Sky & Telescope - June 2024 - 17

masses in these extragalactic events were larger than galactic
sources like V1309 Sco. It emerged that the more massive
the stellar pair, the brighter a flash they produced as they
fell together. In fact, a merger of a 10-solar-mass star with a
companion is about 1,000 times brighter than a similar event
involving a 1-solar-mass star.
Recently, other similarities have come to light. Despite
their range of masses, all of the stars' pre-outburst rises in
brightness shared similar colors. The members were also relatively
compact stars that had just stopped burning hydrogen
in their cores, partway along their evolution toward becoming
red giants. They tended to be blue or yellow stars, of spectral
types B through G.
Missing among all of these blue and yellow progenitor
stars, however, were the puffiest, reddest giants - stars like
what the Sun will evolve into in another several billion years.
These missing events are now turning up as " redder than red "
novae: outbursts that happen at such cool temperatures that
they only glow in infrared light.
Searches for these events began with NASA's Spitzer Space
Telescope and are continuing now using NEOWISE and the
James Webb Space Telescope. These discoveries have taught
us that collisions involving aging red stars look substantially
different than the other stellar crashes we've seen.
When a relatively hot star like the Sun merges with a
companion, we see a red nova that starts out bright in visible
light before eventually giving way to a dusty, infrared-bright
aftermath. When a cooler star (like an old, fluffy red giant)
swallows a companion, the whole process is slower and less
energetic. The traces are dusty and infrared-bright from the
start, with visible light enshrouded by the curtain of dust the
stars spew out as they coalesce.
D
15
16
17
18
19
20
−10 0 10 20 30 40 50 60
Time from outburst peak (days)
140
C
70
140
D
70
I
V
C
R
ANATOMY OF A RED NOVA As the stars spiral
in toward each other, they throw off gas, and the binary
brightens. Here, light curves at different visible
and infrared wavelengths for the red nova in M31
are paired with the author's simulation snapshots,
which show the lead-up to the stars' merger. The
simulation looks at the binary from above, showing
gas density in the orbital plane. Brighter areas show
where gas is denser. The white circle is the primary's
core; the white star is the secondary's core. (In the
inset light curve, BVRI are specific visible and nearinfrared
filters, from bluer to redder in color.)
B
−70
−70
−140
−140
−140
−70
Distance (solar radii)
70
140
−140
−70
Distance (solar radii)
sk yand tele scope .o r g * JUNE 2024 17
70
140
Distance (solar radii)
Apparent magnitude
Distance (solar radii)

http://skyandtelescope.org

Sky & Telescope - June 2024

Table of Contents for the Digital Edition of Sky & Telescope - June 2024

Contents
Sky & Telescope - June 2024 - Cover1
Sky & Telescope - June 2024 - Cover2
Sky & Telescope - June 2024 - 1
Sky & Telescope - June 2024 - Contents
Sky & Telescope - June 2024 - 3
Sky & Telescope - June 2024 - 4
Sky & Telescope - June 2024 - 5
Sky & Telescope - June 2024 - 6
Sky & Telescope - June 2024 - 7
Sky & Telescope - June 2024 - 8
Sky & Telescope - June 2024 - 9
Sky & Telescope - June 2024 - 10
Sky & Telescope - June 2024 - 11
Sky & Telescope - June 2024 - 12
Sky & Telescope - June 2024 - 13
Sky & Telescope - June 2024 - 14
Sky & Telescope - June 2024 - 15
Sky & Telescope - June 2024 - 16
Sky & Telescope - June 2024 - 17
Sky & Telescope - June 2024 - 18
Sky & Telescope - June 2024 - 19
Sky & Telescope - June 2024 - 20
Sky & Telescope - June 2024 - 21
Sky & Telescope - June 2024 - 22
Sky & Telescope - June 2024 - 23
Sky & Telescope - June 2024 - 24
Sky & Telescope - June 2024 - 25
Sky & Telescope - June 2024 - 26
Sky & Telescope - June 2024 - 27
Sky & Telescope - June 2024 - 28
Sky & Telescope - June 2024 - 29
Sky & Telescope - June 2024 - 30
Sky & Telescope - June 2024 - 31
Sky & Telescope - June 2024 - 32
Sky & Telescope - June 2024 - 33
Sky & Telescope - June 2024 - 34
Sky & Telescope - June 2024 - 35
Sky & Telescope - June 2024 - 36
Sky & Telescope - June 2024 - 37
Sky & Telescope - June 2024 - 38
Sky & Telescope - June 2024 - 39
Sky & Telescope - June 2024 - 40
Sky & Telescope - June 2024 - 41
Sky & Telescope - June 2024 - 42
Sky & Telescope - June 2024 - 43
Sky & Telescope - June 2024 - 44
Sky & Telescope - June 2024 - 45
Sky & Telescope - June 2024 - 46
Sky & Telescope - June 2024 - 47
Sky & Telescope - June 2024 - 48
Sky & Telescope - June 2024 - 49
Sky & Telescope - June 2024 - 50
Sky & Telescope - June 2024 - 51
Sky & Telescope - June 2024 - 52
Sky & Telescope - June 2024 - 53
Sky & Telescope - June 2024 - 54
Sky & Telescope - June 2024 - 55
Sky & Telescope - June 2024 - 56
Sky & Telescope - June 2024 - 57
Sky & Telescope - June 2024 - 58
Sky & Telescope - June 2024 - 59
Sky & Telescope - June 2024 - 60
Sky & Telescope - June 2024 - 61
Sky & Telescope - June 2024 - 62
Sky & Telescope - June 2024 - 63
Sky & Telescope - June 2024 - 64
Sky & Telescope - June 2024 - 65
Sky & Telescope - June 2024 - 66
Sky & Telescope - June 2024 - 67
Sky & Telescope - June 2024 - 68
Sky & Telescope - June 2024 - 69
Sky & Telescope - June 2024 - 70
Sky & Telescope - June 2024 - 71
Sky & Telescope - June 2024 - 72
Sky & Telescope - June 2024 - 73
Sky & Telescope - June 2024 - 74
Sky & Telescope - June 2024 - 75
Sky & Telescope - June 2024 - 76
Sky & Telescope - June 2024 - 77
Sky & Telescope - June 2024 - 78
Sky & Telescope - June 2024 - 79
Sky & Telescope - June 2024 - 80
Sky & Telescope - June 2024 - 81
Sky & Telescope - June 2024 - 82
Sky & Telescope - June 2024 - 83
Sky & Telescope - June 2024 - 84
Sky & Telescope - June 2024 - Cover3
Sky & Telescope - June 2024 - 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