Astrophysics (Index)About

neutron star

(NS)
(stellar remnant consisting entirely of solar masses of neutrons)

A neutron star (NS) is an object basically of neutrons, the result of gravitational collapse of a star after it has used up the energy that created the pressure to resist such collapse. Its mass is large enough that gravity overcomes electron degeneracy pressure and causes additional collapse but not so large as to overcome neutron degeneracy pressure, which prevents it from collapsing into a black hole. Typical neutron star mass is 1.4 to 3.2 solar masses with a radius on the order of 10 km. Stars with lesser mass that don't undergo this collapse remain as white dwarfs. Think of a neutron star as roughly "squeezing the Sun so its cross section is about the size of New York City's land area", whereas a white dwarf is more like "squeezing the Sun into the size of Earth". Neutron stars' existence was first proposed in 1934 and the first candidates that have panned out were identified in the 1960s.

The vast majority of detected neutron stars were detected as pulsars (with regular EMR pulses from rotating beams) and magnetars (with erratic pulses), neutron stars that through interaction, produce bursts of EMR that are detectable. Neutron stars are presumed to be extremely hot, from heat generated by the Kelvin-Helmholtz mechanism as they formed, but are so small that they put out very little thermal emission: some nearby ones have been detected with X-rays.

A (central) region within a neutron star can be described as a "mass of neutrons" (neutron degenerate matter), and the density is on the same order as the density of an atomic nucleus. Around it, pressures at different depths produce different states of matter with different densities, with less exotic states toward the surface, which is thought to include iron. Deeper, the material can have superfluid (no friction) and superconducting fluid (no electrical resistance) characteristics. Some theories suggest the center can be a "mass of quarks" rather than nucleons, and/or a density at the center is much as six times that of an atomic nucleus (quark matter, QM or strange quark matter, SQM). The term quark-nova (QN) refers to the (theoretical) event of a neutron star gaining this characteristic and releasing substantial energy once sufficient spin-down eliminated some of the centrifugal force supporting it.

The term proto-neutron star (PNS) refers to a neutron star at the beginning of its life as it goes through some preliminary phases with some slower shrinking, on the order of its first 10 seconds.

The term isolated neutron star (INS) refers to a neutron star that is not part of a binary. As in stars, their evolution is simpler, but with fewer emission mechanisms, with less emission, making them lucky finds, but supernova remnants offer likely locations for searching. Their emission peaks in X-rays due to their high temperature and have been discovered by X-ray observatories.


(star type,degeneracy,stellar evolution)
Further reading:
https://en.wikipedia.org/wiki/Neutron_star
https://astronomy.swin.edu.au/cosmos/N/Neutron+Star
http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/pulsar.html
https://lweb.cfa.harvard.edu/~pberlind/atlas/htmls/neutron.html
https://www.ucolick.org/~bolte/AY4_00/week9/ns-pulsars.html
https://imagine.gsfc.nasa.gov/science/objects/neutron_stars1.html

Referenced by pages:
asymptotic giant branch (AGB)
AT2018cow
binary neutron star (BNS)
binary star
Black Widow Pulsar (B1957+20)
Bondi radius
Canadian Institute for Theoretical Astrophysics (CITA)
Cassiopeia A
Chandrasekhar limit
collapsar
compact object (CO)
continuous gravitational wave
Cooper pair
core collapse
core collapse supernova (CCSN)
Crab Nebula (M1)
Cygnus Loop
diagnostic
effective field theory (EFT)
ejection
electron degeneracy
electron degenerate matter (EDM)
fast radio burst (FRB)
flux freezing
FRB121102
gamma-ray burst (GRB)
globular cluster (GC)
gravitational redshift
gravitational wave (GW)
gravitational wave spectrum
GW detection (GW)
GW170817
Hartle-Thorne metric (HT metric)
high-B radio pulsar (HBRP)
Hulse-Taylor Binary (PSR B1913+16)
HXMT
hypermassive neutron star (HMNS)
hyperon
innermost stable circular orbit (ISCO)
isothermal core
jet
LIGO
magnetar
magnetic dipole braking
mass ratio (μ)
neutron degenerate matter
neutron drip
neutron rich
neutron star merger
neutron-star black-hole merger (NSBH merger)
NGC 3201
NICER
nova (N)
photon sphere
pion (π)
plasmon
post-main-sequence star
pulsar (PSR)
Puppis A
quake
quark
quark matter (QM)
r-process
radio star
rotation period
rp-process
sedimentation
silicon burning
SN 1987A (1987A)
spin (ms)
star
stellar evolution
stellar remnant
stellar rotation
stellar-mass black hole (stellar-mass BH)
strong-field gravity
superfluid
supernova remnant (SNR)
Thorne-Żytkow object (TZO)
tidal tail
Tolman VII object
Tolman-Oppenheimer-Volkoff limit (TOV)
Urca process
velocity kick
white dwarf (WD)
X-ray binary (XRB)
X-ray burster (XRB)
X-ray flash (XRF)
X-ray pulsar
X-ray source

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