Download Fig. 16-7, p.363

Hour 3: Star and Planet Formation,
History of our Solar System,
Planets Around Other Stars
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Interstellar Clouds & Star-Forming Regions
Protoplanetary Disks & Solar System Formation
Two Kinds of Planets & the Condensation Sequence
Era of Heavy Bombardment - Frustration of Life ?
Extrasolar Planets & the “Hot Jupiter” Puzzle
Take-aways:
• Clouds of material between the stars are sites of stars formation
• Earth plus the other planets in our solar system evidently formed
from a disk around the Sun as it formed; such protoplanetary
disks are seen around many young stars
• Planets like Earth are believed therefore to form as normal byproducts of stars forming
• There are two types of planets in our solar system, Earth-like
and Jupiter-like, results of a process we think we understand
• Almost 200 planets have now been found around other stars, but
those planetary systems often have “hot Jupiters” - is our solar
system weird, or are those systems weird ?
• All the planets sustained heavy bombardment from remnant
construction material soon after they formed; that may have set
the timescale for the beginning of life on Earth
Interstellar Clouds
and Star-forming Regions
The Orion
Nebula:
An Active
Star-Forming
Region
Constellation Orion
left: visual wavelength image
right: far-infrared image
p.194c
p.195b
p.194b
Globules
Evaporating gaseous globules
(“EGGs”): Newly forming stars
exposed by the ionizing radiation
from nearby massive stars
p.177b
p.177d
Globules
Bok globules:
~ 10 – 1000
solar masses;
Contracting to
form protostars
Shocks Triggering
Star Formation
Henize 206
(infrared)
Protoplanetary Disks &
Solar System Formation
Fig. 1-7, p.7
p.364a
Table 16-1, p.367
Fig. 16-1, p.357
Fig. 16-2, p.358
Fig. 16-3, p.358
Two Kinds of Planets &
The Condensation Sequence
Two Kinds of Planets
Planets of our solar system can be divided
into two very different kinds:
Terrestrial (earthlike) planets:
Mercury, Venus, Earth, Mars
Jovian (Jupiter-like) planets:
Jupiter, Saturn, Uranus, Neptune
Table 16-3, p.369
Asteroids
Small,
irregular
objects,
mostly in the
apparent gap
between the
orbits of Mars
and Jupiter.
Last remains of
planetesimals
that built the
planets 4.6
billion years
ago!
Fig. 16-7, p.363
The Geology of Comet Nuclei
Comet nuclei contain ices of water, carbon dioxide, methane, ammonia, etc.:
Materials that should have condensed from the outer solar nebula.
Those
compounds
sublime
(transition from
solid directly to
gas phase) as
comets approach
the sun.
Densities of comet
nuclei: ~ 0.1 – 0.25 g/cm3
Not solid ice balls, but
fluffy material with
significant amounts of
empty space.
Fig. 16-4c, p.359
Extrasolar Planets &
the “Hot Jupiter” Puzzle
Fig. 16-5, p.360
Artist’s Conception HD 209458
Planet passing in front of parent star -- size indicates density like Jupiter
Hot Jupiters:
• They seemingly go against the neat “Condensation Sequence”
theory that seems to explain our solar system’s arrangement
• Did the “Hot Jupiters” form “cold”, i.e. at the expected location
beyond the “ice line”, and then migrate toward the Sun ?
• If so, wouldn’t that destroy any Earth-like planets ?
• In our system Jupiter did NOT migrate -- is our system weird
or are the Hot Jupiter systems the unusual ones, but just easier
to detect with present technology ?
Era of Heavy Bombardment Frustration of Life ?
Fig. 16-13b, p.374
p.389c
Fig. 17-9, p.394
Fig. 18-3, p.424
Take-aways:
• Clouds of material between the stars are sites of stars formation
• Earth plus the other planets in our solar system evidently formed
from a disk around the Sun as it formed; such protoplanetary
disks are seen around many young stars
• Planets like Earth are believed therefore to form as normal byproducts of stars forming
• There are two types of planets in our solar system, Earth-like
and Jupiter-like, results of a process we think we understand
• Almost 200 planets have now been found around other stars, but
those planetary systems often have “hot Jupiters” - is our solar
system weird, or are those systems weird ?
• All the planets sustained heavy bombardment from remnant
construction material soon after they formed; that may have set
the timescale for the beginning of life on Earth