hour 3: star and planet formation, history of our solar system, planets around other stars...
TRANSCRIPT
Hour 3: Star and Planet Formation,History of our Solar System,Planets Around Other Stars
• 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 by-products of stars forming
• There are two types of planets in our solar system, Earth-likeand 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 Cloudsand Star-forming Regions
The OrionNebula:
An ActiveStar-FormingRegion
Constellation Orionleft: visual wavelength image
right: far-infrared image
p.194c
p.195b
p.194b
GlobulesEvaporating 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 PlanetsPlanets 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
Last remains of planetesimals that built the planets 4.6 billion years
ago!
Small, irregular objects,
mostly in the apparent gap between the
orbits of Mars and Jupiter.
Fig. 16-7, p.363
The Geology of Comet NucleiComet 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 by-products of stars forming
• There are two types of planets in our solar system, Earth-likeand 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