Sky and Telescope - January 2017 - 27

Big Bang

Direct collapse

Death of massive stars

Star clusters

200
million
years

Initial
seeding
500
million
years
Few halos
are seeded,
but seeds
are ~104
solar masses

Most halos
are seeded,
but seeds
are ~100
solar masses

Some halos
are seeded,
but seeds are
~100 to ~1,000
solar masses

Time since Big Bang

Halos grow
via merging
1 billion
years

Black holes grow
via accretion
and merging

Some
black holes
are ejected

Growth of black holes
and halos with time

3 billion
years

CREDIT
S&T: LEXAXHXTISCIONE,
X X X X X X X X SOURCES:
XXXX
J. G REENE / NATURE COMMUNICATIONS 2012 & M A RTA VOLON TERI

6 billion
years

Direct collapse

Star clusters

Death of massive stars

Today

Few ~109 solar mass
galaxies contain >105
solar mass black holes

Some ~109 solar mass
galaxies contain ~105
solar mass black holes

Almost all ~109 solar mass
galaxies contain ~105
solar mass black holes

Observational
consequences

EVOLUTION OF SEED BLACK HOLES Astronomers suggest three main avenues for creating the universe's supermassive black holes: direct collapse
of gas (left), runaway collisions in star clusters (center), and the death of the first, massive stars (right). The gray circles represent the dark matter halos in
which each process takes place. These halos, and the protogalaxies in them, then grow through merging (center of diagram). Black holes themselves grow
both by merging with each other and by accreting gas. Occasionally a merger is violent enough to kick the black hole out of the galaxy. The fraction of
small galaxies that have massive black holes will depend on which of these scenarios dominated. (The Small Magellanic Cloud is 109 solar masses.)
s k y a n d t e l e s c o p e .c o m

* JANUARY 2017

27


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Sky and Telescope - January 2017

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

Contents
Sky and Telescope - January 2017 - Cover1
Sky and Telescope - January 2017 - Cover2
Sky and Telescope - January 2017 - 1
Sky and Telescope - January 2017 - Contents
Sky and Telescope - January 2017 - 3
Sky and Telescope - January 2017 - 4
Sky and Telescope - January 2017 - 5
Sky and Telescope - January 2017 - 6
Sky and Telescope - January 2017 - 7
Sky and Telescope - January 2017 - 8
Sky and Telescope - January 2017 - 9
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Sky and Telescope - January 2017 - 20
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Sky and Telescope - January 2017 - 24
Sky and Telescope - January 2017 - 25
Sky and Telescope - January 2017 - 26
Sky and Telescope - January 2017 - 27
Sky and Telescope - January 2017 - 28
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Sky and Telescope - January 2017 - 31
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Sky and Telescope - January 2017 - 36
Sky and Telescope - January 2017 - 37
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Sky and Telescope - January 2017 - 40
Sky and Telescope - January 2017 - 41
Sky and Telescope - January 2017 - 42
Sky and Telescope - January 2017 - 43
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Sky and Telescope - January 2017 - 83
Sky and Telescope - January 2017 - 84
Sky and Telescope - January 2017 - Cover3
Sky and Telescope - January 2017 - Cover4
Sky and Telescope - January 2017 - SGA17RAL
Sky and Telescope - January 2017 - 90
Sky and Telescope - January 2017 - SGA17R
Sky and Telescope - January 2017 - SGA17RA
Sky and Telescope - January 2017 - SGA17EAL
Sky and Telescope - January 2017 - 94
Sky and Telescope - January 2017 - SGA17E
Sky and Telescope - January 2017 - SGA17EA
Sky and Telescope - January 2017 - SGA17SAL
Sky and Telescope - January 2017 - 98
Sky and Telescope - January 2017 - SGA17S
Sky and Telescope - January 2017 - SGA17SA
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