nobel Prize in Physics
for his contributions to
astrophysics. In 2016, he
was still working in his
mid-80s, as principal
investigator for the Chandra
Deep Field-South project.Cosmic X-ray
radiation is absorbed
by Earth’s atmosphere.Space-based
telescopes are needed
for X-ray astronomy.Detectors on balloons
and rockets detect
X-rays coming from
all over the sky.A new view of the
universe is revealed in
high-energy radiation.Nothing is going to
happen unless you work
with your life’s blood.
Riccardo Giacconi