Sky and Telescope - July 2017 - 16

STRANGE STELLAR PHYSICS

by Feryal Özel

Neutron Stars
The Inside Story of

It

is a rare opportunity when we can use astronomical observations to push the frontiers of physics in a
way that is not possible in any laboratory on Earth.
Yet neutron stars, the dead, dense remnants of massive stars,
provide us with just that opportunity.
Crushed under the inward pull of gravity once a massive
star's fuel is exhausted, the stellar core that becomes a neutron
star reaches matter densities that are not naturally encountered anywhere else in the universe. (Black holes don't count:
Although they may have inﬁnite energy densities, they hide
behind horizons and are inaccessible.) In fact, the matter that
makes up neutron stars has fundamentally changed character,
taking us into regimes that are still poorly understood in physics. As a result, a lot of recent efforts have focused on probing
these stars' interiors with astronomical observations.
To be sure, there are some aspects of that unusual matter
that we can conﬁdently predict, based on theoretical calculations and laboratory experiments. For example, during the implosion of the star, the electrons that normally
surround the nucleus of an atom in the core get pushed into
the atomic nuclei. There, they combine with the protons
through weak interactions, one of the four types of interactions that take place between particles in the universe. (The
other three are strong, gravitational, and electromagnetic.)
That combination produces a neutron - thus giving this new
star its name - as well as nearly massless, ghostly particles
called neutrinos that rapidly escape from the star, carrying
with them a large amount of energy. The ﬁrst observational
conﬁrmation of this process happened with Supernova
1987A, observed in 1987 in the Large Magellanic Cloud (S&T:
Feb. 2017, p. 36), when two neutrino observatories detected
a burst of particles around the same time as the supernova's
visible light appeared in the sky.
Scientists can't create such neutron-rich matter. Simply
smashing nuclei together and squeezing them to high densities in heavy ion colliders, such as the RHIC experiment in
Brookhaven National Laboratory, doesn't work. First, collisions in accelerators create very hot matter, which behaves

16

J U L Y 2 0 1 7 * SK Y & TELESCOPE

Astronomers
are using X-rays,
gravity & clever
calculations to
discover what lies
within these
extraordinary
objects.

Sky and Telescope - July 2017

Table of Contents for the Digital Edition of Sky and Telescope - July 2017

Contents
Sky and Telescope - July 2017 - Cover1
Sky and Telescope - July 2017 - Cover2
Sky and Telescope - July 2017 - 1
Sky and Telescope - July 2017 - Contents
Sky and Telescope - July 2017 - 3
Sky and Telescope - July 2017 - 4
Sky and Telescope - July 2017 - 5
Sky and Telescope - July 2017 - 6
Sky and Telescope - July 2017 - 7
Sky and Telescope - July 2017 - 8
Sky and Telescope - July 2017 - 9
Sky and Telescope - July 2017 - 10
Sky and Telescope - July 2017 - 11
Sky and Telescope - July 2017 - 12
Sky and Telescope - July 2017 - 13
Sky and Telescope - July 2017 - 14
Sky and Telescope - July 2017 - 15
Sky and Telescope - July 2017 - 16
Sky and Telescope - July 2017 - 17
Sky and Telescope - July 2017 - 18
Sky and Telescope - July 2017 - 19
Sky and Telescope - July 2017 - 20
Sky and Telescope - July 2017 - 21
Sky and Telescope - July 2017 - 22
Sky and Telescope - July 2017 - 23
Sky and Telescope - July 2017 - 24
Sky and Telescope - July 2017 - 25
Sky and Telescope - July 2017 - 26
Sky and Telescope - July 2017 - 27
Sky and Telescope - July 2017 - 28
Sky and Telescope - July 2017 - 29
Sky and Telescope - July 2017 - 30
Sky and Telescope - July 2017 - 31
Sky and Telescope - July 2017 - 32
Sky and Telescope - July 2017 - 33
Sky and Telescope - July 2017 - 34
Sky and Telescope - July 2017 - 35
Sky and Telescope - July 2017 - 36
Sky and Telescope - July 2017 - 37
Sky and Telescope - July 2017 - 38
Sky and Telescope - July 2017 - 39
Sky and Telescope - July 2017 - 40
Sky and Telescope - July 2017 - 41
Sky and Telescope - July 2017 - 42
Sky and Telescope - July 2017 - 43
Sky and Telescope - July 2017 - 44
Sky and Telescope - July 2017 - 45
Sky and Telescope - July 2017 - 46
Sky and Telescope - July 2017 - 47
Sky and Telescope - July 2017 - 48
Sky and Telescope - July 2017 - 49
Sky and Telescope - July 2017 - 50
Sky and Telescope - July 2017 - 51
Sky and Telescope - July 2017 - 52
Sky and Telescope - July 2017 - 53
Sky and Telescope - July 2017 - 54
Sky and Telescope - July 2017 - 55
Sky and Telescope - July 2017 - 56
Sky and Telescope - July 2017 - 57
Sky and Telescope - July 2017 - 58
Sky and Telescope - July 2017 - 59
Sky and Telescope - July 2017 - 60
Sky and Telescope - July 2017 - 61
Sky and Telescope - July 2017 - 62
Sky and Telescope - July 2017 - 63
Sky and Telescope - July 2017 - 64
Sky and Telescope - July 2017 - 65
Sky and Telescope - July 2017 - 66
Sky and Telescope - July 2017 - 67
Sky and Telescope - July 2017 - 68
Sky and Telescope - July 2017 - 69
Sky and Telescope - July 2017 - 70
Sky and Telescope - July 2017 - 71
Sky and Telescope - July 2017 - 72
Sky and Telescope - July 2017 - 73
Sky and Telescope - July 2017 - 74
Sky and Telescope - July 2017 - 75
Sky and Telescope - July 2017 - 76
Sky and Telescope - July 2017 - 77
Sky and Telescope - July 2017 - 78
Sky and Telescope - July 2017 - 79
Sky and Telescope - July 2017 - 80
Sky and Telescope - July 2017 - 81
Sky and Telescope - July 2017 - 82
Sky and Telescope - July 2017 - 83
Sky and Telescope - July 2017 - 84
Sky and Telescope - July 2017 - Cover3
Sky and Telescope - July 2017 - Cover4
https://www.nxtbook.com/nxtbooks/aas/st_202412
https://www.nxtbook.com/nxtbooks/aas/st_202411
https://www.nxtbook.com/nxtbooks/aas/st_202410
https://www.nxtbook.com/nxtbooks/aas/st_202409
https://www.nxtbook.com/nxtbooks/aas/st_202408
https://www.nxtbook.com/nxtbooks/aas/st_202407
https://www.nxtbook.com/nxtbooks/aas/st_202406
https://www.nxtbook.com/nxtbooks/aas/st_202405
https://www.nxtbook.com/nxtbooks/aas/st_202404_qr
https://www.nxtbook.com/nxtbooks/aas/st_202404
https://www.nxtbook.com/nxtbooks/aas/st_202403
https://www.nxtbook.com/nxtbooks/aas/st_202402
https://www.nxtbook.com/nxtbooks/aas/st_202401_aus
https://www.nxtbook.com/nxtbooks/aas/st_202401
https://www.nxtbook.com/nxtbooks/aas/st_202312_aus
https://www.nxtbook.com/nxtbooks/aas/st_202312
https://www.nxtbook.com/nxtbooks/aas/st_202311
https://www.nxtbook.com/nxtbooks/aas/st_202310
https://www.nxtbook.com/nxtbooks/aas/st_202309
https://www.nxtbook.com/nxtbooks/aas/st_202308
https://www.nxtbook.com/nxtbooks/aas/st_202307
https://www.nxtbook.com/nxtbooks/aas/st_202306
https://www.nxtbook.com/nxtbooks/aas/st_202305
https://www.nxtbook.com/nxtbooks/aas/st_202304
https://www.nxtbook.com/nxtbooks/aas/st_202304_qr
https://www.nxtbook.com/nxtbooks/aas/st_202303
https://www.nxtbook.com/nxtbooks/aas/st_202302
https://www.nxtbook.com/nxtbooks/aas/st_202301
https://www.nxtbook.com/nxtbooks/aas/st_202212
https://www.nxtbook.com/nxtbooks/aas/st_202211
https://www.nxtbook.com/nxtbooks/aas/st_202210
https://www.nxtbook.com/nxtbooks/aas/st_202209
https://www.nxtbook.com/nxtbooks/aas/st_202208
https://www.nxtbook.com/nxtbooks/aas/st_202207
https://www.nxtbook.com/nxtbooks/aas/st_202206
https://www.nxtbook.com/nxtbooks/aas/st_202205
https://www.nxtbook.com/nxtbooks/aas/st_202204
https://www.nxtbook.com/nxtbooks/aas/st_202203
https://www.nxtbook.com/nxtbooks/aas/st_202202
https://www.nxtbook.com/nxtbooks/aas/st_202201
https://www.nxtbook.com/nxtbooks/aas/st_202112
https://www.nxtbook.com/nxtbooks/aas/st_202111
https://www.nxtbook.com/nxtbooks/aas/st_202110
https://www.nxtbook.com/nxtbooks/aas/st_202109
https://www.nxtbook.com/nxtbooks/aas/st_202108
https://www.nxtbook.com/nxtbooks/aas/st_202107
https://www.nxtbook.com/nxtbooks/aas/st_202106
https://www.nxtbook.com/nxtbooks/aas/st_202105
https://www.nxtbook.com/nxtbooks/aas/st_202104
https://www.nxtbook.com/nxtbooks/aas/st_202103
https://www.nxtbook.com/nxtbooks/aas/st_202102
https://www.nxtbook.com/nxtbooks/aas/st_202101
https://www.nxtbook.com/nxtbooks/aas/skywatch_2021
https://www.nxtbook.com/nxtbooks/aas/st_202012
https://www.nxtbook.com/nxtbooks/aas/st_202011
https://www.nxtbook.com/nxtbooks/aas/st_202010
https://www.nxtbook.com/nxtbooks/aas/st_202009
https://www.nxtbook.com/nxtbooks/aas/st_202008
https://www.nxtbook.com/nxtbooks/aas/st_202007
https://www.nxtbook.com/nxtbooks/aas/st_202006
https://www.nxtbook.com/nxtbooks/aas/st_202005
https://www.nxtbook.com/nxtbooks/aas/st_202004
https://www.nxtbook.com/nxtbooks/aas/st_202003
https://www.nxtbook.com/nxtbooks/aas/st_202002
https://www.nxtbook.com/nxtbooks/aas/st_202001
https://www.nxtbook.com/nxtbooks/aas/st_201912
https://www.nxtbook.com/nxtbooks/aas/st_201911
https://www.nxtbook.com/nxtbooks/aas/st_201910
https://www.nxtbook.com/nxtbooks/aas/st_201909
https://www.nxtbook.com/nxtbooks/aas/st_201908
https://www.nxtbook.com/nxtbooks/aas/st_201907
https://www.nxtbook.com/nxtbooks/aas/st_201906
https://www.nxtbook.com/nxtbooks/aas/st_201905
https://www.nxtbook.com/nxtbooks/aas/st_201904
https://www.nxtbook.com/nxtbooks/aas/st_201903
https://www.nxtbook.com/nxtbooks/aas/st_201902
https://www.nxtbook.com/nxtbooks/aas/st_201901
https://www.nxtbook.com/nxtbooks/aas/st_201812
https://www.nxtbook.com/nxtbooks/aas/st_201811
https://www.nxtbook.com/nxtbooks/aas/st_201810
https://www.nxtbook.com/nxtbooks/aas/st_201809
https://www.nxtbook.com/nxtbooks/aas/st_201808
https://www.nxtbook.com/nxtbooks/aas/st_201807
https://www.nxtbook.com/nxtbooks/aas/st_201806
https://www.nxtbook.com/nxtbooks/aas/st_201805
https://www.nxtbook.com/nxtbooks/aas/st_201804
https://www.nxtbook.com/nxtbooks/aas/st_201803
https://www.nxtbook.com/nxtbooks/aas/st_201802
https://www.nxtbook.com/nxtbooks/aas/st_201801
https://www.nxtbook.com/nxtbooks/aas/st_201712
https://www.nxtbook.com/nxtbooks/aas/st_201711
https://www.nxtbook.com/nxtbooks/aas/st_201710
https://www.nxtbook.com/nxtbooks/aas/st_201709
https://www.nxtbook.com/nxtbooks/aas/st_201708
https://www.nxtbook.com/nxtbooks/aas/st_201707
https://www.nxtbook.com/nxtbooks/aas/st_201706
https://www.nxtbook.com/nxtbooks/aas/st_201705
https://www.nxtbook.com/nxtbooks/aas/st_201704
https://www.nxtbook.com/nxtbooks/aas/st_201703
https://www.nxtbook.com/nxtbooks/aas/st_201702
https://www.nxtbook.com/nxtbooks/aas/st_201701
https://www.nxtbook.com/nxtbooks/aas/st_201612
https://www.nxtbook.com/nxtbooks/aas/st_201611
https://www.nxtbook.com/nxtbooks/aas/st_201610
https://www.nxtbook.com/nxtbooks/aas/st_201609
https://www.nxtbook.com/nxtbooks/aas/st_201608
https://www.nxtbook.com/nxtbooks/aas/st_201607
https://www.nxtbook.com/nxtbooks/aas/st_201606
https://www.nxtbook.com/nxtbooks/aas/st_201605
https://www.nxtbook.com/nxtbooks/aas/st_201604
https://www.nxtbook.com/nxtbooks/aas/st_201603
https://www.nxtbook.com/nxtbooks/aas/st_201602
https://www.nxtbook.com/nxtbooks/aas/st_201601
https://www.nxtbook.com/nxtbooks/aas/st_201512
https://www.nxtbook.com/nxtbooks/aas/st_201511
https://www.nxtbook.com/nxtbooks/aas/st_201510
https://www.nxtbook.com/nxtbooks/aas/st_201509
https://www.nxtbook.com/nxtbooks/aas/st_201508
https://www.nxtbook.com/nxtbooks/aas/st_201507
https://www.nxtbook.com/nxtbooks/aas/st_201506
https://www.nxtbook.com/nxtbooks/aas/st_201505
https://www.nxtbook.com/nxtbooks/aas/st_201504
https://www.nxtbook.com/nxtbooks/aas/st_201503
https://www.nxtbook.com/nxtbooks/aas/st_201502
https://www.nxtbook.com/nxtbooks/aas/st_201501
https://www.nxtbook.com/nxtbooks/aas/st_201412
https://www.nxtbook.com/nxtbooks/aas/st_201411
https://www.nxtbook.com/nxtbooks/aas/st_201410
https://www.nxtbook.com/nxtbooks/aas/st_201409
https://www.nxtbook.com/nxtbooks/aas/st_201408
https://www.nxtbook.com/nxtbooks/aas/st_201407
https://www.nxtbook.com/nxtbooks/aas/st_201406
https://www.nxtbook.com/nxtbooks/aas/st_mars
https://www.nxtbook.com/nxtbooks/aas/st_201405
https://www.nxtbook.com/nxtbooks/aas/st_201404
https://www.nxtbook.com/nxtbooks/aas/st_201403
https://www.nxtbook.com/nxtbooks/aas/st_201402
https://www.nxtbook.com/nxtbooks/aas/st_201401
https://www.nxtbook.com/nxtbooks/aas/st_201312
https://www.nxtbook.com/nxtbooks/aas/st_201311
https://www.nxtbook.com/nxtbooks/aas/st_201310
https://www.nxtbook.com/nxtbooks/aas/st_201309
https://www.nxtbook.com/nxtbooks/aas/st_201308
https://www.nxtbook.com/nxtbooks/aas/st_201307
https://www.nxtbook.com/nxtbooks/aas/st_201306
https://www.nxtbook.com/nxtbooks/aas/st_201305
https://www.nxtbook.com/nxtbooks/aas/st_201304
https://www.nxtbook.com/nxtbooks/aas/st_201303
https://www.nxtbook.com/nxtbooks/aas/st_201302
https://www.nxtbook.com/nxtbooks/aas/st_201301
https://www.nxtbook.com/nxtbooks/aas/st_201212
https://www.nxtbook.com/nxtbooks/aas/st_201211
https://www.nxtbook.com/nxtbooks/aas/st_201210
https://www.nxtbook.com/nxtbooks/aas/st_201209
https://www.nxtbook.com/nxtbooks/aas/st_201208
https://www.nxtbook.com/nxtbooks/aas/st_201207
https://www.nxtbook.com/nxtbooks/aas/st_201206
https://www.nxtbook.com/nxtbooks/aas/st_201205
https://www.nxtbook.com/nxtbooks/aas/st_201204
https://www.nxtbook.com/nxtbooks/aas/st_201203
https://www.nxtbook.com/nxtbooks/aas/st_201202
https://www.nxtbook.com/nxtbooks/aas/st_201201
https://www.nxtbook.com/nxtbooks/aas/st_201112
https://www.nxtbook.com/nxtbooks/aas/st_201111
https://www.nxtbook.com/nxtbooks/aas/st_201110
https://www.nxtbook.com/nxtbooks/aas/st_201109
https://www.nxtbook.com/nxtbooks/aas/st_201108
https://www.nxtbook.com/nxtbooks/aas/st_201107
https://www.nxtbook.com/nxtbooks/aas/st_201106
https://www.nxtbook.com/nxtbooks/aas/st_201105
https://www.nxtbook.com/nxtbooks/aas/st_201104
https://www.nxtbook.com/nxtbooks/aas/st_201103
https://www.nxtbook.com/nxtbooks/aas/st_201102
https://www.nxtbook.com/nxtbooks/aas/st_201101
https://www.nxtbook.com/nxtbooks/aas/st_201012
https://www.nxtbook.com/nxtbooks/aas/st_201011
https://www.nxtbook.com/nxtbooks/aas/st_201010
https://www.nxtbook.com/nxtbooks/aas/st_201009
https://www.nxtbook.com/nxtbooks/aas/st_201008
https://www.nxtbook.com/nxtbooks/aas/st_201007
https://www.nxtbook.com/nxtbooks/aas/st_201006
https://www.nxtbook.com/nxtbooks/aas/st_201005
https://www.nxtbook.com/nxtbooks/aas/st_201004
https://www.nxtbook.com/nxtbooks/aas/st_201003
https://www.nxtbook.com/nxtbooks/aas/st_201002
https://www.nxtbook.com/nxtbooks/aas/st_201001
https://www.nxtbookmedia.com