AY 101: Test Two Study Guide
Answering questions from the handouts, with a few bonuses
Chapter Six: Solar System Formation
1. The Nebular Hypothesis states that our solar system formed from a solar nebula with an initial rotation by the process of gravitational collapse.
a. Nebula: a large, often irregular looking type of astronomical object whose material lies between the stars; found in what astronomers call the interstellar medium.
b. Gravitational Collapse: occurs when part of an interstellar cloud is cold enough for gravity to overcome the cloud’s random thermal motions.
2. Planetesimals small objects that started out as tiny particles that grew over time through condensation. These can collide together and form larger bodies through the process of accretion.
a. Accretion: when planetesimals have a high enough velocity to collide and merge with others to the point where it gathers a significant gravitational pull to draw in all the other planetesimals in its orbit, thus clearing its orbital path.
3. Terrestrial planets are mostly made of rock and metal, and are located closer to the sun where they were able to form more solid outer layers.
a. Jovian planets are located outside the frost line in the outer solar system, much farther away from the sun. There, they developed thick atmospheres due to their massive sizes, but were not close enough to the Sun for their surfaces to condense into solids, so they are essentially liquid planets. We also discuss several other topics like How do you rearrange an equation?
i. Frost line: the largest distance from the Sun that will allow terrestrial
planets to form. Due to the fact that gases farther away from the sun will condense into ices, and these ices get pulled in by the gravity of the
massive planets to form liquid surfaces.
4. Radiometric dating means using the number of radioactive particles to determine the age of very old materials. It works by measuring the number radioactive isotopes in a sample, then working backwards by how many halflives are presumed to have passed since the material was formed. We also discuss several other topics like What is sensory adaptation and how does it occur?
a. Isotopes: atoms that have more neutrons than protons, and become very unstable and often radioactive.
b. Halflife: the amount of time it takes for one half the amount of radioactive isotopes to decay into other, more stable elements (known constants).
5. We have determined that the solar system is about billion years old by using radiometric dating on unaltered meteorites.
a. Meteorite: a meteor (very small planetesimals) that crashed to the surface of the earth without burning up in the atmosphere.
Chapter Seven: Terrestrial Planets
6. Mercury, being a planet inside the frost line, is a terrestrial planet. However, it is more like the moon than the earth because it has no atmosphere.
7. Venus has a very thick atmosphere made up mostly of CO2 gas that have caused a runaway greenhouse effect. Besides that, its sulfuric acid clouds make it a wholly uninhabitable planet.
a. Greenhouse effect: when certain gasses with more reflective properties act as a sort of filter in the atmosphere of a planet that traps incoming heat from nearby stars to hear up the exterior of the planet.
b. The effect becomes runaway when there are too many gasses in the atmosphere and so much heat is built up that more gases are produced to make the effect even worse, which eventually superheats the atmosphere of the planet. We also discuss several other topics like How can one decide on policies?
8. The Earth’s atmosphere is mostly made up of nitrogen and oxygen, which is odd because they are some of the rarer elements in the universe, and for them so show up in such a concentrated sample is miraculous.
a. The earth appears blue because the elements in its atmosphere (nitrogen and oxygen) tend to reflect blue light from the sun in the day time. This is also what the oceans reflect, adding to the blue color.
9. The moon is too small to hold an atmosphere because of its location relevant to the Sun. Other planets that are the same size or smaller can be found with an atmosphere, but only because they are located far away enough from the Sun’s solar winds.
a. Surface gravity depends on the size of a world, and indicates its ability to draw in gases from space.
b. Lunar maria are the smooth, dark lowlands that can be seen on the moon. c. Lunar highlands are the rougher surfaces that show up as the lighter areas seen on the moon.
i. These are considered to be the older areas that are visible on the moon. 10. Mars is red for the same reason that the earth is blue: the elements that are found on its surface and in its atmosphere reflect red waves of light the most, likely because of the abundance of iron oxide that found on the surface of Mars. Don't forget about the age old question of What is the meaning of sexual contact?
a. Lighteningshaped streaks on the surface of Mars coming down from its mountains are evidence that water once flowed on the planet, but it likely froze or evaporated long ago. If you want to learn more check out What is pattern recognition?
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11. Location relevant to the sun primarily determines the amount of heat a planet receives. 12. The bigger the planet it, the more geologically active it will be, and the warmer it will be on the interior of the planet. Mass also determines the surface gravity a planet will have. 13. Surface gravity is the main force responsible for keeping an atmosphere over a planet.
Chapter Eight: Jovian Planets
1. A “dipole magnetic field” refers to an electromagnetic field that develops out of a planet with magnetic lines that are able to divert away certain electromagnetic wavelengths, and
these line converge at the magnetic poles of that planet. This location is determined by the interior shape of the planet.
a. The earth has a magnetic field because the conductive metals in its inner layers get heated and charged under the earth’s surface, creating a net charge at the top and bottom of the planet that attracts other elements of similar magnetic affiliation.
2. Without a magnetic field, or magnetosphere, the earth would be bombarded by harmful electromagnetic rays that would kill most if not all life on Earth. These waves get sent to Earth when the force of the Sun’s emission (solar wind) shoots the waves at us, but they do not cross the magnetic field lines. Instead they travel along the lines and are dissipated before entering the atmosphere.
a. There are some places on Earth where the harmful waves do make it to the atmosphere, but only as charged photons that emit light when they interact with the earth’s atmosphere. These locations are the Arctic and Antarctic circles, where this interaction between the atmosphere and the charged particles create the aurora borealis.
3. Jovial planets are mostly made of gas and ice, so they have a very thick atmosphere, but not solid surfaces.
a. Jupiter spins so fast that its thick atmosphere streaks in large bands across its visible atmosphere.
b. The “Great Red Spot” is a giant antihurricane about the size of the earth that has been raging for hundreds of years,
4. Jupiter’s clouds are made of hydrogen compounds, and its overall atmosphere is mostly hydrogen and helium. The surface below, however, is completely liquefied. a. Jupiter is unique in that it is the only place in the solar system that has liquid hydrogen.
5. Saturn is a bit smaller than Jupiter, but is still considered a massive gas giant. It has generally the same composition, but due its distance from the Sun, a cold haze surrounds the planet and masks its bands of atmosphere, like those seen on Jupiter.
6. The rings of Saturn are made millions of incredible small planetesimals that are mostly ice and rock. These circle the planet in a disk shape that is extremely thin, only about 1.5 miles.
7. The Cassini Division in Saturn’s rings is the result of orbital resonance with Saturn’s moon, Mimas, which has an orbital period that is exactly twice the orbital period of the fragments in the division.
a. The orbital resonance means that the moon pulls as the fragments in the exact same spot, causing them to be pulled slightly out of their normal orbit and to bump into surrounding fragments, thus clearing that orbital path.
b. The shepherd satellites Pandora and Prometheus reign over the Fring of Saturn and hold a number of fragments in a very thin line with their equal but opposite gravities.
8. The moons of Jupiter (Io, Europa, Ganymede and Callisto) are all either the same size as, or larger than, Earth’s moon. The first three, are also in orbital resonance with each other, and thus have some interesting characteristics.
a. Io is volcanically active due to the tidal heating that is caused by the orbital resonance of the moons. A significant tidal bulge causes it to warp, creating friction and therefore geologic activity within the moon.
9. A subsurface ocean is a body of liquid substance (usually water) that forms underneath a layer of ice that coats the entire world. A subsurface ocean can be found on Europa, a moon of Jupiter.
Chapter Nine: Asteroids and Comets
1. Asteroids are large planetesimals that are generally made of metal and rock. 2. Asteroids are mostly found in the Asteroid Belt located in between Jupiter and Mars. 3. Typical asteroids are about 1,000 km wide, but are oblong in shape which results in a boomeranglike rotation.
4. A comet nucleus is a condensed mass made up of rock and ice that forms in the Kuiper Belt. A typical comet is only a few miles wide.
5. Although a comet is very similar to an asteroid in that it is a colorless rock, but only when it is in the far reaches of the system. When the comet’s orbital period takes it close enough to the Sun, the ices that have formed evaporate straight to a gas, skipping a liquid phase—a process called sublimation.
6. The coma of a comet is the temporary atmosphere that forms around the comet’s nucleus as it passes the sun. This atmosphere will soon be blown away by the Sun’s solar winds. 7. Comets develop tails because, as the ices that make up the nucleus sublimate, the solar wind from the Sun blows the coma outwards and away from it, creating two tails. a. The dust tail, made up of rock particles that become dislodged as the ices sublimate.
b. The gas tail is made up of the sublimated ices.
8. The dust tail curves around towards the orbital path of the comet because it is the heavier of the two tails. The gas tail is much lighter than the gas tail, and so points directly away from the Sun as it is blown away by the solar winds.
9. The tails will always point away from the Sun, so their direction will rotate to accommodate the position of the Sun as the comet passes through its orbit. a.
10. The orbital of a comet is always very elliptical, with very long orbital periods. Chapter Ten: Exoplanets
1. An exoplanet is a planetary object that orbits an alien star.
2. We cannot see exoplanets with telescopes, like we can planets in our own system, because of their immense distance from us, but we can use other methods to detect them. 3. A center of mass is the point at which two object of varying sizes are balanced at, like the point on a pencil where it will balance the heavy eraser and lighter tip. Pluto and Ceres orbit around a center of mass, and so do not have a perfectly straight orbit, but a slight wobble.
4. The radial velocity method is a method of detecting exoplanets by observing stars that have a slight wobble in their orbit, which is measurable through the Doppler effect. The wobble means that the star shares a center of mass with another object, most likely a planet.
a. Since the force of gravity between two objects is determined by their relative masses and the distance between them, we can also determine the mass and orbit size of the planet orbiting the alien star, because the bigger the wobble is, the larger the planet is and the larger the orbit is.
5. The other method for detecting exoplanets is by measuring their transit, or the amount that their star dims when the planet passes in front of it. This only works if the planet’s orbit is edgeon to us observing from Earth.
a. A light curve is a graphical representation of the dip in the brightness of the star caused by the transit. This tells us the size of the planet because larger planets will block more light from reaching us, resulting in a larger dip in brightness.
6. If both of the detection methods are used on the same exoplanet, we can determine the density of that planet because we will have gathered information on the size and mass of that planet.
TO BE CONTINUNED. . .