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SEPTEMBER-OCTOBER 2017
ASTRONAUTICS
(‘Pulsar’ is a portman-
teau of the words
‘pulse’ and ‘star’.) Pul-
sars are nothing other
than neutron stars, or
super-dense remnants
of supernovae gener-
ated by stars with an
initial mass at least 7 to
20 times larger than the
Sun. Most of the neu-
tron stars known today
(a few thousand) fall
into the pulsar classifi-
cation for purely geo-
metric reasons: the
beams of radiation they
hurl into space from
their magnetic poles in-
tersect our line of sight.
This condition makes it
easier to find them. Actually, almost all
neutron stars emit a periodic pulsating
signal, but it does not necessarily face the
Earth. Although it has been half a century
since their discovery, we don’t know much
about neutron stars. Their diameter is
known only vaguely (perhaps up to 20
km), so their mass is therefore uncertain
as well (estimates vary from 1.4 to more
than 2 times more than the Sun), not to
mention the exotic state of the material
inside them, which is subject to awesome
pressure that increases sharply from the
surface to the core, producing layers of
varied, unimaginable densities. The tools
in existence so far have not been able to
provide measurements with enough time
and spectral resolution to analyse the
physics inside neutron stars. The most
painstaking studies done to date have
bove, the
SpaceX CRS-
11 Falcon 9 rocket
lifts off on June 3,
2017 from Launch
Complex 39A at
NASA's Kennedy
Space Center
sending a Dragon
spacecraft on the
company's 11
th
commercial re-
supply services
mission to the
International
Space Station.
The payload in-
cludes NICER.
Left, NICER mis-
sion overview.
The payload also
includes a tech-
nology demon-
stration called the
Station Explorer
for X-ray Timing
and Navigation
Technology (SEX-
TANT) which will
help researchers
to develop a pul-
sar-based space
navigation sys-
tem. [NASA]
