HOMEWORK #4

ASTRONOMERS PROBE ALIEN SKIES

Exercise:

1. a. Planetary Accretion— Gradual growth of small objects by colliding and sticking; creating

objects a few hundred kilometers across. By that time, gravity allowed other materials to stick to it that would not been able to in the early stages.

  1. Brown Dwarf-- Astronomical object intermediate in mass between a planet and a star. Sometimes described as failed stars, brown dwarfs are believed to form in the same way as stars, from fragments of an interstellar cloud that contract into gravitationally bound objects. However, they do not have enough mass to produce the internal heat that in stars ignites hydrogen and establishes nuclear fusion. Though they generate some heat and light, they also cool rapidly and shrink; they may differ from high-mass planets only in how they form.
  2. "Hot" Jupiter’s—Planets with the mass of Jupiter (300 Mass of Earth) but in Mercury-like orbits (i.e., 0.05 to 0.5 AU) around their host star.
  3. Planetary Migration— Most migration scenarios consider the gravitational interactions between the growing planet and the gaseous disk. When a massive object orbits inside a gaseous disk, gravitational interactions between the two give rise to significant changes ("perturbations") in the disk. In particular, if the planet is massive enough, a gap opens in the disk.
  4. Snow Line—The location in the solar system where water changes from liquid to solid (Freezes). For our solar system that would be at 5 AU, the exact location where our Jupiter is now located.

f. Planetary Transit— When orbiting in an edge-on orientation, the planet will pass between its star and the Earth (transit) once each orbit, causing a slight dimming of the star's light.

2. a. Dynamic Equilibrium is when something in the universe is replenished as

quickly as it is used.

Ex-1: Oxygen—it stays at a constant level because as it is used, it gets replenished through photosynthesis from plants.

Ex-2: Dust Clouds—This dust has formed in the Asteroid Belt as rock boulders in that belt collide. This dust lasts approximately about 100,000 years before reaching the Sun. The dust must be continuously replenished in order for it to still be present in the inner Solar System; otherwise it would be long gone. The rate of rock collisions must be equal to the rate of destruction as the dust spirals inward toward the Sun for this to happen.
  1. Oxygen in the Earth’s atmosphere is always being used if it did not get replenished we would very quickly die from a lack of oxygen. Biological photosynthesis produces the required oxygen to keep the balance of use verses reproduction in stable.

 

3. a. D = 2TT x R; Circumference of a Circle.

D = 2TT x 6,700,000 = 42,076,000

V = D / t; Orbital Velocity or Speed

V = 42,076,000km / 302,400 seconds = 139.140km/s

Km / s = 139.140

  1. Convert planets clouds temperature to Celsius (° C) and Kelvin (° K). Cloud is 2000° F. ° C = 5 / 9 ( ° F-32) ° C = 5 / 9 ( 2000° F-32) = 1093° C 1093° C + 273 = 1366° K
  2. The Fahrenheit Scale is based on water turning into a solid (freezing) at 32° and turning into a vapor (boiling) at 212° . Where as, the Celsius Scale is based on water turning into a solid (freezing) at 0° and turning into a vapor (boiling) at 100° . The Kelvin scale however, is based on the zero point of this scale being equivalent to -273.16 °C on the Celsius scale. This zero point is considered the lowest possible temperature of anything in the universe. Therefore, the Kelvin scale is also known as the "absolute temperature scale". At the freezing point of water, the temperature of the Kelvin scale reads 273 K. At the boiling point of water, it reads 373 K.
  3. R = (3xM / 4P xp)1/3

R = (3x1.90x10^27kg / 4P x1330kg-m^3)1/3

R = (5.7^27kg / 16704.8kg-m^3)1/3

R = (3.412^23m)1/3

R = 69752550.25m

 

 
  1. It was interesting how they determined that sodium was present in the atmosphere of a planet orbiting the solar-type star HD 209458. These planets are called "Hot"Jupiters, because they are very large like our Jupiter. They orbit their host star at a very fast rate of 3.5 days at 6.7 million kilometers. These "Hot" Jupiters orbit their sun at about 0.05 AU.

Orbiting its sun at this distance with a sodium-based atmosphere allows the planet to absorb some of the sun’s light. As the planet moves in and out of transit the amount of starlight absorbed varies. The sodium in the planets atmosphere is believed to have combined with other molecules to form sulfides, because the initial amount of sodium found was much less than expected. This sodium supports the hope of astronomers to be able to study the chemical characteristics of extra-solar planets in the very near future.

 

FOURTH PLANET OF A PULSAR

2. a. Neutron Star—Photograph 22.1 on page 494 and 22.5 on page 497.

Any of a class of extremely dense, compact stars thought to be composed mainly of neutrons with a thin outer atmosphere of primarily iron atoms and electrons and protons. Though typically about 12 mi (20 km) in diameter, they have a mass roughly twice the suns and thus extremely high densities (about a hundred trillion times that of water). Neutron stars have very strong magnetic fields. A solid surface differentiates them from black holes. Below it, the pressure is much too high for individual atoms to exist; protons and electrons are compacted together into neutrons. The discovery of pulsars in 1967 provided the first evidence of the existence of neutron stars, predicted in the early 1930s and believed by most investigators to be formed in supernova explosions.
  1. White Dwarf—Photograph 20.14 on page 459

    2. Any of a class of small, faint stars representing the end point of the evolution of stars without enough mass to become neutron stars or black holes. Named for the white color of the first ones discovered, they actually occur in a variety of colors depending on their temperature. They are extremely dense, typically containing the mass of the sun within the volume of the earth. White dwarfs have exhausted all their nuclear fuel and cannot produce heat by nuclear fusion to counteract their own gravity, which compresses the electrons and nuclei of their atoms until they prevent further gravitational contraction. When a white dwarf's reservoir of thermal energy is exhausted (after several billion years), it stops radiating and becomes a cold, inert stellar remnant, sometimes called a black dwarf. White dwarf stars play an essential role in the outbursts of novas, and if mass transfer increases their mass above 1.4 times the sun's mass (the Chandrasekhar limit), they collapse and generate a supernova explosion.

  2. Globular Cluster— Photograph 17.24 on page 400

    3. A large group stars closely packed in a symmetrical, somewhat spherical form. About 100 have been identified in the Milky Way galaxy. Globular clusters contain many more stars (10,000-1 million) than open clusters do and can be several hundred light-years in diameter. Because they are so distant from the solar system, most are not visible to the unaided eye. Omega Centauri and a few others can be seen without a telescope as hazy patches of light.

  3. Open Cluster— Photograph 17.23 on page 400

A group of stars with a common origin, held together by mutual gravitation (not to be confused with a cluster of galaxies). Stars in open clusters are much more scattered than those in globular clusters. All known open clusters contain from about 10 to 1,000 or more stars (about half contain fewer than 100) and have diameters of 5-75 light-years. More than 1,000 have been discovered in the Milky Way galaxy; well-known examples include the Pleiades and the Hyades.