* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Ch. 4 review
Outer space wikipedia , lookup
Advanced Composition Explorer wikipedia , lookup
History of astronomy wikipedia , lookup
Tropical year wikipedia , lookup
Circumstellar habitable zone wikipedia , lookup
Spitzer Space Telescope wikipedia , lookup
Kepler (spacecraft) wikipedia , lookup
Rare Earth hypothesis wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
Astrobiology wikipedia , lookup
Planets beyond Neptune wikipedia , lookup
Astronomical naming conventions wikipedia , lookup
Astronomical spectroscopy wikipedia , lookup
Beta Pictoris wikipedia , lookup
Planets in astrology wikipedia , lookup
Satellite system (astronomy) wikipedia , lookup
Dwarf planet wikipedia , lookup
Star formation wikipedia , lookup
Exoplanetology wikipedia , lookup
Late Heavy Bombardment wikipedia , lookup
Definition of planet wikipedia , lookup
Extraterrestrial life wikipedia , lookup
Directed panspermia wikipedia , lookup
IAU definition of planet wikipedia , lookup
Solar System wikipedia , lookup
Nebular hypothesis wikipedia , lookup
Planetary habitability wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
History of Solar System formation and evolution hypotheses wikipedia , lookup
Ch. 4 – Formation of the Solar System • Stars produce the heavier elements. • Formation of the Solar System (stardust, gravity, rotation, heat, and collisions). • Comparative Planetology (characteristics of the planets of the solar system). • Debris and remnants in the solar system. • • • • • • The heavy elements in the solar system were formed in an earlier generation of stars The early Universe contained only hydrogen, helium, and traces of lithium. All heavier elements were created in the core of stars as they “burned” the hydrogen and helium into carbon, oxygen, neon, calcium, magnesium, silicon, and iron These were then expelled into space by - stellar winds (happening with our sun now) - planetary nebulae (not planets, but similar appearance to early astronomers) - see slides - nova and supernova explosions (which also create the heavier elements, including radioactive elements) Solar Prominence – photo by SOHO spacecraft The solar wind expels some heavy elements into space. from the Astronomy Picture of the Day site Helium Shell Burning on the Horizontal Branch prior to the formation of a planetary nebula. Planetary Nebulae form when the core can’t reach 600 million K, the minimum needed for carbon burning. Another dramatic result of stellar evolution: a supernova remnant which expels heavy elements into space. A Dark Cloud: dust and gas, dense enough to block starlight. Radio Emission reveals the dark dust cloud. Horsehead Nebula (The neck is about 0.25 pc across) A nice example of a dark dust cloud Formation of the Solar System There are several kinds of objects in our Solar System Terrestrial planets: Mercury, Venus, Earth, and Mars Jovians: the “gas giants” Jupiter, Saturn, Uranus, and Neptune “debris” – asteroids, comets and meteoroids, and some objects still being classified: Kuiper Belt, Oort cloud How did these form from interstellar material? Young Stars in Orion This photo shows the nebula in visible light. Young Stars in Orion An IR photo shows the stars clearly, note the four central stars (the Trapezium) Orion Nebula A closer look reveals “knots” or “evaporating gaseous globules” EGGs, some of which may contain protostars. These globules may contain evolving planets as well as a central protostar. Several disks that may be protoplanetary disks are found after blowing up the Hubble photo. Major facts that any theory of solar-system formation must explain • • • • • • • • • • Each planet is relatively isolated in space. The orbits of the planets are nearly circular. The orbits of the planets all lie in nearly the same plane. Direction of planet’s movement in orbit is same as sun’s rotation. Direction of planet’s rotation is same as sun’s rotation. (*usually*) Direction of the various moon’s revolution is same as planet’s rotation. The planetary system is highly differentiated. Asteroids are very old, and not similar to terrestrial planets or Jovian planets. The Kuiper belt is a group of asteroid-sized icy bodies orbiting outside the orbit of Neptune. (KBO – Kuiper Belt Objects) The Oort Cloud is composed of icy cometary objects that do not orbit in the same plane as the planets (the ecliptic). Angular Momentum influences the formation of planetary disks during the collapse of a cloud of gas Beta Pictoris is one example of a protoplanetary disk top: false color image with the central star blocked out to show the disk bottom: artist’s rendition of what the disk might look like if a planet is forming Beta Pictoris has a protoplanetary disk and a planet ! Image from ESO Conservation of Angular Momentum Conservation of Angular Momentum in a figure skater. A Theory of Solar System Formation: A spinning gas cloud condenses to a much smaller size, and begins to rotate much faster due to conservation of angular momentum. This is the protoplanetary disk, also called a “proplyd.” This process explains the fact that all the objects tend to rotate in the same way (or ‘sense’) in a system. Differentiation may be due to the temperatures in the Early Solar Nebula The inner solar system is closer to the early Sun, and so it is hotter. Volatile gases are not condensed on the planets and end up condensing in the Jovian planets further out. This is similar to a process in chemical plants called distillation or fractionation. Sun and Planets (approximate scale of diameters) Ch. 5 - Exoplanets • • • • Planets have been discovered orbiting other stars. Evidence from several sources: - Distortion of protoplanetary disks (proplyds). - Doppler shift of the light of the star, indicating radial velocity shifts. • - Astrometry to measure stellar wobble. • - Detection of dimming of the star, indicating a transit by a planet. (Most of them are found this way.) • Over 1800 exoplanets have been found. Beta Pictoris has a planet Extra-solar Planets are revealed by the Doppler effect, seen when we study the central star Experimental methods have their own particular bias. Doppler surveys find only the large planets. Kepler transit studies have only found short period planets. Kepler has found many planets smaller than Jupiter, so it is adding to the list of smaller planets that Doppler measurements have not seen. Earth-size planets with temperatures suitable for life have been found by the Kepler spacecraft.