Sky & Telescope - December 2021 - 36

LEAH TISCIONE / S&T
ON THE EDGE OF OUR SEATS by Jure Japelj
Cosmic Explo
I
Astronomers drop everything to look for flashes
from gravitational-wave mergers, but often their
searches turn up empty.
t was an afternoon in the summer of 2017. Andrew Levan
waited in line at McDonald's with his two kids. His
thoughts were on his heavily pregnant wife when his work
phone went off. " Come on, not now, " he thought to himself,
but curiosity and his sense of duty got the better of him.
From a deluge of incoming messages, he learned that the
LIGO gravitational-wave observatory had just detected what
looked like a merger of two neutron stars.
As a seasoned astronomer, Levan (now at Radboud University,
The Netherlands) immediately realized the implications:
It was what he and his colleagues had been dreaming about
for decades. In the month to come, he would repeatedly
find himself lying in bed, a newborn baby in one arm and a
laptop in his lap, organizing follow-up observations of the
neutron star merger GW170817, which would become one
of the most famous cosmic explosions to date. " In the end,
it worked more smoothly than you might imagine, but it was
not stress-free, " he says. " It was probably the most exciting
but also the most demanding period in my career. "
Astrophysical transient sources - those that appear and
disappear - pop up in the sky all the time. Caused by different
physical phenomena, one transient can differ a lot from
another. What is common to all is their unpredictable nature
and fast evolution.
Gravitational waves produced by mergers of compact
objects are the latest addition to the transient zoo.
GW170817 radiated both gravitational waves and electromagnetic
radiation, and it was the latter (called the counterpart)
that especially excited Levan and thousands of other
astronomers. That single electromagnetic counterpart confirmed
the predicted link between short gamma-ray bursts
(GRBs) and neutron star mergers, provided a novel way to
measure the Hubble constant, and taught us that mergers
produce rare earth elements, a category of metals. But counterparts
have even more to offer than that, and we have been
trying to catch more of them ever since.
Mergers of Stellar Relics
Under the right conditions, mergers of two neutron stars
(BNS) or a neutron star and a black hole (NS-BH) produce
light across the electromagnetic spectrum. In the moments
36 DECEMBER 2021 * SKY & TELESCOPE

Sky & Telescope - December 2021

Table of Contents for the Digital Edition of Sky & Telescope - December 2021

Contents
Sky & Telescope - December 2021 - Cover1
Sky & Telescope - December 2021 - Cover2
Sky & Telescope - December 2021 - 1
Sky & Telescope - December 2021 - Contents
Sky & Telescope - December 2021 - 3
Sky & Telescope - December 2021 - 4
Sky & Telescope - December 2021 - 5
Sky & Telescope - December 2021 - 6
Sky & Telescope - December 2021 - 7
Sky & Telescope - December 2021 - 8
Sky & Telescope - December 2021 - 9
Sky & Telescope - December 2021 - 10
Sky & Telescope - December 2021 - 11
Sky & Telescope - December 2021 - 12
Sky & Telescope - December 2021 - 13
Sky & Telescope - December 2021 - 14
Sky & Telescope - December 2021 - 15
Sky & Telescope - December 2021 - 16
Sky & Telescope - December 2021 - 17
Sky & Telescope - December 2021 - 18
Sky & Telescope - December 2021 - 19
Sky & Telescope - December 2021 - 20
Sky & Telescope - December 2021 - 21
Sky & Telescope - December 2021 - 22
Sky & Telescope - December 2021 - 23
Sky & Telescope - December 2021 - 24
Sky & Telescope - December 2021 - 25
Sky & Telescope - December 2021 - 26
Sky & Telescope - December 2021 - 27
Sky & Telescope - December 2021 - 28
Sky & Telescope - December 2021 - 29
Sky & Telescope - December 2021 - 30
Sky & Telescope - December 2021 - 31
Sky & Telescope - December 2021 - 32
Sky & Telescope - December 2021 - 33
Sky & Telescope - December 2021 - 34
Sky & Telescope - December 2021 - 35
Sky & Telescope - December 2021 - 36
Sky & Telescope - December 2021 - 37
Sky & Telescope - December 2021 - 38
Sky & Telescope - December 2021 - 39
Sky & Telescope - December 2021 - 40
Sky & Telescope - December 2021 - 41
Sky & Telescope - December 2021 - 42
Sky & Telescope - December 2021 - 43
Sky & Telescope - December 2021 - 44
Sky & Telescope - December 2021 - 45
Sky & Telescope - December 2021 - 46
Sky & Telescope - December 2021 - 47
Sky & Telescope - December 2021 - 48
Sky & Telescope - December 2021 - 49
Sky & Telescope - December 2021 - 50
Sky & Telescope - December 2021 - 51
Sky & Telescope - December 2021 - 52
Sky & Telescope - December 2021 - 53
Sky & Telescope - December 2021 - 54
Sky & Telescope - December 2021 - 55
Sky & Telescope - December 2021 - 56
Sky & Telescope - December 2021 - 57
Sky & Telescope - December 2021 - 58
Sky & Telescope - December 2021 - 59
Sky & Telescope - December 2021 - 60
Sky & Telescope - December 2021 - 61
Sky & Telescope - December 2021 - 62
Sky & Telescope - December 2021 - 63
Sky & Telescope - December 2021 - 64
Sky & Telescope - December 2021 - 65
Sky & Telescope - December 2021 - 66
Sky & Telescope - December 2021 - 67
Sky & Telescope - December 2021 - 68
Sky & Telescope - December 2021 - 69
Sky & Telescope - December 2021 - 70
Sky & Telescope - December 2021 - 71
Sky & Telescope - December 2021 - 72
Sky & Telescope - December 2021 - 73
Sky & Telescope - December 2021 - 74
Sky & Telescope - December 2021 - 75
Sky & Telescope - December 2021 - 76
Sky & Telescope - December 2021 - 77
Sky & Telescope - December 2021 - 78
Sky & Telescope - December 2021 - 79
Sky & Telescope - December 2021 - 80
Sky & Telescope - December 2021 - 81
Sky & Telescope - December 2021 - 82
Sky & Telescope - December 2021 - 83
Sky & Telescope - December 2021 - 84
Sky & Telescope - December 2021 - Cover3
Sky & Telescope - December 2021 - Cover4
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