The three main layers of the sun are referred to as photosphere, chromosphere and the corona. According to the text ‘Discovering the Universe’ by Comins, N.F & Kaufmann III, W.J, 8th edition, each of these layers has different features that makes them different from one another.
The photosphere is the layer that appears to be the major part of the sun where visible light comes from. Photosphere is about 400km thick with a lower density when compared to that of earth standards. This part of the sun also has a blackbody spectrum. In terms of the sun's atmosphere, photosphere is the innermost layers with two other layers above it. Those layers are transparent to the wavelength of visible light making it easier to see through them to the photosphere layer. The photosphere also has another characteristic which is termed the limb darkening. This feature describes seeing of different region with different temperatures with a particular depth in the layer. Farther away to the photosphere is the hottest and brightest region.
The chromosphere is another layer that is above the photosphere. It is made up of spike of gas tagged spicules. This layer is less dense and can only be seen during total solar eclipse when the photosphere is blocked. It is seen as a layer of pinkish strip with about 2000 km thickness. The spicules of chromosphere are located on the boundaries of chromospheric gas known as supergranules.
The outermost region of the sun layers is the corona. This layer has a transition zone separating it from the chromosphere. It is about several million kilometers thick. The temperature of the transition zone is about 1 million K making it has gases that have their electrons stripped off the atoms because of the easy ionization process. The visible light coming from the corona is almost the same as the brightness of the full moon (Comins &Kaufmann 290).
- What do astronomers mean by a "model of the Sun"?
The model of the sun' simply describes a solar model made up of thermonuclear reactions which starts from the core of the sun. The reactions create energy that is then transferred from the core to the photosphere. The energy created in this model is transferred to the outer layers of the sun via the convection form of energy transfer.
The feature of this model of the sun describes a sun with internal structures characterized with luminosity, mass, temperature and density found to be dependent on the distance to the core. This model also describes a sun that has thermonuclear energy core, followed by radiative zone, convective zone, photosphere, chromosphere and finally the corona (Comins &Kaufmann 303).
- What is a neutrino, and why are astronomers so interested in detecting neutrinos from the Sun?
Neutrinos are very small massless particles which are found to travel at a speed close to the speed of light. They are subatomic particles that weakly interact. According to astronomers, neutrinos are particles that are released during the process that is involved in change of proton to neutron during thermonuclear fusion. Part of the major reason why astronomers are interested in detecting neutrinos can simply be ascribed to the fact that neutrinos are usually difficult to detect simply because they rarely interact with ordinary matter. The other factor relates to the fact that sun is transparent to neutrinos. This makes astronomers interested in creating a neutrinos telescope that makes it easier to detect neutrinos which are usually hidden from the view of the normal telescope (Comins &Kaufmann 307).
- Stellar parallax measurements are used in astronomy to determine which of the following properties of stars? a. speeds, b. rotation rates c. distances, d. colors, e. temperatures
Stellar parallax measurements are used in astronomy to determine the distances between the stars. It shows how far away are the nearest stars are (Comins &Kaufmann 317).
- Briefly describe how you would determine the absolute magnitude of a nearby star.
In order to calculate the absolute magnitude of a star, considerations are given to the distance of the stars and its apparent magnitude. This is simply because of the consideration found by astronomers that distances actually affect the brightness of the stars. Far stars appears less bright than closer stars to the earth. Analogy is compared to that of cars full light in the night.
The light of the closer car will be brighter than that far away. The formula for the absolute magnitude is M= m-5 log (d/10). In this equation, M represent the absolute magnitude while the m represent the apparent magnitude. The distance of the star from the earth is represented by d. (Comins &Kaufmann 324)
- What is the mass-luminosity relation? To what kind of stars does it apply?
This relationship is a new trend in the study of stars. It is believed by astronomers that the more luminous a star is, the more massive it will be. This relationship also provides an important property which relates mass-luminosity properties. This indicates that mass suggests what will come from the star in terms of energy production. This factor now seem to be the important factor that needs to be consider when the brightness of stars is the topic of discussion. This factor applies to those main-sequence stars (Comins &Kaufmann 329).
- What is the lowest mass that a star can have on the main sequence? a. There is no lower limit, b. 0.003 M, c. 0.08 M", d. 0.4 Me, e.2.0 M.
There is no lower limit to what a main sequence stars can have (Comins &Kaufmann 335)
- On what grounds are astronomers able to say that the Sun has about 5 billion years remaining in its main sequence stage?
The factors astronomers are considering relates to the facts that they believed that in about 5 billion years, the core of the sun will swell into a giant core. The giants will then have its diameter increase in hundredfold with a core becoming compact. The sun also evolves more rapidly and has more of a shorter main-sequence lifetimes (Comins &Kaufmann 373).
- How is the evolution of a main-sequence star with less than 0.4 Mo fundamentally different from that of a main-sequence star with more than 0'4 M.?
The evolution of main sequence stars lower than 0.4Mo is fundamentally different than those higher than 0.4Mo. Those differences relates to their properties which relates to the core temperatures, energy being produces, properties of the cores and helium transportation. Stars lower than 0.4Mo which are referred to as the Red dwarfs have the lowest core temperatures among all stars.
This group of stars also produces the least amount of energy which results in their transmission of least energy among the two groups of stars. In terms of brightness, those main sequence starts that are higher than 0.4Mo are the brightest among the main sequence stars. Another fundamental difference between the two categories of main sequence stars relates to the fact that lower groups transport the helium created out of their cores. This transmission of helium out of core is basically by convention form of energy transfer.
In order way, as the helium is being transported out of the cores in lower main sequence stars, the gases that are cooler in their hydrogen rich outer layers are moved from that region downwards into the cores. Since this change occurs in the cores of the red dwarfs, there is fusion of the hydrogen into helium resulting in an entire conversion of the mass into helium which is not what happens in the higher main sequence stars.
In the main sequence stars more than 0.4Mo, the hydrogen that is being converted to helium is not all in those stars hence making fusion occurring at the core to be very slow. This changes has been attributed to the fact that the temperature produce at that period of fusion is lower than what is require to allow helium to fuse into other elements. This fact makes those groups of stars to continue to evolve making them different from those stars that are less than 0.4Mo (Comins &Kaufmann 351-361).
- A white dwarf is composed of primarily a. neutrons, b. hydrogen and helium, c. iron, d. cosmic rays, e. carbon and oxygen.
White dwarfs generally made up of carbon and oxygen. These contents become solidify when the white dwarfs loose its heat hence creating a state where the interior temperature becomes lowered to 4000K. The dwarfs then later become giant crystals (Comins &Kaufmann 384).
- What is the Chandrasekhar limit?
This is the upper limit of to the mass of a white dwarf. The limit is 1.4Mo to the white dwarf. It is a mass named after a 1990 Nobel Prize winner, Subrahmanyan Chandrasekhar (Comins &Kaufmann 403)
- Compare a white dwarf and a neutron star. Which of these stellar corpses is more common? Why?
The upper limit to white dwarf is Chandrasekhar limit (1.4Mo) while that of neutron star is called Oppenheimer-Volkov limit (with 3Mo). The dwarf stars are more common simply because of the smaller size and density (Comins & Kaufmann 403).
- Supermassive black holes are found in which of the following locations? a. in the centers of galaxies, b. in globular clusters, c. in open (or galactic) clusters' d. between galaxies, e. in orbit with a single star
Supermassive black holes are found in the centers of galaxies (Comins &Kaufmann 419).
- If the Sun suddenly became a black hole, how would Earth's orbit be affected?
Sun becoming a black hole will affects the earth in several ways. The earth will be affected by the evaporation of black holes. That means the energy of the sun mass will be converted into energy making the earth more hotter (Comins &Kaufmann 426)
Comins, Neil & Kaufmann, William. Discovering the universe. 8th edition. W.H. Freeman and Company, New York. Print.